Mud Brick Construction

Published on January 2017 | Categories: Documents | Downloads: 31 | Comments: 0 | Views: 376
of 88
Download PDF   Embed   Report

Comments

Content

Alternative Methods of Stabilisation for Unfired Mud Bricks

Doug Harper
B.Eng Civil and Structural Engineering School of Civil Engineering & Geosciences, Newcastle University 2011

1

Executive Summary

Mud brick construction dates back, in various forms, for several thousand years. Recently, Interlocking Compressed Soil Blocks (ICSB) have emerged as a viable, sustainable and affordable construction material, suitable for the provision of low cost housing in the developing world. However, questions have been raised as to their long term durability and susceptibility to water damage. Traditionally, unfired mud bricks have been stabilised with cement to overcome these short comings but the use of cement reduces the environmental differential between unfired bricks and fired ones. This report investigates the use of Ground Granulated Blast furnace Slag (GGBS) and Pulverised Fly Ash (PFA) as alternatives to cement for the stabilisation of ICSB. Sample bricks were constructed using varying concentrations of PC, PFA and GGBS and the sample’s compressive strength and Initial rate of Water Absorption (IRA) compared. Simultaneously, a sustainability study was undertaken to contrast the three materials in terms of ease of manufacture, financial cost and implications to health. The PC stabilised bricks displayed the highest compressive strength (4.3-6.0 kN/mm2) followed by the PFA bricks (0.75-0.98 kN/mm2) and then the GGBS samples (0.12-0.17 kN/mm2). Only two of the samples, both stabilised with PC, had compressive strengths acceptable under UK Building Regulations. All of the tested samples had an IRA of less than 0.13 kg/m2/min, significantly below accepted limits. The report concludes that whilst GGBS and PFA are alternative stabilisers for ICSB they do not perform as well as PC in the proportions tested. The sustainability study concludes that GGBS is more sustainable (though the limitations of any definition of sustainability are acknowledged) than PC and PFA. This is contrary to previously published information that would define both GGBS and PFA as more environmentally sound. The use of GGBS and PFA in ICSB ultimately depends on two factors: whether the observed engineering properties are sufficient for the requirement and whether the alternative stabilisers are available.

2

Table of Contents
List of Figures: ......................................................................................................................... 6 List of Tables: ........................................................................................................................... 7 1.0 2.0 3.0
3.1

Introduction ................................................................................................................. 8 Aims and Objectives ............................................................................................... 10 Literature Review ................................................................................................... 11
Background......................................................................................................................... 12 Mud and Earth Construction............................................................................................. 12 Interlocking Compressed Stabilised Blocks ............................................................... 16 3.1.1 3.1.2

3.2 3.3 3.4

A Review of Potential Stabilisers for Unfired Masonry Bricks ......................... 20 A Comparative Study of the Selected Stabilisers ................................................... 22 Testing Procedures for the Mechanical Properties of Masonry ...................... 24 Compressive Strength Testing of Masonry ................................................................. 24 Shrinkage Testing of ICSB .................................................................................................. 25 Absorption Testing of Masonry ....................................................................................... 26

3.4.1 3.4.2 3.4.3 3.5

Key Points from the Literature Review .................................................................... 26

4.0

Proposed Method Statement ............................................................................... 28
4.0.1 4.0.2 4.0.3 4.0.4 Research .................................................................................................................................... 28 Preliminary Experiments ................................................................................................... 28 Laboratory Experiments .................................................................................................... 29 Sustainability Study .............................................................................................................. 30

4.1

Timeline ............................................................................................................................... 31

5.0
5.1

Method Statement .................................................................................................. 33
Constructing the Mud Bricks ........................................................................................ 33 Equipment Required ............................................................................................................ 33 Health and Safety ................................................................................................................... 34 Procedure ................................................................................................................................. 34 Equipment Required ............................................................................................................ 38 Health and Safety ................................................................................................................... 39 3 5.1.1 5.1.2 5.1.3

5.2

Shrinkage Testing ............................................................................................................. 38

5.2.1 5.2.2

5.3.3 5.3 5.3.1 5.3.2 5.3.3

Procedure ................................................................................................................................. 39 Equipment Required ............................................................................................................ 40 Health and Safety ................................................................................................................... 40 Procedure ................................................................................................................................. 40

Absorption Testing .......................................................................................................... 40

5.4

Compressive Strength Testing ........................................................................ 41
5.4.1 5.4.2 5.4.3 Equipment Required ............................................................................................................ 41 Health and Safety ................................................................................................................... 41 Procedure ................................................................................................................................. 42

6.1

Preliminary Experimental Results ............................................................................. 43

6.0
6.2

Results ......................................................................................................................... 43
Main Laboratory Experimental Results.................................................................... 44 Shrinkage Testing .................................................................................................................. 44 Sample Appearance and Texture .................................................................................... 44 Absorption Testing ............................................................................................................... 44 6.2.1 6.2.2 6.2.3

6.2.4 7.0
7.1 7.2 7.3

Compressive Strength Testing .................................................................... 46 Sustainability Study................................................................................................ 49
Ease of Manufacture ........................................................................................................ 50 Financial Cost ..................................................................................................................... 51 Health Implications.......................................................................................................... 53 GGBS (CEMEX, 2008) ........................................................................................................... 53 PC (US Department of Health and Human Services, 1995).................................. 53 PFA (Scotash, 2005) ............................................................................................................. 54

7.3.1 7.3.2 7.3.3 7.4

Quantitative Ecopoints Analysis ................................................................................. 54

8.0
8.1 8.2

Discussion ................................................................................................................ 56
Preliminary Experiments .............................................................................................. 56 Sustainability Study ......................................................................................................... 57 Defining Sustainability ........................................................................................................ 57 Ease of Manufacture ............................................................................................................. 58 Financial Cost .......................................................................................................................... 59 Health Implications .............................................................................................................. 59 Overall Sustainability........................................................................................................... 60 Shrinkage Testing .................................................................................................................. 61 4

8.2.1 8.2.2 8.2.3 8.2.4 8.2.5 8.3 8.3.1

Laboratory Experiments ................................................................................................ 61

8.3.2 8.3.3 8.3.4 8.3.5 8.3.6

Manufacturing Procedure .................................................................................................. 62 Absorption Testing ............................................................................................................... 63 Compressive Strength Testing ......................................................................................... 64 Application of ICSB Technology ...................................................................................... 66 Limitations to the Research .............................................................................................. 67

9.0

Conclusions ............................................................................................................. 69

10.0 Recommendations for Future Research ......................................................... 71 References: ............................................................................................................................ 73 Appendices ............................................................................................................................ 77
Appendix 1 - Project Management Statement ..................................................................... 78 Appendix 2 – Risk Assessment for Laboratory Work ....................................................... 80 Appendix 3 – Ecopoints PFA....................................................................................................... 81 Appendix 4 – Ecopoints GGBS .................................................................................................... 82 Appendix 5 – Samples of Raw Data for the Compressive Strength Testing .............. 83

5

List of Figures:
Figure 1 - Examples of Earthen Architecture in India (Source: www.banasura.com ) ...................................................................................... Error! Bookmark not defined. Figure 2 - Example of a Modern Earthen Structure in Riyadh, Saudi Arabia (Source: www.rael-sanfratello.com) .......................................................................................... 14 Figure 3 - Rammed Earth Construction Underway in India (Source: www.banasura.com) ................................................................................................... 14 Figure 4 - Makiga Press (Source: www.makiga-engineering.com) ............................. 17 Figure 5 - Examples of Interlocking Blocks (Source: www.goodearthtrust.org.uk) ....... 17 Figure 6 - Proposed Project Timeline .......................................................................... 32 Figure 7 - Raw Materials for Soil Mix .......................................................................... 36 Figure 8 - Mixed Homogenous Soil ............................................................................. 36 Figure 9 - Empty Brick Moulds .................................................................................... 37 Figure 10 - Completed Bricks in Moulds (L-R, stabilised with PC, GGBS, PFA, shrinkage test) ............................................................................................................ 37 Figure 11 - Bricks and Shrinkage Test Left for Curing ................................................. 38 Figure 12 - Shrinkage Testing Mould .......................................................................... 39 Figure 13 - The Experimental Setup for the Absorption Testing .................................. 41 Figure 14 – The Experimental Set-up for the Compressive Strength Testing .............. 42 Figure 15 - Compressive Strength of the Bricks Tested at 'Get Sheltered' .................. 43 Figure 16 – The Appearance of the Bricks after Curing (Top: GGBS, Btm Left: PC, Btm Right: PFA) ................................................................................................................. 44 Figure 17 - The Initial Rate of Water Absorption for the Samples ................................ 45 Figure 18 - A Comparison of the Compressive Strength of the Samples ..................... 46 Figure 19 - Stress-Strain Curves for the PC Stabilised Bricks ..................................... 47 Figure 20 - Stress-Strain Curves for the PFA Stabilised Bricks ................................... 47 Figure 21 - Stress-Strain Curves for the GGBS Stabilised Bricks................................ 47 Figure 22 - The Appearance of a Selection of Samples after Compressive Strength Testing........................................................................................................................ 48 Figure 23 - Interrelationship between the Spheres of Sustainability (Source: Tanguay, et al. 2009).................................................................................................................. 49

6

List of Tables:
Table 1 - Types of Earth Construction Methods (adapted from UN HABITAT 2009). .. 15 Table 2 - Comparison of Interlocking Blocks to its Alternatives (Source: UN Human Settlements Programme) ............................................................................................ 19 Table 3 - Comparison of the Energy Costs of GGBS, PFA and PC (Sources: Oti, 2008 & 2009, Reddy, 2004 & 2001, Ash Solutions Ltd, 2009)............................................. 22 Table 4 - Engineering Parameters and Performance of Unfired Clay Bricks and Mainstream Bricks (Source: Oti, 2009) ....................................................................... 24 Table 5 - Raw Material Quantities for Mud Brick Construction .................................... 35 Table 6 - Compressive Strength Testing of the Bricks Tested at 'Get Sheltered' ......... 43 Table 7 - Absorption Testing Results .......................................................................... 45 Table 8 - Compressive Strength Results ..................................................................... 46 Table 9 - A Comparison of the Costs of Fired Bricks and ICSB (adapted from Smith, 2010) .......................................................................................................................... 52 Table 10 – A Comparison of Estimated Stabiliser Cost in Ugandan Shillings and Cost per ICSB ..................................................................................................................... 53 Table 11 - An Overall Comparison of the Sustainability of the Stabilisers ................... 60

7

1.0

Introduction

Mud brick construction is not a new technology and dates back, in various forms, for several thousand years. Recently it has been utilised and investigated as a possible form of sustainable construction in the developing, and the developed, world.

There has been a large amount of interest and subsequent research into the use of interlocking mud bricks as an economical and environmentally sound method of satisfying the housing demand in many countries, particularly those of sub-Saharan Africa and the Middle East.

Mud bricks perform considerably better, in environmental terms, than fired bricks. They have significantly less embodied energy, contribute fewer CO2 emissions and help to promote the local economy and local labour. At first glance they appear to be an ideal candidate for an economically viable sustainable construction material. However, the major drawback of unfired mud bricks is that they tend to be less durable than their fired counterparts and are more susceptible to water damage. Traditionally, unfired mud bricks have been stabilised with cement to overcome these short comings but the use of cement reduces the environmental differential between unfired bricks and fired ones. Research into alternative stabilisers is both relevant and necessary to ensure unfired mud bricks remain a competitive alternative to modern construction methods.

This project, which is conducted in association with Engineers Without Borders (EWB), will look at two alternatives to cement for stabilizing unfired mud bricks. Ground

Granulated Blast-furnace Slag (GGBS) and Pulverized Fly Ash (PFA) have been selected as the alternative stabilisers. These are both by-products of existing industry (steel production and coal fired power stations respectively) and are considered to be more sustainable than Portland Cement (PC). They are also used as cement

alternatives in soil stabilisation in the UK and around the developed world. Specific research into their use in earthen construction is lacking.

This research project focuses on two main areas; the structural integrity of bricks made with the alternative stabilisers and the potential sustainability of the stabilisers in the developing world. 8

The structural integrity will be measured by 3 tests; compressive strength, shrinkage and absorption. These tests will be performed on hand made mud bricks prepared in the laboratory.

Sustainability will be assessed by the availability of GGBS and PFA in Uganda and Tanzania, the relative costs of these products compared to PC and by looking at any potential hazards associated with adopting these stabilisers.

9

2.0

Aims and Objectives

The aim of this individual research project is to investigate sustainable alternatives to cement for the stabilisation of unfired mud bricks. To achieve the aim, the following objectives will apply:  Undertake a literature review to establish the current position of research relating to the topic. Identify two alternatives to cement for mud brick stabilisation. Compare the alternatives to cement for cost, ease of manufacture and embodied energy. Investigate mud bricks made with the alternative stabilisers and compare them, quantitatively, to cement stabilised bricks for three mechanical properties: o o o  Compressive strength. Absorption. Shrinkage.

