Effect of Mixing Coffee Husk Ash and as a Cement Replacement on the Strength of Concrete

Abstract

Concrete is one of the materials used to strengthen structures. In addition, concrete technology is constantly evolving and is most frequently applied in the construction of buildings. As one of the components of concrete, cement has the potential to harm the environment, from the extraction of raw materials through manufacture to ash pollution. Coffee husks, which are abundant in the Takengon area in the Central Aceh district and are particularly festive, are one among the various organic wastes in Aceh. Silica, a key component in the creation of cement, can be found in coffee residue. In this study, the impact of using fly ash and coffee husk ash in place of OPC cement on concrete's compressive strength was investigated. The research methodology followed SNI 7656-2012 guidelines. Coffee husk ash was baked for five hours at a temperature between 200 and 250 °C with 5%, 10%, and 15% fly ash by weight of OPC cement. There are 24 cylindrical specimens, each measuring 15 cm in diameter and 30 cm in height. Testing was done on concrete that was 7 and 28 days old. The study's findings include the concrete's seven-day age and compressive strengths of 0% (12.27 MPa), 5% (10.52 MPa), 10% (9.99 MPa), and 15%. (9, 09 MPa). Compressive strength with percentages of 0% (21.47 MPa), 5% (13.16 MPa), 10% (10.74 MPa), and 15% at the age of 28 days (5.13 MPa). The designed concrete has a compressive strength of 20 MPa at 28 days of age and a percentage of 0% of 21.47 MPa. The results of testing the compressive strength of concrete show that the lower the percentage of the mixture of coffee husk ash and fly ash, the less compressive strength of the concrete. This is because coffee husk ash contains an excessive amount of silica (SiO2), which prevents cement's reaction with lime and prevents the concrete mixture from having enough water to achieve maximum bonding.