Study of Recycled Spent Coffee Grounds as Aggregates in Cementitious Materials

Most spent coffee grounds (SCGs), a byproduct of brewing coffee, are buried in landfill sites, and their decomposition produces significant greenhouse gases. As the recent warming of the Earth’s climate has made it imperative that industries reduce greenhouse gas emissions, the present study investigates the viability of recycling SCGs for use as a partial replacement of aggregates in concrete materials. Cement mortar samples with a fixed cement-to-water ratio and varying amounts of SCGs were fabricated and tested. Mechanical strength tests revealed that an appropriate amount of SCGs can improve compressive strength. However, since strength deterioration was also observed in samples with too much or too little SCG content, finding the optimal amount is necessary for implementation. The samples’ thermal conductivity decreased as the amount of SCGs increased, capturing the effective insulating substance of air within the SCGs’ porous structure. The increased insulating capacity of concrete materials resulting from the addition of SCGs could be beneficial in terms of a building’s lifecycle cost and carbon emissions. Thus, the SCGs once disposed of in landfills to emit greenhouse gases can be transformed into an appealing and eco-friendly building material if the proper concrete mix ratio is used.