The Research On The Damage Of Concrete Under The Salt Scaling

Durability is one of the most important properties index to evaluating the quality of the concrete. But the sulphate attack has been become one of the serious problems for years which is unfavorable to durability of the concrete. Though a lot of original achievements and experiences has been proposed with the thorough research, there are still many unsloved by now. Some hydro-junction of concrete project not only destroyed by chemical attack but aslo suffered the fator of the freezing and thawing cycle in part of northwest of our country. The situation of destruction in concrete is very seriously. Combined with the Yindaruqin project,re-Srarched experimentally western,on the effect of salt and freeze-thaw,to explore its performance,and provided a basis.The freezing resistance of concrete in water and 5% bitter salt(Mg₂SO₄) solution were researched. The effects of the substitution ratio of concrete by fly ash,air content and sand ratio and water binder ratio on the strength of the concrete and freezing resistance of concrete were investigated. The mechanism of sulphate attack in concrete is elucidated through analyzing its reaction types. The damage model of apparent injury about concrete is proposed. In this paper, we obtain the following results:(1) With the increasing the ratio of the fly ash,the freezing resistance of concrete was improved, early stage strength of concrete was declined,but the later stage strength of concrete was good. The concrete was replaced by 25% fly ash which was good for the freezing resistance of concrete;(2) In the same substitution ration of cement by fly ash, drawing-in proper air could stave the receding of the relative dynamic modulus of elasticity, but it has bad effect on the strength of the concrete;(3) The strength of the concrete and the freezing resistance of concrete is declined by increasing the water binder ratio,but the proper sand ratio could improved the salt-frost resistance of concrete when the concrete have the same water binder ratio.(4) The mechanism of sulphate attack in concrete is investigated and the three stages are proposed by the apparent damage of concrete. The three stages are induction period, attenuation period, failure period.