Thesis Bachelor of Science in Civil Engineering University of Rizal System-Morong 2023

This study was conducted to determine the effectiveness of utilizing ground granulated blast-furnace slag and rice husk ash in stabilizing an expansive soil. After conducting several soil property tests following ASTM standards, the researchers determined the effectiveness of the additives in terms of the resulting soil parameters. This study was conducted during the first and second semesters of the academic year 2022-2023. Expansive soils are problematic soils that exhibits shrink-swell behavior. Due to the continual cycle of wet to dry soil, buildings built on this soil may require foundation repair because they rise or sink unevenly. Due to the rising cost of commercially-available soil stabilizers, environmental issues have been associated with the production of these admixtures. RHA is classified as an effective pozzolan that can undergo chemical reactions resulting in the formation of compounds that exhibit cementitious properties and help improve soil strength. GGBS, on the other hand, has latent hydraulic properties that permit its most common application as a cement additive in concrete structures, allowing it also to act as a binder added to RHA to possibly increase soil strength. This was the reason that the researchers chose to conduct the study entitled, Utilization of Ground Granulated Blast-Furnace Slag and Rice Husk Ash as Expansive Soil Stabilizer, to determine the effectiveness of ground granulated blast-furnace slag and rice husk ash in stabilizing soil. In this study, the researchers used an experimental type of research to collect measurable data and conduct analysis. Clay soil collected from Brgy. May-Iba, Teresa, Rizal was classified as expansive based on the soil parameters set by NSCP 2015. The additives used in the study had also undergone physical and chemical composition tests. Soil mixtures were prepared following the design proportions of 15% GGBS + 10% RHA + 75% Soil, 12.5% GGBS + 12.5% RHA + 75% Soil, and 10% GGBS + 15% RHA + 75% Soil. The samples were molded and cured for 7 days, 14 days, and 28 days. After the curing periods have ended, the researchers transported the soil samples to the testing laboratory and conducted various tests to determine the soil mixtures’ specific gravity, grain size, liquid limit, plastic limit, modified proctor compaction, percent of swell, shrinkage limit, and unconfined compressive strength. The researchers also used a two-way analysis of variance to determine if the mixture ratios and the curing periods have a significant effect on the resulting soil properties and indices. The tests on the soil mixtures revealed that mixtures with GGBS and RHA exhibited improvements in the liquid limit, percent of swell, plasticity index, swell index, and unconfined compressive strength. Mixture with 10 percent GGBS and 15 percent RHA garnered a decrease of 11.40 percent in the liquid limit. A decrease of 2.69 percent in the percent of swell was found on a mixture with 12.5 percent of GGBS and 12.5 percent of RHA. A decrease of 13.8 percent in the plasticity index was found on a mixture with 10 percent GGBS and 15 percent RHA. While a decrease of 0.323 percent in the swell index and an increase of 1.979 MPa were found on the soil mixture with 12.5 percent of GGBS and 12.5 percent of RHA. For the analysis of variance test on the significant relationship of mixture ratio to the soil properties and indices, the p-values for the specific gravity, liquid limit, plastic limit, maximum dry density, optimum moisture content, percent of swell, shrinkage limit, plasticity index, liquidity index, swell index, shrinkage index, and unconfined compressive strength were all less than 0.5. While for the analysis of variance test on the significant relationship of the curing period to the soil properties and indices, the p-values for the plastic limit, maximum dry density, optimum moisture content, percent of swell, plasticity index, liquidity index, swell index, shrinkage index, and unconfined compressive strength were all greater than 0.5. Based on the findings, it is concluded that the addition of GGBS and RHA can effectively enhance the soil’s liquid limit, percent of swell, plasticity index, swell index, and unconfined compressive strength. The mixture containing 10 percent GGBS and 15 percent RHA is effective in improving the soil’s liquid limit and plasticity index. While the mixture containing 12.5 percent of GGBS and 12.5 percent of RHA was effective in enhancing the soil’s percent of swell, swell index, and unconfined compressive strength. Additionally, based on the Two-way ANOVA, it is concluded that the mixture ratio has a significant difference in the liquid limit, plastic limit, maximum dry density, optimum moisture content, percent of swell, shrinkage limit, plasticity index, liquidity index, swell index, shrinkage index, and unconfined compressive strength. While the curing period has no significant difference in the plastic limit, maximum dry density, optimum moisture content, percent of swell, plasticity index, liquidity index, swell index, shrinkage index, and unconfined compressive of soil samples. The researchers recommend that further studies should be conducted on utilizing GGBS and RHA sourced from different places, a study utilizing GGBS and RHA on different soil types, and examining the enduring strength of the stabilized expansive soils, utilizing curing methods that replicate the realistic conditions encountered on-site.