Faculty Publications
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Item Utilization of Recycled Concrete Aggregates Processed Using the Ball Milling Method in Cement-Treated Bases for Pavements(Springer Science and Business Media Deutschland GmbH, 2024) Chiranjeevi, K.; Kumar, D.H.; Kumar, A.J.; Thapas, N.D.S.; Ravi Shankar, A.U.Pavement construction and maintenance have become very common worldwide as traffic volumes and vehicular axle weights continue to rise as the global population grows and technology advances. The extensive utilization of natural resources implies that their existence for long-term availability cannot be assured. Using materials from the various damaged and collapsed structures will save money and find a solution to the trash disposal issue. These materials have inferior engineering properties compared to conventional materials and cannot be used directly in pavement applications. These materials must be processed or stabilized by mechanical and chemical stabilization techniques. Processing of Recycled Concrete Aggregates (RCAs) has gained more importance in improving the physical properties. In the current investigation, construction and demolition (C&D) waste was processed in two stages successively. In the first stage, C&D waste was subjected to manual crushing and further processed through jaw crushing. The aggregates were processed through ball milling in the second stage. The natural aggregates are entirely replaced with the RCA in cement-treated bases (CTBs) at 3, 5, and 7% stabilization levels. Mechanical and durability properties were evaluated. The RCA produced from the ball milling method performs better than the unprocessed RCA. The mix having 7% cement content with processed RCA met the specifications for CTB. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.Item Fatigue and Engineering Properties of Chemically Stabilized Soil for Pavements(Springer, 2013) Lekha, B.M.; Ravi Shankar, A.U.; Goutham, G.Soil stabilization is a technique to improve the weak soils and making them to meet certain requirements of the specific engineering projects. The type of soils available in Dakshina Kannada region of Karnataka State is laterite and Lithomarge clay. Its Plasticity Index is very high due to the presence of high percentage of silt and clay content. In the present investigation, an attempt is made to study the behaviour of laterite with and without adding chemicals. A chemical named Zycosoil, when added to water and mixed with soil alters its engineering properties that depend upon the type of the soil and dosage of chemical. These chemicals are liquid additives, which act on the soil to reduce the voids between soil particles and minimize adsorbed water in the soil for maximum compaction. In the present study, the effectiveness of Zycosoil in stabilizing the laterite soils of South Canara district is investigated through laboratory experiments. Various geotechnical properties are studied and correlations between different geotechnical properties and improvement in the soil properties with different percentages of chemical additions are derived. The important properties such as index properties, compaction characteristics, unconfined compressive strength parameters, California bearing ratio values and fatigue behaviour were studied. The results obtained indicate that there is an improvement in almost all properties with the addition of Zycosoil. © 2012 Indian Geotechnical Society.Item A study on initial setting time and the mechanical properties of AASC using the PS ball as fine aggregate(Springer, 2019) Talkeri, A.H.; Ravi Shankar, A.U.India is the second largest producer of cement in the world with an annual production of 455 Million Tonnes (MT) which is expected to reach up to 550MT by 2020. In India, the increased demand for cement in the construction industry is required to meet the needs of infrastructure development. However, the production of Portland cement releases significant amounts of CO2 to the atmosphere. Therefore, it is necessary to look for sustainable solutions for concrete production by the use of supplementary cementitious materials. The alternative replacement for Ordinary Portland Cement (OPC) can be Ground Granulated Blast Furnace Slag (GGBS), Fly-ash, Silica fume, Rice-husk ash, which is the various industrial by-products. In this present work, an attempt was made to develop Alkali Activated Slag