 



Summarize whether the cement alternatives are a viable engineering alternative. Investigate the availability of the alternative stabilisers in the developing world using Uganda and Tanzania as benchmarks. Analyze whether the alternatives will be viable in the developing world. Investigate whether there would be any social implications to the use of cement alternatives in the developing world. Recommend future research.



 



10

3.0

Literature Review

Construction with earth or clay has been around for thousands of years. In the 1970’s it was estimated that there were more than 80 million earthen dwellings in India without considering significant numbers in Africa and China (Norton, 1997). It may be conservative to suggest that over two billion of the worlds’ population live in buildings primarily made from earth or clay.

Additionally, UN-HABITAT estimates that 3 billion people lack decent housing. With a continually growing global population, this figure is likely only to rise. In Uganda, for example, demand exists for 1.6 million new homes each year; this is met by a supply of a mere 100,000. Building new homes on such a scale requires large amounts of construction materials. Traditional building methods such as fired masonry or concrete are environmentally damaging on many fronts – deforestation occurs to provide firewood, concrete involves large amounts of embodied energy etc (The Good Earth Trust, 2008).

In contrast to traditional fired masonry, building with unfired mud or clay bricks reduces the cost of construction and the environmental impact. Importantly it also promotes local business and employment. As a potential construction material it seems to tick all the sustainability boxes and has great potential in the developing world.

The Good Earth Trust aims to promote the use of Interlocking Compressed Stabilised Blocks (ICSB) in the developing world with an eventual aspiration to transform the market so that people will opt for this technology rather than fired bricks: „…to do this we take a multi-pronged approach through awareness raising, advocacy, technical and business training, capacity building, research & development of the technologies, and the provision of information and guidance. In our advocacy work we target the government to ensure they are aware of the technology and include it in building codes, technical specifications, and policy. We also advocate to Agencies, NGOs, and the private sector to adopt these technologies in the projects and work they do. In selected areas, we engage directly with local communities to implement practical projects to understand what is needed to promote the adoption of the technology at community levels.‟ 11 (The Good Earth Trust, 2008)

This project aims to research alternative stabilisers for compressed earth blocks. To do so, further information on current ICSB technology is required. This information will be presented, via a literature review, in 4 parts:

1. Background. 2. A review of potential stabilisers for unfired masonry bricks. 3. Comparative study of embodied energy, cost and manufacture of selected stabilisers. 4. Testing procedures for the mechanical properties of masonry.

3.1
3.1.1

Background
Mud and Earth Construction

Although mud and earth construction has been around for thousands of years it is important to ask whether it is still relevant today. Hadjri et al. (2007) interviewed ten residents of earthen buildings about five key points: durability, affordability, living conditions, aesthetics and their general performance compared to a ‘modern’ house. Their findings are as follows: 1. Durability – Half of the residents indicated that their dwelling was durable, with a lifespan of more than 20 years. The other half reported a lifespan of just 10 years with regular maintenance required. The latter category reported the

major factors in lack of durability were water and/or termite damage. 2. Affordability – All residents agreed that earthen dwellings were affordable when compared to modern dwellings. 3. Living Conditions – 8 out of 10 interviewees stated that their homes offered very comfortable living conditions with excellent thermal properties; cool in summer and warm in winter. The other two were less impressed. However, it should be noted that the two who complained about conditions lived in buildings roofed with corrugated iron resulting in excessive heat transmission.

12

4. Aesthetics – Four interviewees appreciated the appearance of earthen architecture, two were indifferent but four found the appearance less pleasing compared to ‘modern’ dwellings. 5. General Preference – 70% of residents stated that they would not live in an earthen home if they had the financial resources to do otherwise. This was mainly due to the fact that earthen dwellings were associated with poverty and a lower social class.

These results show that there are still issues with the perceptions of earthen architecture in the developing world (Hadjri, et al., 2007) and that any drive to promote earthen architecture as a realistic alternative to ‘modern’ building materials must be combined with an educational programme.

Earthen architecture, however, has changed considerably in recent years with better understanding and increased use. The current trend for sustainable living combined with greater understanding of the thermal benefits, safety and potential durability of earth has led to substantial advances in the quality and appearance of mud and clay based buildings (Burroughs, 2009). Some examples of earthen architecture, old and new, are shown in Figs 1 to 3 These examples show that with the correct materials, dedication and imagination, earth structures can be as impressive as more modern construction methods.

Figure 1 - Examples of Earthen Architecture in India (Source: www.banasura.com)

13

Figure 2 - Example of a Modern Earthen Structure in Riyadh, Saudi Arabia (Source: www.raelsanfratello.com)

Figure 3 - Rammed Earth Construction Underway in India (Source: www.banasura.com)

14

There are six predominant methods of earthen construction; these are summarized in Table 1:
Table 1 - Types of Earth Construction Methods (adapted from UN HABITAT 2009).

1

Compressed Earth Block These are construction blocks made from a mixture of soil and a stabilizing agent compressed by different types of manual or motor driven press machines. ICSB are a variation of this. Adobe Blocks These are similar to compressed earth blocks and often considered their precursor. Adobe blocks are usually made of a compacted mixture of clay and straw but are less uniform in size and shape than compressed earth blocks. Cob In cob construction a mix of clay, sand and straw is made, then moulded and compressed into flowing forms to make walls and roofs. Rammed Earth This involves the making of a mould into which the soil, inclusive of a weatherproofing agent, is compacted and left to dry. Subsequently the mould is removed and the earthen form remains. Earth Sheltering This refers to the use of earth on the structure of a building. It includes earth berming, in-hill construction and underground construction.

2

3

4

5

6

Wattle and Daub This consists of a wooden or bamboo frame laid vertically and horizontally reinforced on which earthen daub is packed.

This project will focus solely on compressed earth blocks and their modern evolution; the interlocking compressed stabilised block (ICSB).

15

3.1.2

Interlocking Compressed Stabilised Blocks

In the past the traditional method of making blocks from compacting earth used wooden moulds (similar to Adobe in Table 3-1). The blocks were then either woodfired or left to dry in the sun. In recent years the development of mechanical presses has superseded the more primitive technology in most areas of the world (Norton, 1997). In the 1950’s the Chilean engineer Raul Ramirez created the CINVA-RAM press at the Inter American Housing Centre in Columbia. Methods of producing earth blocks have continually developed since and there are now a diverse range of both manual and motor driven presses catering for all scales of production.

The CINVA-RAM and similar machines provided a cost effective and more environmentally friendly method of construction. However, skilled labourers were still required to construct the blocks and significant amounts of cement and mortar were required. To counter this, the Human Settlements Division of the Asian Institute of Technology and the Thailand Institute of Scientific and Technological Research worked together to modify the CINVA-RAM to produce interlocking blocks. These interlocking blocks reduced the need for cement and for skilled tradesmen. As a result the cost of construction was considerably reduced and the structural stability improved (UN Human Settlements Programme, 2009). An example of a modern variation of the

CINVA-RAM, a Makiga press, is shown in Fig 4. Interlocking blocks have developed in complexity since their early forerunners and now double interlocking and curved blocks are available.

16

Figure 4 - Makiga Press (Source: www.makiga-engineering.com)

An example of double interlocking blocks is shown in Fig 5; the interlocking fins on the top and side of the blocks are easily identifiable. Also clear from this Figure is the high quality outward appearance of the constructed blocks.

Figure 5 - Examples of Interlocking Blocks (Source: www.goodearthtrust.org.uk)

There are many advantages of

interlocking

blocks including

environmental

considerations, ease of use and quality of performance.

Table 3-2 compares an

interlocking block to some of the alternatives over a range of properties (source: (UN Human Settlements Programme, 2009). 17

Additional advantages of ICSB include: 1. Health – Curved blocks can be used to build water tanks, latrines and septic tanks. These basic facilities are lacking in many areas of the developing world and their provision can dramatically reduce disease. 2. Environment – ICSB are an environmentally sound alternative to traditional fired blocks. In Uganda, for example, the firing of traditional masonry has led to vast deforestation and destruction of wetlands (UN Human Settlements Programme, 2009). 3. Ease of Use – ICSB machines are comparatively easy to use and maintain. Construction using the blocks also requires less skill than traditional masonry. 4. Economics – ICSB construction is cheaper than traditional methods. Raw materials can usually be sourced in the area of construction and the stabilised blocks are weatherproof and require no further rendering. 5. Structural – ICSB technology compares favourably with traditional methods of construction (Norton, 1997).

18

Table 2 - Comparison of Interlocking Blocks to its Alternatives (Source: UN Human Settlements Programme)

19

3.2

A Review of Potential Stabilisers for Unfired Masonry Bricks

Browne (2005) tested handmade bricks and found they typically display strengths of 2 N/mm2 compared to machined bricks that provide strengths of more than 4 N/mm2. This shows that handmade bricks satisfy the strength required for simple structures, for example single storey shelters, and machined bricks (made with a Makiga ram for example) are suitable for more complicated buildings.

However, the biggest drawback with mud block construction is the concerns over its durability. Earthen structures are considered to last, on average, approximately 20% less time than similar structures built by more traditional methods (Norton, 1997). Traditionally cement or lime is added to stabilize the block and improve its’ durability but some research has been done into chemical admixtures (Vinod, et al., 2010). This research was inconclusive but chemicals can be discounted for use in the developed world due to cost, difficulty of supply and the potential cost of training tradesmen.

The problem with cement stabilisation is that ICSB technology is promoted as an environmentally friendly construction material. The addition of a cement stabiliser

lessens the embodied energy differential between ICSB and traditional fired blocks. It is, therefore, important to investigate alternatives to cement.

Previous researchers, including Davis (2003) and Longland (1985), have suggested lime as a suitable alternative, especially in clayey soils. Lime production is less

intensive than cement production but more lime is required to deliver similar results (Sivapullaiah, et al., 2000). Lime as a stabiliser will not be investigated further in this research project other than as an additive to activate the pozzolanic reaction.

Soil stabilisers are used in a variety of contexts including structural (ICSB), geotechnical (pavement design) and geo-environmental (soil stabilisation), Jegendan et al. (2010) investigated the use of cement blends for soil stabilisation and suggested the following as possible alternatives to cement: 1. Ground Granulated Blast-furnace Slag (GGBS) – This is a by product of the steel industry which occurs when iron ore is separated from the remaining slag. This slag is tapped off and rapidly quenched in water to promote its

20

cementitious properties. GGBS is used throughout the UK and approx 2 million tonnes are used per annum (Jegendan, et al., 2010). It is commonly used as an additive in cement mixes and lime can used to activate the reaction rather than PC. Better durability is expected with higher GGBS content but it also slows the curing time (Oti, et al., 2009). 2. Pulverised Fly Ash (PFA) – Fly ash is a by product from coal fired power stations and over 6 million tonnes are produced annually in the UK (Jegendan, et al., 2010). Of this, approximately 3.5 tonnes are used in the construction industry. Coal is ground into a fine dust prior to combustion and it is the finer ash which is cementitious. PFA requires water and a source of alkali, usually calcium hydroxide, to stabilize soil, an application for which it has been used for many years. The benefits of using PFA in terms of enhanced durability and sustainability have been well documented in other applications including pavement stabilisation (Sear, 2007), (Shafique, et al., 2004) and (Jegendan, et al., 2010). 3. Cement Kiln Dust (CKD) – This is a by-product of cement manufacture quality control. CKD is collected from cement kiln exhaust gasses and consists of particles of clinker, unreacted calcined raw materials, and fuel ash. The

generation of CKD is environmentally questionable as it is related to cement manufacture with its associated high embodied energy. However, although

CKD production is reducing due to improved processes a large amount is still disposed of in landfill. Studies have shown that CKD is a useful soil stabiliser and can also be used as an alkali activator for GGBS ((Jegendan, et al., 2010).

Other soil stabilisers suggested include reactive magnesia and zeolite though these have been discounted due to high prices and expected problems of availability in the developed world. Coutand et al. (2006) investigated the use of Sewage Sludge Ash (SSA) as an admixture in mortars. However, they concluded that SSA had a fundamentally different chemical composition when compared to PFA which made it less suitable as a stabiliser. This was mainly due to the low content of silica in SSA which meant its pozzolanic activity was limited. SSA does not meet the European standards as a

21

mineral admixture but could be used as a low grade pozzolan (Coutand, et al., 2006). It will not be considered further in this project.

3.3

A Comparative Study of the Selected Stabilisers

Housing construction methods in the developed and the developing world need to fulfil a variety of criteria. These include; energy consumed in the manufacturing processes, problems associated with long distance transportation, consumption of raw materials and natural resources, recycling, the impact on the environment and long term sustainability (Reddy, 2004). comparison of stabilisers. It is unrealistic to consider all these factors in a

Some prioritization is necessary and this review will

concentrate on energy consumed in the manufacturing process (embodied energy), cost of transportation and financial cost. When considered together these factors will indicate the environmental impact and give some suggestion as to the long term sustainability of each stabiliser. Oti et al. (2009) found that the embodied energy and carbon dioxide emissions of fired bricks are 4186 MJ/t and 202 Kg CO2/t respectively and comparatively, Portland Cement (PC) stabilised unfired bricks have an embodied energy of 1025 MJ/t and emissions of 125 Kg CO2/t. Clearly, in terms of energy, unfired bricks, even when stabilised with PC, are a much better material for long term sustainability.

