Study on the calcium dissolution of self-compacting recycled concrete

Abstract

Considering the effects of the replacement rate of recycled coarse aggregate (RCA), content of fly ash (FA), and solution temperature, the accelerated calcium dissolution test of self-compacting recycled concrete (SCRC) was simulated by using ammonium chloride solution. The results show that the physical properties (the mass loss ratio and the dissolution depth) and the strength degradation of SCRC increase with the increase of the replacement rate of RCA and solution temperature. With the increasing content of FA, the physical properties decrease approximately linearly, while the strength degradation first decreases and then increases. For the SCRC with 50% RCA and a dissolution age of 56 days, the dissolution depth of SCRC with the FA contents of 10%, 20%, and 30% decreased by 3.85%, 10.00%, and 15.56% respectively compared with that of SCRC without FA, and the degradation rate of compressive strength also decreased by 11.60%, 25.91%, and 15.01%, respectively. The peak stress of the stress-strain curve of SCRC under axial compression is negatively correlated with the dissolution age, replacement rate of RCA, and solution temperature, while the peak strain is positively correlated with these variables. When the dissolution age is more than 28 days, the calcium silicate hydrate (C-S-H) gels produced by low-volume (10%, 20%) FA after complete hydration lead to an increase in peak stress and a decrease in peak strain of SCRC, while high-volume (30%) FA has the opposite effect due to incomplete hydration. Finally, the performance degradation model of SCRC under calcium dissolution was established.