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Special Concrete & its Types………… | Concrete Civil Engineering

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Special Concrete & its Types…………

Introduction

  • Special types of concrete are those with out-of-the-ordinary properties or those produced by unusual techniques. Concrete is by definition a composite material consisting essentially of a binding medium and aggregate particles, and it can take many forms.
  • These concretes do have advantages as well as disadvantages.

 

 

Types of Special Concrete

  1. High Volume Fly Ash Concrete
  2. Silica Fume Concrete
  3. GGBS, Slag Based Concrete
  4. Ternary Blend Concrete
  5. Light Weight Concrete
  6. Polymer Concrete
  7. Self Compacting Concrete
  8. Colored Concrete
  9. Fiber-Reinforced Concrete
  10. Previous Concrete
  11. Water-Proof Concrete
  12. Temperature Controlled Concrete

 

 

High Volume Fly Ash Concrete

  • Is used replace a portion of the Portland cement used in the mix.
  • According to IS: 456-2000 replacement of OPC by Fly-ash up to 35% as binding material is permitted.
  • HVFAC is a concrete where excess of 35% of fly-ash is used as replacement.

 

 

Silica Fume Concrete

  • Very fine non-crystalline silica produced in electric arc furnaces as a byproduct.
  • Highly reactive pozzolan used to improve mortar and concrete.
  • Silica fume in concrete produces two types of effect viz.
  1. Physical Effect
  2. Chemical Effect

 

 

GGBS, Slag based Concrete

  • By-product of the iron manufacturing industry, replacement of Portland cement with GGBS will lead to significant reduction of carbon dioxide gas emission.
  • GGBS powder is almost white in color in the dry state. Fresh GGBS concrete may show mottled green or bluish-green areas on the surface mainly due to the presence of a small amount of sulphide.
  • Due to its longer setting time, it can be transported to distant places but care should be taken while casting because there are chances that bleeding may take place.

 

 

Ternary Blend Concrete

  • Ternary concrete mixtures include three different Cementitious materials i.e. combinations of Portland cement, slag cement, and a third Cementitious material. The third component is often fly ash, but silica fume is also common.
  • Other material in combination with Portland and slag cement, such as rice husk ash are not currently in common usage.

 

 

Light Weight Concrete

  • Structural lightweight concrete is similar to normal weight concrete except that it has a lower density.
  • Made with lightweight aggregates.
  • Air-sry density in the range of 1350 to 1850 kg/m3.
  • 28 days compressive strength in excess of 17 Mpa.

 

 

Polymer Concrete

  • Polymer concrete is part of group of concretes that use polymers to supplement or replace cement as a binder. The tires include polymer-impregnated concrete, polymer concrete, and Polymer-Portland-Cement concrete.
  • Polymer concrete may be used for new construction or repairing of old concrete.
  • It can also be used as a replacement for asphalt pavement, for higher durability and higher strength.
  • Polymer concrete is also composed of aggregates that include silica, quartz, granite, limestone, and other high quality material.

 

 

Self Compacting Concrete

  • Self-compacting concrete is an innovative concrete that does not require vibration for placing and compaction. It is able to flow under its own weight, completely filling formwork and achieving full compaction, even in the presence of congested reinforcement.
  • The hardened concrete is dense, homogeneous and has the same engineering properties and durability as traditional vibrated concrete.

 

 

Colored Concrete

  • Colored concrete can be produced by using colored aggregates or by adding color pigments or both.
  • It surfaces are to be washed with acid, a delay of approximately two weeks after costing is necessary.
  • Synthetic pigments generally give more uniform results.
  • The amount of color pigments added to a concrete mixture should not be more than 10% of the mass of the cement.

 

 

Fiber Reinforced Concrete

  • The role of randomly distributes discontinuous fibers is to bridge across the cracks that develop provides some post-cracking “ductility”.
  • The real contribution of the fibers is to increase the toughness of the concrete under any type of loading.
  • Fiber reinforced concrete may be defined as a composite materials made with Portland cement, aggregate, and incorporating discrete discontinuous fibers.

 

 

Previous Concrete

  • Low water-cement ratio, low-slump concrete resembling popcorn held together by cement paste.
  • Produces a concrete with a high volume of voids and a high permeability that allows water to flow through it easily.
  • Previous concretes have also been used in tennis courts and greenhouses.

 

 

Previous Concrete

  • Low water-cement ratio, low-slump concrete resembling popcorn held together by cement paste.
  • Produces a concrete with a high volume of voids and a high permeability that allows water to flow through it easily.
  • Previous concrete is used in hydraulic structures as drainage media, and in parking lots, pavements, and airport local groundwater supply by allowing water to penetrate the concrete to the ground below.

 

 

Water-Proof Concrete

  • Top proof waterproof concrete contains two specially formulated admixtures. The first reduces the water/cement ratio, increasing the density of the mix and minimizing the size of the pores. The second fills the remaining pores ensuring a completely watertight finish. This means there is no need for external membranes, reducing cost and labour.

 

 

Mass Concrete

  • Mass concrete includes not only low-cement –content concrete used in dams and other massive structures but also moderate to high cement content concrete in structural members of bridge and buildings.
  • As the interior concrete increases in temperature and expands, the surface concrete may be cooling and contracting.
  • The width and depth of cracks depends upon the temperature differential, physical properties of the concrete, and the reinforcing steel.

 

 

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