Conference Papers
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Item Effect of wastewaters on the geo-technical properties of laterite(2005) Sunil, B.M.; Shrihari, S.Soil contamination arises from variety of sources, which include acid rain, hazardous liquid and solid waste from industries, animal waste, salt-water intrusion, etc. Literature relevant to the soil-pollutant interaction reveals that soil properties and behaviour is influenced and altered due to contamination by pollutant. The soil pollutant interaction depends on various factors such as nature and chemical composition of soil, dielectric constant of pore fluid, organic matter etc. Sulphur dioxide and oxides of nitrogen are the two most important parameters responsible for acid rain. Atmospheric pollution has resulted in the precipitation having pH less than 5.6 disturbing the nature's delicate balance and also contamination of soil. The soil and ground water contamination will result in Socio-economic and environmental impact. Several studies by various researchers have highlighted the influence of physico-chemical factors on the engineering properties of soil. The alteration of characteristic properties of the soil in the vicinity of industrial plants occurs mainly as a result of their pollution. Literature review on the effect of acid rain on soils indicated that the pH value of soils generally decreased with continuous infiltration. The major soil chemical parameters affecting the contaminant partitioning are hydrogen ion concentration in the soil, which influences all chemical reactions and biological activities. Laterites and lateritic soil have a very important place in Civil Engineering activities in India, especially in the South and Central parts. They form a good foundation material and are composed essentially of hydrated aluminium and iron oxides. In this paper, the results of an investigation on the effect of pH on the characteristic properties of laterite soil procured from the quarry near Mangalore, located on the western coast of south India, has been discussed. The effect of pH on the characteristic properties of laterite was studied under different pH conditions (i.e. pH =5.0, pH=7.0, pH=8.0). The pH of water in which the laterite blocks were soaked (up to ninety days) was maintained using buffers. The important properties considered for the study are: compressive strength of laterite blocks, Atterbeig limits, shear strength properties and chemical characteristics of laterite soil (pH, conductivity, alkalinity, hardness, chloride, sulphate and ammonia nitrogen). From the investigation it is observed that the engineering properties and chemical characteristics of laterite soil are altered in all the three pH conditions (pH=5.0, pH=7.0, pH=8.0). The compressive strength of laterite blocks reduced under all the pH conditio is and considerable reduction in strength was observed when the pH of water was maintained as 5.0. The pH of adjoining water body has remarkable influence on the pH of soil. Accordingly when the pH of water was low (p -1=5.0), the corresponding pH of soil decreased from its initial value. Similarly soil pH increased when the pH of water was maintained as 8.0 for soaking up to ninety days. The various other effects on the engineering behaxiour and chemical characteristics of laterite are noted and discussed in the present work.Item Stabilization of lateritic soil using bio-enzyme(2008) Mithanthaya, I.R.; Ravishankar, A.U.Soil stabilization is a technique aimed at increasing or maintaining the stability of a soil mass, or otherwise improving its engineering properties. Various techniques are being used for stabilization of soil. Sub-base is an integral part of the road pavement structure. The main function of the sub-base is to provide a stress transmitting medium for spreading the surface wheel load in such a manner as to prevent shear and consolidated deformations. A number of researchers worked on characterizing variousus properties of the laterite soil and found that the following problems could be associated with the laterite: 1)In the majority of cases, the laterite doesn't satisfy conventional specifications for road construction materials especially road base. 2) The laterit undergoes property changes during construction; gradation being considered to be the most sensitive. To improve on the above deficiencies and consequently to improve on there field performance characteristics, laterites need to be stabilized. Bioenzyme - stabilization is a newer technique for strengthening the sub-base soil. The Bioenzyme alters the engineering properties of soil such as the capacity to bear loads. These enzymes are liquid additives, which act on the soil to reduce the voids between soil particles and minimize absorbed water in the soil for maximum compaction. The locally available laterite soil procured from the field is used to improve the strength and bearing capacity. One type of Bio-enzyme namely TerraZyme has been used for stabilization of laterite soil. In this study soil with variable enzyme dosages were tested for stabilization process and strength of the stabilized soil has been evaluated after curing period of one week, two weeks, three weeks and four weeks. The tests were carried out to determine the consistency