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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.

This study analyzes the effect of white soil as a substitution of fly ash on geopolymer binders. Fly ash from Tanjung Jati Jepara, white soil from Kupang, water and NaOH as alkaline activators are mixed into binders and tested for setting time with a Vicat tool. The water factor of the binder was used 0.5. The white soil substitution in fly ash using a percentage of 0 to 30 of the weight of fly ash. Fly ash and white soil used had the particle size smaller than 0.074 mm or passed the number 200 sieve and had a moisture content of 0%. The results show that the setting time of geopolymer binder with substitution white soil in the range of 52.5 to 105 minutes for the initial setting time and is between 180 to 225 minutes for the final setting time. This value approaches the same as the setting time of Portland cement in SNI 15-2049-2004. From the 7 variations tested, the binder with 15% of white soil has a faster setting time compared to other variations, i.e 52.5 minutes for initial and 180 minutes for final setting time. The temperature when testing affects the setting time of the geopolymer binder

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