Faculty Publications

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

Publications by NITK Faculty

Browse

Subject: search.filters.subject.Hydration

Search Results

Now showing 1 - 10 of 30
  • No Thumbnail Available
    Item
    Ultrasonic velocities, densities, and viscosities of glycylglycine and CoCl2 in aqueous and aqueous ethanol systems at different temperatures
    (2010) Santosh, M.S.; Bhat, D.K.; Bhatt, A.S.
    Ultrasonic velocity (u), density (?), and viscosity (?) have been measured for glycylglycine and CoCl2 in aqueous and aqueous ethanol systems at T = (288.15 to 318.15) K. Using the experimental values, the adiabatic compressibility (?s), molar hydration number (nH), apparent molar compressibility (KS?), apparent molar volume (V?), limiting apparent molar compressibility (KS ?{symbol}0), limiting apparent molar volume (V?{symbol}0), their constants (SK, SV), viscosity coefficients of A and B parameters of Jones-Dole equation, relative viscosity (?r), and excess Gibbs free energy of activation (? G* E) were calculated and the results of all these parameters have been discussed in terms of solute-solvent and solute-solute interactions. © 2010 Elsevier Ltd. All rights reserved.
  • No Thumbnail Available
    Item
    Effect of different curing regimes and durations on early strength development of reactive powder concrete
    (Elsevier Ltd, 2017) Hiremath, P.N.; Yaragal, S.C.
    The early strength development of Reactive Powder Concrete (RPC) has been investigated under different curing regimes and compared with standard water curing condition. Four different curing regimes have been considered: ambient air curing, hot air curing, hot water bath curing and accelerated curing. The effect of hot air curing on strength development of RPC at different temperatures and durations are studied in detail. The present study is focused on the effect of combined curing regimes on the early strength development of RPC. Test results indicate that, among the four different curing regimes, hot water bath curing gives higher strength. The combined curing regime has considerably enhanced the compressive strength of RPC by about 63% as is evident by the rise in compressive strength from 110 MPa (standard curing) to 180 MPa (combined curing). Microstructure studies were also conducted to understand the arrangements of hydrated particles and development of other secondary hydrated products under different curing conditions using scanning electron microscope and X-ray diffraction spectroscopy respectively. © 2017 Elsevier Ltd
  • No Thumbnail Available
    Item
    Hydrophilicity of the hydrophobic group: Effect of cosolvents and ions
    (Elsevier B.V., 2019) Dilip, H.N.; Chakraborty, D.
    Classical molecular dynamics simulations were performed to study the effect of cosolvents and ions on the solvation structure of zwitterionic glycine in liquid water. Simulations were carried out for 2 M and 1 M concentration of TMAO, Urea, KCl and LiCl solutions to observe the changes in liquid structure of water near the glycine molecule. Radial distribution functions and spatial distribution functions showed the presence of protective hydration layer near the C ? in presence of TMAO which gets reduced in case of urea, KCl and minimum in case of LiCl. LiCl is found to disrupt severely the solvation structure near the glycine molecule. For LiCl system, a small hydration layer is found near C ? unit at higher distances which is mainly due to the first hydration shell of lithium ion bonded to the carboxylate group. Presence of these hydration layers gives extra stabilization energy to the glycine water system. Stabilizing and destabilizing effect of water near the glycine molecule is calculated in terms of Potential Mean Force. The anomalous behaviour of lithium salts with respect to Group I cation salts in protein stabilization can be explained on the basis of this behaviour. We found maximum hydrogen bond lifetime for water molecules in presence of TMAO followed by LiCl, KCl and least in case of urea. The higher lifetimes in presence of ions are found mainly due to their electrostatic force. The stabilization of the hydrophobic part of the glycine molecule can be correlated with the stabilization of proteins in presence of these cosolvents. © 2019 Elsevier B.V.
  • No Thumbnail Available
    Item
    Early age, hydration, mechanical and microstructure properties of nano-silica blended cementitious composites
    (Elsevier Ltd, 2020) Snehal, K.; Das, B.B.; Akanksha, M.
    This study was carried out to understand the influence of nano-silica on hydration properties of binary, ternary and quaternary blended cement paste and mortar containing micro to nano sized admixtures including fly ash (FA), ultrafine fly ash (UFFA) and nano-silica in colloidal form (CNS). Characterization methods such as thermogravimetric analysis (TGA), X-ray diffraction studies (XRD) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) was employed to quantify the hydration products. Further, early age and mechanical properties were also investigated for binary, ternary and quaternary cementitious system blended with nano-silica. The optimized proportions of blended paste and mortar are designed through modified Andreasen and Andersen particle packing model. The experimental test results revealed that the optimum dosage of CNS in binary blended cement composites is 3%. The presence of nano-silica in cementitious system amplified the hydration and pozzolanic activity, thereby promoting densified microstructure at nano scale. The flow test indicated the intensified demand for water absorption and reduced workability with the rise in level of incorporation of CNS particles in cement paste. Quaternary blended mix performed superior hydration along with strength properties amongst all the blended samples. © 2019 Elsevier Ltd
  • No Thumbnail Available
    Item
    Effect of cosolvents in the preferential binding affinity of water in aqueous solutions of amino acids and amides
    (Elsevier B.V., 2020) Dilip, H.N.; Chakraborty, D.
