Faculty Publications

Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736

Publications by NITK Faculty

Browse

Author: search.filters.author.Ravi Shankar, A.U.Subject: search.filters.subject.Slags

Search Results

Now showing 1 - 9 of 9
  • No Thumbnail Available
    Item
    Air-cured Alkali activated binders for concrete pavements
    (Chinese Society of Pavement Engineering, 2015) Palankar, N.; Ravi Shankar, A.U.; Mithun, B.M.
    The present study focuses on the possibility of use of alkali activatedbinders for use in concrete pavements. Alkali Activated Slag Concrete (AASC) and Alkali Activated Slag Fly ash Concrete (AASFC) are prepared and the properties are compared with Ordinary Portland Cement Concrete (OPCC). The Ground Granulated Blast FurnaceSlag (GGBFS) and Fly Ash (FA) are blended in the ratios 100:0, 75:25, 50:50 and 25:75 as binder and activated using strong alkaline solution. Trial mixes are carried out to identify the optimal Activator Modulus (Ms) for each combination of GGBFS and FA. The mix design for the optimal activator modulus is optimised to achieve sufficient strength for Pavement Quality Concrete (PQC) and the fresh and mechanical properties are studied in detail. The results indicate the properties of AASC and AASFC are similar or slightly better than conventional OPCC and satisfy the minimum strength requirements for concrete pavements. The application of alkali activated binders will minimise the environmental hazards occurring from augmented OPC production, along with effective utilisation of industrial waste materials and conservation of natural resources. © Chinese Society of Pavement Engineering.
  • No Thumbnail Available
    Item
    Durability studies on eco-friendly concrete mixes incorporating steel slag as coarse aggregates
    (Elsevier Ltd, 2016) Palankar, N.; Ravi Shankar, A.U.; Mithun, B.M.
    The present study discusses the durability performance of alkali activated concrete mixes containing steel slag as coarse aggregates. Steel slag aggregates, a waste product obtained from iron and steel industry are incorporated as coarse aggregates in alkali activated slag concrete (AASC) and alkali activated slag fly ash concrete (AASFC) by replacing traditional natural aggregates. The mix design for AASC and AASFC mixes are optimised to obtain sufficient strength for structural purposes and then steel slag coarse aggregates are incorporated at different replacement levels (0%, 50% and 100% by volume of total coarse aggregate content). Durability properties such as long term ageing performance, water absorption, volume of permeable voids, resistance to sulphuric acid attack and resistance to magnesium sulphate attack are studied in detail and compared with conventional Ordinary Portland Cement Concrete (OPCC). The ecological and economical analysis of concrete mixes is also carried out. It was found that the AASC and AASFC mixes displayed better durability performance as compared to OPCC. The inclusion of steel slag aggregates slightly reduced the durability performance of AASC and AASFC mixes. The AASC and AASFC with steel slag aggregates displayed lower energy requirement and lower production cost as compared to OPCC, thus proving it to be eco-friendly. © 2016 Elsevier Ltd. All rights reserved.
  • No Thumbnail Available
    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.
  • No Thumbnail Available
    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.
  • No Thumbnail Available
    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.
  • No Thumbnail Available
    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.
  • No Thumbnail Available
    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.
  • No Thumbnail Available
    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.
  • No Thumbnail Available
    Item
    Alkali activated slag-fly ash concrete incorporating precious slag as fine aggregate for rigid pavements
    (Chang'an University, 2022) Talkeri, A.; Ravi Shankar, A.U.
    This study aims to develop the alkali activated slag-fly ash concrete (AASFC) using precious slag (PS) ball as the fine aggregate. The slag-fly ash proportion, sodium silicate/sodium hydroxide (SS/SH) ratio and sodium hydroxide concentration are the prime variables. The fresh concrete properties like workability, setting time and the hardened concrete properties of AASFC developed under ambient curing were analyzed and similar way by replacing with fly ash (FA). The sodium hydroxide concentration of 8 M, 10 M and 12 M, SS/SH ratio of 1.0, 1.5 and 2.0, alkaline liquid to binder ratio of 0.35 and variation in slag-fly ash proportion as major inputs for mix design. The test results showed that, the fresh state of AASFC blend has a shorter setting time of 12–16 min, because of calcium mineral from the FA, the workability and setting time of AASFC mix was enhanced by the addition of the tri-sodium phosphate as a retarder. At the higher SS/SH extent, the workability and setting time exaggerated, whereas the increased FA content and sodium hydroxide concentration had a greater influence on the fresh state of concrete. Also, the sodium hydroxide concentration, SS/SH ratio and slag-fly ash proportion are the most inducing parameters on the workability, setting time and strength parameters of AASFC. © 2021 The Authors