Waste Management

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Waste management



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Environ Eng Policy (2002) 3: 15±18 DOI 10.1007/s100220100034

Waste management strategies for concrete
A. Masood, T. Ahmad, M. Arif, F. Mahdi

Abstract Recycling and reuse of waste such as building rubble, concrete lumps, etc. generated at construction and demolition sites form part of a wider, complex issue, primarily relating to improving supplies of construction material and solving problems of disposal of waste construction material. Within the framework of the sustainable development of the environment, the use of waste materials with minimum environmental impact has received much attention. The conversion of a large amount of demolished waste into an alternative resource will conserve the depleting natural resources of building materials. Demolished waste is mainly used as a non-stabilized base or sub-base in highway construction. The present paper discusses the recycling process and makes an effort to assess a safe and economic use of recycled concrete as a structural grade material for the construction industry. Extensive tests of structural properties such as compressive strength, ¯exural strength and split tensile strength of recycled concrete were carried out, in which cement and similarly ®ne aggregate were partially replaced by demolished waste to obtain recycled concrete and recycled aggregate concrete whose properties were compared with results for the conventional concrete.

Introduction One of the greatest challenges of the present time is to evolve strategies for the utilisation of the large amounts of building and industrial wastes that are the result of the development of modern society. Whether the waste originates from natural disasters or from human controlled activities, utilisation of the waste by recycling will provide opportunities for saving energy, time and resources. In particular, wherever a combined project involving demolition and new construction is begun, the recycling of large amounts of building waste at the work site or nearby becomes easy and economical if a suitable waste management approach is followed. At present, a very limited amount of building waste is recycled, the major portion being deposited or used as ®ll material (Biojen 1996). With the increase in construction activities and shortage of suitable land®ll sites, building waste is becoming a serious problem forcing professionals and researchers to focus on
Received: 27 September 2000 / Published online: 22 June 2001 Ó Springer-Verlag 2001 A. Masood (&), T. Ahmad, M. Arif, F. Mahdi Civil Engineering Department, A.M.U., Aligarh-202 002, India

the reuse of building waste in construction. From the purely economic point of view, recycling of building waste can only be attractive when the recycled product is competitive with the natural resources in relation to cost and quality. Recycled material will generally be competitive where there is a shortage of both raw materials and suitable deposit sites. With the use of recycled material, economic savings may also be achieved in the cost of transportation of building waste and raw materials without any compromise in the quality of the end product. Estimates of demolished concrete in European Countries and the U.S.A. each year are close to 100 million tonnes (Kishore 1996). In these countries recycling of debris has already been started due to lack of disposal sites and strict anti-pollution laws. As per the survey conducted by the European Demolition Association (EDA) (Buchner and Sholten 1992), quite a large number of recycling plants are in operation in many European countries (Singh and Sharma 1998). A similar estimate of quantity of concrete discharged in Asia each year would also reveal a staggering ®gure. Although the problem in other parts of the world is not as alarming as in the West, it will not be long before these countries may also have to think seriously of reusing demolished concrete for the production of recycled concrete. A total system for recycling, considering aspects such as identi®cation of source, collection of construction waste and aggregate preparation, therefore, has to be developed, followed by mix design, proper construction techniques and design methods to obtain strong and durable concrete structures. Investigations carried out earlier indicate a positive and encouraging trend towards utilisation of recycled aggregate for construction purposes, especially for pavements of all types (Singh and Sharma 1998). However, some reservations have been expressed with regard to certain properties of recycled aggregate and recycled aggregate concrete when it is used for structures (Kishore 1996). Comprehensive work is in progress to overcome these reservations and to form a code of practice to be used as guidelines for the utilisation of recycled aggregate for construction purposes (Kishore 1996). A signi®cant amount of experimental work has been carried out during the last three decades to investigate the properties of recycled aggregate concrete (Graf 1973; Buck 1977; Frondistou 1977). More recently the performance of quarry waste as ®ne aggregate in concrete has also been studied (Babu 1996). The water absorption of coarse recycled aggregates increases with decrease in size of the aggregates regardless of the original concrete (Hansen and Narud


Environ Eng Policy 3 (2002)


1983). The experimental investigations indicate a prospective future use of recycled concrete (Masood et al. 1998). Some of the potential areas of application of recycled material are given in Table 1. With the price of the cement soaring, a reduction in its consumption will substantially reduce the cost of construction, save energy used in the manufacturing process and above all reduce the environmental hazard due to uncontrolled quarrying operations. The present investigation aims at assessing the strength of recycled concrete using partial replacement of cement and ®ne aggregate with demolished waste.

waste that is expected at the plant. The quality of the available debris is very important as it affects the quality of the recycled products and the possibilities of their use. Recycling plants have the following requirements (Hansen 1986; 1992; Gottfredsen and Thogerson 1994; Fergusan et al. 1995). ± A weighing bridge to weigh the debris received and the aggregate produced ± Suf®cient storage space to stock different type of debris and different grades of recycled aggregates produced ± Equipment for pre-processing the waste and to reduce large elements (hammers, hydraulic nippers, pressure jigs, etc.) ± Necessary handling equipment to feed the installation and for loading and unloading ± Equipment for preliminary sieving to eliminate earth, gypsum, sand etc. before the material is fed into the crusher ± A primary crusher, generally a Jaw crusher ± An electromagnetic system for separating steel pieces from the debris ± Sieving equipment for separating aggregates less than 4.75 mm in size ± A secondary crushing and sieving installation for further reduction of aggregates to the required size and for splitting them into different fractions.