Concrete (AASC) using Precious Slag (PS) ball as fine aggregate. The development of AASC was made with GGBS as the principal binder. Mixes were developed with binder content 443 kg/m3, Sodium Silicate (SS)/Sodium Hydroxide (SH) ratio of 1 and their performance when exposed to ambient temperature were studied. Alkali binder ratio (0.3) with 8, 10, 12 and 14M NaOH was selected for all the AASC mixes. The test results showed that the slump values for the different mixes satisfying the MoRTH guidelines for concrete pavements. The AASC mixes have higher compressive strength ranging between 41–64 MPa. The fatigue life of the AASC mix was has improved by the addition of PS ball, at the higher concentration of NaOH. © 2019, Chinese Society of Pavement Engineering. Production and hosting by Springer Nature.Item Use of Stabilized Lateritic and Black Cotton Soils as a Base Course Replacing Conventional Granular Layer in Flexible Pavement(Springer, 2020) Amulya, S.; Ravi Shankar, A.U.The present work investigates the improved properties of lateritic and black cotton soils stabilized with ground granulated blast furnace slag (GGBFS) and alkali solutions. The alkali solution includes a mixture of sodium hydroxide and sodium silicate. The lateritic and black soils are treated with 30% GGBFS and the alkali solutions consisting of 6% Na2O having silica modulus (Ms) of 0.5, 1.0 and 1.5 at a constant water binder ratio of 0.25. The treated samples were air-cured for 0 (immediately after casting), 3, 7 and 28 days at ambient temperature. The treated lateritic soil with 0.5 and 1.0 Ms is found durable after 3, 7, and 28 days curing. Whereas, the treated BC soil found durable with Ms 0.5 at modified Proctor density after 28 days curing. The formation of calcium silicate hydrate and calcium aluminosilicate hydrate structures resulted in a remarkable improvement of compressive strength, flexure and fatigue life of treated soils due to dissolved calcium ions from GGBFS, silicate and aluminium ions from alkali solutions. The microstructure image of the durable soil sample shows the crystal orientation of particles. The design of high and low volume roads is proposed by replacing the conventional granular layer with the durable stabilized soil and stress–strain analysis is carried out using pavement analysis software. © 2020, Springer Nature Switzerland AG.Item Replacement of Conventional Base Course with Stabilized Lateritic Soil Using Ground Granulated Blast Furnace Slag and Alkali Solution in the Flexible Pavement Construction(Springer, 2020) Amulya, S.; Ravi Shankar, A.U.The use of cement/chemical-treated base and sub-bases is widely recommended in the pavement construction. Therefore, this paper investigates the behaviour of stabilized lateritic soil as a base course in flexible pavement by replacing the granular base course. The lateritic soil was stabilized with 25% Ground Granulated Blast Furnace Slag (GGBFS) along with the alkali solutions such as sodium hydroxide and sodium silicate at a varying sodium oxide (Na2O) contents of 4, 5 and 6%, silica modulus (Ms, a ratio of silica to sodium oxide) of 0.5, 1.0 and 1.5 and a constant water binder ratio (w/b) of 0.25. The maximum compressive strengths of 5452 and 6593 kPa were achieved for a treated sample consisting of 6% Na2O and 1.0 Ms cured for 28 days at the light and heavy compactions, respectively, which is due to the formation of calcium silicate hydrates when calcium oxide-rich GGBFS reacts with water. Further with the curing period results in an increase in strength due to the formation of calcium alumino-silicate hydrates when GGBFS reacts with alkali solutions. The durability of the samples was evaluated by wetting–drying and freezing–thawing tests. The samples passing the required durability criteria were tested for flexural strength and fatigue life. Scanning electron microscope images showed closely packed crystal orientation indicating high strength. Low and high volume pavements were designed using stabilized soil as a base course, and the strains were evaluated using pavement analysis software. It is suggested that the conventional granular base layer can be replaced with the stabilized soil. © 2020, Indian Geotechnical Society.Item Stabilisation of lithomargic clay using alkali activated fly ash and ground granulated blast furnace slag(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2020) Amulya, A.; Ravi