Conference Papers
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Item Experimental Investigation of Black Cotton Soil Stabilized with Lime and Coconut Coir(Springer, 2018) Ravi Shankar, A.U.; Panditharadhya, B.J.; Karishekki, S.; Amulya, S.Expansive soil occurring above the water table undergo volume changes with change in moisture content. In expansive soils, increase in water table causes swelling–shrink behaviour which leads to cracks and differential settlement resulting in several damages to the pavements, canal beds and linings, foundations, buildings, etc. An attempt is made in this paper to study the effect of adding lime-coir fiber on geotechnical properties of black cotton soil. In the present study an effort is made to obtain the optimum dosage of lime for stabilization of black cotton soil abundantly available in Karnataka state of India. The study incorporates investigation of basic geotechnical properties like grain size distribution, specific gravity, consistency limits and engineering properties like Maximum Dry Density (MDD), Optimum Moisture Content (OMC), Unconfined Compressive Strength (UCS) and California Bearing Ratio (CBR). Swelling properties have been determined by conducting Free Swell Index (FSI) test. Durability of the soil is studied by conducting wet-dry cycle and freeze-thaw cycles (WD and FT tests). Fatigue test has been conducted to determine the fatigue life of treated and original soil. Further chemical analysis was conducted to determine the chemical composition of untreated and treated soil. The optimum dosage of lime obtained was 4%. The investigations were carried out to study the effect of addition of coir fibers which are obtained from local market to evaluate the extent of modification on MDD, OMC, UCS and CBR of the soil. Maximum improvement in UCS and CBR values are observed when 1% of coir are mixed with the soil. Soil stabilized with Lime-Coir fiber has shown better results when compared to soil stabilized with lime alone. It is concluded that the proportion of 1% coir fiber in a soil is the optimum percentage of materials having maximum soaked CBR value. Hence, this proportion may be economically used in road pavement and embankments. © Springer Nature Singapore Pte Ltd. 2018.Item Areca Fiber Reinforced Alkali-Activated Black Cotton Soil Using Class F Fly Ash and Limestone Powder for Pavements(Springer Science and Business Media Deutschland GmbH, 2022) Chethan, B.A.; Ravi Shankar, A.U.Alkali activation has gained importance in place of cement treatment in construction due to reduced CO2 emissions. The precursors that are rich in silica, alumina, and calcium can be used for soil stabilization with a suitable alkali solution. In this investigation, 0–45% class F fly ash with a constant 5% limestone powder was used to stabilize black cotton soil. These mixes were reinforced with 0.5% areca fibers and stabilized using the alkali solution. Alkali solution was prepared using 8 molar NaOH solution and Na2SiO3 solution with Na2SiO3/NaOH of 1.5. The use of limestone powder has favoured the quick UCS gain on 3 days of room temperature curing. Fiber reinforcement has shown a significant influence on flexural strength and fatigue life improvement. Areca fibers reinforcement has resulted in enormous resistance to plunger penetration during the unsoaked CBR test. However, on further 4 days of soaking, samples lost the bonding and exhibited low CBR. The SEM images showed the compact microstructure of the set mix. The formation of cementitious products is evident from the XRD micrograms due to the dissolution of silica, alumina, calcium, and other compounds by the alkali solution. When subjected to wetting–drying and freezing–thawing durability tests, the set mixes were failed due to leaching of mineral constituents and further breaking of soil structure. Even though stabilized specimens exhibited significant strength improvement in dry conditions, they are unsuitable in wet conditions. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.Item Alkali Activated Black Cotton Soil with Partial Replacement of Class F Fly Ash and Areca Nut Fiber Reinforcement(Springer Science and Business Media Deutschland GmbH, 2023) Chethan, B.A.; Ravi Shankar, A.U.; Chinnabhandar, R.K.; Kumar, D.H.Alkali activation has received great attention for improving the soil properties with suitable precursor materials. Industrial byproduct class F fly ash was suitably utilized to improve Black Cotton (BC) soil properties along with ordinary Portland cement by various researchers. However, the CO2 emission associated with cement production has enforced the evaluation of alternative binders. Laboratory investigations were conducted on BC soil by admixing various fly ash dosages (0–50%) and reinforcing the mix with 0.5% areca nut fiber. Alkali activator solution prepared using 8 molar sodium hydroxide solution (SH) and sodium silicate solution (SS) at 1.5 SS/SH ratio showed significant improvement in Unconfined Compressive Strength (UCS) of stabilized BC soil on 7 and 28 days curing. The reinforcement was effective in improving the flexural strength of stabilized mixes. Exorbitant unsoaked California Bearing Ratio (CBR) values were observed on 28 days of curing. However, the samples could retain low soaked CBR values despite reinforcement. Scanning Electron Microscope (SEM) images showed the reduction of shrinkage cracks and strong bonding of fibers in the stabilized mix. X-Ray Diffraction (XRD) patterns evidenced the formation of various hydration products due to the alkali reaction, which resulted in the high strength gain of mixes at ambient temperature curing. The leaching of mineral constituents from the set mix lead to the failure of durability samples. Due to nondurability, the alkali activation with a selected precursor cannot suit pavement materials requirements. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.