Analisis Substitusi Faba pada Semen untuk Pembuatan Paving Block

Abstract

The utilization of fly ash and bottom ash (FABA) as a partial replacement for cement is an alternative approach to reduce coal combustion waste and the use of conventional cement in paving block production. This study aimed to evaluate the effect of FABA substitution at 0%, 5%, 10%, and 15% of cement mass on the compressive strength of paving blocks at 28 days and to identify the most effective FABA composition. An experimental method was applied using Holland-type paving blocks measuring 20 × 10 × 8 cm. FABA from PT Pusri was used with three internal FA:BA proportions at each substitution level, namely 100:0, 75:25, and 50:50. Fine aggregate was Tanjung Raja sand, while Baturaja cement and clean water were used as the binder and mixing water. Material characterization included sieve analysis, specific gravity, unit weight, and mud content. Compressive strength was determined using a compression testing machine after 28 days of curing. The results show that the control mixture had an average compressive strength of 13.00 MPa. The highest value among FABA mixtures was 13.16 MPa at 5% FABA with an FA:BA ratio of 50:50. At 10% and 15% FABA, the highest values were 12.83 MPa and 12.33 MPa, respectively. Overall, increasing FABA content above 5% tended to reduce compressive strength. The paving blocks were classified as quality D according to SNI 03-0691-1996.