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Author: search.filters.author.Lahoti, MukundSubject: search.filters.subject.Compressive strength

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    Use of alkali-silica reactive sedimentary rock powder as a resource to produce high strength geopolymer binder
    (Elsevier, 2017-11) Lahoti, Mukund
    This paper reports on an innovative way to utilize alkali-silica reactive (ASR) rocks as a natural resource to produce high strength geopolymer binder. Excavation of the Jurong rock caverns in Singapore has produced large quantities of sedimentary rocks. These rocks, however, cannot be used for ordinary Portland cement concrete production due to their ASR reactivity. An alternative way to beneficially utilize these rocks is to produce geopolymer binder. The excavated rocks were classified based on petrography into four types and then converted to powder form in a sequence of steps. The rock powders were used to synthesize geopolymers by replacing metakaolin in different replacement ratios. Results showed that geopolymer binder with 67 wt% rock powder and only 33 wt% metakaolin can achieve a high compressive strength of 80 MPa. Incorporation of sedimentary rock powder enhanced the compressive strengths by 15–30% as compared to pure metakaolin geopolymers. Microstructure analysis revealed that the enhancement in compressive strengths were primarily due to the densification of binder by filling the voids in matrix with rock powders.
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    A succinct review on the use of NMR spectroscopy in monitoring hydration, strength development, and inspection of concrete
    (Elsevier, 2022) Lahoti, Mukund
    NMR is a very useful technique used in analytical chemistry for quality and molecular structure determination of a compound as well as its chemical environment. It works on the principle of the energy gap between two nuclei of an atom for an applied external magnetic field, due to their opposite spins. The potential of the three sub-categories of NMR (H-NMR or proton NMR, liquid-state NMR, and solid-state NMR) for monitoring hydration reaction in cement paste, early-age strength development in fresh concrete, and the inspection of hardened concrete has been elucidated in this paper. Powerful features of NMR in identifying the chemical environment and structure have made it possible for this technique in the evaluation of concrete subjected to sulfate attack and the estimation of the effect of alumino-silicate precursor on the strength of geopolymer. In this manuscript, various other applications of NMR in the non-destructive testing, quality checks, and monitoring of reactions in concrete and cement have been reviewed.