Axial compression behavior of reinforced geopolymer concrete columns with demolished concrete lumps

Abstract

Abstract This paper presents results of an experimental study on the axial compression behavior of reinforced geopolymer concrete columns with demolished concrete lumps (DCLs). A total of 22 reinforced concrete short columns were tested under axial compression. The test variables include the type of fresh concrete (ordinary Portland cement concrete (CC) and geopolymer concrete (GC)), strength level of fresh concrete (FC) and demolished concrete, and replacement ratio of FC by DCLs. The test results were used to evaluate the effect of strength difference between fresh and demolished concrete, and replacement ratio of FC by DCLs on bearing capacity and deformation ductility of geopolymer concrete columns with DCLs. Data from these tests showed that the axial compression behaviors of short columns made of geopolymer concrete and ordinary concrete with DCLs were similar. The ultimate bearing capacity and stiffness of recycled concrete columns with DCLs decrease with an increase in replacement ratio. Nevertheless, the maximum reduction in bearing capacity of geopolymer recycled concrete columns is only 10%, when the replacement ratio of FC by DCLs is 24%. The strength difference between fresh concrete and DCLs has a significant influence on mechanical properties of recycled concrete columns, especially for geopolymer recycled concrete columns. Compared to ordinary recycled concrete columns with DCLs, geopolymer recycled concrete columns with DCLS exhibit a slight lower bearing capacity, but a higher ductility.