Characterization of high-quality concrete using fly ash and silica fume slag materials from boiler ash

High strength concrete is currently a very important part in construction, namely construction that has very high strength. The strength of concrete depends on the material used and its size. The size of the concrete constituent materials affects the porosity of the resulting concrete because porosity affects the strength of the concrete. For this reason, efforts are made to use concrete constituent materials that can reduce porosity in concrete. Various materials can be used as additives to give concrete high strength. Among these materials are fly ash and silica fume. Fly ash is a product of coal combustion and functions as a substitute for pozzolanic materials in cement as much as 0, 5, 7.5, 10, 12.5, 15, and 17.5% because it has a very fine grain size < 350 mesh and silica fume ash, which functions as a substitute for fine aggregate 0, 10, 15, 20, 25, 30, and 35% which comes from the ashes of burning refined palm shells with a size < 350 mesh. Materials were prepared, namely: cement, fine aggregate, coarse aggregate, fly ash, silica fume, and weighing water. All the ingredients were stirred until homogeneous and put into a cube-shaped mold measuring 150 x 150 x 150 mm while compaction was carried out using an iron stick, then the mold was left for 24 hours, removed from the mold then soaked in water and soaked in water for 28 days. The compressive strength test and characterization of XRF and XRD and SEM were carried out. Based on the research as outlined in the graph, the maximum compressive strength of substitution of 12.5% fly ash into cement is 45.20 MPa, while the substitution of silica smoke from boiler slag into fine aggregate has a maximum compressive strength of 25% of 50.84 MPa. The results of the XRF characterization of high strength concrete showed that the dominant compounds were 54.60% CaO, and 32.50% SiO2, followed by other compounds. The results of the XRD test showed that the phases formed were calcite (Ca), quartz (SiO2), and anorthite (CaAl2Si2O8) and the distribution of C-S-H was fairly even in the concrete. Thus, fly ash and burning ash of palm shells can affect the compressive strength of concrete for the better, namely the strength increases higher than normal concrete.