    Effects of two naturally occurring osmolytes, urea and trimethylamine-N-oxide (TMAO) on the solvation structure of hydrophobic moiety of alanine, glycine, N-methylacetamide and acetamide are investigated by classical molecular dynamics simulations. Our results are analysed in terms of site-site radial distribution functions (RDF), spatial distribution functions (SDF), number of hydrogen bonds, orientation profile, KB integrals, preferential binding coefficient and hydrogen bond dynamics. RDF and SDF showed presence of an extra hydration shell near the hydrophobic unit when TMAO is present in the solution. This hydration shell mainly consists of broken hydrogen bonds. In urea-water solution, intramolecular association is favoured compared to intermolecular association: which is in contrast to the TMAO-water solution. Alanine, glycine, NMA and acetamide showed preferred interactions with the water molecules in presence of TMAO compared to urea. Urea and TMAO both are found to be excluded from the alanine, glycine, NMA and acetamide surface but presence of urea was slightly favoured at higher distances in case of NMA and acetamide. The strong hydrogen bond between TMAO-water increases the hydrogen bond lifetime of other hydrogen bonds in the system. The preferential binding affinity of water with the protein molecules and strong hydrogen bonds are found to be the key reasons for stability in presence of TMAO. © 2019 Elsevier B.V.
  • No Thumbnail Available
    Item
    Growth and comparative studies on oxalic acid dihydrate, potassium oxalate hydrate and potassium hydrogen oxalate oxalic acid dihydrate single crystals
    (Elsevier Ltd, 2020) Mahendra, K.; Udayashankar, N.K.
    Single crystals of Oxalic acid dihydrate (OAD), Potassium oxalate hydrate (KOH), Potassium hydrogen oxalate oxalic acid dihydrate (KHOOD) were grown using solvent evaporation technique. Unit cell parameters of the crystals were studied using single crystal XRD (SCXRD) and the crystal parameters were found to match with the reported values. Structural properties were studied using powder XRD analysis. Optical absorption studies were carried out to determine the light absorption by the crystal and the optical bandgap was also calculated using Tauc's relation. Emission and thermal properties of the OAD, KOH and KHOOD crystals were studied using photoluminescence spectroscopy (PL) and TGA-DTA measurements respectively and explained in detail. Electrical studies were also carried out to find the resistivity of the material. The hardness of the synthesized crystal was also explored and the parameters such as stiffness constant, yield strength, fracture toughness and brittleness were evaluated and compared. © 2019 Elsevier Ltd
  • 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
    Influence of Integration of Phase Change Materials on Hydration and Microstructure Properties of Nanosilica Admixed Cementitious Mortar
    (American Society of Civil Engineers (ASCE) onlinejls@asce.org 1801 Alexander Bell DriveGEO Reston VA 20191 Alabama, 2020) Snehal, K.; Das, B.B.; Kumar, S.
    The present study demonstrates the influence of integrating phase change materials (PCMs) on hydration and microstructure properties of nanosilica admixed cementitious mortar. First, the optimized dosage of nanosilica in correspondence to compressive strength was determined. Subsequently, the desired proportion of PCMs was identified pertaining to a designated compressive strength of 35 MPa at the curing age of 28 days. The hydration and microstructure studies were carried out through thermo gravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM), respectively. Further, thermal properties were determined by means of differential scanning calorimetry (DSC). Incorporation of nanosilica into the cementitious mortar was found to have a positive influence on early strength development and durability, however, there was found to be an increase in chemical shrinkage as compared to the control mixture. PCMs integrated cementitious mortar improved the thermal efficiency as well as reduced the chemical shrinkage, but adversely affected the mechanical, hydration, and durability properties. With respect to development of compressive strength of the cementitious mortar, it is found that n-octadecane PCMs performed better amidst other PCMs, such as paraffin and sodium carbonate hydrates. Further, studies were carried out on cementitious mortar having both nanosilica (optimized proportion) and PCMs (the best performing). From the results, it is found that cementitious mortar comprising of both nanosilica and PCMs have compensated the drawbacks of one another. Blended mortar (having both nanosilica and PCMs) showed superior strength gain at early age, better durability resistance, low chemical shrinkage, and superior thermal performance. © 2020 American Society of Civil Engineers.
  • No Thumbnail Available
    Item
    Ferrochrome ash – Its usage potential in alkali activated slag mortars
    (Elsevier Ltd, 2020) Kumar, K.B.; Yaragal, S.C.; Das, B.B.
    This study is an attempt to develop a sustainable construction material, i.e., alkali activated slag (AAS) in combination with ferrochrome ash (FCA) as a replacement to ordinary Portland cement (OPC). The effect of the various levels of FCA (0, 25, and 50%) replacing ground granulated blast furnace slag (GGBS) in AAS mortars with 4% of Na2O dosage is studied. Further, five levels of the modulus of silica (Ms = 0.75, 1.00, 1.25, 1.5, and 1.75) are chosen to achieve targeted compressive strength at 28 days under ambient temperature curing conditions. The compressive strength decreases with the increase in level of the FCA replacement. The targeted design compressive strength is achieved with 25% FCA replacement to GGBS in the AAS mortar system with Ms = 1.25. In addition, microstructure and mineralogical studies are undertaken to ascertain the formation of different hydration products with the aid of the scanning electron microscope (SEM) and the X-ray diffractometer (XRD). Gismondine and calcium aluminate silicate hydrate (C-A-S-H) are the major hydration products in the AAS mortar mixes. Sodium aluminate silicate hydrate phases (N-A-S-H) are also observed prominently as the FCA replacement level increases in the AAS mortar mixes. The Fourier-transform infrared spectroscopy (FTIR) confirms the presence of the Si–O-(Si or Al) functional group. The addition of FCA in the AAS system is of vital significance in the reduction of the embodied carbon dioxide (ECO2eq), embodied energy (EEeq) and cost. © 2020 Elsevier Ltd