Faculty Publications
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Item Laboratory and theoretical evaluation of clogging behaviour of porous friction course mixes(2010) Suresha, S.N.; George, V.; Ravi Shankar, A.U.The clogging of porous friction courses (PFCs) plays a major role in their resulting performance. Clogging occurs due to deposition of external and internal materials, leading to the loss of permeability and drainage characteristics of PFCs. In this study, investigations were conducted to determine the effect of clogging and de-clogging on the permeability of PFC mixes. Tests were conducted to study the effect of three different clogging materials on PFC mixes prepared using four different aggregate gradations. Permeability tests were conducted using the falling-head concept on cylindrical PFC specimens. The influence of the particle size ratios and the effective air voids on the permeability of fresh, clogged and de-clogged PFC specimens was analysed. Experimental results on the permeability observed were compared with those predicted using theoretical models. Although, the theoretical models tend to overestimate the permeability values, statistical analyses indicate good correlations with the observed results.Item Investigations on Alkali-Activated Slag/Fly Ash Concrete with steel slag coarse aggregate for pavement structures(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2017) Palankar, N.; Ravi Shankar, A.U.; Mithun, B.M.The present investigation is conducted to evaluate the effect of steel slag coarse aggregates on mechanical properties and fatigue behaviour of Alkali-Activated Slag Fly Ash Concrete (AASFC) mixes. AASFC mixes were prepared with steel slag coarse aggregates by replacing natural coarse aggregates at various replacement levels (0, 25, 50, 75 and 100% by volume). Various mechanical properties and fatigue performance were tested and compared with conventional Portland concrete. The incorporation of steel slag aggregates resulted in decrease in mechanical strength of AASFC mixes. The fatigue lives of AASFC mixes containing steel slag were found to be lower than AASFC with natural coarse aggregates. Two-parameter Weibull distribution was used for statistical analysis of fatigue data and it was observed that the fatigue data of concrete mixes can be approximately modelled using Weibull distribution. Steel slag aggregates reported acceptable performance in AASFC mixes for its use in pavement quality concrete. © 2015 Informa UK Limited, trading as Taylor & Francis Group.Item A Study on Elastic Deformation Behavior of Steel Fiber-Reinforced Concrete for Pavements(Springer, 2019) Chandrashekar, A.; Palankar, N.; Durga Prashanth, L.; Mithun, B.M.; Ravi Shankar, A.U.The present study discusses the experimental investigation of steel fiber-reinforced concrete slabs on ground under wheel load with the objective of understanding the stress behavior when subjected to central and edge wheel loading. The steel fiber-reinforced fly ash concrete slabs of 900 mm × 900 mm, 150 mm thickness were investigated in this study. Strain gauges and data acquisition system were used to measure the strains at the center and the edge of the slab under the action of the load. The load versus strain relationship under central and edge loading for reference concrete and steel fiber fly ash concrete showed a linear variation even up to the pressure of 2.5 MPa, which is much beyond the conventional tyre inflation pressure of 0.8 MPa. The load versus strain graphs clearly signify the higher modulus of elasticity of fly ash steel fiber-reinforced concrete. The stresses were calculated using IITRIGID software and ANSYS software and were found matching significantly. The value of modulus of elasticity of fly ash steel fiber-reinforced concrete (FS) using ANSYS model for experimental values of load and strains measured was approximated to 34,000 N/mm2 and was found to closely match with the experimentally obtained modulus of elasticity. No significant effect of Poisson’s ratio of concrete on load–strain characteristics was observed within the range 0.15–0.2 of concrete. © 2019, The Institution of Engineers (India).