Abstract

Expansive soil swells when it is wet, and it will shrink when it dries. Due to this behavior of the soil, the strength and other properties of soil are inferior. To improve its properties, it is necessary to stabilize the soil with different stabilizers. Soil stabilization is a process to treat the soil to maintain, alter, or improve expansive soil performance. In this study, the potential of 'Fino' as stabilizing additive to expansive soil was investigated for the improving engineering properties of expansive soil to be used as subgrade material. The evaluation involved the determination of the Free Swell test, CBR test, Atterberg's limits, and the Proctor test of expansive soil in its natural state as well as when mixed with varying proportions of 'Fino.' The practices were performed on six proportions 5%, 10%, 15%, 20%, 25% and 30 % with expansive soil. The research result indicated a considerable reduction in Swelling, and the Maximum dry Density of soil was improved. Optimum moisture content decreased in increasing 'Fino.' At 30% of 'Fino,' the CBR values of expansive soil increased from 1.06% to 5.94%, Liquid Limit decreased from 95.2% to 29.4%, plasticity index decreased from 57.24% to 17.82% and the degree of expansion of the natural subgrade soil has reduced from 'very high to medium.' Hence, it is concluded that the 'Fino' at 30% has shown significant improvement in the expansive soil's engineering properties meeting the ERA and AASHTO Standard specifications requirements for road subgrade material.

Abstract

Unsuitable soil materials along the alignment of road projects have a significant influence on planning, design, construction, and maintenance. Expansive soils are susceptible to considerable volume changes due to seasonal variations and moisture content. Most soils found in Jimma and Ambo Zones composed of plastic clay soil, causing severe damage at the intermittent of pavement sections. This research study conducted laboratory investigation considering combinations of materials blended to stabilize the expansive soil for subgrade construction. An experimental type of study performed started by collecting specimens. Two clayey soil specimens considered to test the free swell index obtained from a depth of 1.5m to remove the organic impurities. Results indicated the chemical analysis of pumice contained 82.68%, while its physical properties of the test of fineness specific surface and residue on 45 microns showed 3770 cm2/gm and 30%, respectively. As the lime content increased, the CBR strength also increased. But, if the percent content of lime decreased with an increasing pumice content, the CBR value did not show any significant increase. Both the chemical and physical properties satisfied the requirements according to ASTM C-618. Hence, this experiment obtained 7% lime + 3% pumice as an optimum mix ratio to stabilize expansive soils.

Abstract

Abstract

{| style="width: 100%;" |- | style="vertical-align: top;"|''Some environmental issues are industrial wastes and cement productions, which cause high gas emissions. Cement is vital in the global construction industry. The research goal was to find a cheaper material locally. Using OPC, calcined Montmorillonite clay powder (CMMT) and waste Khat Husk Ash (KHA) were tested as a partial replacement. Water entering the interlayer molecular spaces and adsorption, a material in expansive soil, causes Montmorillonite clay to expand more than other clays. Most of Ambo's land is expansive soil, from which samples were taken to determine Montmorillonite clay content. The average temperature required to calcine MMT clay was performed at 800⁰C using a muffle furnace, ground to the fineness of 150μm, and its chemical composition was investigated. Similarly, the waste KH was heated at a temperature of 600⁰C. The proportions by weight are applied for the OPC, Calcined MMT clay powder and Waste Khat Hush Ash as follows: Proportion-A (100%: 0%: 0%); P-B (85%:10%:5%); P-C (75%:20%:5%); P-D (65%:30%:5%); P-E (55%:40%:5%) and P-F (45%:50%:5%). The production of concrete for the C-25 Grade mix design was performed based on the ASTM manual, ERA manual, and the ACI code to evaluate the strengths and durability of concrete. These materials were calcined and then tested for strength and durability using ASTM C 618-5 to determine the chemical compounds at various temperatures. The experiments used aggregates up to 25mm in size. The results showed that when OPC was partially replaced with Calcined MMT clay powder and KHA, the consistency and setting time remained within the ASTM C-191 Standard Specifications. Moreover, the compressive, flexural, and split tensile strengths gradually decreased from the control specimen as the replacement was increased. The optimal amount of calcined MMT clay powder and Waste KHA indicated up to 15% by weight to replace OPC content in normal concrete mix production. The benefit cost analysis revealed that using OPC with calcined MMT clay powder and KHA is more cost-effective than using OPC alone.'' | style="vertical-align: top;"|'''ARTICLE HISTORY''' Received: xxxxx 2021 Accepted: xxxx 2021