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Geopolymers have become one of the alternative materials for environmentally friendly concrete. Pozzolan materials with high alumina-silicate content such as fly ash and bottom ash (FABA), basalt, and clay are potential materials for geopolymer concrete synthesis. In Indonesia, the amount of FABA, basalt, and clay is very abundant. The purpose of this study was to determine the properties and character of geopolymer concrete with the composition to which additives were added. Geopolymers were activated using a mixture of NaOH and Na2SiO3. The mixture of activator and geopolymer material was cured at a temperature of 80°C for 12 hours. Concrete samples are formed in cubes for compressive strength tests and molded beams for flexural strength tests. Variations in the use of fibers in flexural strength test samples are applied to determine the effect of fibers on the deflection threshold of geopolymer concrete. The results of the cube concrete compressive strength test ranged from 0.04–0.47 MPa with the highest compressive strength at the C3 variation of 0.47 MPa. The flexural strength ranges from 0.11–2.15 MPa with the highest flexural strength at variation C3 of 2.15 MPa. The use of fibers can provide a better deflection threshold despite reducing the maximum flexural strength. The use of fibers needs to be regulated to obtain a good flexural strength with a proportional deflection threshold. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Geopolymer has been widely used in various fields. This paper reports the pH increase of acid mine drainage (AMD) by treatment with geopolymer materials. The test specimens were made from fly ash, sandstone, and crystalline limestone from waste mining materials in East Kalimantan. They were made by mixing 14 M NaOH solution, Na2SiO3, and waste mining materials. The crushed geopolymer with 80 mesh in particle size was applied for treating the acid solution. The increased pH of acid mine drainage solution may be mainly caused by combination of CaO and soluble Na2O content in the geopolymer materials. The formula codes V3 and V4 were found to be the more effective in treating the acidity, increasing up to 6.3 with geopolymer powder as much as 1.5 gram in 200 ml of acid mine drainage (AMD) solution. Meanwhile, the role of sandstone has an inverse effect on the resulting pH. This experiment can be of practical implication in either developing geopolymer products for AMD remediation in a passive way or recycling geopolymer residue for AMD treatment in an active method. [ABSTRACT FROM AUTHOR]