Assessing the Effects of Coffee Husk Ash (CHA) and Eggshell Powder (ESP) as Partial Replacements for Cement and Spent Coffee Grounds (SCG) as Partial Replacement for Sand on the Compressive Strength of Concrete

Sustainability is a global concern, with waste production and the carbon emissions from the construction industry contributing significantly. This study assesses the utilization of waste products as partial replacements for cement and sand. Coffee Husk Ash (CHA) and Eggshell Powder (ESP) for cement and Spent Coffee Grounds (SCG) for sand. In phase one, 50x50mm mortar samples with CHA and ESP in 5%, 10%, 15%, and 20% partial cement replacements were tested for compressive strength. The highest compressive strength after 28 days was observed in samples with 10% cement replacement containing (1) 75% ESP with 25% CHA and (2) 100% ESP. Phase two confirmed these results using 100x200mm concrete samples with water-cement ratios of 0.4 and 0.6 and adding 15% SCG as partial sand replacement. The highest compressive strength increase, 17.75%, occurred with a 0.4 W/C ratio and 10% cement replacement (75% ESP and 25% CHA) without sand replacement.