Durability of Cement Mortar Containing Black Rice Husk Ash under Sodium Sulfate and Magnesium Sulfate Attack

Abstract

The objective of this research was to study the durability of cement mortar containing blackrice husk ash (BRHA) under sulfate attack. In this study the BRHA obtained from electrical generatingpower plant using rice husk as fuel and from rice mill were ground for 240 minutes (the specificsurface area of BRHA from electrical generating power plant and rice mill equal to 4,780 and 5,760cm2/g respectively). The tested properties included expansion in term of length change and strengthloss. The variables studied were the percentage replacements of BRHA by weight in Portland cementtype I (0%, 10%, 30%, and 50%) and water-to-binder materials (w/b) ratios (Portland cement andBRHA) (0.55 and 0.65). The sodium sulfate (Na₂SO₄) and magnesium sulfate (MgSO₄) with theconcentration of 5% by weight in accordance with the ASTM C 1012 standard were used.

From the tested results of sulfate resistant property, it was found that the expansion (lengthchange) of specimens in sodium sulfate solution is more than those in magnesium sulfate solution.When the percentage replacements of BRHA in Portland cement increased, the rate of expansion ofcement mortars containing BRHA decreased. At the percentage replacements of BRHA in Portlandcement equal to 20% and 30%, it was found that the expansion of the mortars is smaller than thatmixed with sulfate-resistant cement. Whereas the rate of strength loss increased when those ofmortars were immersed in magnesium sulfate, the strength loss is more than those exposed insodium sulfate.