Faculty Publications

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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 Ltd
Synergistic effect of nano silica on carbonation resistance of multi-blended cementitious mortar
(Elsevier Ltd, 2023) Snehal, K.; Das, B.B.; Barbhuiya, S.
Confiscation of alkaline buffer in a blended cementitious system surges the risk of carbonation. Understanding the carbonation mechanism and kinetics of multi-blended cementitious systems in correspondence to microstructural properties is the need of the hour. In this context, the change in the microstructure of binary, ternary, and quaternary blended cementitious mortar mix comprising of fly ash or/and ultra-fine fly ash or/and nano-silica upon accelerated carbonation (3.5% CO2; 70% RH) was studied. All multi-blended mixes were proportioned using modified Andreasen and Andersen particle packing theory. Permeable porosity and carbonation parameters such as carbonation depth, rate of change in compressive strength, and carbonation shrinkage were measured. Further, qualitative/quantitative estimation of carbonation phases was done using characterization techniques such as TGA and FTIR. In control mix with solely OPC, the reaction of CO2 with calcium-bearing phases showed chemo-mechanical changes leading to 18% improvement in strength at 30 days of exposure. The optimized multi-blended cementitious systems with nano-silica exhibited higher resistance to carbonation kinetics. Phase assemblages quantified through TGA within depth of carbonation imply a negligible concentration of portlandite (CH). However, mixes without nano-silica exhibited a significant reduction in bound water content associated with C–S–H/AFt/AFm phases and intensified the precipitation of calcium carbonate (CaCO3) phase. Asymmetric stretching band of C–O–C at 1424 cm−1 corresponding to calcite phase measured using FTIR validates the outcomes of TGA. © 2023 Elsevier Ltd
Effect of CO2 curing on phase compositions of nano silica blended cementitious mortar partially replaced with carbonated recycled fine aggregates
(Elsevier Ltd, 2025) Trivedi, S.S.; Ansari, F.; Das, B.B.; Barbhuiya, S.
This manuscript examines the quantification of CO2 uptake, hydration and carbonation phases such as calcium hydroxide (Ca(OH)2, CH), calcium carbonate (CaCO3, CC), magnesite (MgCO3), hydromagnesite (MgCO3.Mg(OH)2.4H2O, Hmgs), siderite (FeCO3) and subsequent carbonation and hydration degrees (CD, HD) in cementitious mortar (CM) incorporating colloidal nano silica (CNS) and carbonated and uncarbonated recycled concrete fine aggregates (RCF) subjected to accelerated carbonation curing (carbonated RCF- CRCF, Non-carbonated RCF- NCRCF). The RCF was prepared through multi cycle jaw crushing technology followed by repeated abrasion cycles and subsequently treated using accelerated carbonation. The mass loss resulting from the breakdown of these compounds at specific temperature ranges (220–350 °C for Hmgs, 250–400 °C for FeCO3, 400–500 °C for CH, 460–900 °C for MgCO3, and 600–800 °C for CC and CO2) was calculated using a thermogravimetric (TG) analyzer. The main findings of this research work confirms the presence of vaterite, calcite, tobermorite (Ca2.25[Si3O7.5(OH)1.5].8H2O or CSH gel), and magnesite polymorphs for CM incorporating 6–9 % CRCF and 1 % CNS as validated by the increased areas of peaks from fourier transform infrared spectroscopy (FTIR) analysis at 714 cm?1, 875 cm?1, 1007 cm?1, and 1405 cm?1, respectively which is further recognized by the increased peak intensities in X-ray diffraction (XRD) analysis. The important findings from the scanning electron microscopy (SEM) analysis revealed the development of additional C-S-H and calcite phases filling the pores and densifying the matrix in CRN mixes while the Ca/Si atomic ratio significantly decreased up to 67 % for CRN-19 mix as found by the energy dispersive X-ray spectroscopy (EDAX). The fresh and hardened state properties of blended mixes highlight the increase in dry density and compressive strength that are found maximum for CRN-19 mix of 57.9 MPa at 28 days owing to the highest rate of strength contribution of 27.95 % from the mix components such as 9 % CRCF and 1 % CNS. However, the flowability is observed to get reduced for all the mixes with CRN-13 mix illustrating approximately 83 % flow values with reference to the control mix. Furthermore, the durability performance of CRCF based primary mixes and all the secondary blends are found to show lowest ingress of chloride ions and permeable porosity values, illustrating up to 73 % and 39 % fall respectively to that of control mix at 28 and 56 days cured samples. Based on the comprehensive investigation and analysis, it is recommended to use pre-carbonated RCF and CNS for developing sustainable CM and achieving CO2 sequestration. © 2025 Elsevier Ltd

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