Published on March 2017 | Categories: Documents | Downloads: 38 | Comments: 0 | Views: 288
of 4
Download PDF   Embed   Report



Self-consolidating concrete or self-compacting
concrete (SCC) is characterized by a low yield, high deformability, and moderateviscosity necessary to

ensure uniform suspension of solid particles during transportation, placement (without external compaction), and
thereafter until the concrete sets.
Such concrete can be used for casting heavily reinforced sections, places where there can be no access
to vibrators for compaction and in complex shapes of formwork which may otherwise be impossible to cast, giving a
far superior surface than conventional concrete. SCC was conceptualized in 1986 by Prof. Okamura at Ouchi
University, Japan.
The first generation of SCC used in North America was characterized by the use of relatively high content of binder
as well as high dosages of chemicals admixtures, usually superplasticizer to enhance flowability and stability. Such
high-performance concrete had been used mostly in repair applications and for casting concrete in restricted areas.
The first generation of SCC was therefore characterized and specified for specialized applications.
The relatively high cost of material used in such concrete continues to hinder its widespread use in various segments
of theconstruction industry, including commercial construction, however the productivity economics take over in
achieving favorable performance benefits and works out to be economical in pre-cast industry. The incorporation of
powder, including supplementary cementitious materials and filler, can increase the volume of the paste, hence
enhancing deformability, and can also increase the cohesiveness of the paste and stability of the concrete. The
reduction in cement content and increase in packing density of materials finer than 80 µm, like fly ash etc. can reduce
the water-cement ratio, and the high-range water reducer (HRWR) demand. The reduction in free water can reduce
the concentration of viscosity-enhancing admixture (VEA) necessary to ensure proper stability during casting and
thereafter until the onset of hardening. It has been demonstrated that a total sand content of about 50% of total
aggregate is favorable in designing for SCC.
The major breakthrough in SCC technology came with the advent of third generation poly-carboxylic ether based
polymers, used as admixtures. The further developments were subsequent with introduction of VEA, to improve
stability without undue increase in binder, which could cause plastic shrinkage of concrete.

Hycrete is a water-based concrete admixture that reduces water absorption and moisture vapor transmission and
inhibits corrosion of steel reinforcement in concrete. Hycrete admixtures are used in multi-family residential,
commercial, industrial, and infrastructure applications to waterproof concrete structures, protect flooring systems from
moisture-related failures and enhance concrete durability and corrosion protection.
Hycrete admixtures are engineered to reduce water absorption and moisture vapor transmission in concrete and
protect steel reinforcement from corrosion.
Hycrete admixtures are used in infrastructure applications to protect concrete from sulfate degradation.

Silica fume
Silica fume, also known as microsilica, (CAS number 69012-64-2, EINECS number 273-761-1) is
an amorphous (non-crystalline) polymorph of silicon dioxide, silica. It is an ultrafine powder collected as a by-product

of the silicon and ferrosilicon alloy production and consists of spherical particles with an average particle diameter of
150 nm. The main field of application is as pozzolanic material for high performance concrete.
It is sometimes confused with fumed silica (also known as pyrogenic silica, CAS number 112945-52-5, EINECS
number 231-545-4). However, the production process, particle characteristics and fields of application of fumed silica
are all different from those of silica fume.

Silica fume is added to Portland cement concrete to improve its properties, in particular its compressive
strength, bond strength
Addition of silica fume also reduces the permeability of concrete to chloride ions, which protects the reinforcing
steel of concrete fromcorrosion, especially in chloride-rich environments such as coastal regions and those of humid
continental roadways and runways
Silica fume also blocks the pores in the fresh concrete so water within the concrete is not allowed to come to the

Fly ash
Fly ash, also known as flue-ash, is one of the residues generated in combustion, and comprises the fine
particles that rise with the flue gases. Ash which does not rise is termed bottom ash. In an industrial context, fly ash
usually refers to ash produced during combustion of coal. Fly ash is generally captured by electrostatic precipitatorsor
other particle filtration equipment before the flue gases reach the chimneys of coal-fired power plants, and together
with bottom ash removed from the bottom of the furnace is in this case jointly known as coal ash. Depending upon
the source and makeup of the coal being burned, the components of fly ash vary considerably, but all fly ash includes
substantial amounts of silicon dioxide (SiO2) (both amorphous andcrystalline) and calcium oxide (CaO), both being
endemic ingredients in many coal-bearing rock strata.