Terminology The Building Contractors Society of Japan in its comprehensive report has de®ned various terms used for recycled aggregate and recycled aggregate concrete (Anon 1981). In the present paper the following have been used: Conventional concrete Concrete produced with natural sand as ®ne aggregate and gravel or crushed rock as coarse aggregate. Recycled concrete Concrete produced by partially replacing cement with demolished waste hereafter referred to as cement replaced concrete. Recycled aggregate concrete Concrete produced by partially replacing ®ne aggregate with demolished waste hereafter referred to as ®ne aggregate replaced concrete.

Experimental investigations As a part of a comprehensive experimental programme, compressive, ¯exural and split tensile strengths were determined of concrete using demolished waste as a partial Recycling operation of building waste replacement of cement to obtain recycled concrete. Similar The recycling of building waste after a disaster or demo- tests were also carried out using demolished waste as a lition of old structures seems a feasible solution in reha- partial replacement of ®ne aggregate to obtain recycled bilitation or new construction. For planning and aggregate concrete. A nominal mix of 1:2:4 was used with a dimensioning of the recycling process and plant, it is water cement ratio of 0.5. Tests were also carried out to necessary to know the quantity and quality of the building ascertain the properties of the constituents.

Table 1. The potential areas of application of recycled materials

Recycled material Crushed concrete

Use As aggregate

Areas of application ± ± ± ± ± ± ± Concrete roads and aprons Drainage work Shallow storage tanks R.CC pipes and culverts Sewage/water treatment plants Permeable backing to earth retaining structures Bedding materials to reinforced concrete structures Building partition walls Floors and foundation Garbage/refuse disposal plant Base course materials in pavements Runways, taxiway and aprons Parking lots and other yards Cable trenches

Crushed concrete/brick Crushed concrete Crushed concrete/brick Crushed concrete/brick or recycled aggregate (<4.75 mm) As aggregate in new asphalt As unbound base course As ®ll material

± ± ± ± ± ± ±

A. Masood et al.: Waste management strategies for concrete

concrete (partially replacing ®ne aggregate by demolished waste) 150-mm cubes, 150-mm´300-mm cylinders and 500-mm´100-mm´100-mm beams were cast along with parallel specimens in conventional concrete. The specimens were cured for 28 days under wet gunny bags. The compressive strength of cubes was determined at a loading rate of 14 N/mm2/min on a 2,000 kN compression testing machine. For the split tensile strength, cylinders were tested on the same machine. The beams were tested under two point load condition to simulate a pure ¯exure state in a 500-kN universal testing machine. Six replications were used for each test and the average values were taken. The test results of the specimens are presented in Tables 2±5 and shown in Fig. 1.


Fig. 1. Comparison of stress strain curves of different cubes

Constituents Conventional concrete was made with ordinary Portland cement (43 grade), natural sand and crushed stones of 20 mm maximum size. A water:cement ratio of 0.5 was adopted for casting all the specimens. The ®neness modulus of ®ne and coarse aggregate was found to be 2.18 and 6.4, respectively. The silt content of the ®ne aggregate was 2.5%. The source of demolished waste was the site of a demolished 90-year old school building. Demolished waste collected from the site mainly comprised lime concrete and lime mortar. The waste was transported, crushed and tested in the laboratory for its impurities, chemical con- Concluding remarks stituents, and then proper sizing of the material was ob- Recycling and reuse of building waste has been found to be an appropriate solution to the problems of dumping tained by sieving through a set of sieves. hundreds of thousands of tons of debris and hauling natural aggregates from a great distance. These materials Testing have proven to be valuable building materials on technical, For determining the compressive, splitting tensile and ¯exural strength for recycled concrete (partially replacing environmental and economic grounds. The strengths obcement by demolished waste) and for recycled aggregate tained justify to a certain extent the use of such materials.
Table 2. Properties of different types of concrete (DW demolished waste, CR cement replaced, FAR fine aggregate replaced, CC conventional concrete)

Test results and discussions The 28-day compressive strengths of cubes with 20% replacement and similarly 20% ®ne aggregate replacement by demolished waste are close to each other and are between 75 and 77% of that of conventional concrete cubes. The stress±strain curves of different cubes are shown in Fig. 1. The workability of the concrete decreases with increase in the quantity of demolished waste. The slump and compaction factor test results for both conventional and recycled concrete are reported in Table 2. The secant modulus of elasticity of recycled concrete and recycled aggregate concrete are tabulated in Table 3. The 28-day ¯exural strength retention of the two recycled concretes as shown in Table 4 are close to the ¯exural strength of conventional concrete. The 28-day split tensile strength of cylinders with 10% and 20% cement replaced is between 83 and 90% of that of conventional cylinder split tensile strength as shown in Table 5. A comparison of the strength and economy of recycled concrete with 20% cement replacement by demolished waste indicates a cost saving of 15%. The results for recycled aggregate concrete indicate that demolished concrete waste might be a satisfactory replacement for natural aggregates from the point of view of the major properties of concrete. The results are in close agreement with those reported earlier (Masood et al. 1998).

