On the Rice Husk Ash Admixing with Cement: Preparation, Characterization and Analysis

On the Rice Husk Ash Admixing with Cement: Preparation, Characterization and Analysis

ABSTRACT

Rice husk is the outermost part of rice paddy, it covers about 20 to 25 % of the rice weight. Rice husk can be converted into rice husk ash (RHA) by burning process. The chemical composition of rice husk is found to vary from one sample to another due to the differences in the type of paddy, crop year, climate and geographical conditions.^[1]

Cement is a binder, a substance used in construction that sets, hardens and adheres to other materials, binding them together.^[2] Cements are classified as calcium silicate and calcium aluminate cement. Calcium silicate cement is further classified into Portland and Slag, while calcium aluminate is classified into High alumina and Pozzolona cement.^[3]

Portland cement is by far the most common type of cement in widespread use around the world. This cement is made by calcining limestone (CaCO₃) with other materials (such as clay) to 1450 °C in a kiln. Calcium oxide, so formed is then chemically fluxed with the other materials to form calcium silicates and other cementitious compounds. The resulting clinker is ground with a small amount of gypsum into a powder to make 'ordinary Portland cement', the most commonly used type of cement (often referred to as OPC).

Rice husk ash (RHA) fulfils the physical characteristics and chemical composition of mineral admixtures. RHA is composed mostly of silica in amorphous form (85-90%) and it has a highly micro-porous structure which makes it suitable to replace cement.

In the present work, rice husk ash is prepared and characterized. A varied percentage of RHA is used as an admixture with ordinary Portland cement in concrete to formulate samples. Further, compressive and flexural strength parameters of concrete are determined by Vicat test, float test, compression test and initial & final setting times. It has been found that rice husk ash substitution for ordinary Portland cement up to 30% is acceptable. On increase in RHA percentage, compressive strength decreases rapidly.

References

[1] Chandrasekhar S, Satyanarayan KG, Pramada PN and Raghavan P. Review processing, properties and applications of reactive silica from rice husk-an overview. Journal of Materials Science (Norwell), 2003; 38(15):3159 - 3168.

[2] https://en.wikipedia.org on 11 April 2017.

[3] Jackson, N. and Dhir, R.K., Civil Engineering Materials, 4th Edition, Macmillan ELBS, Hong Kong, 1991; pp 144 –160.