This project aims to investigate alternative stabilisers to PC for ICSB technology and will focus on the use of GGBS and PFA. Table 3 compares these potential stabilisers with PC in terms of energy costs during manufacture and construction.

Table 3 - Comparison of the Energy Costs of GGBS, PFA and PC (Sources: Oti, 2008 & 2009, Reddy, 2004 & 2001, Ash Solutions Ltd, 2009)

Ser

Stabiliser

Embodied Energy (MJ/t)

CO2 Emissions During Manufacture (per t) 1000 kg 70 kg 800 kg 25 kg

1 2 3 4

Portland Cement GGBS PFA No stabiliser

5000 1300 900 525

Energy in Transportation for 100km (MJ/t) 100 100* 400 -

*- No values were found in current literature for transportation costs of GGBS but it was assumed they would be very similar to PC.

22

Table 3 shows that GGBS and PFA are competitive with PC in terms of energy cost. However, bricks with no stabiliser are the most environmentally appealing. Unfortunately a lack of stabiliser means the brick is susceptible to water damage and has poor durability when compared to a stabilised brick making it unviable (Oti, et al., 2009).

In the UK GGBS and PFA retail for about the same price and making concrete with these admixtures rather than PC is no more expensive (Vincent, 2010). This should be similar across the world as both GGBS and PFA are by products of existing industry. However, it should be noted that in previous studies GGBS has replaced up to 70% of PC compared to 40% for PFA and can be more durable (Vincent, 2010). Therefore, GGBS may deliver greater financial savings when looking at whole life cycle costs.

In conclusion, when considering embodied energy, transportation costs and financial cost we can list the potential stabilisers in descending order of preference as follows: GGBS, PFA, PC.

There is no literature investigating the use of PFA as a sustainable stabiliser for mud brick construction, however, some initial research has been conducted into the use of GGBS. Studies into the compressive strength of unfired bricks stabilised with GGBS/PC mixtures realized results of 2.7-5 N/mm2 in the laboratory and 3.4-7.4 on an industrial scale. These results are within the range specified by UK building regulations (5 – 8 N/mm2) but at the lower end (Oti, et al., 2009).

Table 4 (source: Oti, 2009) illustrates some of the engineering parameters and performance of unfired clay bricks stabilised with PC / lime and GGBS mixes with mainstream bricks. Due to the early nature of the research there is no published information on the complete range of engineering properties.

23

Table 4 - Engineering Parameters and Performance of Unfired Clay Bricks and Mainstream Bricks (Source: Oti, 2009)

Ser

Parameter

Fired Clay

Sun Baked

PC Stabilised Unfired Brick 8 – 12% PC Internal / external walls Dependant on stabiliser

1 2 3 4

Firing Stabiliser Content Design Application Robustness / Durability

X Internal / external walls Frost resistant

Internal walls Susceptible to water damage

5 6 7

Cost Use of PC Breathability

High No

Low No

High x Impeded by PC

GGBS/PC Mix Stabilised Unfired Brick 1.5 % Lime, 5% GGBS Internal / external walls Robust and durable with activated GGBS blend Low Yes

This research further reinforces the idea that GGBS is an ideal replacement stabiliser for PC.

3.4

Testing Procedures for the Mechanical Properties of Masonry

For this project three engineering properties have been selected to investigate the strength and durability of the blocks stabilised with the cement alternatives:

1. Compressive strength. 2. Shrinkage. 3. Absorption.

Each of these properties will be tested by the European standards or the equivalent accepted standard for ICSB technology. 3.4.1 Compressive Strength Testing of Masonry

The European standard for the compressive strength of clay masonry units is BS EN 772-1:2010 (though this draft has yet to be approved it varies little from the 2000 version).

The standard specifies a number of different conditioning procedures: air dry, oven dry, conditioning to 6% moisture content and conditioning by immersion. Previous research

24

suggests that immersing unfired bricks is unnecessary as if the bricks are handled correctly and the building is properly detailed it is unlikely that bricks will be immersed whilst in use (Heath, et al., 2009).

For this project, and to simulate most closely the conditions likely to be found in Uganda and Tanzania, air drying the samples will be used. To achieve this in line with the European standard, samples must be stored at room temperature (>15oC) at a relative humidity of approximately 60% for 14 days before testing.

The compressive strength is determined using a compressive strength testing machine. This machine must have an error of less than 2% (BSI, 2010). Further details of the testing machine are as follows: “The testing machine shall have adequate capacity to crush all the test specimens, but the scale used shall be such that the failure load on the specimen exceeds one-fifth of the full scale reading. The machine shall be provided with a load-pacer or equivalent means to enable the load to be applied at the rate given in 8.2. The testing machine shall be equipped with 2 steel-bearing platens. The stiffness of the platens and the manner of load transfer shall be such that the deflection of the platen surfaces at failure load shall be less than 0.1 mm measured over 250 mm. The platens shall either be through hardened or the faces case hardened. The testing faces shall have a Vickers hardness of at least 600 HV when tested in accordance with EN ISO 6507-1.” (BSI, 2010)

The European standard states that the minimum number of samples to be tested is six. However, this is for industrial scale production and is unrealistic for handmade bricks constructed to compare stabilisers. 3.4.2 Shrinkage Testing of ICSB

UN HABITAT recognizes that the laboratory testing of ICBS technology is not always viable, particularly in the developing world. Instead it recommends a number of ICSB specific tests to determine whether a site, and more importantly its soil, is suitable for the creation of unfired mud bricks (UN Human Settlements Programme, 2009).

These tests include a sedimentation test and a shrinkage test. Only the shrinkage test will be considered in this project. This test is important to ensure that ICSB will not 25

shrink so much during curing as to prove difficult to work with during subsequent construction. Another drawback to significant shrinkage is the appearance of cracks which can decrease durability, increase water absorption and have an adverse affect on appearance. Shrinkage can be controlled with stabilisers. Depending on the soil type and the shrinkage observed during initial testing the amount of stabiliser will vary. Typically, when using PC, ratios of 5% are used but this can increase to 10% with higher levels of clay (Browne, 2009).

3.4.3

Absorption Testing of Masonry

The European standard for absorption testing of clay masonry units is BS EN 77211:2010.

The principle of absorption testing is to immerse a face of the masonry unit in water for a set period and determine the increase in mass. For clay masonry units the bed face is the one that is tested (BSI, 2010).

3.5

Key Points from the Literature Review

The following key points have been drawn out from the literature review:  

Various forms of earthen construction have been used for thousands of years. A stigma is still attached to earthen construction in the developing world where it is associated with poverty and low social standing. Therefore, an educational programme will need to run concurrently to any concerted ICSB drive promoting it as a viable, modern and sustainable construction material.

 

ICSB technology has numerous advantages over rival earthen construction methods notably in strength, appearance and ease of use. Ground Granulated Blast-furnace Slag (GGBS) and Pulverized Fly Ash (PFA) are potential alternatives to Portland Cement (PC) as stabilisers for ICSB technology.



GGBS and PFA are both favourable to PC in terms of embodied energy and CO2 emissions. They also represent no significant additional financial cost.

26



GGBS is the preferred stabiliser according to current research. However, there is a lack of current research into the engineering properties of unfired bricks stabilised with PFA.

 

BS EN 772-1:2010 gives the procedure for compressive strength testing of clay masonry units. UN HABITAT provides a range of tests to ensure the suitability of sites for ICSB. The shrinkage test is useful to determine the amount of stabiliser and the suitability of the local soil.



BS EN 772-11:2010 gives the procedure for absorption testing of clay masonry units.

27

4.0

Proposed Method Statement

In order to achieve the aim of this research project each of the objectives outlined above will be taken in turn. To simplify the methodology it has been divided into a number of Sections; research, preliminary experiments, laboratory experiments and a sustainability study.

4.0.1

Research

The first three objectives are driven largely by the literature review and studying published professional research. The outcome of the literature review is summarized in paragraph 3.5 but most importantly GGBS and PFA have been selected as the stabilisers to investigate.

Further research is required into a manufacturer of GGBS and PFA who will be willing to support the project.

4.0.2

Preliminary Experiments

Get Sheltered, an EWB workshop designed to discuss various aspects of sustainable construction in the developing world, is to be held at Newcastle University on the 20 Nov 10. This workshop will include a session on mud bricks during which ICSB

technology will be introduced to the participants by the researcher before a number of mud bricks, some stabilised with lime or PC, will be made.

It is proposed that Get Sheltered be used as a set of preliminary experiments for the project. The following outcomes are expected:   

Familiarization with hand-made mud brick construction techniques. Construction of moulds suitable for the main laboratory experiments testing compressive strength and absorption. Familiarization with compressive strength testing procedures for masonry units.

28



Production of reference data for hand-made bricks stabilised with PC, lime and no stabiliser (these will be included in the Results Section of this project).

4.0.3

Laboratory Experiments

Laboratory experiments will be used to determine the engineering properties of mud bricks stabilised with PC, GGBS and PFA.

The following points will remain extant:  

Bricks will be hand made by the researcher and no press will be used. Three bricks with each stabiliser will be made. The amount of stabiliser in each brick will vary in order to test the extremes of expected optimum stabiliser content (e.g. 5-10% for PC).

 

Moulds will be constructed to ensure all hand-made bricks are of the same dimensions. The bricks will be used for both compressive testing and for absorption testing. The absorption test will be conducted first and there will be seven days between the two tests to allow the bricks to dry out.

 

The curing period before testing will be 30 days. Compressive strength will be tested to EN 772-1 by the procedure detailed below:

1. Clean the bedding surface to ensure even contact is maintained. 2. Measure the width and length of the loaded area and calculate the loaded area. 3. Align the specimen in the testing machine without using any extra packing. 4. Apply loading at a rate of 0.05 N/mm2/s (the approved rate for masonry with a strength <10N/mm2). 5. Record the maximum load. 6. Calculate the strength of the specimen by dividing the maximum load by the loaded area and express to the nearest 0.1 N/mm2 

Shrinkage will be measured by the procedure detailed below:

29

1. Construct a wooden box with internal dimensions of 40mm x 40mm x 600mm. 2. Grease the box and insert the clay / sand mix to be tested. 3. Compact the mix well. 4. Leave to cure in the shade for at least 7 days. 5. Measure the amount of shrinkage and calculate as a percentage of the initial dimensions. This value can be used to compare the shrinkage of soil mixes. 

Absorption will be measured using the procedure detailed below:

1. Measure the dimensions of the test face and determine the gross area. 2. Measure the dry weight of the specimen. 3. Immerse the specimen in water up to a depth of 5mm (+/-1mm) for 24 hours (BSI, 2003). 4. Measure the new weight of the specimen. 5. Calculate the initial rate of water absorption using the formula in BS EN 772-11:2010 Section 8.3. 

Results for the bricks stabilised with PC, GGBS and PFA will be compared to each other both quantitatively and graphically.

4.0.4

Sustainability Study

This part of the project will fulfil the objectives concerned with the sustainability, availability and potential implications of using the proposed stabilisers in the developing world. Geographically, it will use Tanzania and Uganda as it is benchmarks.

The price and availability of GGBS and PFA will be initially sought from The Good Earth Trust who have ongoing projects in those countries. A comparative study of the health and social implications will be undertaken using existing published information.

The sustainability study is likely to be a relatively small part of the final project.

30

4.1

Timeline

The key milestones for this project were the PIR submission date (3 Dec 10) and the Project submission date (20 May 11). All laboratory testing will take place during the period Jan – Mar 11 and a Gantt chart showing the proposed timeline for the project is at Fig 1 (shaded tasks are ones that were completed by 3 Dec 10).

31

Figure 6 - Proposed Project Timeline

32

5.0

Method Statement

The points in the Proposed Method Statement remain extant throughout this section and technical details of the compressive strength, absorption and shrinkage tests can be found in that section. The experimental steps are detailed in chronological order and a table detailing the exact timeline of the project is at Appendix 1.

5.1

Constructing the Mud Bricks

Mud bricks are, by their very nature, simple to construct. They require only three raw materials; soil, water and a stabiliser, in varying proportions. Production of mud bricks, particularly in the developing world, is done by unskilled labourers. This means that the measuring and mixing of the materials is usually approximated and is at best measured using crude units such as ‘bags of sand’ or ‘wheelbarrows full’ (UN Human Settlements Programme, 2009). This is one of the main advantages of this form of construction. The percentage of stabiliser used usually varies depending on the soil type but is typically between 5 and 20% with the higher proportions being applicable to clayey soils (Browne, 2009). The method detailed below was adapted from that used at the ‘Get Sheltered’ workshop in Nov 10. This was, in turn, learnt from another EWB workshop hosted by Paul Jaquin, an individual who has done considerable research into earthen construction. It is noted that the method is not incredibly detailed but this recreates well the circumstances expected on a typical earthen construction site. 5.1.1 Equipment Required

The following equipment and materials were required to construct the bricks:       

60 Kg sand (coarse Leyton sand). 36 Kg pea shingle. 8 Kg powered clay (whole white e china clay). 5 Kg PC. 5 Kg GGBS. 5 Kg PFA. 5 Kg lime. 33

           

Safety footwear. Heavy duty balance (up to 20 kg, 0.1 Kg accuracy). Accurate balance (up to 2.5 Kg, 0.001 Kg accuracy) Shovel. Mixing tray for sand/clay. Wheelbarrow. PPE for lime (goggles, masks, gloves, lab coats). Moulds for bricks (pre-made, as used at ‘Get Sheltered’). Oil for lining moulds. Water source. Trowel. Permanent marker.