Type of concrete Cement concrete Recycled concrete

Designation DW (CC) CR concrete CR concrete CR concrete FAR concrete FAR concrete FAR concrete

Average compressive Compaction factor Slump (mm) stress (N/mm2) 27.40 21.40 20.40 13.20 22.20 21.20 20.40 0.914 0.898 0.895 0.893 0.908 0.902 0.900 6 2 0 0 3 0 0

0% 10% 20% 30% Recycled aggregate 10% concrete 20% 30%

Environ Eng Policy 3 (2002)

Table 3. Modulus of elasticity of different types of concrete (DW demolished waste, CR cement replaced, FAR fine aggregate replaced, CC conventional concrete)

Type of concrete Conventional concrete Recycled concrete


Modulus of Maximum Stress at 33% Strain at 33% Modulus of elasticity ´10±4 elasticity of max. of max. stress stress ratioa (N/mm2) stress (N/mm2) 9.13 7.13 6.80 4.40 7.40 7.06 6.80 1.5 1.3 1.6 1.3 1.8 1.5 1.4 0.608 0.548 0.425 0.338 0.411 0.470 0.485 1.000 0.901 0.692 0.561 0.676 0.773 0.804

0% DW (CC) 27.40 CR CR CR FAR FAR FAR 21.40 20.40 13.20 22.20 21.20 20.40


10% 20% 30% 10% Recycled aggregate 20% concrete 30%


Taken with respect to 0% DW Babu KK (1996) Performance of quarry waste as fine aggregate in concrete. In: Proceedings of International Seminar on Civil Engineering Practices in the Twenty First Century, Roorkee, India, vol 2, pp 926±934 Biojen J (1996) Waste materials and alternative products: pro's and con's. In: Concrete for environment enhancement and protection. E & FN Spon, London, pp 587±598 Buchner S, Sholten LJ (1992) Demolition and construction debris recycling in Europe. European Demolition Association (EDA) Buck AD (1977) Recycled concrete as a source of aggregate. ACI J 74(5):212±219. Fergusan J, Kermode ON, Nash CL, Sketch WAJ, Huxford RP (1995) Managing and minimizing construction waste. Institution of Civil Engineers, Thomas Telford Publications, London, pp 1±60 Frondistou YS (1977) Waste concrete as aggregate for new concrete. ACI J 74(8):373±376 Gottfredsen FR, Thogerson F (1994) Recycling of concrete in aggressive environment, demolition and reuse of concrete and masonry. RILEM Proc 23:309±317 Graf O (1973) Crushed brick concrete, sand stone concrete and rubble concrete. U.S. army engineer water ways experiment station, Translation no.73±1, Viksburg Hansen TC (1986) Recycled aggregate and recycled concrete aggregate. Second state of art report, development 1945±1985. RILEM TC ± DRC, Mater Struct 19(3):201±248 Hansen TC (1992) Recycling of demolished concrete masonry. RILEM report no. 6. E & FN Spon, London, pp 316 Hansen TC, Narud H (1983) Strength of recycled concrete made from crushed concrete coarse aggregate. Concrete Int ±Design Constr 5(1):79±83 Kishore R (1996) Recycled concrete± an alternative material of the twenty first century for construction, Proceedings of International Seminar on Civil Engineering Practices in the Twenty First Century, Roorkee, India, vol 2, pp 964±973 Masood A, Ahmad T, Ghani F, Rawat DS (1998) Variation in strength of concrete on addition of demolished waste. ICJ, pp 395±399 Singh SK, Sharma PC (1998) Recycling and use of building waste in constructions±A review. In: All India Seminar on Concrete for Infrastructural Development, pp 317±329

Table 4. Flexural strength retention of different types of concrete

Type of concrete Cement concrete Recycled concrete

Percentage of demolished waste 0

Flexural strength (N/mm2) 4.80 4.40 4.25 4.00 4.60 4.45 4.30

Percentage strength retained 100.00 91.67 88.54 83.00 95.83 92.70 89.50

10 20 30 Recycled aggre- 10 gate concrete 20 30

Table 5. Splitting tensile strength of different types of concrete


Percentage of demolished waste 0 10 20 30

28-day strength (N/mm2) 4.81 4.30 4.00 2.37


However, more research and ®eld experimentation is needed for modifying the design procedures and speci®cations for adopting recycled concrete and recycled aggregate concrete in construction.


Anon (1981) Proposed standards for the use of recycled aggregate and recycled aggregate concrete. Building contractors society of Japan, Committee on disposal and reuse of construction waste (translated into English)

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