The effect of adding natural fibers on the geopolymer characterization and mechanical performance

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.