Mechanical Properties of Large Slump Concrete Made by Post-Filling Coarse Aggregate Mixing Procedure

High-performance pumping concrete has been widely used in high-rise building construction because of its superior qualities. However, early cracking problems can occur in cast-in-place pumping concrete, which is due to the excessive use of cement. In this paper, an innovative concrete mixing procedure called "post-filling coarse aggregate concrete" (PFCC) was adopted and applied to large slump concrete. The influence of the post-filling coarse aggregate (PFA) ratio on the mechanical properties of large slump concrete were investigated. Three different concrete strength grades (C30, C40 and C50) and five different PFA ratios (0%, 10%, 15%, 20%, 25%) were considered. The designed slump for the reference concrete was 180-200 mm. Experimental tests on the compressive strength of cubic specimens, axial compressive strength of prism specimens, splitting tensile strength, modulus of rupture and modulus of elasticity were performed. All tests were conducted in room conditions. Results showed that the slump of the PFCC decreases as the PFA ratio increases. It also indicated that, in general, the mechanical properties of PFCC are not linearly increasing as the PFA ratio rises, and there exists a turning point. Based on the experimental investigation and analysis in this study, the optimum post-filling coarse aggregate ratio is recommended to be 20%.