Shankar, A.U.; Praveen, M.A suitable ground improvement technique is essential in order to confront the problems associated with lithomargic clay for road construction. The efficacy of alkaline solutions such as sodium hydroxide and sodium silicate along with class F fly ash and Ground Granulated Blast Furnace Slag (GGBS) as additives to improve the properties of lithomargic clay is examined. The different mixes are prepared by replacing the soil with 20%, 30%, and 40% of GGBS and fly ash. The Maximum Dry Density (MDD) obtained from the soil replaced with 40% GGBS and for the soil replaced with 30% fly ash. An activator modulus of 1.25 is kept constant for the varying sodium oxide dosage at 2, 3 and 4 per cent. The Unconfined Compressive Strength (UCS) of the alkali-activated soil cured for 3, 7 and 28 days is determined and compared with the UCS of the soil replaced with fly ash and GGBS at both standard and modified proctor densities. The different mixes are tested for the durability, California Bearing Ratio (CBR). The soil is replaced with GGBS and fly ash does not pass the durability test while the alkali-activated mixes with 4% sodium oxide dosage is found to be durable. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.Item Utilization of lateritic soil stabilized with alkali solution and ground granulated blast furnace slag as a base course in flexible pavement construction(Springer, 2020) Amulya, A.; Ravi Shankar, A.U.; Singh, A.; Pammar, K.H.The natural aggregates are depleting in developing countries due to the excessive usage in road and building construction. In the present study, the engineering properties of abundantly available lateritic soil stabilized with Ground Granulated Blast Furnace Slag (GGBS) and alkali solutions like Sodium hydroxide and Sodium silicate was evaluated. The suitability of stabilized soil as a base course in flexible pavements was investigated. The lateritic soil was treated with 15, 20, 25 and 30% of GGBS and alkali solutions consisting of 5% of Sodium oxide with Silica Modulus (Ms) of 0.5, 1.0 and 1.5 at a constant water binder ratio of 0.25. The improved unconfined compressive strength, flexural strength, and fatigue life were observed from the soil treated with 30% of GGBS and alkali solution having Ms 1.0 air-cured for 28 days at ambient temperature. The improvement is due to the formation of Calcium Silicate Hydrates and Calcium Alumino Silicate Hydrates from an exothermic reaction between Calcium ions and the dissolved silicates and aluminates present in GGBS and alkali solutions. The samples treated with 25, 30% of GGBS and alkali solution having 1.0 Ms cured for 28 days found to be durable in Wetting-Drying and Freezing-Thawing tests. The compact and densified crystal orientation of the treated soil samples was observed from the microstructure images obtained from the Scanning Electron Microscope technique. The design of low and high volume roads was suggested with stabilized soil and strains developed at different locations on the proposed pavement were analyzed using pavement analysis software. © 2020, Chinese Society of Pavement Engineering. Production and hosting by Springer Nature.Item Effect of Flash Flood and Weather Changes on Unconfined Compressive Strength of Cement- and Fly Ash-Stabilized Black Cotton Soil Used as Road Materials(Springer, 2023) Chethan, B.A.; Ravi Shankar, A.U.Stabilized soil naturally undergoes variation in moisture content and temperature during seasonal weather changes. In this investigation, the influence of these weather changes on unconfined compressive strength (UCS) of black cotton (BC) soil stabilized with ordinary Portland cement (43 grade) and class F fly ash was studied. Cement dosage was varied from 3 to 10%, along with different combined dosages of (cement + fly ash) (where fly ash < 32%) for stabilizing various mixes. The UCS specimens were cured for 0 (immediately after preparation) 3, 7, 28, 60, and 90 days in a desiccator and subsequently submerged for 24 h in water to ensure saturation. The flash flood effect was evaluated in terms of strength reduction by correlating UCS of saturated specimens (UCSs) with UCS of desiccator-cured specimens. The stabilized materials’ resistance to wetting–drying (WD), freezing–thawing (FT) durability tests and subsequent UCS retained over time were determined. The UCS values increased substantially at higher cement and fly ash contents and