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 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 Strength and Durability Characteristics of Cement and Class F Fly Ash-Treated Black Cotton Soil(Springer, 2021) Chethan, B.A.; Ravi Shankar, A.U.This paper analyses improvement of the strength and durability characteristics of black cotton (BC) soil treated with cement and Class F fly ash for pavements. The increase in cement dosage (3–14%) improved the UCS, but the specimens could not resist WD durability cycles. In order to improve, industrial by-product Class F fly ash was used in addition to the cement. Different combinations of cement (10, 12, and 14%) and fly ash (10, 15, 20, 25, and 30%) replacements were evaluated for strength and durability characteristics. The higher dosage of fly ash reduced the plasticity with uniform distribution of cement cluster formations, leading to higher UCS. The soil mixes with (cement + fly ash) stabilizer combinations (10 + 30), (12 + 30), (14 + 25), (14 + 30) were stable against WD test with soil loss < 14%. Mix with (14 + 25) stabilizer showed a maximum retained UCS of 3.6 MPa at 2.9% moisture content (MC) after 12 WD cycles. However, most of the mixes showed high resistance to the FT test. The retained UCS of FT tested specimens was more due to low variations in moisture content. Mix with (14 + 30) stabilizer showed a maximum retained UCS of 2.6 MPa at 23.3% MC after 12 FT cycles. The soil samples with high cement and fly ash contents, with 90 days curing, can exhibit significant strength and more resistance to WD and FT cycles with soil loss < 14%. After drying, severe damage to WD specimens was observed due to the drastic absorption of water during the wetting cycle. Durable samples showed good plunger penetration resistance with an expansion of < 2%. Scanning electron microscopy (SEM) images showed the formations of cemented interclusters. CSH formed resulted in strength improvement, as observed from XRD patterns. The 7 days cured WD specimens did not exhibit any volume expansion on soaking, thawing in water. A maximum volumetric shrinkage of 3.2% on drying and 1.91% on freezing was observed for stabilized soil. Hence, the stronger and durable stabilized soil mixes with high volume stability can be used for pavements. © 2021, Indian Geotechnical Society.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 Mechanical properties of pavement quality concrete with aluminium industry waste as a binder(Elsevier Ltd, 2023) Panditharadhya, B.J.; Mulangi, R.H.; Ravi Shankar, A.U.Utilizing industrial marginal materials in the production of concrete makes it economical by reducing the cost of cement and reduces the environmental risk associated with Ordinary Portland Cement (OPC) production. Aluminium Dross (AD) is an industrial by-product from aluminium industry obtained during resmelting of aluminium ore in the furnace at high temperatures. Dumping of this waste in landfill makes it difficult to facilitate large area required and causes nuisance to the surrounding environment. Also, it is required to minimize the use of Ordinary Portland Cement (OPC) due to higher energy consumption involved in its production. AD is pre-treated and tested by Toxicity Characteristic Leaching Procedure (TCLP) to check its leachability. In this study, mechanical properties of concrete along with flexural fatigue behaviour are discussed with respect to partial replacement of AD for OPC. Strength properties of concrete at 15% AD replacement is comparable with that of control concrete. Scanning Electron Microscope (SEM) image of the concrete mix with 15% AD is taken to observe minor voids in comparison with the SEM image of normal concrete mix. Flexural fatigue behaviour is evaluated at varying stress levels and found that the concrete with 15% AD is satisfying the requirements to be used as Pavement Quality Concrete. © 2023Item Laboratory investigation on cement-treated recycled concrete aggregate bases for flexible pavements(Elsevier Ltd, 2023) Chiranjeevi, K.; Hemanth Kumar, D.; Yathish, R.G.; Ravi Shankar, A.U.India's economy is progressing fast, and many infrastructure development programs are going on. Especially the road network expansion is going on many folds. As a result, natural coarse aggregates are getting depleted, which has an impact on environmental sustainability. Utilizing the resources from the many aged and demolished structures will be cost-effective and solve the disposal problem of these wastes. India's government insists on using marginal material, demolished waste, or recycled aggregates as alternative materials for road construction. New codes developed by IRC and MoRTH recommend Cement Treated Bases (CTB) and Cement Treated Sub-Bases for pavement lower layers. In light of this, the present study attempts to utilize Recycled Concrete Aggregates (RCA) obtained from construction and demolition (C&D) waste in the CTB. The efficiency of RCA was checked at various replacement levels ranging from 0% to 100% with cement stabilization of 3%, 5%, and 7%. The strength properties like Unconfined Compressive Strength (UCS), Flexural Strength and durability were evaluated. The microstructural characteristics and elemental analysis of the cement treated recycled concrete aggregate mixtures were examined. The research yielded the highest potential RCA of up to 50% with a cement content of 5%, meeting the Indian Road Congress (IRC) criteria for CTB. © 2023