Study On The Performance Of High Volume Blast Furnace Slag-fly Ash Cementing Materials And Concrete

With the development of high performance concrete technology, using high-quality mineral admixture is not only advantageous to solving the problem of environmental protection and energy conservation. Moreover, it has been a kind of important component in modifying the concrete. In order to improve structure and function of concrete, there is often use the technique which put various different active mineral admixtures in concrete. In this paper, slag and fly ash were taken as the research subjects. The influence of blast furnace slag powder-fly ash composite mineral admixture on the performance of ordinary Portland (OPC)cement were studied as cement is replaced by 50%～70% slag powder and fly ash without admixture and specious technology.Researching the basic physical, mechanical properties and durability index of cements, it proved that adding blast furnace slag and fly ash can not only satisfy the basic physical and mechanical properties, but also improve the durability of concrete. The results show that substituting 50%～70% OPC with the composite mineral admixture will greatly decrease the early age strength, while the late age strength of the cementing material will be little affected. Adding sulfate containing industrial waste will greatly increase the early age strength, with little influence on late age strength. By adding blast furnace slag and fly ash, the shrinkage and corrosion resistance of the cementitious materials can be improved. Slag-fly ash composite cement is similar to ordinary cement concrete in fundamental performance, but dominates on chloride ion erosion, falls short on carbonization performance and the frost resistance.The hydration products and paste structure of complex binders composed of Portland cement and blast furnace slag-fly ash mineral admixture were investigated with the aid of modern analysis method such as SEM, XRD and MIP. The results demonstrate that synthetic effects of powder slag and fly ash can improve the reaction of lava ash, and decrease the Ca (OH)₂ . The pore structure and distribution become better. Paste makes denser, thereby increasing the sulfate resistance and chloride ion erosion of composite cementitious material and concrete.