Production of sustainable plastering mortar containing waste clay brick aggregates

Numerous clay bricks produced by the demolition of old buildings occupy large amounts of valuable land resources and cause serious environmental pollution in the process of transportation, landfill and storage. The objective of this work is to evaluate the feasibility of using waste clay bricks as fine aggregates (CBFA) to prepare sustainable plastering mortar meeting the requirements of GB/T 25181-2019. The effects of CBFA on fresh and hardened properties of plastering mortar have been studied by water requirement, water retention, consistency loss rate, setting time, compressive strength, tensile bonding strength and drying shrinkage. Furthermore, the microstructure of plastering mortar has also been studied to understand the mechanism of CBFA on plastering mortar. The results demonstrate that CBFA can improve water retention of plastering mortar at all dosages (30%, 40%, 50% and 60%), and enhance compressive strength as well as tensile bond strength at 30% dosage. In addition, CBFA can refine the pore diameter and optimize interfacial transition zone (between cement paste and CBFA) of plastering mortar. Nevertheless, CBFA can increase consistency loss rate, drying shrinkage and porosity, and shorten setting time of plastering mortar. In summary, the maximum amount of CBFA in the plastering mortar that can meet the standard requirements is 50% of the total amount of fine aggregates. The utilization of CBFA to prepare plastering mortar not only expands the application range of waste clay bricks and reduces the consumption of natural river sand, but also produces economical green plastering mortar and benefits the sustainable development of building materials.