5.1.2

Health and Safety

In addition to the existing safety rules of the laboratory a project specific risk assessment was completed prior to the laboratory sessions. The format used was standard for the Newcastle University Geotechnical Laboratories and is reproduced at Appendix 2.

The main risk was from using lime and this was mitigated by the wearing of correct PPE (lab coat, safety glasses, safety footwear and a mask).

5.1.3

Procedure

In line with the Section 4.0 nine bricks were made in total, three with each stabiliser.

For this project, stabiliser percentages of 10%, 15%, and 20% were used to provide a range of a data as outlined in Section 4.0. These values were chosen as the

homogeneous soil that was used had high clay content. Normality of the stabiliser content across all 3 stabilisers also allows ease of comparison and consistency of results. The use of differing stabiliser quantities is considered further in Section 8.0.

In concrete preparation, and in other uses of GGBS as a cement replacement material, the established practice is to replace PC on a 1:1 basis (ACI Committee, 1987). PFA 34

is different from GGBS because it contains little calcium and therefore is unable to react cementitiously unless there is lime from another source present. In common construction practice PFA would not completely replace PC but would rather replace up to 60%. However, in order to keep as many variables as possible constant PFA replaced 100% of the PC during this research. For each PFA stabilised brick the PC was replaced with the same volume of Lime/PFA in a ratio 1:2 (Caltrone, 2010).

Table 5 shows the quantities of each raw material required for the mud bricks constructed for this project. Each brick was given an identifier to make reporting the results more concise. These comprised of the letters A - I and are shown in Table 5.
Table 5 - Raw Material Quantities for Mud Brick Construction

Type of Stabiliser

Raw Material Soil (+/- 0.1 kg)

10% 9.0 A 1000 1.0 9.0 D 1100 0.67 0.33 9.0 G 1000 1.0 H E B

% Stabiliser 15% 8.5 1100 1.5 8.5 1250 1.0 0.50 8.5 1200 1.5 I F C

20% 8.0 1150 2.0 8.0 1350 1.33 0.67 8.0 1050 2.0

PC

Water (+/- 10ml) PC (+/- 0.01 kg) Soil (+/- 0.1 kg)

PFA

Water (+/- 10ml) PFA (+/- 0.01kg) Lime (+/- 0.01kg) Soil (+/- 0.1 kg)

GGBS

Water (+/- 10 ml) GGBS (+/- 0.01 kg)

The bricks were constructed using the following method:

1. A manufactured soil mix was used for all bricks (and the shrinkage testing). This mix was made by the researcher and was used to ensure that the only variables changed during the research were the type and quantity of stabiliser. By creating a homogeneous soil in the laboratory results can be more easily and more accurately compared. The proportions chosen for the soil mix gave a clay content of just under 8%; this is similar to the typical soil type in much of Uganda [Mwebeze, 2007]. The soil was made as follows, in two batches:

a. 60 Kg of sand was weighed.

35

b. 36 Kg of pea shingle was weighed.

c. 8 Kg of dry clay was weighed.

d. The raw materials were mixed together on a mixing tray. shows the raw materials and Fig 8 shows the mixed soil.

Fig 7

Figure 7 - Raw Materials for Soil Mix

Figure 8 - Mixed Homogenous Soil

2. The moulds used for the bricks were previously constructed using 5mm plywood and were of the dimensions 145mm (w) x 300 mm (l) x 110 mm (d). These dimensions were chosen as a suitable size to represent ICSB technology which typically requires 35 bricks to cover 1m2, giving a profile surface area of 0.028m2, compared with 0.033m2 for the bricks manufactured during this project 36

[Smith, 2010].

These were lined with mould oil (to prevent the brick from Fig 9 shows the empty

sticking to the mould) prior to brick construction. moulds.

Figure 9 - Empty Brick Moulds

3. The raw materials were mixed in the required proportions for each sample.

4. One brick with each proportion of materials from Table 5 was constructed, compacted well and levelled. Fig 10 shows the completed bricks in the moulds.

Figure 10 - Completed Bricks in Moulds (L-R, stabilised with PC, GGBS, PFA, shrinkage test)

5. The moulds for each brick were clearly marked.

6. The moulds were left to cure for 28 days prior to absorption testing. For the initial curing period they were left loosely covered with plastic, as shown in Fig 11, for 7 days (The Good Earth Trust, 2008). This was to create a humid

37

environment which would prevent the clay from setting before the cementitious reaction was complete. After 7 days several holes were made in the plastic to allow the evaporated water to escape. The plastic was kept in place to increase the temperature and help recreate the humid conditions expected in the developing world.

Figure 11 - Bricks and Shrinkage Test Left for Curing

No replicates of the bricks were made as this would have placed unnecessary time constraints on the project. The sample size selected is the minimum size to allow a comparison to be made between the different stabilisers.

5.2

Shrinkage Testing

The shrinkage testing was conducted at the same time as the curing of the mud bricks.

5.2.1

Equipment Required

The following equipment was required:    

Safety boots. Soil mix as made in Section 5.1. Mould. Trowel.

38

5.2.2

Health and Safety

As this experiment was carried out at the same time as the construction of the mud bricks in Section 5.1 the same risk assessment was used (reproduced at Appendix 2).

5.3.3

Procedure

The following procedure was followed:

1. In order to achieve a mould similar to the one detailed in the UN HABITAT guide one of the internal batons was removed from a spare mud brick mould constructed for ‘Get Sheltered’. This left a rectangular mould of dimensions 615 mm (l) x 145 mm (w) x 110 mm (d). The mould is shown in Fig 12.

Figure 12 - Shrinkage Testing Mould

2. The mould was filled with 20kg of the soil mix, rehydrated with 2000 ml of water. No stabiliser was added.

3. The soil was compacted and levelled off before being left to cure in the same conditions as the mud bricks for 14 days.

4. The shrinkage was calculated as per the method outlined in Section 4.0.3.

39

5.3

Absorption Testing

The absorption testing was undertaken over a 24 hour period 28 days after the bricks were constructed. It was conducted in line with the Proposed Method Statement, specifically Section 4.0.3.

5.3.1

Equipment Required

The following equipment was required:   

Metal trays x 2. Water source. PPE.

5.3.2

Health and Safety

No additional Risk Assessment was required because of the basic nature of the test.

5.3.3

Procedure

As stated, the proposed method was adhered to. Additional details are as follows:

1. The bricks were exposed to water (depth = 5mm) for a period of 24 hours. Fig 13 shows the experimental setup.

40

Figure 13 - The Experimental Setup for the Absorption Testing

2. The water was topped up once during this period.

3. The Initial Rate of Water Absorption was calculated in line with BS EN 772:2010 Section 8.2.

5.4
5.4.1

Compressive Strength Testing
Equipment Required

The following equipment was required:   

Compressive strength testing machine (as specified in the Section 4.0). Brick samples, as prepared above. Wood packing.

5.4.2

Health and Safety

The Risk Assessment at Appendix 2 was used for this procedure. No additional controls were required.

41

5.4.3

Procedure

The procedure used was as detailed in the Section 4.0. The only variation was the use of wooden packing to distribute the load over the surface of the brick. This was necessary due to the design of the machine. Fig 14 shows the experimental set up.

Figure 14 – The Experimental Set-up for the Compressive Strength Testing

The bricks were tested sequentially, on the same day. This meant that all the bricks benefited from the same curing time.

42

6.0
6.1

Results
Preliminary Experimental Results

The experiments conducted at ‘Get Sheltered’ proved to be less extensive than at first hoped. Nevertheless a range of mud bricks were constructed using the same method as for those in the main laboratory experiments allowing familiarisation with the procedure. Some previously constructed bricks, which had cured for 28 days, were tested for their compressive strength. These bricks were stabilised with lime or PC and one contained no stabiliser. A fired brick (from Uganda) and a regular house brick, as used in masonry construction in the UK, were also tested. compressive strength testing are shown in Table 6.1 and Figure 15.
Table 6 - Compressive Strength Testing of the Bricks Tested at 'Get Sheltered'

The results of the

Ser 1 2 3 4

Brick Parameter Description Failure load (N) Area (mm ) Compressive Strength (N/mm )
2 2

1 Lime stab 40196 41300 0.97

2 PC stab 17427 41300 0.42

3 No stab 51617 41300 1.25

4

5

Fired brick House brick 62352 29000 2.15 249376 22360 11.2

Compressive Strength (N/mm2)

12 10 8 6

4
2 0 Lime stab PC stab No stab Fired brick House brick

Type of Brick
Figure 15 - Compressive Strength of the Bricks Tested at 'Get Sheltered'

43

6.2

Main Laboratory Experimental Results

6.2.1

Shrinkage Testing

The shrinkage test produced no shrinkage after the prescribed period. Even after extending the test to 28 days, the observed shrinkage was still negligible.

6.2.2

Sample Appearance and Texture

Fig 16 shows the appearance of the samples once they had been removed from the moulds. The PFA and PC stabilised samples (A-F) presented as expected with a dense, hard texture. In contrast, samples G-I were very delicate, crumbling on touch and with obvious surface cracking.

Figure 16 – The Appearance of the Bricks after Curing (Top: GGBS, Btm Left: PC, Btm Right: PFA)

6.2.3

Absorption Testing

The formula used to calculate the Initial Rate of Water Absorption is taken from BS EN 771-11:2010:

Where:

44

Cws = Initial Rate of Water Absorption (kg/m2/min)

The results of the absorption testing are shown in Table 7 and Figure 17.
Table 7 - Absorption Testing Results
Initial rate of Change in mass (g) Water Absorption (kg/m2/min)

Mass before Sample
Stabiliser

Mass after absorption test (g)

%

absorption test (g)

A B C D E F G H I GGBS PFA PC

10 15 20 10 15 20 10 15 20

10240 10340 10560 9550 9480 9360 9580 9470 9070

10450 10430 10620 10040 10030 10090 10040 10260 9700

210 90 60 490 550 730 460 790 630

0.033524904 0.014367816 0.009578544 0.078224777 0.087803321 0.116538953 0.073435504 0.126117497 0.100574713

0.14 Initial Rate of Water Absorption (kg/m2/min) 0.12 0.1 0.08 0.06

0.04
0.02 0 A B C D E Sample
Figure 17 - The Initial Rate of Water Absorption for the Samples

F

G

H

I

45

6.2.4

Compressive Strength Testing

Sample raw data for the compressive strength testing is reproduced at Appendix 5. Table 8 and Fig 18 compare the compressive strength of the various samples using all the raw data recorded. Figs 19 – 21 show stress-strain curves for the bricks made with the three stabilisers. Fig 22 shows the appearance of a selection of the bricks at the conclusion of the test.
Table 8 - Compressive Strength Results

Sample

Stabiliser PC

% 10 15 20

Ultimate Load (kN)

Area (mm )

2

Compressive Strength 2 (N/mm )

A B C D E F G H I
7 6 5 4 3 2 1 0

187.751 247.544 262.501 32.519 33.331 42.703 5.011 6.277 7.407

43500 43500 43500 43500 43500 43500 43500 43500 43500

4.316114943 5.690666667 6.034505747 0.747563218 0.766229885 0.981678161 0.115195402 0.144298851 0.170275862

PFA

10 15 20

GGBS

10 15 20

Compressive Strength (N/mm2)

A

B

C

D

E Sample

F

G

H

I

Figure 18 - A Comparison of the Compressive Strength of the Samples

46

0.007 0.006 Stress (kn/mm2) 0.005 0.004 0.003 0.002 0.001 0 10% Stabilizer 15% Stabilizer 20% Stabilizer

0

0.05

0.1
Strain

0.15

0.2

Figure 19 - Stress-Strain Curves for the PC Stabilised Bricks

0.0012 0.001 Stress (kN/mm2) 0.0008 0.0006 0.0004 0.0002 0 0 0.05 Strain
Figure 20 - Stress-Strain Curves for the PFA Stabilised Bricks

10% Stabilizer 15% Stabilizer 20% Stabilizer

0.1

0.15

0.00018 0.00016 0.00014 0.00012 0.0001 0.00008 0.00006 0.00004 0.00002 0 0 0.02 0.04 0.06 0.08 0.1 Strain

Stress (kN/mm2)

10% Stabilizer 15% Stabilizer 20% Stabilizer

Figure 21 - Stress-Strain Curves for the GGBS Stabilised Bricks

47

PC:

PF A: A:

GGB S: S:

Figure 22 - The Appearance of a Selection of Samples after Compressive Strength Testing

48

7.0

Sustainability Study

More than 20 years since the Brundtland Commission brought sustainable development to international prominence the issue still arouses much debate as to how it should be defined, interpreted and assessed. Proponents of the theory have Others, more

designed earnest procedures for the measuring and reporting of it.

sceptical to the concept are of the opinion that the World Commission for Environment and Development (WCED) definition is ‘an idea so vague that everyone can agree to it’ (Lindsay, 2001). They assert that sustainable development is an oxymoron and that neo liberal discourse on the subject focuses almost solely on the economic rather than any social or environmental aspects (Davidson, 2010).

