Experimental study on recycled cement prepared from waste concrete

Abstract

In this paper, waste concrete of different strength grades is used as a substitute for calcareous and siliceous materials. The effects of waste concrete with different strength grades, various raw material compositions, distinct calcination temperatures, burnability of cement clinker, lithofacies characteristics and microscopic morphology hydration products are studied systematically. The results demonstrate that waste concrete is conducive to the low temperature formation of clinker mineral phase, which promotes the firing of clinker and the incorporation of low-strength grade waste concrete benefits the calcination of raw material more obviously. Under the same conditions, the content of f-CaO in recycled cement clinker shows an upward trend with the increase of the strength grade of KH and waste concrete. Meanwhile, if the amount of waste concrete exceeds 40%, the stability of recycled cement would be poor. Alite and Belite crystals are formed with obvious characteristic peaks in the waste concrete calcined regenerated cement clinker of different strength grades. However, each sample group has different degrees of over-burning phenomenon, it is difficult to identify the adhesion between A and B minerals in clinker. The regenerated cement hydration products have different degrees of C-S-H gel and ettringite formation, the hydration products of recycled cement prepared by waste concrete with low strength grade are more compact.