THE EFFECT OF KAOLIN AS A SUBSTITUTION MATERIAL ON FLY ASH BASED GEOPOLYMER MORTAR WITH 6 MOLAR NaOH CONCENTRATION

Abstract

Cement production has the disadvantage that the remaining production results in carbon emissions (CO₂) which is not good for the environment. Research continues to be carried out and various innovations have emerged in an alternative effort to replace cement, commonly called geopolymer. Geopolymer is a product consisting of Silica (Si) and Alumina (Al) as raw maeterials and then dissolved using sodium silicate and sodium hydroxide. In this research, geopolymer mortar uses fly ash as raw material which is then substituted with kaolin at a certain ratio. The purpose of this study was to determine the effect of kaolin substitution on fly ash-based geopolymer mortar with 6 Molar NaOH concentration. The method used in this research is experimental with a quantitative approach and direct data collection techniques. The test specimens used 10%, 20%, 30%, 40%, 50%, and 60% kaolin percentage against fly ash with room temperature treatment. Mortar testing was carried out at the maximum age of the mortar, which is 28 days to determine the effect of kaolin substitution on compressive strength value. The results of the study obtained the highest compressive strength at 10% kaolin substitution percentage. At 20% and 30% kaolin percentage still meet the minimum compressive strength of mortar M which is 17.2 MPa. While at a percentage of kaolin> 30% the test results are less than optimal because they do not meet the compressive strength plan of 20 MPa. So that the recommended kaolin content as a substitute material for fly ash-based geopolymer mortar is at a percentage below 30%.