However, there is broad consensus that the concept is multi dimensional, advocating a complicated, and often subjective, interrelationship between social, environmental and economic factors (as shown in Fig 23). Many definitions exist but most typically

suggest some responsibility to current and future generations as well as an appreciation that the natural environment is not an infinite resource to be continually degraded (Walton, et al., 2005). Perhaps the most commonly quoted definition is that proposed by the WCED: „…development that meets the need of the present without compromising the ability of future generations to meet their own needs.‟ (World Commission on Environment and Development, 1987)

Figure 23 - Interrelationship between the Spheres of Sustainability (Source: Tanguay, et al. 2009)

49

One method of measuring sustainability and one that is popular with a number of public administrators is the use of Sustainable Development Indicators (SDIs). However, the sheer number of SDIs and the lack of common interpretation of their meaning means that their use is still problematic (Tanguay, et al., 2009).

In the context of this report this presents difficulty in determining exactly how to define sustainability and how to compare the different stabilisers.

To counter this difficulty the report will broadly endorse the WCED definition and investigate the proposed alternative stabilisers, GGBS, PFA and PC, across four areas:    

Ease of Manufacture (environmental, economic, and social). Financial cost (economic). Health implications (social, environmental). Quantitative eco-points analysis (environmental).

Whilst it is acknowledged that this approach has its limitations, so do the alternatives and this method will at least provide both quantitative and qualitative results for discussion.

7.1

Ease of Manufacture

PFA and GGBS are both by products of existing industry. Details of their manufacture are contained in Section 3.2 above.

PC is not a by-product.

Instead its manufacture consists of a tightly controlled

combination of calcium, silica, aluminium, iron and small amounts of other materials. Gypsum is added at the final grinding stage in order to regulate the setting time.

Two methods of production exist for PC; wet and dry.

In both methods the raw

materials (calcium carbonate and silica) are mixed together and fed into large rotating kiln cylinders. These are heated to approx 1450oC to create the conditions necessary for the chemical reactions to take place. A substance called clinker is produced,

50

cooled and then ground with gypsum to produce cement powder (Portland Cement Association, 2011).

The cement manufacturing procedure is extremely energy intensive and the environmental implications of producing PC, in comparison to PFA and GGBS, have already been stated in Table 3.

7.2

Financial Cost

The financial cost of ICSB technology varies, depending on a number of factors primarily the availability of quality material on site, the transportation costs and the amount of mortar used. A financial estimate for 1 m2 of ICSB wall compared to 1 m2 of fired brick wall is shown in Table 9. In this table it should be noted that marram is a grass traditionally added as a further stabiliser/aggregate. The discrepancy in mortar requirements between fired bricks and ICSB is due to the ‘fins’ designed into the ICSB blocks, these reduce the need for mortar. However, more labour is required for the ICSB blocks as they are usually made locally (or even on site) rather than being delivered from a manufacturing plant.

51

Table 9 - A Comparison of the Costs of Fired Bricks and ICSB (adapted from Smith, 2010)

Per 100 Bricks Fired Bricks Blocks: Purchase cost Mortar: Coarse sand (3 wheelbarrows) Fine sand (2 wheelbarrows) PC (25 kg) Labour: 1 x mason (per day) 0.5 x labourer (per day) Total (Ugandan Shillings / m (50 bricks)) ICSB Blocks: Marram (6 wheelbarrows) PC (25 kg) Mortar: Coarse sand (3 wheelbarrows) Fine sand (2 wheelbarrows) PC (25 kg) Labour: 1 x mason (per day) 3.5 x labourers (per day) Total (Ugandan Shillings / m (35 bricks))
2 2

Per 400 Bricks

Per Brick

15000

150

6300 6000 28000

63 60 280

10000 2500

25 6 29213

8400 28000

84 280

6300 6000 28000

16 15 70

10000 17500

25 44 18690

Table 9 shows that ICSB technology is financially more viable than fired bricks but this table was based on mud bricks that had been stabilised with PC. Unfortunately, finding prices for GGBS and PFA in Uganda or Tanzania proved unsuccessful. However, a model has been developed to adjust the costs proposed for PC stabilised blocks to give a proposed cost for blocks stabilised with GGBS and PFA.

Prices for PC, GGBS and PFA in the UK were found ([A1 Building Supplies, 2011], [Benny Industries, Unknown], [ValueUK, 2011], [The Building Lime Company, 2011]). These are presented in Table 10. By comparing the UK PC price to the Ugandan PC price a multiplication factor of 7197.94 can be applied to all prices to give an 52

approximate Ugandan price, assuming availability. Table 10 also compares the price, in Ugandan Shillings, of producing 1 x ICSB with the various stabilisers using the variables detailed in Table 9.
Table 10 – A Comparison of Estimated Stabiliser Cost in Ugandan Shillings and Cost per ICSB

PC UK Price (GBP per 25 kg) 3.89

GGBS 6.00

PFA / Lime 3.78 (PFA) 9.97 (Lime) = 5.84

Ugandan Price (Ugandan Shillings per 25 kg) Total cost of producing 1 x ICSB (Ugandan Shillings)

28000 18690

43187 24005

42036 23602.25

7.3
7.3.1

Health Implications
GGBS (CEMEX, 2008)

For use as a stabiliser or concrete admix GGBS is supplied as a fine powder or dust. As with all dusts it can irritate the eyes, skin, respiratory system or gastro-intestinal tract. When mixed with water the resulting solution can be alkali. Current industry practice in the UK is that appropriate protective clothing should be worn to minimize contact with the skin and eyes. The substance is stable in normal conditions and, provided reasonable care is taken, is not hazardous in the quantities that would be used for ICSB stabilisation.

7.3.2

PC (US Department of Health and Human Services, 1995)

PC is also used in powered form, comprising a grey, fine, odourless powder. The health risks associated with the substance are similar to GGBS, notably that the dust can cause eye irritation and prolonged or repeated contact with the skin can cause dermatitis. Protective clothing (boots and gloves) should be worn when handling

cement but the use of a respirator is unnecessary unless heavy exposure is anticipated.

53

7.3.3

PFA (Scotash, 2005)

PFA also presents as a grey, odourless dust. However the health risks associated with it are markedly lower than either GGBS or PC. It is still recommended to wear

protective clothing but there is no clinical evidence of skin inflammation, respiratory problems (unless excessive amounts have been inhaled) or issues associated with ingestion.

However, it should be noted that PFA requires lime to initiate the cementitious reaction and this has health and safety implications of its own (CEMEX, 2007). Lime can burn skin in the presence of water and there is risk of serious damage to the eyes. Protective clothing must be worn at all times, including eye protection and face masks. It should also be noted that the reaction between water and lime is highly exothermic.

7.4

Quantitative Ecopoints Analysis

The environmental impacts of construction are hard to analyse as they impact on a number of different areas, for example water resource quality and climate change. Comparing directly different situations is unhelpful and inaccurate as it involves subjective judgement on the scope of influence and their relative importance. For example is a mineral extraction programme that significantly impacts water quality but has very little effect on climate change a better or worse construction practice than an industry with the reverse environmental implications?

To enable greater accuracy in such assessments BRE (formerly the Building Research Establishment) have developed Eco-points.

The parameters that Eco-points consider include climate change, fossil fuel depletion, freight transport, toxicity and waste disposal. BRE have then attempted to normalize the environmental impact of these activities by comparing them to a norm. This norm has been taken as the average impact of a UK citizen, calculated by dividing the total UK impact by the population of the UK. The system has also, in consultation with industry experts and stakeholders, assigned a weighting to each environmental impact (BRE, 2009). The result is a single figure score for the environmental impact of a material where the higher the number, the higher the impact.

54

The Eco-point summaries for PFA and GGBS are reproduced in Appendices 3 and 4. The Eco-point summary for PC was not available but several articles and papers detail the score at around 4.1 ([A1 Building Supplies, 2011] [Portland Cement Association, 2011]). This is largely due to the huge amounts of embodied energy involved in the production of cement compared to the other two substances which are merely byproducts of existing industry. To summarise, the Eco-point scores are as follows:   

GGBS: 0.35 Eco-points. PFA: 0.066 Eco-points. PC: Approx 4 Eco-points.

55

8.0
8.1

Discussion
Preliminary Experiments

The results from the preliminary experiments were not as expected. The compressive strength of all the unfired bricks was disappointingly low (0.42-1.25 N/mm2) and short of the 5-8 N/mm2 required by current Eurocode, and UK Building Regulation, standards (Oti, et al., 2009). Another notable observation is that the unfired brick without a

stabiliser performed recorded the highest compressive strength during testing. There are a number of potential reasons for this: 1. Unknown Provenance. The manufacture of the bricks took place at an

external location and by unknown individuals. This means there is plenty of scope for inaccuracy, both in terms of the manufacturing procedure and the materials used. For example, substandard or badly stored lime may have been used and this could have affected the results. Other factors, which remain unknown, that could have affected the performance of the bricks include the manner of storage, the curing period and how they have been treated since manufacture (e.g. have they been dropped, have they been exposed to water etc).

2. Appropriate Ratios of Materials. The mix of materials that was used for the production of the bricks in the preliminary experiment is also unknown. Although there were estimates of a uniform addition of 20% of stabiliser across the bricks this has not been confirmed. This makes any comparison with the results from the main laboratory experiments virtually worthless and also casts doubt on the appropriateness of the mix proportions. 3. Uneven Loading on the Bedding Plane. The tested bricks were particularly coarse. The nature of the compressive strength testing machine means that the application of the load is, therefore, uneven (because a point load is transferred across the bedding plane by a piece of additional material and there is no cushioning between the two to mitigate for uneven surfaces). Even with a piece of soft wooden packing to try and lessen the effects there were still raised

56

points on the bedding plane which will have taken the brunt of the load. This source of error could potentially be reduced by testing one of the surfaces that were in contact with the mould (and, therefore, smoother). However, EN 772-1 states that the bedding plane to be loaded is the one that should be tested. Testing the brick on its side, for example, would give skewed results because it would be testing the compressive strength in a plane not loaded in usual use. The most obvious way to provide a more level bedding surface is to use a mould that contains the brick on all surfaces. Testing of ICSB that has been produced in a press will probably sidestep this potential source of inaccuracy as the bricks will be more uniform.

The preliminary experiments were still a worthwhile exercise. The results show that the compressive strength of both the fired brick and the house brick (2.15 N/mm2 and 11.2 N/mm2 respectively) are superior to the unfired bricks. This confirms that although unfired mud bricks are an adequate solution for affordable housing they are not as efficient at carrying load as more traditional methods of construction. Another positive outcome from the preliminary experiments was the hands-on experience of making mud bricks. This proved invaluable when conducting the main laboratory experiments as a manufacturing method was already known and had been practiced.

8.2

Sustainability Study

8.2.1

Defining Sustainability

The first paragraphs of Section 7.0 alluded to the problems with attempting to define sustainability and outlined the areas which would be considered in the context of this report. For clarity these are reproduced below:    

Ease of Manufacture (environmental, economic, and social). Financial cost (economic). Health implications (social, environmental). Quantitative eco-points analysis (environmental).

57

The decision to use these four areas was based on the fact that they would produce both qualitative and quantitative results for comparison. Each of these areas will be discussed in turn.

8.2.2

Ease of Manufacture

If it is assumed that a product or service is ‘more sustainable’ if its manufacturing process is least harmful to the environment then it is apparent that PFA and GGBS are inherently ‘more sustainable’ products than PC. As PFA and GGBS are by-products of existing industry so their production contributes no more environmental damage than the primary industry. Indeed, the environmental damage caused by the production of these stabilisers has already been compared in Section 3.3. However, this is a fairly simplistic overview and the environmental considerations, and the longevity, of the primary industry must be taken into account.

Coal fired power stations, the industry behind the production of PFA, have a limited lifespan as the global reserves of coal are finite. However, as recently as 2009 the UK government announced plans for 4 new plants before 2020. There are natural concerns about this apparent pursuance of ‘dirty’ technology and questions raised as to the merit of investing in existing technology rather than pursuing greener energy options such as nuclear power and renewable energy. However, since it is reasonable to assert that ‘green’ technology in the developing world is likely to lag behind that of the developed world then it is also reasonable to assume that coal fired power stations will continue to be used in the areas where ICSB technology is most likely to be employed. This claim is reinforced by the fact that there are currently plans in place to build a new 200MW coal powered plant in Tanzania. Therefore, whilst it is certainly not a solution that will be applicable forever, PFA will be produced for the foreseeable future though the rate of production may slow if power stations continue to improve efficiency. The use of PFA will also help to reduce the environmental impact of coal fired power stations by committing less waste to landfill and creating worthwhile products out of a greater percentage of raw materials.