Class F fly ash[edit source | editbeta]
The burning of harder, older anthracite and bituminous coal typically produces Class F fly ash. This fly ash
is pozzolanic in nature, and contains less than 20% lime (CaO)

Class C fly ash[edit source | editbeta]
Fly ash produced from the burning of younger lignite or subbituminous coal, in addition to having pozzolanic
properties, also has some self-cementing properties. In the presence of water, Class C fly ash will harden and gain
strength over time. Class C fly ash generally contains more than 20% lime (CaO).

The ways of fly ash utilization include (approximately in order of decreasing importance):

Concrete production, as a substitute material for Portland cement and sand

Grout and Flowable fill production

Waste stabilization and solidification

Cement clinkers production - (as a substitute material for clay)

Mine reclamation

Stabilization of soft soils

Road subbase construction

As Aggregate substitute material (e.g. for brick production)

Mineral filler in asphaltic concrete

Embankments and other structural fills (usually for road construction)

Geopolymers are new materials for fire- and heat-resistant coatings and adhesives, medicinal applications, hightemperature ceramics, new binders for fire-resistant fiber composites, toxic and radioactive waste encapsulation and
new cements for concrete. Polymers are either organic material, i.e. carbon-based, or inorganic polymer, for example
silicon-based. The organic polymers comprise the classes of natural polymers (rubber, cellulose), synthetic organic
polymers (textile fibers, plastics, films, elastomers, etc.) and natural biopolymers (biology, medicine, pharmacy.
a geopolymer is essentially a mineral chemical compound or mixture of compounds consisting of repeating units, for
example silico-oxide (-Si-O-Si-O-), silico-aluminate (-Si-O-Al-O-), ferro-silico-aluminate (-Fe-O-Si-O-Al-O-) or
alumino-phosphate (-Al-O-P-O-), created through a process of geopolymerization.

Low-tech building materials (clay bricks),
Low-CO2 cements and concretes;

Ground granulated blast-furnace slag
GGBS is used to make durable concrete structures in combination with ordinary portland cement and/or
other pozzolanic materials. GGBS has been widely used in Europe, and increasingly in the United States and in Asia

(particularly in Japan and Singapore) for its superiority in concrete durability, extending the lifespan of buildings from
fifty years to a hundred years.
Use of GGBS significantly reduces the risk of damages caused by alkali–silica reaction (ASR), provides higher
resistance to chlorideingress — reducing the risk of reinforcement corrosion — and provides higher resistance to
attacks by sulfate and other chemicals.

Durability[edit source | editbeta]
GGBS cement is routinely specified in concrete to provide protection against both sulphate attack and chloride attack.
GGBS has now effectively replaced sulfate-resisting Portland cement (SRPC) on the market for sulfate resistance
because of its superior performance and greatly reduced cost compared to SRPC.

Energetically modified cement
Energetically modified cements (EMC) arecementitious materials made from pozzolans (e.g. fly ash, volcanic
ash, pozzolana) as well as silica sand andblast furnace slag (and their blends)
This permits:

Performance improvement across a broad range of applications;[3]

Environmental considerations — with energy andcarbon dioxide (CO2) savings, without noxious emissions;[4]

Sustainability benefits — requiring less water, and providing better durability.[5][

All concretes comprising energetically modified cements are highly durable: any cementitious material undergoing
EMC Activation will likely marshal improved durability concretes — including concretes made with Portland cement
treated with EMC Activation.

Sponsor Documents

Or use your account on


Forgot your password?

Or register your new account on


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

Back to log-in