Rheological properties of mortar containing recycled powders from construction and demolition wastes

Abstract

Various types of recycled powders (RPs) can replace cement or fly ash in preparing concrete due to the acceptable impact on the mechanical properties. However, the workability of concrete containing RPs may decrease significantly that render their practical application. This paper investigated the rheological properties of mortar containing different RPs processed from the construction and demolition wastes, which were clay brick powder (CBP), mixed brick powder (MBP) and dust powder (DP). Firstly, the basic properties of RPs were studied for a better understanding the effect on the properties of mortar. Then, the rheological properties of mortar were examined with different RPs to determine the influence of different RPs and superplasticizer dosage, respectively. The experimental results showed that RPs had higher content of Al2O3 and alkali and lower content of SO3, and accordingly, the hydration heat of pastes with RPs were found higher than that of cement paste in the first 30 min. The yield stress, plastic viscosity and thixotropy increased significantly with the use of different RPs, among which mortar with DP were the maximum. Mortar with MBP showed better rheological behavior. Whereas, CBP presented the worst compatibility with SP.