The Influence Of Additives On Transport Properties Of Chloride In Concrete

With the rapid development of the construction industry, the concrete is still the most commonly used as a building material. Because of the more strict requirements for concrete performance of modern architectural engineering,the durability of ordinary concrete has been unable to meet the actual needs of the project. However, the high performance concrete as a new type of concrete can meet the requirements of people on the durability of various harsh environments. The rapid development of high performance concrete makes mineral admixture has been widely used in practical engineering. Fly ash and slag as admixture added in the concrete, it not only save cost, protect the environme nt, but also can improve the durability of concrete. Therefore, study on the admixture of concrete has significant environmental benefits, economic benefits and social benefits.In this paper The chloride diffusion coefficient of concrete is determined by RCM method and the impact of mineral admixture type and dosage of concrete resistance to chloride ion penetration is analyzed. The results show that Effect of slag on reducing the chloride ion permeability coefficient is greater than that of fly ash in the same cementitious system. By using different concentrations of sodium chloride solution and calcium chloride solution, as well as saturated lime water soaked mortar specimens and testing porosity of mortar after a certain age, the reasons for the change of porosity of mortar are analyzed based on this point of that contains chlorine salt crystal ization,The dissolution of calcium hydroxide and Friedel's salt in this paper. The conclusion shows that mineral admixtures can reduce the dissolution of calcium hydroxide and the porosity change caused by calcium hydroxide solution decreases with the increase of minera l admixtures. In addition, The free chloride concentration and total chloride ion concentration of the cement mortar specimens were tested after soaking in Sodium chloride solution and effect of the dosage of mineral admixture on chloride binding capacity is studied. The result shows that the chloride binding capacity of mortar is improved with the increase of the content of mineral admixture. Finally, portland cement and sulphate resistant cement are used to prepare concrete specimens and the chloride diffusion coefficient of concrete specimens cured for 28 days is measured by RCM method. In this paper effect of C3 A content of on chloride ion permeability is analyzed and the conclusion shows that the better resistance to chloride ion permeability of concrete is, with the higher C3 A content and the lower the chloride diffusion coefficient...