Effect of rice-husk-ash admixture on the strength and workability of concrete

Abstract

For over two decades, rice-husk-ash has been discovered to be a highly reactive pozzolana and has been used to substitute a portion of the cement content in concrete mix in order to reduce the cost of concrete manufacture and environmental hazards posed by rice-husk in rice producing areas. This research focuses on the possibility of using rice-husk-ash as strength enhancement admixture in concrete. Rice-husk-ash was added in small percentages of 2, 4, 7, 10 and 12% to concrete mixtures. The workability was tested using slump test, while strength of the cubes after 28 days curing were obtained with a universal testing machine. The results showed that for concretes of medium workability the strength of the concrete containing RHA increased to 25% above the normal concrete of the same mix proportion at 7%. Further addition of RHA above 7% and below 10% reduced the workability very low but still good for mass concrete. Above 10%, improvement in strength ceased and the concrete became very dry. Based on the result of the tests, addition of 7% RHA by weight of cement will improve the strength of the concrete without appreciable change in the initial workability. In the case where the initial workability may be altered from medium to low workability, up to 10% RHA may be added. In other words RHA can be added to concrete mix up to 10% by weight of the cement content as long as the resulting change in the workability remains acceptable for the concreting work in question.

Keywords: Rice-husk-ash, admixture, Concrete strength, Workability