Lalombi Tropical Peat Soil Improvement Using Iron Oxide admixture and Cement

Abstract Peat soil has a relatively high water content of up to 400%. With a high moisture content, peat soil can hinder construction work. For this reason, in construction planning, an investigation must be carried out on the characteristics and strength of the soil, especially the properties of the soil that affect the bearing capacity of the soil to withstand the load of the construction on it. This study aimed to determine the characteristics and changes in the bearing capacity of peat soil after mixing with cement and iron oxide admixture. The variation of mixing iron oxide is 0%, 4%, 8%, and 16%, while for variation of cement mixture is 5%. This research was conducted on the soil, including testing physical and mechanical properties. Engineering properties tests include direct shear and consolidation tests. This research conducted the elemental chemical content in peat soil and SEM (Scanning Electron Microscope) test. Based on the classification of peat soil at this location with an ash content-value of 29.41%, it can be classified as High Ash Peat (peat with ash content > 25%). In the direct shear test, the cohesion value and the shear angle continued to increase as the percentage of the iron oxide mixture increased to 16%, where the shear angle changed from 7.60º to 45°. In the consolidation test, the original soil Cc value of 0.00820 decreased with the addition of iron oxide to 16%; the Cc value decreased to 0.00277. The decrease in Cc indicates that the soil becomes easily compacted, and The value of the Coefficient of Consolidation (Cv) on peat soil was 0.00535 cm²/sec. The most significant increase in the original soil with a mixture of 16% iron oxide was 0.01463 cm²/sec. The Chemical results have been given a mixture of 16% iron oxide and 5% cement, the change of C (Carbon), Fe (Ferrum) and Ca (Calcium). The value of O (Oxygen) in peat soil was 48.05% and then decreased to 43.67%, this indicates that the pores in the peat soil are reduced, and when the pores are reduced, the peat soil becomes denser. The value of Si (Silica) also decreased from 30.01% to 21.21%. This occurred because silica reacted with lime. After all, silica is an adhesive that binds lime, making the granules denser. Peat soil’s Fe (Ferrum) value was 3.12%, then increased to 16.72%. This also helped the soil to become stronger because of the higher specific gravity of iron. Peat soil’s Al (aluminium) value was 12.15% after being given a mixture of iron oxide and cement increased to 12.16%.