Faculty Publications
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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 LtdItem 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.Item Effect of phase-change materials on the hydration and mineralogy of cement mortar(ICE Publishing, 2020) Snehal, K.; Das, B.B.The influence of direct incorporation of thermally efficient phase-change materials (PCMs) on the hydration and mineralogical properties of cement mortar was investigated. To assess the viability of bulk addition of PCMs to a cementitious system, tests of the early age, hydration, mechanical, durability and mineralogical properties were carried out. Organic PCMs showed an increase in setting time, while inorganic materials exhibited fast setting characteristics. Surface temperature was also found to be lower for cement paste with incremental dosages of PCM. However, chemical shrinkage was found to be reduced in the presence of PCM except for the inorganic type. It was observed from the results that PCMs negatively influenced the rate of strength development of a cementitious mortar. The slow rate of strength development was found to be attributed to interrupted hydration, which was confirmed through mineralogical studies. Further, from the thermo-gravimetric analysis, it was observed that the presence of PCMs in a cementitious system increased calcium hydroxide content and reduced the content of water related to hydration products. © 2020 ICE Publishing: All rights reserved.Item Acid, alkali and chloride resistance of binary, ternary and quaternary blended cementitious mortar integrated with nano-silica particles(Elsevier Ltd, 2021) Snehal, K.; Das, B.B.This paper investigates the quantification of ettringite (Ca6Al2(SO4)3(OH)12.26H2O, AFt), gypsum (CaSO4.2H2O, Gy) and Friedel's salt (Ca4Al2(OH)12Cl2.4H2O, Fs) formed for binary, ternary and quaternary blended cementitious mortar mixes that were exposed to acid (H2SO4), alkali (Na2SO4) and chloride (NaCl) solutions. Quantification was carried out through a thermogravimetric analyzer by characterizing the mass loss associated to the decomposition of these compounds at specific boundaries of temperature (50–120 °C for AFt, 120–150 °C for Gy and 230–380 °C for Fs). Binary, ternary and quaternary blended cementitious mortar mixes were designed by adopting modified Andreasen and Andersen particle packing model. A long-term exposure period was spanned to the duration of 180 days for all kind of aggressive media and its effect on engineering properties of blended cementitious mortar were measured. Deterioration due to acid (H2SO4) exposure is found to be more intense due to the synergistic action of acid and sulfates. It is to be noted that for acid exposure period of 180 days, control mortar underwent an acute density and strength losses of 18% and 59%, respectively. However, cementitious mortar mix consisting of 3% nano-silica performs the best against aggressive media. The optimistic resistance to the formation of AFt and Gy was also found to be offered by quaternary blended mix. A similar trend was also observed in the formation of Fs for the mortar mixes exposed to NaCl solution. Significant improvement in particle packing density by the inclusion of micron to nano sized finer particles for quaternary blended mortar mix has minimized the permeable porosity, thus reduced the susceptibility to the formation of voluminous compounds. Enhanced pozzolanic activity due to the presence of nano-silica could be one of the primary reasons for quaternary blended mortar to perform better against the aggressive media that can be adopted in the practice considering sustainability and economical point of view. © 2021 Elsevier LtdItem Influence of aggressive exposure on the degradation of nano-silica admixed cementitious mortar integrated with phase change materials(Elsevier Ltd, 2022) Snehal, K.; Das, B.B.; Barbhuiya, S.The objective of the present study is to evaluate the stability of cementitious mortar incorporated with phase change material (PCM, n-octadecane) at aggressive exposure conditions such as acid (1% H2SO4), alkali (5% Na2SO4) and chloride (5% NaCl). Thermogravimetric analysis (TGA) was performed to characterize and quantify the amount of deleterious compounds such as ettringite (Ca6Al2(SO4)3(OH)12·26H2O, AFt), gypsum (CaSO4·2H2O Gy) and Freidel's salt (Ca2Al(OH)6(Cl, OH)·2H2O, Fs) formed due to the action of SO42− (acidic and alkaline media) and Cl− (chloride media) ions at the continuous exposure period of 180 days. Mass loss associated to the thermal degradation of n-octadecane PCM (CH3(CH2)16CH3) at various exposure solutions was also calculated at the temperature boundary of 250–300 °C. This study also highlights the introduction of optimized nano-silica dosage (3%) into the PCM based cementitious mortar to counteract the undesirable facets of PCMs on cementitious system. Results revealed that incorporation of PCM in cementitious mortar augmented the amount of AFt, Gy (at acid and alkali exposure solution) and Fs (at chloride exposure