Physicochemical Properties of Cementitious Materials with Spent Coffee Ground Ash

Abstract

Abstract With the increasing global consumption of coffee, a substantial amount of spent coffee grounds (SCG) is generated. To address this, research has focused on recycling SCG as a renewable fuel, including the production of SCG pellets. When used as fuel in biomass-fired power plants, SCG pellets generate SCG ash, which necessitates effective utilization strategies. This study evaluates the potential of SCG ash as a supplementary cementitious material (SCM) by investigating its effects on concrete properties. SCG ash was produced by drying SCG at 110 °C and combusting it at 900 °C. Concrete specimens were prepared by replacing ordinary Portland cement (OPC) with SCG ash at 5%, 10%, and 15% substitution levels. Fly ash (FA) and blast furnace slag (BFS) were also incorporated to analyze hydration kinetics. X-ray diffraction (XRD) and thermogravimetric analyses confirmed the presence of calcite in SCG ash specimens, while mercury intrusion porosimetry indicated increased porosity with higher SCG ash content. Isothermal calorimetry revealed reduced hydration heat with increasing SCG ash replacement. Notably, concrete containing 5% SCG ash exhibited mechanical properties and durability comparable to plain concrete. Based on these findings, 5% was determined to be the optimal SCG ash substitution level. This study suggests that incorporating SCG ash into concrete can reduce CO₂ emissions from cement production while providing a sustainable recycling method for SCG ash.

Keywords

• Spent coffee ground ash
• Supplementary cementitious materials
• Hydrates analysis
• Compressive strength
• Microstructure