Compressive Strength Loss Weight Loss and Expansion of Concrete Containing Ground Black Rice Husk Ash and Silica Fume under Sulfate Solution Attacks

Abstract

The objective of this research was to study the influence of ground black rice husk ash (BRHA) andsilica fume on sulfate resistance of concrete. The tested properties consisted of physical and chemicalproperties of ground BRHA and silica fume, compressive strength loss, expansion and weight loss ofconcrete. The sulfate solutions were sodium sulfate (Na₂SO₄) and magnesium sulfate (MgSO₄) with theconcentration of 5% by weight in accordance with the ASTM C 1012 standard. The water-to-binder ratiosof concrete were 0.25, 0.35 and 0.45 and the percentage replacements of ground BRHA and silica fume inPortland cement Type I were 0 , 10 and 20 by weight of binder.

From the tested results of sodium sulfate attack, it was found that the compressive strength loss,expansion and weight loss of concrete decreased when increasing the percentage replacements of groundBRHA and silica fume. In the case of magnesium sulfate attack, it was observed that the rate of expansionand weight loss decreased when increasing the percentage replacements of ground BRHA and silica fume.On the other hand, the compressive strength of concrete due to magnesium sulfate attack increased whenincreasing the percentage replacements of silica fume, but decreased when increasing the percentagereplacements of ground BRHA. Furthermore, the rate of the compressive strength loss, expansion andweight loss of concrete due to sodium and magnesium sulfate attacks increased when increasing water-tobinderratios.

This research can be concluded that at the replacement levels of ground BRHA 20% by weight ofbinder and 0.25 water-to-binder ratios, the sulfate resistance of concrete including compressive strengthloss, expansion and weight loss were improved. Additionally, in the case of the economics, it was observedthat the cost of fineness ground BRHA was much lower than that of silica fume. Since the ground BRHAwas a by-product from agriculture and also friendly to the environment, therefore, the ground BRHA wassuitable material to be used as a pozzolanic material for sulfate resisting concrete.