Both fossil and renewable fuel sources are used widely to produce electricity around the globe. The dependency on fossil fuels for energy leads to the depletion of reserves and various forms of pollution. Coal fly ash (CFA) is one of the most burning issues in the whole world due to its large amount of production in thermal power plants. Every year a million tons (MTs) of CFA are generated globally of which almost half is utilized in various forms, while the remaining half remains unused, leading to various types of pollution. Hence, there is an immediate requirement for CFA management approaches for the efficient and sustainable use of fly ash. In the present review, the authors emphasize the status of energy and its supply and demand. A detailed description of coal fly ash-based thermal power plants, fly ash production, and utilization is provided. Moreover, the current and emerging applications of CFA are also provided.

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Status of Coal-Based Thermal Power Plants, Coal Fly Ash Production, Utilization in India and Their Emerging Applications

This research appraised the effects of recycling senilia senilis waste seashells as a full or partial substitution for natural coarse aggregate (granite) in eco-friendly concrete production. The design mix employed a 1:2:4 concrete mix ratio for M25 grade, a w/c ratio of 0.5, river sand as fine aggregate, ordinary Portland cement (OPC) as a binder, and varying proportions of crushed seashells and granite as coarse aggregates (0:100, 10:90, 20:80, 30:70, 40:60, and 50:50). Laboratory tests revealed that workability requirements were only met with a 10%–40% seashell addition, workability decreased with increasing seashell percentages. The compressive strength increased with curing age but decreased with the additions of seashells. The seashell-modified mixes failed to reach the design target strength for M25 concrete. Nonetheless, the 10 and 20% seashell-modified mixes achieved the required strength for M20 concrete. Split tensile strength increased with curing age for all mixes, the seashell-modified mixes yielded slightly reduced tensile strength values compared to the unmodified mix at all curing stages. However, the 10%, 30%, and 40% seashell-modified batches attained recommended split tensile strength values on the 28th day. Furthermore, high correlations were observed between the datasets of the some of the measured parameters, and variations for Split tensile strength as a function of seashell percentage and compressive strength were developed discretely by fitting the experimental data to the numerical models. Relationships were also developed for compressive strength and workability as functions of seashell percentage. Eco-friendly building construction recycling waste seashells is encouraged as it offers positive economic and environmental prospects.

The use of Senilia senilis seashells as a substitute for coarse aggregate in eco-friendly concrete

The utilization of solid waste in useful product is becoming a great deal of worth for individuals, organizations, and countries themselves. The powder of waste glass and silica fumes are also considered major waste materials across the globe. In this paper, the physico-chemical, thermal, and morphological properties of both waste powders are investigated in order to determine their suitability for use as a partial replacement for cement in basic concrete. They are suitable for use in concrete due to their pozzolanic and other basic properties. Extensive testing, in terms of the compressive strength test, the slump test, and the flexural strength test, has been carried out to study the replacement of cement in the range of 5–15% by waste glass powder for curing ages of 7 and 28 days. The FTIR analyses of both materials are studied for determining the effect of characteristics of chemical bonding and intense bands with bending vibrations of O–Si–O bonds. Experimental results indicate towards the potential utilization of wastes in concrete in terms of green concrete.

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Comparative Analysis of Waste Materials for Their Potential Utilization in Green Concrete Applications

Magnesium is among the lightest structural metals available, with the capacity to replace traditional alloys in mass-saving applications while still providing increased stiffness and strength. The inclusion of reinforcing components into the metallic matrix has a substantial impact on stiffness, specific strength, wear behaviour, damping behaviour, and creep properties when compared to typical engineering materials. Due to their outstanding physical and mechanical characteristics along with low density, magnesium metal matrix composites are viable materials for numerous applications. This study discusses how to choose an appropriate technique and its process parameters for synthesising magnesium-based metal matrix composites (MMCs) and gives an overview of the impacts of various reinforcements in magnesium and its alloys, emphasising their benefits and drawbacks. The essential applications of various magnesium-based MMCs are also critically examined in this article. The impact of reinforcement on the microstructure as well as mechanical characteristics are thoroughly examined. 

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Manufacturing Techniques for Mg-Based Metal Matrix Composite with Different Reinforcements

The reactivity effect of calcium carbonate, present in ground oyster shells and limestone filler, on the formation of carboaluminate phases in ground granulated blast furnace slag blended cement pastes was reported in this paper. Six different binary and ternary blended cement pastes were prepared using ground granulated blast furnace slag, ground oyster shells and limestone filler with different replacement levels (from 5 to 35%). The carboaluminate formation was assessed and quantified directly using X-ray diffraction (XRD), and indirectly by following the aluminate phase’s reaction (heat flow) and consumed calcium carbonate using Isothermal Calorimetry (IC) and Thermogravimetric Analysis (TGA), respectively. Further, the overall reaction degree calculated based on TGA results and the compressive strength were determined to support the findings obtained. The results revealed that the calcium carbonate present in ground oyster shells is more reactive when compared to that present in limestone filler, where more formed hemi- and monocarboaluminate phases were observed in mixtures containing ground oyster shells. An enhancement in compressive strength and overall reaction degree was observed by adding 5% ground oyster shells as cement replacement.

Sarah Khan

Papers

Characterization of fly ash for potential utilization in green concrete

Experimental design of green concrete and assessing its suitability as a sustainable building material

Renewable energy for carbon footprint reduction of green geopolymers material’s production for built-environment

Construction and demolition waste-based geopolymers for built-environment: An environmental sustainability assessment