Symbiotic effects of coffee husk ash incorporated ternary AAB system on qualitative, durability and sustainable characteristics

The present novel research work emphasizes the characterization of binder materials, the performance of alkali-activated ternary binder paste & mortar consisting of coffee husk ash (CHA), rice husk ash (RHA), and ground granulated blast furnace slag (GGBS). The material characterization for the binder materials were carried out using advanced microstructural analysis techniques. A total of nine binder pastes are prepared using GGBS (70–50%), CHA (20–40%), and RHA (10%) with 4 M, 6 M & 8 M sodium hydroxide (NaOH) solution. The tests conducted on fresh and hardened pastes include setting time, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and thermogravimetric analysis, indicated the presence of CSH, and NASH gel. The mortar mixes prepared with nine binder proportions are tested for slump, compressive strength, flexure strength, direct tensile strength, water absorption and ultrasonic pulse velocity (UPV). The compressive strength of hardened alkali-activated ternary mortar mix ranges between 31.2 and 52.2 MPa at 90 days. The durability performance of the mortar mixes was investigated through exposure to acid and sea water attack, while the sustainability of materials was determined by material production cost and carbon dioxide emission. The percentage of cost benefit of using AAB mix as compared to OPC, ranges between 23.24% and 34%. The M6 AAB mix (60% GGBS, 30% CHA and 10% RHA with 8 M NaOH) was found to be optimum, making it suitable for use in construction as an alternate to OPC mix in terms of strength, durability, and sustainability.