Experimental Study on the Precast Beam Concrete with Composite Cementing System Composed of Limestone Powder and Silica Fume
The working performance,physical and mechanical properties of precast beam concrete with different proportions of limestone powder and silica fume replacing fly ash are studied,and the effect on the microstructure of concrete is analyzed by scanning electron microscopy,which reveals the mi-croscopic mechanism of the influence of limestone powder and silica fume mixed cementing system on concrete properties from the microscopic level.The results of the study show that the best perform-ance of precast beam concrete is achieved by replacing 67%of fly ash with limestone powder and 33%of fly ash with silica fume.Compared to the base concrete,the slump value increases by 10%,the slump expansion value increases by 6.3%,the 1 h slump and expansion loss through time reduces by 33.3%and 37.5%respectively,the 3 d,7 d and 28 d compressive strengths increases by 3.2%,4.2%and 12.6%respectively,the 3 d,7 d and 28 d modulus of elasticity increases by 3.5%,3.7%and 6.1%respectively,and the dry shrinkage is close to that of the base concrete.The proportion of C—S—H gel in the microstructure of concrete of composite cementing system is greatly increased,and C—S—H gel gathers into layers,which plays a better role in filling and bonding of concrete.The working and mechanical properties of precast beam concrete mixed with limestone powder and silica fume in proper proportion are better than those of single fly ash,and the dry shrinkage deformation of concrete is not affected.
万方数据
维普
