Effect of Carbonation on the Interfacial Microstructure of Recycled Concrete

Abstract

The effect of carbonation on the micro hardness and width of interface transition zone of recycled concrete was studied, and the mechanism of carbonation reaction on recycled concrete was revealed from the micro level. The micro hardness of recycled concrete was measured before and after carbonization by means of micro hardness tester. The results show that the hardness of the recycled concrete with the same strength grade is increased and the width of the interface transition zone decreases in different degree at the old aggregate-new slurry interface after 28d carbonization. The micro hardness of the old paste- new slurry interface increases, and the width of the transition zone decreases slightly. The influence of old aggregate-old paste interface micro hardness is similar to that of old aggregate-new slurry interface. Carbonation can improve the compactness of the cement paste and the micro hardness of the interface transition zone. In the recycled concrete with same strength grade, the influence of interfacial porosity and carbonation on the interface: old aggregate-new slurry interface＞old aggregate-old paste interface ＞old paste- new slurry interface.