Faculty Publications
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Item Recuring studies on concretes subjected to elevated temperatures and suddenly cooled by water quenching(Multi-Science Publishing Co. Ltd, 2015) Yaragal, S.C.; Kittur, M.M.; Babu Narayan, K.S.Concrete is found to undergo degradation when subjected to elevated temperatures during an accidental event, such as fire and lose substantial amount of its original strength. The loss of strength in concrete is mainly attributed to the decomposition of Calcium Silicate Hydrate (C-S-H) and release of chemically bound water, which begins when the exposure temperature exceeds 500°C. When such a concrete is supplied with water and allowed to recure, it is found to recover substantial amount of its lost strength. This work is carried out to investigate the effect of recuring on strength recovery of un-blended and blended concrete specimen (100 mm cubes) subjected to elevated temperatures from 400°C to 700°C, in steps of 100°C, for a retention period of two hours at the designated temperatures. The concrete cubes immediately after exposure were subjected to thermal shock by quenching them in water, and then temperature of thermally shocked concrete is allowed to cool to room temperature. The cooled specimen were then recured in water for 1, 3, 7, 14, 21, 28, 56 days and tested for compressive strength recovery. These studies were carried out for Portland Cement (PC) based concrete and Portland & Granulated Blast Furnace Slag (70% PC + 30% GGBS) based concrete (blended concrete), and some interesting results are presented and discussed in this paper. © 2015, Multi-Science Publishing Co. Ltd. All rights reserved.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.