PENGARUH KONSENTRASI NAOH TERHADAP MIKROSTRUKTUR MORTAR GEOPOLIMER DENGAN PRECURSOR FLY ASH DAN ABU SEKAM PADI
Abstract
Mortar geopolymer is a mortar that does not use Portland cement so the mortar produced is environmentally friendly. Geopolymer mortar is formed from chemical reaction not from hydration reaction as conventional mortar (Davidovits, 1999). This study used rice husk ash waste (RHA) and fly ash as cement substitution material. The aim of this study is to determine the optimum composition of geopolymer mortar mixture with fly ash and rice husk ash precursors with NaOH solution to produce high compressive strength of geopolymer mortar, to know the effects of NaOH solution concentration on microstructure of geopolymer mortar, and to know the effects of fly ash and husk ash rice as a precursor to microstructure of geopolymer mortar. Variations of molarity to the effects of NaOH concentration were 8M, 10M, 12M, 14M and 16M. The percentage ratios of fly ash and rice husk ash used were FA 100%: RHA 0%, FA 75%: RHA 25%, FA 50%: RHA 50%, and FA 25%: RHA 75%. The use of RHA is expected to accelerate the secondary hydration reaction for the formation of new CSH. The implementation methodology used in accordance with ASTM and ACI. The tests conducted in this study include fresh mortar test, 28-day mortar compressive strength, and SEM test. Fresh concrete test included slump flow test and setting time test. The results showed that the decrease of slump flow value with the increase percentage of RHA to the activator. The percentage of FA 100%: RHA 0% to 8 molar of NaOH concentration showed the largest slump flow value was 112 cm. The result of setting time test increases with the increase of fly ash percentage to NaOH concentration. The percentage of FA 100%: RHA 0% with 16 molar of NaOH concentration showed the longest setting time. The percentage ratio of FA 100%: RHA 0% with a 16 molar of NaOH concentration indicated the maximum 28-day concrete compressive strength value of 57.213 MPa with a specific density of 1.15 kg/m3 and a solid and complex CH structure.