limits, CBR, unconfined compressive strength and permeability of the soil specimens with and without enzyme for a curing period of one week to four weeks. The effect of enzyme on different percentages of sand blended laterite soil was also studied for the curing periods. The enzyme treated soil showed significant improvement in CBR (California bearing ratio) and UCS (Unconfined Compressive strength) with curing. © AES-Advanced Engineering Solutions.Item Durability Studies on the Lateritic Soil Stabilized with GGBS and Alkali Solutions(American Society of Civil Engineers (ASCE) onlinejls@asce.org 1801 Alexander Bell DriveGEO Reston VA 20191 Alabama, 2019) Amulya, S.; Ravi Shankar, A.U.; Panditharadhya, B.J.In order to use the locally available lateritic soil as a base course for pavement construction, the engineering properties of the soil need to be enhanced. Hence, the experimental investigation of the lateritic soil stabilized with the ground granulated blast furnace slag (GGBS) and combination of alkali solutions such as sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) has been conducted. The various parameters which affect the properties of the soil like binder (GGBS) content, sodium oxide (Na2O) dosage, silica modulus (Ms), and water to binder ratio (w/b) are considered. In the present investigation, the GGBS content of 25%, Na2O of 6%, Ms of 0.5, and w/b of 0.25 are chosen. The Atterberg's limits, standard and modified proctor compaction tests, unconfined compressive strength (UCS), and durability tests were conducted on the stabilized soil. The UCS of 28 days cured and stabilized samples at standard and modified proctor densities is showing 775% and 580% increase with respect to natural soil and 98% and 142% increase with respect to 0 days cured samples respectively. The chosen combination of soil mixture passes all 12 cycles of wetting and drying (WD) and freeze and thaw (FT) with weight loss of 5.2% and 1% at standard proctor density and 8% and 2.5% at modified proctor density respectively after 7 days of curing. © 2019 American Society of Civil Engineers.Item Experimental Studies on Lateritic Soil Stabilized with Cement, Coir and Aggregate(Springer Science and Business Media Deutschland GmbH info@springer-sbm.com, 2021) Ravi Shankar, A.U.R.; Priyanka, B.A.; AvinashThe characteristics of subgrade soil play a vital role in designing the pavement structure so that the pavement has required support from the bottom layer. During adverse weather conditions and higher traffic loads moving on any pavement, it should be able to withstand the impact and perform well for longer duration. Load is transmitted from pavement to the subgrade layer and distributed evenly through the soil particles. All types of soil are not capable of handling such impacts by their own and needs additional stabilization processes. Several stabilization processes are available in which the best one has to be taken into consideration. Fibers such as coconut coir are important in giving extra stability to the soil particles. Cement is well-known material in construction sector along with aggregates. Lateritic soil is available abundantly in coastal areas of southern parts of India which has porous structure and demands stabilization when the intended purpose is specific and requires higher strength and durability. In this study, coconut coir along with cement and aggregate are taken as stabilization materials to stabilize lateritic soil. Initially, basic properties of soil like plastic limit, liquid limit and plasticity index are determined. Grain size analysis is done and modified Proctor test is conducted to determine the optimum moisture content (OMC) and maximum dry density (MDD) of the soil. Unconfined compression test (UCS), California bearing ratio test (CBR), flexural fatigue analysis, durability properties with respect to wet-dry cycles and freeze–thaw cycles are evaluated for untreated and treated soil specimen. As per UCS values, cement can be taken at an optimum dosage of 6%. The coir fibers from natural husk of coconut and aggregates of 10 mm below size were added to the soil–cement mixes and an optimum dosage of coir and aggregate is determined. The study showed positive results in terms of CBR values of cement-aggregate treated soil. © 2021, Springer Nature Singapore Pte Ltd.Item Experimental Investigations on RBI Grade 81 Stabilized Lateritic Soil(Springer Science and Business Media Deutschland GmbH, 2021) Chethan, B.A.; Das, S.; Amulya, S.; Ravi Shankar, A.U.R.The effectiveness of the addition of RBI Grade 81 (stabilizer) (dosages of 2, 4, 6, and 8%) to stabilize the largely encountered lateritic soil during construction was investigated. Stabilized lateritic soil mixes were evaluated by conducting a series of experiments, viz., standard and modified compaction, unconfined compressive strength, and California bearing ratio at various curing periods. Mixes under both standard and modified compaction energies have shown the highest density at a 6% stabilizer dosage. A remarkable increase in unconfined compressive strength was observed for the specimens prepared at a 6% stabilizer dosage corresponding to the modified compaction density. An increase in the percentage of stabilizer has increased the California bearing ratio of treated mixes. Exorbitant