with the curing period, whereas a notable reduction in UCSs values was observed for saturated samples. However, the samples with high cement and fly ash contents exhibited low moisture susceptibility with lesser strength reduction. The UCS and UCSs values are linearly correlated with R2 values > 0.9. All the specimens were intact with improved volume stability at higher cement and fly ash dosages during saturation and drying. Mixes with high cement and fly ash dosages shown improved resistance to WD cycles, whereas at a low dosage, most of the mixes failed during the second wetting cycle due to a drastic absorption of water after the first drying cycle. All FT specimens were intact with considerable strength retained after 12 cycles exhibiting a minimal mass loss. The formation of hydration products has justified the strength gain as observed from scanning electron microscope (SEM) images, energy dispersive X-Ray analysis (EDAX), and X-ray diffraction (XRD) plots. © 2021, The Author(s), under exclusive licence to Chinese Society of Pavement Engineering.Item Investigations on Bio-enzyme Stabilized Pavement Subgrades of Lateritic, Lithomargic and Blended Soils(Springer, 2023) Marathe, S.; Ravi Shankar, A.U.The pavement is a structure, which is laid to support the wheel load and to spread the load stress to a wider area on the top of the soil subgrade. The process of changing the engineering properties of natural soil, to improve its strength, bearing capacity and other engineering properties by the addition of suitable stabilizer and admixture is collectively known as stabilization of soil. It is very much essential to improve the soil strength, bearing capacity and other engineering properties to sustain the loads acting on the pavement. By modifying the subgrade soil properties, the crust thickness of the pavement reduces. This paper focuses on the effect of TerraZyme stabilization on three types of major soils available in the coastal Karnataka region. The study deals with the improvement in the engineering properties of these soils after subjecting to TerraZyme chemical stabilization. Initially, tests were carried out to study the mechanical properties like compaction, permeability, unconfined compressive strength (UCS) and California Bearing Ratio (CBR value). Further, the effect additions of TerraZyme chemical in various dosages to soil were observed in terms of their modified proctor compaction, UCS and CBR values. The curing effect on UCS and CBR was investigated. The structural design of pavement for the high-volume roads (as per IRC:37-2018) is proposed by strengthening the conventional subgrade soil layer with TerraZyme and the pavement analysis is carried out. © 2021, The Author(s), under exclusive licence to Chinese Society of Pavement Engineering.Item Optimisation of recycled concrete aggregates for cement-treated bases by response surface method(Taylor and Francis Ltd., 2023) Chiranjeevi, K.; Kumar, D.H.; Srinivasa, A.S.; Ravi Shankar, A.U.Sustainability is a primary concern that needs to be addressed since infrastructure development requires significant natural resources. Using Recycled Concrete Aggregates (RCA) for road construction has numerous benefits in saving natural resources and the environment. In the present investigation, the demolition waste is being used for road construction, partially/fully replacing natural aggregates. The Cement Treated Recycled Concrete Aggregate (CTRCA) specimens were prepared at 3%, 5%, and 7% cement with various blends of RCA and Natural Coarse Aggregates (NCA) ranging from 0 to 100%. The strength characteristics in terms of Unconfined Compressive Strength (UCS), Flexural Strength (FS), Elastic Modulus, Indirect Tensile Strength (ITS) and durability tests were conducted on cured samples. Microstructural analysis using Scanning Electronic Microscope (SEM) revealed that the pores and cracks in the old mortar have a detrimental influence on the mechanical properties of CTRCA mixes. However, Energy Dispersive Spectroscopy (EDS) and durability tests have shown positive results. The Response Surface Method (RSM) was utilised to optimise the RCA and cement content in CTRCA mixes. The research resulted in the maximum possible RCA of up to 70% with a cement content of 5.8%, which met the Indian Road Congress (IRC) specifications for Cement Treated Bases (CTB). © 2023 Informa UK Limited, trading as Taylor & Francis Group.