The Experimental Research Of Sulfate Attack Resistance Of Concrete

Concrete sulfate attack is always an important part of concrete durability research.With the exploitation of the West China,the demand of resistance to the sulfate attack of the concrete is urgent.But until now,in China there is no experiment method to disclose the mechanism of the sulfate attack,especially for the use of forecasting the performance of concrete undergoing the sulfate attack.Therefore,it is very urgent to do further study on the subject of sulfate attack.This paper study is part of the western traffic science and technological project "research of durable performance of bridge concrete and tracking technology".According to the requirements of the project,the following research works have been carried out:(1) The research of sensibility of several indexes to valuate the performance of concrete in different solutionFor the specimen in 5%Na₂SO₄ and MgSO₄,some indexes are tested including the press strength,the flexural strength,the loss of mass and the loss of dynamic modulus of elasticity.The study shows that:the attack in Na₂SO₄ solution is severer than that in MgSO₄ solution in the same condition.For the attack in Na₂SO₄ solution,the flexural strength,the press strength and the loss of dynamic modulus of elasticity is more proper than the loss of mass;For attack in MgSO₄,the flexural strength,the press strength and the lose of dynamic modulus of elasticity is not suitable to describe the sulfate attack;the loss of mass can indicate the decomposition of the C-S-H,but it is not very sensitive.(2) The effect of the concentration on the course of attack;Increasing the concentration of the solution can accelerate the pace of the sulfate attack. For the long-term immersion,the press strength decreases quickly,while the flexural strength, the loss of dynamic modulus of elasticity and the loss of mass are not sensitive.For dry-wetting cycles,with the increasing of concentration,all the indexes decrease quickly including the flexural strength,the press strength,the loss of dynamic modulus of elasticity as well as the loss of mass.(3) The effect of different water cement ratio,cement amount,fly ash amount on the attack courseThrough the research of specimen with three kind of water cement ratios,three kind of cement amount,three kind of fly ash amount,it can shows that:The larger the water cement ratio is,the larger the pace of attack is.The cement amount of the concrete has little effect on the sulfate attack.The fly ash amount of the concrete can improve the performance of sulfate attack resistance of concrete.So in order to improve the performance of sulfate resistance,we can decrease the water cement ration.