Durability of conventional concretes containing black rice husk ash

In this study black rice husk ash (BRHA) from a rice mill in Thailand was ground and used as a partial cement replacement The durability of conventional concretes with high water binder ratios was investigated including drying shrinkage autogenous shrinkage depth of carbonation and weight loss of concretes exposed to hydrochloric (HCl) and sulfuric (H2SO4) acid attacks Two different replacement percentages of cement by BRHA 20% and 40% and three different water binder ratios (0 6 0 7 and 0 8) were used The ratios of paste volume to void content of the compacted aggregate (gamma) were 12 1 4 and 1 6 As a result when increasing the percentage replacement of BRHA the drying shrinkage and depth of carbonation reaction of concretes increased However the BRHA provides a positive effect on the autogenous shrinkage and weight loss of concretes exposed to hydrochloric and sulfuric acid attacks In addition the resistance to acid attack was directly varied with the (SiO2 + Al2O3 + Fe2O3)/CaO ratio Results show that ground BRHA can be applied as a pozzolanic material and also Improve the durability of concrete (C) 2010 Elsevier Ltd All rights reserved