Recycling of different industrial wastes as supplement of cement for sustainable production of mortar

Abstract

Day by day, soaring demand for natural resource devouring and CO2-producing material, cement in the construction industry, poses enormous ecological risk, accelerating the requirement of an alternative or supplementary cementitious material (SCM). In contrast, retrieval of a massive amount of industrial waste needs proper attention to alleviate the environmental burden. This research aims to utilize three common industrial wastes: recycled concrete dust (RCD), ladle furnace slag (LFS), pyrolysis carbon black (PCB) as SCM in cement-based composites, offering a sustainable approach towards the green atmosphere. The study experimentally compares the performance of 13 different mortar mixes, substituting the ordinary Portland cement (OPC) with varying weight percentages (0% as control, 5%, 10%, 15%, and 20%) of each waste. Including chemical composition analysis of OPC and alternative binders; several physical properties, mechanical properties, particularly compressive strength, flexural capacity, strength at elevated temperatures, strength activity index (SAI), durability characteristics are performed on afore-mentioned mortar mixes. Moreover, the failure pattern, microstructure, and presence of chemical substances in the composites are examined. This investigation also highlights the strength-CO2 emission measure and economic viability of the material considering waste processing charges. The results satisfy ASTM standard strength requirements for all 13 mixes, a minimum 75% SAI was achieved in all cases except 20% cement replacement level of PCB. Compared to the conventional control mix, 5% RCD blended mortar exhibited 9% higher compressive strength. In contrast, PCB showed a continuing decline in compressive strength, with a reduction up to 45% for 20% replacement level. Incorporating 10% slag as SCM, improved performance was obtained in terms of compressive strength (+7.9%), flexural strength (+11.7%), strength at 800 °C (+22%), strength-CO2 ratio (+15%), economy index (+9.1%) while compromising workability (−62.7%) and durability.