increase in the soaked California bearing ratio values of the stabilized mixes was observed for higher dosages (6 and 8%). Hence, RBI Grade 81 amended lateritic soil mixes enhance the strength of the subgrade. © 2021, Springer Nature Singapore Pte Ltd.Item Laboratory Investigations on Lateritic Soil Stabilized with RBI Grade 81, Coconut Fiber and Aggregates(Springer Science and Business Media Deutschland GmbH, 2022) Chethan, B.A.; Ravi Shankar, A.U.Soil stabilization is an excellent old technique adopted to improve the properties of any weak soil. In the recent past, many chemical stabilizers came to the market. In this study, a commercial stabilizer-RBI Grade 81’s (dosage 2–8%) potential to improve lateritic soil properties was investigated. At 6% RBI Grade 81 dosage, the effect of reinforcement was evaluated by using 0.5 and 1.0% coconut fibers. Strength improvement of 6% RBI Grade 81 stabilized soil admixed with <12.5 mm size aggregates (5, 10, and 15%) was studied to know the effect of granular layer demolition waste incorporation. CBR and UCS tests were used for strength evaluation. Considerable improvement in mix strength was observed above 6% RBI Grade 81 dosage on 28 curing days for the soil incorporated with fibers and aggregates. A linear fit was established between UCS and soaked CBR, which shows a high correlation (>0.9), and Prob > F is <0.06 depicting high reliability for the estimation of soaked CBR from UCS. Further, fatigue and durability tests were carried out to understand stabilized soil’s behavior under dynamic load application and performance during monsoon to simulate the submerged condition of the pavement in dense rainfall areas (>3500 mm). Stabilized lateritic soil mixes sustained freeze–thaw cycles effectively with weight loss of <14%. However, even at an 8% RBI Grade 81 dosage, the mix has not satisfied the wetting–drying test requirement. Stabilized soil blends showed excellent fatigue performance under repeated loads. The 6% RBI Grade 81 treated soil mixes can be used for modified subgrade. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.Item Laboratory Investigation of Lateritic Soil Stabilized with Arecanut Coir Along with Cement and Its Suitability as a Modified Subgrade(Springer Science and Business Media Deutschland GmbH, 2023) Chethan, B.A.; Lekha, B.M.; Ravi Shankar, A.U.If a pavement is constructed on weak soil, its lifespan drastically reduces due to the low strength induced by moisture-induced destresses. Such soils may undergo considerable changes in volume. In order to modify these properties, soil stabilization can be done. By stabilizing the soil along with the improvement in strength, its durability can be increased. Stabilization may be of chemical or mechanical type. In this investigation, lateritic soil was stabilized using 0.2–1% arecanut coir, and its compaction characteristics were evaluated. The lateritic soil is found to be nondurable. The reinforcement alone could not improve the strength and durability effectively. Therefore, 3% binding agent ordinary Portland cement (43 grade) was added to the mix. Due to cement stabilization, UCS and CBR values were improved, and the optimum values were observed at 0.6% arecanut coir dosage. The addition of cement has resulted in a change in silica, alumina, and calcium oxide contents, thereby contributing to the formation of hydration products. The samples with 1% coir and cement have completed 12 wet–dry cycles, but the weight loss observed was >14%. All the specimens showed low soil loss under freeze–thaw cycles. The performance of cured specimens under fatigue loading was satisfactory. Since the specimens could not pass wet–dry durability criteria, they can be considered for modified subgrade. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Utilization of GGBS-Based Geopolymer Lateritic Soils for Sustainable Pavements(Springer Science and Business Media Deutschland GmbH, 2023) Thotakura, T.V.; Sunil, B.M.; Venkata Rao, M.V.Nowadays geopolymers have been recognized as eco-friendly materials as well as potential replacement of ordinary Portland cement (OPC) and lime, which are cementitious materials with three-dimensional tetrahedral frameworks of Al and Si. This paper presents experimental investigation on compaction characteristics such as optimum moisture content (OMC) and maximum dry density (MDD) and unconfined compressive strength (UCS) of a lateritic soil chemically altered with alkali activator along with precursor as ground granulated blast furnace slag (GGBS) with varying amounts of GGBS content. GGBS was added to the lateritic soil up to 30% in increments of 5%. Scanning electron microscopy (SEM) was undertaken on the geopolymer blends to know the micro-structural behaviour and chemical compounds. The results revealed that the unconfined compressive strength (UCS) of the GGBS-based geopolymer soils improved with addition of GGBS content. The micro-structural analysis confirmed the both pozzolanic reaction and ionic exchange takes place in the alkali-activated lateritic blends. The impetus for the utilization of geopolymers can be consuming GGBS in large quantities in their synthesis with the potential to reduce the use of high carbon footprint ordinary Portland cement. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.