solution) formation, responsible for the amplified rate of deterioration. It is important to be noted that after long term exposure of 180 days no traces of PCM was observed in PCM based cementitious mortar mixes, which signifies the mixes no longer holds the capacity to store energy. However, co-occurrence of nano-silica (3%) in PCM based cementitious mixes curtailed the negative impact of PCM on cementitious mortars exposed to aggressive conditions significantly. Further, differential thermogravimetric (DTG) curve shows an additional endothermic peak at 250–300 °C for 3% nano-silica modified PCM based cementitious mixes even after exposure to aggressive ions that implies the ability of the mix to sustain the thermal efficiency characteristics of PCMs. © 2022 Elsevier LtdItem Influence of Geopolymerization Factors on Sustainable Production of Pelletized Fly Ash-Based Aggregates Admixed with Bentonite, Lime, and GGBS(American Society of Civil Engineers (ASCE), 2023) Sharath, B.P.; Snehal, K.; Das, B.B.; Barbhuiya, S.This experimental research investigates the influence of geopolymerization factors such as Na2O dosages, water and mineral admixture [bentonite (BT), burnt lime (BL), and ground granulated blast furnace slag (GGBS)] on physiomechanical properties of the pelletized fly ash (FA)-based aggregates. Taguchi's L9 orthogonal array was adopted to design the mixing ratios for three kinds of fly ash-based aggregates (in the combinations of FA-BT, FA-BL, and FA-GGBS). The degree of geopolymerization of the produced aggregates was characterized using thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and a scanning electron microscope (SEM). Most influential response indices in the production of pelletized aggregates were identified using gray relational analysis. The physiomechanical characteristics of the fly-ash aggregates were significantly improved by admixing BL than that of GGBS and BT. However, pelletization efficiency was seen to be superior for GGBS-substituted fly-ash aggregates. The quantified amount of hydration products, i.e., sodium alumino-silicate hydrate (N-A-S-H)/calcium alumino-silicate hydrate (C-A-S-H) for fly ash-based aggregates intensified on increasing Na2O and mineral admixture dosages. The results strongly suggest the existence of a linear relationship between the quantified amount of N-A-S-H/C-A-S-H and individual pellet strength of produced aggregate. The FTIR spectrum showed strong and broadened bands of Si-O terminal for all types of aggregates, representing the conversion of unreacted minerals to chains of aluminosilicate gel (geopolymerized hydration product). Further, it can also be inferred from gray relational analysis that among all other factors, Na2O content significantly impacted the engineering properties of produced fly ash-based aggregates. © 2023 American Society of Civil Engineers.Item Life cycle assessment and environmental impact of blended cementitious mortar with incinerated biomedical waste Ash as partial replacement to cement(Elsevier Ltd, 2025) Tripathi, P.; Joshi, S.; Snehal, K.; Das, B.B.In a sustainability-driven world, repurposing industrial byproducts into construction materials is vital for reducing environmental impact and resource conservation. Incinerated biomedical waste ash (IBWA), typically regarded as hazardous landfill waste poses significant environmental challenges. However, high calcium (?45 %) and silicate phases in IBWA contribute to hydration and pozzolanic reaction making it a potentially sustainable cementitious material. From this perspective, this study investigates the life cycle assessment and environmental impact of blended cementitious mortar incorporated with IBWA as a partial replacement for cement, focusing on its ecological and technical benefits. A cradle-to-gate life cycle assessment (LCA) confirmed that uutilization of IBWA in cementitious mortar conserves natural resources, reduces embodied energy consumption, lowers CO2 emissions, and minimizes eutrophication and human toxicity potential by capturing heavy metal within hydration products. To ensure environmental safety, TCLP-ICP-MS analysis was conducted, which affirms that IBWA leachate concentrations were well below EPA regulatory limits and further reduced during hydration, stabilizing heavy metals (Cr, Cu, Hg, Ni, Pb, etc.) in the solidified matrix. The optimal IBWA dosage of 10 % offered a balance between both technical performance and sustainability. The porous and non-spherical morphology of IBWA increased water demand and inter-particle friction, and its SiO? + CaO content (>50 %) enhanced cement hydration. Thermogravimetric analysis (TGA), Xray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analyses confirmed the progressive formation of secondary hydration products (C-S-H, and C-A-S-H), contributing to densified microstructure (Ca/Si ratio: ?1.2). The final sustainable performance score of 0.77 for the IBWA10 mix signifies an eco-efficient and balanced formulation, offering structural integrity along with environmental and economic advantages. © 2025 Elsevier Ltd