Incorporation of clay brick wastes and calcium hydroxide into geopolymers: Compressive strength, microstructure, and efflorescence

Abstract

This study aimed to evaluate the incorporation of clay brick waste (CBW) into geopolymers for the production of sustainable building materials. Eight mixtures were prepared with and without the incorporation of calcium hydroxide (CH) and with 0 %, 25 %, 50 %, and 75 % of the mass of metakaolin (MK) replaced by CBW. Physical-mechanical tests evaluated the macrostructural properties and scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction analyses evaluated the microstructure. The results showed that the incorporation of CH significantly improved the physic-mechanical properties of the produced geopolymers due to the formation of C-A-S-H gel in the geopolymer matrix. Thus, CH produced an increase in compressive strength of 357.8 %, 157.6 %, and 95.2 % at 7, 28, and 91 days in the mixture with high CBW content. SEM/EDS analysis showed that Fe3+ partially replaced Al3+ in the geopolymer matrix with the incorporation of CBW. In addition, the partial replacement of Al3+ by Fe3+ from CBW in the N-A-S-H gel contributed to the mitigation of efflorescence with increasing CBW content. Therefore, the results showed that CH contributes to the production of CBW-based geopolymers with satisfactory compressive strength for use as construction materials.