Fired clay brick waste as low cost and eco-friendly pozzolana active filler in gypsum-based binders

Abstract

A broader utilization of calcined gypsum in external applications remains limited mainly due to its high solubility in water. This drawback can be improved by combining it with supplementary cementitious materials and an activator of pozzolanic reactions (cement or lime). This paper aims to explore the feasibility of utilizing non-conventionally used fired clay brick waste, a by-product from brick production, to design gypsum-based binders with improved water resistance. A comprehensive study of the system consisting of calcined gypsum, fired clay brick waste, and lime was done from a microscopic (mineral composition, porosity development, and morphology) to macroscopic (basic physical and mechanical properties) point of view up to 90 days of age. Additionally, a simplified environmental study was conducted using the Life Cycle Assessment method. Amorphous phase and ettringite were the main hydration products. The mechanical tests revealed that the pozzolanic reactions caused by the addition of fired clay brick waste were delayed, which was reflected by a slow increase in strength within the studied period. Contrary to the reference binders, the compressive strength of the samples containing the lowest percentage of fired clay brick waste provided the most promising results even after 90 days of water curing. Considering that the newly designed ternary binders are prepared from low-cost and eco-friendly pozzolana active waste, the results presented in this study could help eliminate the disposal of fired clay brick waste and convert it into useful binder material suitable for green building rendering and restoration work of historical buildings.