Mechanical Properties of Concrete with Al_2O_3 Hollow Sphere Added under Impact Loading

摘要

The aim of this paper was to study the mechanical properties and damage evolution of concrete added with Al2O3 hollow sphere (AHSC) under impact loading. The impact compression experiments were carried out by a 100-mm-diameter split Hopkinson pressure bar apparatus. The mechanical performance, including strength, deformation and failure pattern, were analyzed. The damage factor (DF) was defined as the dissipation of concrete constitutive energy and the damage evolution was explored. The results show that the evolution of AHSC dynamic stress fell into four stages: elastic stage, plateau stage, densification stage, and failure stage. The plateau stage, which did not exist in the dynamic stress-strain curves of plain concrete (PC), could help AHSC better absorb energy under impact loading. Along with the increase of strain rate, the dynamic strength increase factors (DIF) of both AHSC and PC increased continuously. Furthermore, the DIF of AHSC was larger than that of PC at the same strain rate. Moreover, the critical strain shared the same law with DIF, indicating that the addition of Al2O3 hollow sphere could improve the deformation property of concrete. The analysis of failure patterns of specimens indicated that the damage degree got higher with the increasing strain rate, and AHSC was more seriously damaged than PC at the same strain rate. On the basis of the increasing rate of DF, the dynamic damage evolution could be divided into three periods. There was a jumping period in the damage evolution curve of AHSC, and this phenomenon became more obvious with the increase of strain rate.