GGBS is a by-product of the steel manufacturing process and the demand for steel is increasing. Attempts are being made to streamline industry processes and make them more sustainable, particularly regarding the recycling of steel. However, it is

reasonable to deduce that steel, and by inference GGBS, production will continue for 58

the foreseeable future. Steel is a key industry in Uganda with Sembule Steel providing steel products to more than 10 countries in East and Central Africa [USGS, 2006]. This alludes to the possibility of GGBS production in the area. The sustainability of GGBS, in terms of ease of manufacturing, can therefore be placed on a par with PFA. If the primary industry for both materials persists then they will continue to be, at least theoretically, available.

It is widely known, and reported, that cement production is an extremely energy intensive manufacturing process that cannot claim to have good environmental credentials. However, the cement industry is suggesting reformist agendas to There is strong

modernize production and improve the reputation of the industry.

scepticism about these reforms, however, as the cement producers are disadvantaged by basic chemistry. The chemical reaction that produces cement releases large

amounts of CO2 and about 60% of the CO2 emissions from manufacture are from this reaction. To minimize emissions the cement industry is attempting to reduce the fuel input in production. However, if demand for concrete continues to rise faster than the emissions are reduced then the negative environmental effect of cement manufacture will continue to worsen. For this reason, and in terms of ease of manufacture, PC is the least sustainable stabiliser tested in this project.

8.2.3

Financial Cost

The financial cost of the stabilisers is easier to compare as there is quantitative data available from the model detailed in Section 7.2. If it is assumed that ‘more sustainable’ in a financial context is defined as lower cost then the relative ranking of the stabilisers would be: PC (18690 UGS per ICSB), GGBS (23602.25 UGS per ICSB) then PFA (24005 UGS per ICSB).

8.2.4

Health Implications

There is no major difference in the potential stabilisers in terms of health implications. However, PFA requires lime to initiate the cementitious reaction and this is a potentially hazardous material.

59

In a social context it can be assumed that ‘more sustainable’ means least hazardous. As a result the stabilisers can be ranked in the following order: PC and GGBS are equal followed by PFA.

8.2.5

Overall Sustainability

This project is attempting to rank the proposed stabilisers in terms of their overall sustainability and the problems with this approach have been made clear. It is

incredibly difficult, not to mention subjective, to compare such different substances over such a diverse range of factors. However, Table 11 and the preceding

paragraphs, attempt to do that. Table 11 shows the stabilisers ranked according to three of the four key areas considered above. It ranks each stabiliser against each area allocating a 1 (green) for the most sustainable and a 3 (red) for the least. The final column shows an overall sustainability ‘score’ according to the research carried out for this project and the criteria discussed in Sections 8.2.2 to 8.2.4. This score was calculated by adding together the individual scores for each key area.
Table 11 - An Overall Comparison of the Sustainability of the Stabilisers

Stabiliser PC PFA GGBS
‘sustainable’ option.

Ease of Manufacture

Financial Cost

Health Implications

Total

3 1 1

1 3 2

1 3* 1

5 7 4

*Although PFA is considerably less harmful than either GGBS or PC the requirement for lime makes it the least

Table 11 shows that, according to the sustainability study in Section 7.0, GGBS is the most sustainable followed by PC and then PFA. This is at odds with the eco-points scores which rank the stabilisers in the following order: PFA, GGBS and then PC. Since the eco-points system and the sustainability study in this report are effectively trying to achieve the same result (although the eco-point system considers many more factors) this is a surprising outcome. 2 possible reasons for this discrepancy will be considered here. The first is that the eco-point system is based on the energy This report has attempted to rate the

consumption of a typical UK resident.

60

sustainability of the stabilisers from a Ugandan and Tanzanian perspective.

The

financial cost for example, which has been calculated in UGS, has had a significant impact on the overall sustainability score achieved from this research. The second, and perhaps more considerable, reason for the discrepancy is one of the fundamental drawbacks of the concept of sustainability; subjectivity. Any author or authority can, intentionally or otherwise, skew the results of such a subjective idea. Whilst every intention can be made to be as neutral as possible there is always a vested interest by the compiler of any research. This may vary from a desire to produce the best possible report, thesis or article to providing evidence in support of the claims of a financial backer. It is not being proposed that all measures of sustainability have inherent

intentional inaccuracy but it would be naïve to take all published data simply at face value.

A final point to note from the sustainability study is that this entire report has been conducted under the assumption that PFA and GGBS are available in the developing world. Whilst it has been proved that the industry that produces these by-products exist in Uganda and Tanzania, and are likely to do so for the foreseeable future, there has been no definitive evidence found that PFA and/or GGBS are refined, marketed and sold in those countries. If these substances are not available, or need to be imported from further afield, then any environmental and financial advantage will be negated. Conversely, questions can be asked if the products aren’t available in the developing world yet the industry that produces them exists. It is worth further

investigation to see if the economic, commercial and social conditions exist to make their sale worthwhile.

8.3

Laboratory Experiments

8.3.1

Shrinkage Testing

The shrinkage testing returned a result of zero shrinkage, despite increasing the curing time to allow the soil to dry further. unexpected result: There are several possible reasons for this

1. The Use of an Artificial Homogeneous Soil. As described in Section 5.0 an artificial homogeneous soil was used for the construction of all the bricks.

61

Although this allowed more accurate comparison of the various samples it also meant that the soil was devoid of the differences (e.g. void ratios and variable water content) that would influence the shrinkage of a natural material. 2. Inappropriate Curing Conditions. The shrinkage mould was left to cure at room temperature (approx 20OC) and normal humidity. This may not have provided the ideal curing conditions for shrinkage to occur. The effect of this, however, is likely to be minimal because the curing time was extended when no shrinkage was observed initially. 3. Lack of Hydration. The shrinkage testing mix was hydrated with 2000ml of water. This was estimated from the amount of water required to hydrate the bricks and may not have been sufficient to properly hydrate the soil to obtain any significant shrinkage.

Although the shrinkage testing produced disappointing results the reason for undertaking the test should be reiterated. The test has been adapted from the UN HABITAT test for calculating the required amount of stabiliser. Since this project

intended to investigate the use of alternative stabilisers in mud bricks, the percentage of stabiliser was likely to be varied. Therefore, the utility of the test in this instance is fairly limited. No shrinkage would suggest that a low proportion of stabiliser is required as one of the key roles of the stabiliser is to prevent shrinkage. Even the 10% bricks, the lowest tested percentage of stabiliser, should, therefore, not have been affected by shrinkage during the project. In practical application the amount of stabiliser tends to be around 10% (Browne, 2009). This published data, and the negligible shrinkage, gives additional credence to the stabiliser percentages chosen for the main laboratory experiments.

8.3.2

Manufacturing Procedure

The manufacturing procedure is a potential source of inaccuracy in the Method Statement. As previously stated, the procedure used was adapted from a technique taught at EWB workshops. However, an element of judgement was required when calculating mix proportions and curing times. Although previous research and standard

62

procedures were consulted to shape the method used in this project (notably UN HABITAT and Oti, 2009) there is no professional standard for this type of brick manufacture.

Other sources of inaccuracy in the manufacturing procedure include the mixing technique (which could be improved by the use of a mechanical mixing device), the source of the materials (which was taken on trust from the laboratory technicians) and the curing conditions (which, although designed to simulate a practical environment, were subject to the vagaries of the laboratory).

8.3.3

Absorption Testing

The Initial Rate of water Absorption (IRA) ranged from 0.01 Kg/m2/min for the 20% PC brick (sample C) to 0.13 Kg/m2/min for the 15% GGBS brick (sample H).

The PC bricks (samples A-C) performed as expected and the IRA decreased with increased proportions of stabiliser. This is not surprising as higher cement content will decrease the porosity of the material and cement is a water resistant material when cured.

Conversely, the PFA bricks (samples D-E) performed contrary to expectation because the IRA increased with increased stabiliser content. This is probably due to the

presence of excess lime in the PFA bricks which would not have been fully hydrated during the cementitious reaction. The excess lime would then absorb the water during the absorption testing adversely affecting the IRA results.

The results from the GGBS bricks (samples G-I) are unreliable. There is no pattern to the IRA as the 15% brick (sample H, 0.13 Kg/m2/min) exceeds both the 10% brick (sample G, 0.07 Kg/m2/min) and the 20% brick (sample I, Kg/m2/min). There is no obvious explanation for these results and, when combined with the disappointing compressive strength results discussed in Section 8.3.4, the conclusion must be that the manufacture of the GGBS bricks was in some way unsatisfactory. discussed in further detail in Sections 8.3.2 and 8.3.4. This is

The results from all the samples, however, are positive. The IRA of a brick has a significant effect on the eventual overall strength of a masonry wall. For example, if the 63

IRA of a brick rises from 2 Kg/m2/min to 4 Kg/m2/min then the strength of the wall will be reduced by 50%. Bricks with large IRA values will draw moisture from the mortar and reduce its effectiveness. (Whilst it is appreciated that one of the appeals of ICSB technology is the reduced reliance on mortar there is still a need for some). Bricks with an IRA of greater than 2 Kg/m2/min are considered difficult to lay with traditional mortars. All of the samples tested in this research have displayed IRAs of significantly less than 2 Kg/m2/min and, therefore, would be acceptable in traditional construction [Claybricks and Tiles Sdn, 1998-2007].

There is one important aspect of the absorption testing method that should be considered and potentially adapted for future research. BS EN 772-11:2010 Section 8.3 details the absorption testing procedure that was followed during this research. That document states that the sample should be submerged in water up to a depth of 5mm (+/- 1mm) for 24 hours. It makes no mention of whether the water level should be topped up during that 24 hour period. When using samples as permeable as unfired bricks this becomes a noteworthy omission. If the water was to be kept at a constant level throughout the 24 hour period then it is likely that the IRA results would be very different (indeed, the GGBS bricks would probably have been unusable for further testing had this been the case). As mentioned in Section 5.0 the water, in this

absorption test, was topped up once during the 24 hour period and this may have affected the results for the PFA and GGBS bricks. Careful consideration should be given to this, and to the proportion of lime in the PFA mix, if the research is to be repeated. Further discussion on the applicability of the Eurocodes to this type of

construction material is contained in Section 8.3.5.

8.3.4

Compressive Strength Testing

The compressive strength of the bricks varied from 0.12 N/mm2 for the 10% GGBS brick (sample G) to 6.03 N/mm2 for the 20% PC brick (sample C).
2

The mean

compressive strength for all the samples was 2.11 N/mm which is below the desired minimum of 5 N/mm2 required for UK building regulations. This is not unexpected, however, as previous research into similar bricks yielded compressive strengths of 2.7 – 7.4 N/mm2 (Oti, et al., 2009). These are also below the required building regulation standards. The results from this project, however, were still significantly below the published findings.

64

Specifically, and surprisingly, the GGBS stabilised bricks (samples G-I) performed least well with a compressive strength range of 0.12 – 0.17 N/mm2. However, increased percentages of stabiliser improved the performance of the bricks as expected. Previous research had been conducted into GGBS stabilised unfired bricks by Oti and they performed much better in his work (2.7 – 5 N/mm2). The PFA bricks (samples D-F) produced a compressive strength range of 0.75 – 0.98 N/mm2 with a slightly anomalous result for the 15% brick (sample E, 0.77 N/mm2) which should have been higher when compared to the 10% brick (sample D, 0.75 N/mm2). The compressive strength results were all below 1 N/mm2 which is lower than expected.

The PC bricks (samples A-C) exhibited the highest compressive strength by a large margin. This is not an unexpected result and reinforces the selection of PC as the preferred stabiliser in current ICSB practice. Samples A-C produced a compressive strength range of 4.32-6.03 N/mm2 though the value for C is estimated as it exceeded the load capacity of the testing machine. stabiliser content. These results also increased with the

Samples B and C (15% and 20% PC stabiliser respectively)

displayed compressive strengths over 5.0 N/mm2 and would thus be acceptable to UK building regulations.

