Sanjay Kumar

Bio: Sanjay Kumar is an academic researcher from Council of Scientific and Industrial Research. The author has contributed to research in topics: Fly ash & Geopolymer. The author has an hindex of 24, co-authored 44 publications receiving 2698 citations.

Influence of granulated blast furnace slag on the reaction, structure and properties of fly ash based geopolymer

Abstract: Ground granulated blast furnace slag (GBFS) has been used to alter the geopolymerisation behaviour of fly ash. The influence of varying amount of GBFS (5–50%) on the reaction kinetics has been studied using isothermal conduction calorimetry. It was observed that the reaction at 27 °C is dominated by the GBFS activation, whereas the reaction at 60 °C is due to combined interaction of fly ash and GBFS. The reaction product of geopolymerisation has been characterised using X-ray diffraction and scanning electron microscopy–X-ray microanalysis. Alumino–silicate–hydrate (A–S–H) and calcium–silicate–hydrate (C–S–H) gels with varying Si/Al and Ca/Si ratio are found to be the main reaction products. Coexistence of A–S–H and C–S–H gel further indicates the interaction of fly ash and GBFS during geopolymerisation. Attempt has been made to relate the microstructure with the properties of the geopolymers.

Innovative methodologies for the utilisation of wastes from metallurgical and allied industries

Abstract: This paper is an overview on the utilisation of solid wastes with focus on blast furnace slag, red mud and fly ash generated in large quantities from iron and steel industry; primary aluminium production and coal fired power plants, respectively. Innovative methodologies, based on the recent research by the authors, are highlighted and these include: (a) smelting reduction of red mud to produce pig iron and titania rich slag, (b) mechanical activation of the slag and fly ash to prepare improved blended cements in terms of higher usage of waste and enhanced cement properties, (c) synergistic usage of fly ash, blast furnace slag and iron ore tailings in the preparation of floor and wall tiles and (d) preparation of synthetic granite from fly ash as a value added product.

Mechanical activation of granulated blast furnace slag and its effect on the properties and structure of portland slag cement

Abstract: Mechanically activated granulated blast furnace slag (GBFS) was used in the range of 50–95% to replace clinker in portland slag cement (PSC). The slag and clinker were activated separately using an attrition mill and mixed to prepare cement formulations. Use of activated slag resulted in a remarkable increase in strength vis-a-vis commercial slag cement. Both 1-day and 28-day strength were found to increase with an increase in slag content up to 70%. The strength of the sample containing 80–85% slag was comparable to the commercial cement used as a reference. It was observed that mechanical activation of slag was more critical from the point of view of strength development. The hydrated cement samples were characterised using powder X-ray diffraction (XRD), scanning electron microscopy with X-ray microanalysis (SEM-EDS) and simultaneous thermogravimetry and differential thermal analysis (TG/DTA). It is established that microstructural changes resulting from enhanced reactivity of slag and densification are related with the improvement in cement strength.

Hallmarks of mechanochemistry: From nanoparticles to technology

Abstract: The aim of this review article on recent developments of mechanochemistry (nowadays established as a part of chemistry) is to provide a comprehensive overview of advances achieved in the field of atomistic processes, phase transformations, simple and multicomponent nanosystems and peculiarities of mechanochemical reactions. Industrial aspects with successful penetration into fields like materials engineering, heterogeneous catalysis and extractive metallurgy are also reviewed. The hallmarks of mechanochemistry include influencing reactivity of solids by the presence of solid-state defects, interphases and relaxation phenomena, enabling processes to take place under non-equilibrium conditions, creating a well-crystallized core of nanoparticles with disordered near-surface shell regions and performing simple dry time-convenient one-step syntheses. Underlying these hallmarks are technological consequences like preparing new nanomaterials with the desired properties or producing these materials in a reproducible way with high yield and under simple and easy operating conditions. The last but not least hallmark is enabling work under environmentally friendly and essentially waste-free conditions (822 references).