混凝土不均匀性的表征及其对硬化性能的影响

Characterization of concrete inhomogeneity and its influence on the hardened concrete properties

为了研究新拌混凝土不均匀性对硬化性能的影响,制备了坍落度在130~260 mm的大流动度C50混凝土,通过砂率、矿物掺合料掺量和减水剂掺量调节混凝土的流动性,取不同部位(中心、边缘)混凝土测试工作性、力学性能、渗透性能等。结果表明:当中心、边缘混凝土骨料离析率组间变异系数不超过5%时,对混凝土的力学性能无明显影响;随着骨料离析率组间变异系数的增加,混凝土力学性能降低;同组间对比时,各组边缘混凝土的氯离子扩散系数、气体渗透系数均高于中心混凝土,中心混凝土的孔隙率较低,有害级孔和多害级孔占比低于边缘混凝土,中心、边缘混凝土的骨料离析率和水胶比组间变异系数较大的组别,孔径分布及孔隙率的差值也较大,氯离子扩散系数和气体渗透系数的差值也较大;总体上,新拌混凝土越均匀,硬化后的综合性能越好。

In order to study the effect of inhomogeneity of fresh concrete on its hardened performance,high fluidity C50 concrete with a slump of 130~260 mm was prepared.The fluidity of the concrete was adjusted by sand ratio,mineral admixture content,and polycarboxylate superplasticizer content.Different parts(center,edge)of the concrete were tested for workability,mechanical properties,permeability,etc.The results show that when the coefficient of variation between the segregation rate groups of the center and edge concrete aggregates does not exceed 5%,it has no significant effect on the mechanical properties of concrete.As the coefficient of variation between the segregation rate groups increases,the mechanical properties of concrete decrease.When comparing within the same group,the chloride ion diffusion coefficient and gas permeability coefficient of the edge concrete in each group are higher than those of the center concrete.The porosity of the center concrete is lower,and the proportion of harmful and multi harmful pores is lower than those of the edge concrete.The groups with larger inter group variation coefficients of aggregate segregation rate and water binder ratio in the center and edge concrete also have larger differences in pore size distribution and porosity,and larger differences in chloride ion diffusion coefficient and gas permeability coefficient.Overall,the more uniform the freshly mixed concrete,the better its comprehensive performance after hardening.