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Author: search.filters.author.Lahoti, MukundSubject: search.filters.subject.Thermal performance

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    Enhancing the resistance of cementitious composites to environmental thermal fatigue using high-volume fly ash and steel slag
    (Elsevier, 2024-10) Lahoti, Mukund
    Daily fluctuations in environmental temperature induce thermal fatigue and cause degradation in concrete structures. This study introduces a novel approach of utilizing high-volume fly ash, steel slag fine aggregates, and basalt-polypropylene fibres to prevent degradation against environmental thermal fatigue (ETF). Five mixes were considered with variations in fine aggregate type, fibre length and volume. The compressive and flexural strengths were analysed after exposure to 60, 120, 180, 240, and 300 ETF cycles between 20 and 60 °C (at constant relative humidity). The residual compressive strength of mix with 100 % river sand and 100 % steel slag as fine aggregates was ∼106 % and ∼112 % respectively after 300 ETF cycles. The developed cementitious composites performed significantly better than the mixes utilized in the existing literature. The mix with 100 % steel slag aggregate even demonstrated a continual rise in compressive strength as opposed to mixes with river sand whose strength declined after 180 or 240 ETF cycles. Flexural strength also improved up to 180 ETF cycles and then started to decline in all mixes. A thorough microstructural analysis was also conducted using scanning electron microscopy, differential scanning calorimetry, and mercury intrusion porosimetry to gain further insights into the underlying mechanism of the newly introduced matrix composition against ETF.
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    Thermal Performance of Metakaolin-Based Geopolymers: Volume Stability and Residual Mechanical Properties
    (Wiley, 2017-01) Lahoti, Mukund
    This chapter describes how a series of metakaolin (MK)-based geopolymer specimens measuring 50 mm cubes with different Si/Al ratios were prepared and exposed to different heating profiles in an electric furnace. The crumbling of cement paste into small pieces while geopolymer specimens retained satisfactory compressive strengths points towards the potential of geopolymers to perform soundly as a fire resistant material and also the need to impart sufficient volume stability and strengths when subjected to high temperatures. On exposure to elevated temperatures, geopolymers either retain their amorphous condition or transform to a crystalline microstructure in an experiment. The general agreement based on previous research is that geopolymers possess a stable inorganic framework subject to elevated temperatures unlike OPC which suffers breakdown of its hydration products. The dissolution of fumed silica into sodium hydroxide solution was done to obtain a clear solution. Solutions were stored for about 24 hours before use to allow them to cool down to room temperature and to achieve equilibrium.
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    Tailoring sodium-based fly ash geopolymers with variegated thermal performance
    (Elsevier, 2020-03) Lahoti, Mukund
    Sodium-based fly ash geopolymers show great fire resistance potential and commercial advantage for structural applications. Hence, in current research, tailoring of sodium-based geopolymer mix design without changing the fly ash source has been studied. It was found that a wide variety of residual compressive strength ranging from significant reduction (~80%) to maintaining significant enhancement (~150%) after being exposed to 900 °C was observed. The contributory mechanisms were discovered by investigating their chemical stability, pore structures, volume stability, and strength endurance prior to and after exposure to high-temperature using different microstructure characterization techniques including XRD, FTIR, MIP, dilatometry, and SEM. Crack formation due to moisture migration, pore shrinkage, and re-crystallization of nepheline adversely affected compressive strength. Matrix densification due to shrinkage of pore and stronger inter-particle bonding due to viscous sintering, favored compressive strength gain. This work discusses at length these competing mechanisms influencing the residual compressive strength.