A.A Ramezanianpour - Professor of Concrete Technology and Durability Research Center, Department of Civil Engineering Amirkabir University of Technology, Tehran, Iran
P Pourbeik - MSc Student, Department of Civil Engineering, Amirkabir University of Technology,Tehran,Iran.
F Moodi - Assistant Professor of Concrete Technology and Durability Research Center,Department of Civil Engineering Amirkabir University of Technology, Tehran, Iran.

Deterioration of concrete structures in sulfate environments is a well-known phenomenon.Cement chemistery is an important parameter in coping with sulfate attack.C3A and Ca(OH)2 leading to expansion ,cracking and strength reduction.The use of pozzolans such as fly ash,silica fume,natural pozzolans and rice husk ash(RHA) can improve the sulfate resistance of concrete.It was observed that the sulfate resistance of blended cements were significantly higher in sulfate environments.This study investigates the effect of RHA replacing by cement on the durability of concrete due to sulfate attack.Three RHA replacement levels were considered in the study which are 7%,10% and 15% by weight of cement.After specified initial moist curing period(28 days) concrete specimens were immersed in sodium sulfate & magnesium sulfate solution.The degree of sulfate attack was evaluated by measuring compressive strength reduction of concrete cubes and their weight losses.Expansion observed in ordinary Portland cement mortar prisms were larger than expansion that for RHA mortar prisms when tested according to ASTM C 1012.Sulfate performance of concrete depends primarily on permeability. RHA replacement of cement is understood to reduce the rate of diffusion of aggressive ions such as sulfates.

RHA, Sulafe attack, Durability, Expansion