Analysis of Geopolymer Mortar Compressive Strength Based on Fly Ash and GGBFS as Patch Repair Material

Abstract Damages that often emerge in concrete include cracks, delamination, spalling, wear, fracture, porous, voids (perforated). These damages need to be repaired, one of which is by patch repair. With consideration of strength and frugality, a self-made repair material was developed using mortar as a base material, i.e., geopolymer mortar. Geopolymer mortar is a mortar with natural materials and materials that have a high content of silica oxide and alumina (such as Fly Ash and GGBFS) as a binder that must be activated with an alkaline activator in the form of sodium hydroxide (NaOH) and sodium silicate (Na 2 SiO 3 ). The use of Fly Ash and GGBFS as a binder to replace cement in geopolymer mortar has a positive impact from an environmental point of view because it can reduce the use of cement and can reduce environmental pollution due to Fly Ash and GGBFS waste. In this research, the effect of variations in Fly Ash and GGBFS and variations in the molarity of NaOH on the compressive strength of geopolymer mortar were investigated, in order to obtain the optimum composition of the geopolymer mortar mixture that meets the requirements of compressive strength as a repair material. From the results of the research, the maximum compressive strength occurred in GF91 16 M mortar at 56 days of 73.77 MPa was obtained. Geopolymer mortar has a higher compressive strength and a cheaper price when compared to Sika Grout mortar so that the use of geopolymer mortar as a patch repair material is better than Sika Grout mortar in terms of strength and frugality.