Paper Title
Effect of Chemical Characteristics on Fly Ash on Compressive Strength of High-Volume Fly Ash Concrete (HVFAC)

Abstract
The use of fly ash in concrete mixtures continues to be developed in the construction industry. In addition to aiming to utilize waste from coal combustion at the steam power plant, its use can also reduce CO2 emissions caused by cement production activities. An example of its use is in producing high-volume fly ash concrete (HVFAC) with the addition of chemical admixture. Several studies have been carried out to determine the optimal mix design composition with the results indicating that satisfactory compressive strength of HVFAC is strongly influenced by the type and chemical characteristics of fly ash used. Therefore, this research aims to analyze the effect of chemical characteristics on fly ash on the compressive strength of HVFAC at 3, 7, 14, 28, and 56 days using the experimental method. The specimens were made with three variations, one of the normal concrete mixture using 100% Ordinary Portland Cement (OPC) as a control specimen, while the other two are of the HVFAC mixture comprising blended cement (20% OPC + 80% fly ash) from different sources. The comparison (M0), HVFAC-1 (M1) and HVFAC-2 (M2) mixtures used 100% OPC, OPC+fly ash A, and OPC+fly ash B, respectively. The results showed that the compressive strength of all HVFACs at all ages was lower than normal concrete with M2 having a higher compressive strength than M1 at 3, 7, and 14 days. However, at 28 and 56 days, the reverse was the case, thereby indicating that fly ash's chemical characteristics affect concrete's compressive strength at its Al2O3, SiO2, and CaO contents. Keywords - HVFAC, Fly Ash, Chemical Characteristic, Compressive Strength.