Influence of stone dust content on carbonation performance of manufactured sand concrete (MSC)

Abstract

This study investigates the influence of stone dust content on the carbonation performance of manufactured sand concrete (MSC) to improve its durability and promote the application of manufactured sand. The carbonation depth, pH of the pore solution, and half-cell potential of the rebar were tested using MSC with different stone dust contents. The mechanism of MSC carbonation was also analysed using scanning electron microscopy (SEM). The test results showed that the carbonation depth and corrosion probability of the rebar first decreased and then increased with an increase in stone dust content. The carbonation depth and pH of the pore solution of MSC can be divided into complete carbonation, partial carbonation, and non-carbonation zones. When the stone dust content was 7% and at different carbonation ages, the carbonation depth reached its minimum value, the half-cell potential of the rebar reached its maximum value, and the end depth and length of the partial carbonation zone reached their minimum values. Meanwhile, the rebar half-cell potential was only in the medium-probability corrosion zone when the carbonation age was 120 d and the stone dust content exceeded 7%, whereas the remaining cases remained in the low-probability corrosion zone. SEM showed that a low stone dust content increased the density of concrete through physical filling and chemical reactions. However, high stone dust content reduced the working performance of concrete and increased its porosity after forming. In conclusion, the optimum stone dust content was 7% when comprehensively evaluating the carbonation properties of the MSC.