Utilization of fly ash and bottom ash from TanjungJati B Coal-Fired Power Plant in Jepara, Central Java, on the quality of cellular lightweight concrete

The research aims to address waste-related issues by producing Cellular Lightweight Concrete (CLC) bricks using fly ash and bottom ash as fine aggregates. The variations used encompass cement, fly ash, bottom ash, and sand compositions. The ratio between cement and fine aggregates utilized is 1:3. The variations in the composition of fine aggregates include P (100% sand), F (100% fly ash), B (100% bottom ash), F1B1 (50% fly ash and 50% bottom ash), F1B2 (33.3% fly ash and 66.7% bottom ash), F1B3 (25% fly ash and 75% bottom ash), F2B1 (6.7% fly ash and 33.3% bottom ash), and F3B1 (25% fly ash and 75% bottom ash). The parameters employed comprise compressive strength testing, density, and water absorption evaluation of the CLC bricks at ages 14, 28, and 35 days, also thermal conductivity at the 35-days sample. The sample age exhibits a proportional relationship with compressive strength and water absorption, while displaying an inverse relationship with density. At the 35-day sample age, the F composition demonstrates the highest compressive strength (14.74MPa) and the lowest water absorption (11%). Meanwhile, the B composition exhibits a compressive strength value of 5.9MPa and the lowest density (1.12g/cm 2 ). Conversely, the P composition showcases the highest density (1.59g/cm 2 ). Density affects thermal conductivity, the lower the density, the lower the thermal conductivity, which means that the heat conductivity will be smaller.