Faculty Publications
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Item Implication of concrete with chemical admixture cured in low temperature on strength, chloride permeability and microstructure(Springer, 2019) Ghosh, A.H.; Das, B.B.Concrete does not gain complete strength when cured in low temperature as the hydration of cement does not take place completely. The concrete cured in cold weather does not gain early strength and leads to improper setting and uneven strength gain due to the freezing of the water mixed with the cement. Hence, there are many strength-related problems faced at site due to cold weather particularly in parts of north India where the temperature reaches below freezing point of water during the winter season. The study focused on the effect of combination of accelerator, superplasticizer and air-entraining admixture on microstructure, compressive strength and chloride ion penetration of concrete cured at +5 °C and a comparative study with normal cured concrete with chemical admixture. Five different mixes were used containing varying amount of accelerators, superplasticizers and air-entraining admixture of a manufacturer which are available for use in India. The results for compression strength show that the concrete mix with higher dosage of accelerator had higher strength. The strength results were nearly the value of normal cured concrete with chemical admixture. Rapid chloride permeability test showed very low permeability for all of specimens of last mix, and results were nearly comparable to normal cured concrete. The microstructure study of concrete with admixture ensures a dense structure formation resulting in higher strength at low temperature. © Springer Nature Singapore Pte Ltd. 2019.Item Fast Setting Steel Fibre Geopolymer Mortar Cured Under Ambient Temperature(Springer, 2021) Prasanna, K.M.; Theodose, I.; Shivaprasad, K.N.; Das, B.B.Cement and cementitious materials are being used worldwide as the most popular multipurpose construction materials but the greenhouse gas such as carbon dioxide (CO2) produced during its manufacturing process creating a huge environmental hazard, thus efforts have been made for alternative binders. Geopolymer binder is new age binder alternative to ordinary Portland cement in infrastructure projects because it is produced from eco-friendly and industrial waste materials. This study was aimed to produce fast setting with ground-granulated blast-furnace slag (GGBS) in fly ash-based geopolymer mortar incorporated with steel fibres cured under ambient temperature. In this research, alkaline to binder ratio was varied from 0.5 to 0.8, crimped steel fibre are varied from 0.5 to 1.5% by total volume of binder and combination of fly ash (FA) and GGBS (100%:0%, 90%:10%, 80%:20%, 70%:30%, 60%:40% and 50%:50%) as binder were used for preparation of fibre geopolymer mortar. The tests conducted include stetting time and flowability of geopolymer mortar, compressive strength and microstructural characterisation of steel fibre geopolymer mortar. The tests for compressive strength were carried out on standard size of mortar samples at curing period of 3, 7 and 28 days. It is noted from the test results that increase in GGBS content setting times were decreased; however, the compressive strength of fly ash-based geopolymer mortar increased. The highest compressive strength at 28 days of curing period was found to be 69.5 MPa, which is obtained with content of 1% of steel fibres and alkaline to binder ratio of 0.6 with 50%:50% binder’s proportions. Further, it is observed that the incorporation of steel fibres in plain geopolymer mortar have enhanced the compressive strength and optimum dosage of fibres was found to be 1%. © 2021, Springer Nature Singapore Pte Ltd.Item Influence of Fineness of Mineral Admixtures on the Degree of Atmospheric Mineral Carbonation(Springer Science and Business Media Deutschland GmbH info@springer-sbm.com, 2021) Farsana, C.; Das, B.B.; Snehal, K.Global carbon dioxide concentration is rising at the rate of 2 ppm every year, which had led to the demand of sustainable development. In construction industry, manufacturing of cement is the main source of global anthropogenic carbon dioxide emissions. Carbon capture and storage is a recent technology which had helped to sequester carbon dioxide from atmosphere and thus helps in reducing the greenhouse effect to a certain extent. This study mainly focuses on the atmospheric mineral carbonation of mineral admixtures like fly ash (FA), ground granulated blast furnace slag (GGBS), and silica fume (SF), which are the industrial by-products and are being treated as waste. This study also focuses on the effect of fineness of different mineral admixtures on the degree of atmospheric mineral carbonation. Fly ash with three different levels of fineness (FA, FA I, and FA II), GGBS with three different levels of fineness (GGBS, GGBS I, and GGBS II), and silica fume were mixed with activators like lime and gypsum and were left for atmospheric mineral carbonation. Mineralogical characterisations were done using X-ray diffraction (XRD), thermo gravimetric analysis (TGA), and scanning electron microscopy (SEM). Degree of carbonation of the samples was analyzed and calculated using the TGA results. From the comparative analysis of all the samples, it was found that GGBS II had highest degree of carbonation. It was also observed that calcium-based compounds like calcite, aragonite, vaterite, calcite magnesium syn, gismondine, waikarite, calcium silicate hydrate, diopside, calcium sulfate, and portlandite were formed in the samples after 45 and 90 days of atmospheric mineral carbonation. However, it was observed that with increasing levels of fineness of mineral admixtures, there was no significant change in the degree of atmospheric mineral carbonation. © 2021, Springer Nature Singapore Pte Ltd.