The effect of white soil on geopolymer mortar porosity

Abstract

This study analysed the effect of white soil as a filler on geopolymer mortar. The materials used were fly ash, white soil from Kupang as fillers, sand, water, and NaOH as alkaline activator. The comparison of geopolymer mortar mixture was 1 Pca: 3 Sand with water factor 0.5. The Pca was composed by white soil and fly ash with alkaline activator and water. The percentage of white soil used were 5, 10, 15, 20, 25 and 30%. The white soil chosen passed the number 200 sieve. Moreover, the dimension of mortar used was 5 x 5 x 5 cm. To remove the water content from the mortar, the oven was set at 60 °C for 24 hours until the mortar weight did not change. The result shows that porosity decreases with the increase of white soil percentage. Increase in the white soil percentage by 5, 10, 15 and 20% can reduce porosity by 0.9, 2.7, 2.5 and 2.9%. Nevertheless, the white soil, with a percentage of 25 and 30, increased porosity by 3.7 and 3.8%, respectively. This happened because in these percentages, the white soil hardens faster than the other percentages, impacting the compaction process on the mould.