EFFECT OF KAOLIN USE AS SUBSTITUTE IN GEOPOLIMER MORTAR BASED ON FLYING SOIL WITH 12 MOLAR NaOH ON STRENGTH TEST

Abstract

Greenhouse gas emissions from cement manufacturing contribute to global warming, so it is necessary to develop environmentally friendly alternative materials. One such alternative is geopolymer mortar, which uses fly ash and kaolin as a cement substitute. An alkaline solution consisting of 12 molar NaOH and sodium silicate is used as an activator to make this geopolymer mortar. This research aims to determine the effect of using kaolin as a substitute in fly ash-based geopolymer mortar using 12 molar NaOH on the compressive strength of the mortar. The research method applied is experimentation with data collection through direct observation. Cube-shaped mortar samples measuring 5 cm x 5 cm x 5 cm were tested at 28 days and cured at room temperature. This research uses a variety of 7 mix designs with a fly ash composition range of 90% -40% and kaolin substitution of 10% -60%. Based on the research results, it shows that the highest compressive strength at 28 days was achieved in mix design 2 (90% fly ash and 10% kaolin) with an average compressive strength of 32.78 MPa. Therefore, the use of kaolin as a substitute for fly ash in geopolymer mortar is not only a more environmentally friendly solution but also increases the compressive strength in a certain percentage.

Key Words: Fly ash, Kaolin, compressive strength, geopolymer mortar