There are several factors pertaining to the compressive strength testing that should be considered further: 1. Uneven Bedding Planes. The same issues discussed in Section 8.1 are applicable to the main laboratory experiments. should be followed to mitigate them. The same suggestions

2. Materials Provenance.

The GGBS bricks (samples G-I) produced

surprising results across both areas of interest. A question must, therefore, be raised as to the quality, and the provenance, of the raw material. Published research by Oti has realized much improved results (see above). Whist the surprisingly poor results in this research may be attributable to inappropriate material storage or handling it is important to remember the eventual practical application of ICSB technology. Construction sites, and construction workers, across the world are unlikely to favour GGBS to PC if

65

the change involves complicated handling or storage implications. Alternatively, the results could be due to another reason, perhaps inaccurate manufacture (but this should have affected the other stabilisers as well because all of the sample were made in the same way) or unsuitable mix proportions. 3. Machine Reliability. The machine used to test the compressive strength was modern and complied with all the requirements stated in EN 772-1. Therefore, machine reliability can be discarded as the reason for the low compressive strength results. 4. Subsequent Testing on the same Samples. Both the absorption test and the compressive strength testing were carried out on the same samples. This may have influenced the results, particularly for the bricks that showed a higher rate of IRA (i.e. the GGBS bricks). Excess water in the bricks may have reduced their strength. Although this is a valid source of potential error it should be remembered that one of the concerns surrounding the use of unfired bricks is their susceptibility to water damage If it proved the case that the compressive strength was considerably reduced by the previous absorption testing then it doesn’t breed confidence in the use of GGBS bricks in a practical environment

8.3.5

Application of ICSB Technology

In summary, the results of the engineering property testing indicate that whilst all of the bricks performed adequately in terms of IRA, the vast majority were not sufficiently strong in terms of compressive strength to be considered as a construction material according to UK Building Regulations. However, it is important to define exactly what the requirements are for ICSB technology. The primary use, certainly in the developing world, is to provide affordable housing and for low scale construction projects. Even the diverse projects discussed in Section 3.0 all share a fairly limited ambition in terms of construction scope. Therefore, it may not be essential for ICSB to satisfy the

requirements of construction materials that are used in more complex developments.

If the application of ICSB technology in the developing world is limited to small scale projects then the loads that would be expected to act on the structure would be 66

considerably less than, for example, a 2 storey house in the UK. Design could be undertaken without recourse to snow loads, which would further lessen the expected forces. The primary loads are likely to be the dead weight of the structure and wind loading. In this situation a compressive strength of less than 1 kN/mm 2 may be

adequate though it is still unlikely that the GGBS blocks produced for this research would be of any considerable utility due to their brittle nature.

There is a strong argument for the creation of a specific standard for this type of technology. This standard could contain substantial information relating to the use of ICSB technology including:     

Manufacturing guidance.

Typical mix proportions for different shrinkage results.

Testing procedures.

Minimum required engineering properties.

Curing procedures.

Although the UN HABITAT guide gives some of the information listed above it is not presented in a scientific way nor is it comprehensive. professional standard is recommended in Section 10.0. Research into a new

8.3.6

Limitations to the Research

Several limitations to the research conducted during this project have been alluded to throughout this report. The major limitations are summarized below and should be given due consideration if the research is to be repeated: 1. Manufacturing Process. ICSB is made using a press in the practical

environment. The bricks tested in these experiments were hand-made and, despite best intentions, will not have been compressed as well as those made in a press. This is likely to have negatively affected both the IRA and

compressive strength results. 67

2. Sample Size. The sample size was necessarily small due to time and labour constraints. A larger variety of samples would have meant anomalous results had less credence. 3. Whole Life Analysis. The manufactured bricks were only tested in the short term and the long term durability has not been addressed.

68

9.0

Conclusions

The following conclusions can be drawn from this research: 

Current research on alternative stabilisers for unfired mud bricks is fairly limited. Some published data is available for bricks stabilised with Ground Granulated Blast furnace Slag (GGBS) but none is available for Pulverised Fly Ash (PFA). However, the use of these substances as admixtures in other applications is well documented.



PFA and GGBS were identified as potential alternatives to PC for unfired mud brick stabilisation.



GGBS was assessed as ‘more sustainable’ than PC in terms of cost, ease of manufacture. embodied energy and health implications. PFA fared worse than both the alternatives, mainly due to the requirement for lime to facilitate the cementitious reaction.



Bricks manufactured with the alternative stabilisers, at a range of proportions, were compared across three mechanical properties: o

Compressive

Strength.

The PC stabilised bricks performed

considerably better than either the GGBS or PFA stabilised bricks. Only the PC bricks exhibited a compressive strength greater than 1 N/mm2. o o Absorption. All of the bricks tested had an acceptable Initial Rate of Water Abortion (IRA) according to current standards. Shrinkage. The soil used in these experiments displayed zero

shrinkage after 14 days curing. 

The PFA and GGBS stabilised bricks tested were not a viable engineering alternative according to UK Building Regulations. However, the PFA bricks may be adequate depending on their practical application.



The availability of the alternative stabilisers in the developing world remains unknown.

69



PFA and GGBS are viable admixtures in the developing world since their primary industries will exist for the foreseeable future.



There are no known social implications to the use of PFA or GGBS in the developing world.

70

10.0 Recommendations for Future Research
The following list outlines some recommended topics for further research. This is not an exhaustive list and there are many more variables that could be adjusted or amended. The topics detailed here are those which have become obvious avenues of exploration after the research undertaken during this project; there are countless others involving mud bricks in general and other sustainable construction materials.

1. More Extensive Testing. Due to time constraints the sample size considered in this report was very small. Indeed, it was the smallest possible sample size that allows useful comparison. There is scope to increase the number of bricks tested, the variations in mix composition, the number of stabilisers tested and different curing conditions. 2. Repeat Research with GGBS. Due to the disappointing results obtained for the GGBS stabilised bricks it would be useful to repeat the experiments with greater emphasis on the provenance of the materials, the mix proportions and the curing method. 3. Long Term Durability. Research into unfired mud bricks is partially justified by the concerns surrounding their long term durability and susceptibility to water damage. This has not been addressed in this project. There is considerable value in undertaking research to compare the long term durability of bricks stabilised with alternatives to PC, ideally in a location which is likely to use the technology (e.g. Uganda). Cross referencing the results of these experiments with research into the absorption rates of bricks stabilised with PC alternatives could give useful clues as to what, chemically, is affecting the durability. 4. Chemical Changes. Detailed research into the chemical reactions that take place during cementation would be useful. There has been some research already undertaken in this area but there is still scope to clarify the chemistry that occurs when using alternative stabilisers. The results may drive a

consistent approach to mix compositions that could be implemented in a practical environment.

71

5. Testing on Bricks made with a Press. Perhaps the most limiting factor in this research, and others, is that the bricks tested were hand-made and not made using a Magika press (or similar). This is likely to have an effect on the

uniformity of the shape, the chemical structure and, ultimately, on the performance of the bricks. This research could be combined with that

suggested in Part 1 of this Section as using a press is likely to speed up the manufacture of the bricks so a larger sample could be used. 6. Appropriate Manufacturing Standard. Section 8.3 highlights some of the

shortcomings that manifest themselves as a result of applying Eurocode standards to technology that doesn’t require such rigorous testing and application. The development of a specific manufacturing standard for ICSB technology could be a useful step forward. In an ideal world this could then be applied to all ICSB building and help to standardize practices. Unfortunately this is unlikely to happen, at least in the short to medium term, due to the conditions, and locations, where ICSB is likely to be considered an option. However, there is still value in such a standard.

7. Availability.

The availability of the alternative stabilisers was discussed in

8.2.5. There are 2 distinct research possibilities in this area. Firstly, in-country research to assess the availability of the stabilisers and secondly a cost-benefit analysis into the feasibility of sourcing and distributing them if they aren’t currently available.

72

References:
A1 Building Supplies. (2011). Retrieved 03 14, 2011, from A1 Building Supplies Limited: http://www.a1building.co.uk/index.php?osCsid=0fpg0kb115v4gqs4j75r7grcr0

ACI Committee. (1987). Ground Granulated Blast Furnace Slag as an Admixture. 87a (226) . ACI.

Ash Solutions Ltd. (2009). Fly Ash BSEN 450 Product Information. Retrieved Nov 10, 2010, from Aggregate.com: www.aggregate.com/Documents/TDS/fly-ash-techdata.pdf

Benny Industries. (Unknown). How to Buy Fly Ash. Retrieved 03 14, 2011, from Fly Ash Bricks Information: http://flyashbricksinfo.com/flyash-brick-machine-pricequotation.html

BRE. (2009). Ecopoints: A Single Score Environmental Assessment. Glasgow: BRE.

Browne, G. (2009). Stabilised Interlocking Rammed Earth Blocks. Southampton: Southampton Solent University.

BSI. (2003). BS EN 771-1:2003. Specifications of Masonry Units . Brussels: BSI Group.

BSI. (2010, Jun 29). BS EN 772-1:2010. Part 1 - Determination of Compressive Strength . London: BSI Group.

BSI. (2010). BS EN 772-11:2010. Part 11: Determination of water absorption of aggregate concrete, autoclaved aerated concrete, . Brussels: BSI Group.

Burroughs, S. (2009). Relationships Between the Strength and Demsity of Rammed Earth. Construction Materials (CM3).

Caltrone, G. (2010). Fly Ash Addition in Clayey Materials to Improve the Quality of Solid Bricks. Retrieved January 31, 2011, from Constructionz: www.constructionz.com

73

CEMEX. (2008). Ground Granulated Blast Furnace Slag Material Safety Datasheet. Rugby: CEMEX UK.

CEMEX. (2007). Hydrated Lime - Material Safety Datasheet. Rugby: CEMEX.

Claybricks and Tiles Sdn. (1998-2007). The Basics of Bricks. Retrieved 05 02, 2011, from Clay Bricks: http://www.claybricks.com/more_info/basic-of-bricks.html

Coutand, M., Cyr, M., & Clastres, P. (2006). Use of Sewage Sludge Ash as Mineral Admixture in Mortars. Construction Materials , 159 (CM4), 153-162.

Davidson, K. (2010). Reporting Systems for Sustainability: What are they Measuring? 2011.

Hadjri, K., Osmani, M., Baiche, B., & Chifunds, C. (2007). Attitudes Towards Earth Building for Zambian Housing Provision. Engineering Sustainability , 160 (ES3), 141169.

Heath, A., Walker, P., Fourie, C., & Lawrence, M. (2009). Compressive Strength of Extruded Unfired Clay Masonry Units. Constructions Materials 162 , 105-112.

Jegendan, S., Liska, M., Osman, A., & Aj-Tabbaa, A. (2010). Sustainable Binders for Soil Stabilisation. Ground Improvement , 163 (G11), 53-61.

Lindsay, G. (2001, May). The Holy Grail of Sustainable Development. Retrieved Feb 14, 2011, from Indiana University: http://www.indiana.edu/

Mwebeze, S. (2007). Uganda. Retrieved 03 14, 2011, from Grasslands and Pastural Crops: http://www.fao.org/ag/AGP/AGPC/doc/Counprof/uganda.htm#2.%20SOILS%20AND% 20TOPOGRAPHY

Norton, J. (1997). Building With Earth. London: Intermediate Technology Publications.

Oti, J. E., Kinuthua, J., & Bai, J. (2009). Compressive Strength and Microstructural Analysis of Unfired Clay Masonry Bricks. Engineering Geology , 109, 230-249.

74

Oti, J. E., Kinuthua, J., & Bai, J. (2009). Unfired Clay Bricks: From Laboratory to Industrial Production. Engineering Sustainability , 229-237.

Oti, J. E., Kinuthua, J., & Bai, J. (2008). Using Slag for Unfired Clay Masonry Bricks. Construction Materials , 147-155.

Portland Cement Association. (2011). How Portland Cement is Made. (PCA) Retrieved 02 25, 2011, from Cement and Concrete Basics: http://www.cement.org/basics/howmade.asp

Reddy, B. V., & Kumar, P. (2001). Embodied Energy of Common and Alternative Building Materials and Technologies. Energy and Buildings , 129-137.

Reddy, V. (2004). Sustainable Building Technologies. Current Science , 899-907.

Scotash. (2005). Health and Safety Information - Pulverised Fly Ash. Kincardine: Scotash.

Shafique, S. B., Edil, T., Benson, C., & Senol, A. (2004). Incorporating a Fly-ash Stabiliser Layer into Pavement Design. Geotechnical Engineering , 157 (GE4), 239249.

Sivapullaiah, P. V., Sridharan, A., & Bhaskar, K. (2000). Role of Amount and Type of Clay in the Lime Stabilisation of Soils. Ground Improvement , 4, 37-45.

Smith, E. (2010). Interlocking Stabilised Soil Blocks: Appropriate Technology that Doesn't Cost the Earth. 88 (15/16).

Tanguay, G., Rajaonson, J., & Lefebvre, J.-F. (2009). Measuring the Sustainability of Cities: An Analysis of the Use of Local Indicators. 10.

The Building Lime Company. (2011). Price List. Retrieved 03 14, 2011, from The Building Lime Company: http://www.buildinglime.co.uk/price.html

75

The Good Earth Trust. (2008). What We Do. Retrieved October 2010, from Good Earth Trust: http://www.goodearthtrust.org.uk/index.html

UN Human Settlements Programme. (2009). Interlocking Stabilised Soil Blocks. Nairobi: UN Habitat.

US Department of Health and Human Services. (1995). Occupational Health and Safety Guidance for Portland Cement. US Government.

