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Author: search.filters.author.Das, B.B.Subject: search.filters.subject.Deterioration

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    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 Ltd
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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