Development of eco-friendly brick waste-based geopolymers: effect of calcium incorporation on rheology, compressive strength, microstructure, and eco-efficiency

Abstract

This study investigated the development of geopolymers from low-reactivity residual precursors for the development of eco-efficient geopolymers. Brick waste (BW) was used as the sole precursor. Calcium hydroxide (CH) was used to enhance the properties of the geopolymers. Semi-adiabatic calorimetry and rheological tests evaluated the fresh state. Compressive strength, water absorption, and void index tests evaluated the mechanical properties. XRD, SEM, and EDS analyses investigated the microstructure. Embodied energy and carbon emissions were used to analyze the sustainability of the geopolymers. The results showed that the incorporation of high levels of CH increased the yield stress, plastic viscosity, and thixotropy. Conversely, the incorporation of CH was essential to improve compressive strength. The increase in compressive strength varied between 61.1 % and 126.2 % at 28 days due to the incorporation of CH. Microstructural analyses indicated that the C-A-S-H gel promoted an increase in compressive strength. Semi-adiabatic calorimetry showed that CH incorporation accelerated the geopolymerization reactions. Compressive strength was limited by the zeolite formation observed in the 20 % CH mixture. The sustainability analysis showed that the mixtures with 10 % and 15 % CH produced higher eco-efficiency and better results in terms of rheological and compressive strength, respectively. In conclusion, this study showed that geopolymers can be produced from low-reactivity waste materials, contributing to the development of sustainable construction materials.