31-05-2012, 03:36 PM
ECO-FRIENDLY RICE HUSK ASH CONCRETE
ECO-FRIENDLY RICE HUSK ASH CONCRETE.doc (Size: 264.5 KB / Downloads: 311)
ABSTRACT:
Concrete is the most commonly used construction material. The demand for concrete is increasing rapidly due to many constructional projects. As we are in modern era we cannot stop up to this, latest development is the admixtures. Lots of research is done on several admixtures which imparts strength, durability and workability to concrete. The paper is about one of such admixtures, Rice Husk Ash (RHA).
RHA makes concrete stronger and resistant to corrosion. RHA is produced on combustion of Rice Husk, which is available plenty in southern Asia. But combustion produces lot of carbon dioxide which adversely effects the ecosystem. The paper discusses about the best methods of producing RHA from Rice Husk with minimum emission of carbon dioxide.
INTRODUCTION:
Concrete occupies a unique position among modern construction materials. It is the only material manufactured at construction sites. It gives considerable freedom to the architect to mould the structural element to any shape or form, a freedom which is not possible with other materials.
Now a days, performance expectations from concrete structures are more demanding. As a result concrete is required to have properties like high fluidity, self compactability, high strength, high durability, better serviceability and long service life. This increasing demand for producing durable construction materials is the outcome of the fast polluting environment. Supplementary cementitious materials prove to be effective to meet most of the requirements of durable concrete.
RHA IN CONCRETE:
Blending of reactive RHA in concrete has become a common recommendation almost in all the international building codes. Owing to its technical and economical advantages, it has gained its importance.
ADVANTAGES OF RHA IN CONCRETE:
The use of RHA in concrete has been associated with the following essential assets:
- Increased compressive and flexural strengths
- Reduced permeability
- Increased resistance to chemical attack
- Increased durability
- Reduced effects of alkali-silica reactivity
- Reduced shrinkage due to particle packing, making concrete denser
- Enhanced workability of concrete
- Reduced heat gain through the walls of buildings
- Reduced amount of super plasticizer
- Reduced potential for efflorescence due to reduced calcium hydracids several improvements for the concrete characteristics.
WORKABILITY:
RHA particles have the highest surface area and fineness and lower reaction ability than cement. RHA particles fill into the spaces made by larger cement particle, decrease frictional forces of RHA-ordinary Portland cement (OPC) system and improve packing ability thereby reducing yield stress. The steep increase in plastic viscosity with the replacement levels suggests that fineness and shape of RHA play critical role. The more the fineness the more is the number of contacts among the particles and hence the more is the resistance to flow.