USGS. (2006). 2006 Minerals Yearbook Uganda. US Department for the Interior.

ValueUK. (2011). Portland Cement 25kg Bags. Retrieved 03 14, 2011, from

ValueMEDIA: http://www.valuemedia.co.uk/popprods.htm?Product=566897

Vincent, T. H. (2010). Mastering Different Fields of Civil Engineering Works. Retrieved Nov 15, 2010, from Civil Engineering Portal: http://www.engineeringcivil.com/which-ofthe-following-cement-replacement-material-is-better-pfa-or-ggbs.html

Vinod, J. S., Indraratna, B., & Mahamud, A. (2010). Stabilisation of an Erodible Soil Using a Chemical Admixture. Ground Improvement , 163 (GI1), 43-51.

Walton, J. S., El-Haram, M., Castillo, N., Horner, M., & Price, A. (2005). Integrated Assessment of Urban Sustainability. 158 (ES2).

World Commission on Environment and Development. (1987). Our Common Future. Oxford: Oxford Press.

76

Appendices
Appendix 1 - Project Management Statement ......... Error! Bookmark not defined.8 Appendix 2 – Risk Assessment for Laboratory Work ......................................... 80 Appendix 3 – Ecopoints PFA................................................................................ 81 Appendix 4 – Ecopoints GGBS ............................................................................ 82 Appendix 5 – Samples of Raw Data for the Compressive Strength Testing…..83

77

Appendix 1 - Project Management Statement
The following table summarises the main activities conducted each week during the course of the project. It should be read in conjunction with the Project Timeline in Section 4.0. There were no major alterations to the conduct of the project throughout its duration.

Week Commencing 28 Jun 10 Jun – Sep 10

Activities Completed Initial project meeting with Claire Furlong. Background research conducted. Literature review started.

27 Sep 10

Memorandum Of Understanding (MOU) received from Engineers Without Borders (EWB).

11 Oct 10 25 Oct 10

Paul Jaquin (PJ) appointed as EWB liaison. Return to NCL, project meeting with Charlotte Paterson (CP) and Chandra Vemury (CV).

8 Nov 10

Project meeting with CP and CV. Aims/objectives agreed. PIR compiled.

15 Nov 10

Draft PIR submitted to CP and CV. ‘Get Sheltered’ workshop.

22 Nov 10 29 Nov 10 13 Dec 10

Proposed Method Statement compiled. PIR submitted. Get Sheltered results written up and analysed. PIR returned. Feedback from Paul Joaquin (PJ) received.

10 Jan 11

Project meeting with CP and CV. PIR feedback discussed. PJ feedback discussed. Project timeline agreed.

31 Jan 11

Mix composition researched. Sustainability study started. Bursary awarded by EWB.

78

7 Feb 11

Method statement for brick construction completed. Lab sessions booked / raw materials arranged. Project meeting with CP and CV. Method statement discussed and improvements suggested.

14 Feb 11

Risk Assessment compiled. Mud brick preparation and shrinkage testing started completed. Methodology improved.

21 Feb 11

Curing method adapted. Sustainability study continued (ease of manufacture and health implications). Methodology completed for mud brick construction and shrinkage testing.

28 Feb 11

Project meeting with CP and CV. Methodology and sustainability study drafts discussed. Sustainability study continued. Shrinkage testing complete.

14 Mar 11

Sustainability study continued, financial cost model designed. Compressive strength testing booked. Absorption testing conducted. Absorption and shrinkage testing results compiled.

21 Mar 11 28 Mar 11

Compressive Strength testing undertaken completed. Results compiled and presented. Project meeting with CP and CV.

25 Apr 11

Style and content of results presentation amended. Discussion, conclusions and recommendations for future research started.

2 May 11 9 May 11

Discussion, conclusions and recommendations continued. Discussion, conclusions and recommendations completed. Draft copy complete. Editing started.

16 May 11

Project completed and handed in.

79

Appendix 2 – Risk Assessment for Laboratory Work
Risk Assessment For Assessment Undertaken Supervisory Review Assessment Review

Newcastle University CEGs Geotechnical Engineering Laboratory

Date: 14 Feb 11 Name: D Harper Signed: [Original signed]

Date: 16 Feb 11 Name: S Patterson Signed: [Original signed]

Date: N/A

Hazard

People at Risk

Existing Controls Information Location Controls Needed

Mixed hazards of non related experiments Slips, trips and falls

All

Do not touch non related experiments or equipment

All

Proceed with caution in the lab. No running. Any liquid spillage reported and cleaned up.

Heavy masses around lab

All

Care taken to employ correct handling techniques. Safety footwear to be worn at all time.

Hazards associated with lime

Researcher

PPE worn when handling lime (goggles, lab coats, masks. safety footwear).

Shattering of samples during compressive strength testing. Hazards associated with OPC

All

Eye protection to be worn during testing.

Researcher

PPE to be worn (as above).

NB. All existing Risk Assessments relating to the Geotechnical laboratory remain extant.

80

Appendix 3 – Ecopoints PFA

81

Appendix 4 – Ecopoints GGBS

82

Appendix 5 – Samples of Raw Data for the Compressive Strength Testing
The following tables show selected raw data from the compressive strength testing.

PC 10%
Compressive extension Strain Compressive load Stress Compressive extension Strain

PC 15%
Compressive load Stress Compressive extension Strain

PC 20%
Compressive load Stress

(mm)

(kN)

(kN/mm2)

(mm)

(kN)

(kN/mm2)

(mm)

(kN)

(kN/mm2)

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8

0 0.004545 0.009091 0.013636 0.018182 0.022727 0.027273 0.031818 0.036364 0.040909 0.045455 0.05 0.054545 0.059091 0.063636 0.068182 0.072727

0.01 0.087 0.463 2.609 6.624 15.505 32.925 59.336 89.964 118.033 144.202 164.97 177.027 182.817 186.192 186.85 186.486

2.3E-07 0.000002 1.06E-05 6E-05 0.000152 0.000356 0.000757 0.001364 0.002068 0.002713 0.003315 0.003792 0.00407 0.004203 0.00428 0.004295 0.004287

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8

0 0.004545 0.009091 0.013636 0.018182 0.022727 0.027273 0.031818 0.036364 0.040909 0.045455 0.05 0.054545 0.059091 0.063636 0.068182 0.072727 83

0.008 0.12 0.717 1.83 3.49 5.475 7.822 10.596 13.708 17.381 21.897 27.243 33.588 41.629 55.026 75.524 96.898

1.84E-07 2.76E-06 1.65E-05 4.21E-05 8.02E-05 0.000126 0.00018 0.000244 0.000315 0.0004 0.000503 0.000626 0.000772 0.000957 0.001265 0.001736 0.002228

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8

0 0.004545 0.009091 0.013636 0.018182 0.022727 0.027273 0.031818 0.036364 0.040909 0.045455 0.05 0.054545 0.059091 0.063636 0.068182 0.072727

0.007 0.104 0.476 0.998 1.73 3.444 6.372 11.365 20.574 35.471 57.308 86.041 115.226 142.606 167.36 185.306 195.407

1.61E-07 2.39E-06 1.09E-05 2.29E-05 3.98E-05 7.92E-05 0.000146 0.000261 0.000473 0.000815 0.001317 0.001978 0.002649 0.003278 0.003847 0.00426 0.004492

8.5 9 9.5 10 10.5

0.077273 0.081818 0.086364 0.090909 0.095455

184.853 182.43 181.227 178.901 173.8

0.004249 0.004194 0.004166 0.004113 0.003995

8.5 9 9.5 10 10.5 11 12 12.5 13 13.5

0.077273 0.081818 0.086364 0.090909 0.095455 0.1 0.109091 0.113636 0.118182 0.122727

116.117 135.197 154.178 171.173 185.471 196.809 215.178 222.341 228.311 232.854

0.002669 0.003108 0.003544 0.003935 0.004264 0.004524 0.004947 0.005111 0.005249 0.005353

8.5 9 9.5 10 10.5 11

0.077273 0.081818 0.086364 0.090909 0.095455 0.1

204.197 212.43 220.945 229.456 237.869 246.398

0.004694 0.004883 0.005079 0.005275 0.005468 0.005664

84

PFA 10%
Compressive extension Strain Compressive load Stress Compressive extension Strain

PFA 15%
Compressive load Stress Compressive extension Strain

PFA 20%
Compressive load Stress

(mm)

(kN)

(kN/mm2)

(mm)

(kN)

(kN/mm2)

(mm)

(kN)

(kN/mm2)

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9

0 0.004545 0.009091 0.013636 0.018182 0.022727 0.027273 0.031818 0.036364 0.040909 0.045455 0.05 0.054545 0.059091 0.063636 0.068182 0.072727 0.077273 0.081818

0.009 0.043 0.293 1.099 2.595 4.378 7.902 12.767 17.536 21.5 24.389 26.983 29.181 30.848 31.879 32.425 32.261 30.7 27.86

2.07E-07 9.89E-07 6.74E-06 2.53E-05 5.97E-05 0.000101 0.000182 0.000293 0.000403 0.000494 0.000561 0.00062 0.000671 0.000709 0.000733 0.000745 0.000742 0.000706 0.00064

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5

0 0.004545 0.009091 0.013636 0.018182 0.022727 0.027273 0.031818 0.036364 0.040909 0.045455 0.05 0.054545 0.059091 0.063636 0.068182 0.072727 0.077273 0.081818 0.086364

0.008 0.054 0.351 0.851 1.55 2.238 3.786 7.207 12.039 17.814 22.901 26.54 28.978 30.549 31.766 32.579 33.115 33.305 32.567 30.176

1.84E-07 1.24E-06 8.07E-06 1.96E-05 3.56E-05 5.14E-05 8.7E-05 0.000166 0.000277 0.00041 0.000526 0.00061 0.000666 0.000702 0.00073 0.000749 0.000761 0.000766 0.000749 0.000694

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5

0 0.004545 0.009091 0.013636 0.018182 0.022727 0.027273 0.031818 0.036364 0.040909 0.045455 0.05 0.054545 0.059091 0.063636 0.068182 0.072727 0.077273 0.081818 0.086364

0.008 0.184 0.26 0.477 0.732 1.088 1.486 2.011 3.053 4.718 7.552 11.403 15.519 18.639 23.508 28.572 33.106 37.052 40.224 41.302

1.84E-07 4.23E-06 5.98E-06 1.1E-05 1.68E-05 2.5E-05 3.42E-05 4.62E-05 7.02E-05 0.000108 0.000174 0.000262 0.000357 0.000428 0.00054 0.000657 0.000761 0.000852 0.000925 0.000949

85

10

0.090909

27.699

0.000637

10 10.5 11

0.090909 0.095455 0.1

42.579 39.546 38.801

0.000979 0.000909 0.000892

86

GGBS 10%
Compressive extension Strain Compressive load Stress Compressive extension

GGBS 15%
Strain Compressive load Stress Compressive extension

GGBS 20%
Strain Compressive load Stress

(mm)

(kN)

(kN/mm2)

(mm)

(kN)

(kN/mm2)

(mm)

(kN)

(kN/mm2)

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5

0 0.004545 0.009091 0.013636 0.018182 0.022727 0.027273 0.031818 0.036364 0.040909 0.045455 0.05 0.054545 0.059091 0.063636 0.068182 0.072727 0.077273 0.081818 0.086364

0.013 0.091 0.196 0.056 0.184 0.435 0.531 0.62 0.626 0.677 1.001 1.395 2.104 3.055 3.887 4.606 4.922 4.989 4.921 4.591

2.99E-07 2.09E-06 4.51E-06 1.29E-06 4.23E-06 0.00001 1.22E-05 1.43E-05 1.44E-05 1.56E-05 2.3E-05 3.21E-05 4.84E-05 7.02E-05 8.94E-05 0.000106 0.000113 0.000115 0.000113 0.000106

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6

0 0.004545 0.009091 0.013636 0.018182 0.022727 0.027273 0.031818 0.036364 0.040909 0.045455 0.05 0.054545

0.003 0.266 0.688 1.17 1.863 2.813 3.849 4.772 5.557 6.04 6.254 6.215 5.876

6.9E-08 6.11E-06 1.58E-05 2.69E-05 4.28E-05 6.47E-05 8.85E-05 0.00011 0.000128 0.000139 0.000144 0.000143 0.000135

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5

0 0.004545 0.009091 0.013636 0.018182 0.022727 0.027273 0.031818 0.036364 0.040909 0.045455 0.05 0.054545 0.059091

0.008 0.118 0.329 0.692 1.14 1.823 2.86 4 5.057 6.08 6.875 7.327 7.314 6.961

1.84E-07 2.71E-06 7.56E-06 1.59E-05 2.62E-05 4.19E-05 6.57E-05 9.2E-05 0.000116 0.00014 0.000158 0.000168 0.000168 0.00016

87

88

Sponsor Documents

Or use your account on DocShare.tips

Hide

Forgot your password?

Or register your new account on DocShare.tips

Hide

Lost your password? Please enter your email address. You will receive a link to create a new password.

Back to log-in

Close