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Coal fired thermal plants in India produce about 131 million tons of coal ash, which comprises about 25 million tons of coal bottom ash. Utilization of coal bottom ash has environmental advantages also which are of great importance in the present context of sustainability of natural resources. The replacement of river sand with industrial by-products such as coal bottom ash in concrete can prove both technically and economically beneficial to the construction industry. In this study, laboratory tests were conducted to assess the possibility of the use of coal bottom ash as a substitute material of river sand in concrete. River sand was substituted with coal bottom ash by mass in concrete at 0, 30, 50, 75 and 100% replacement level. The test results show that 28 d compressive strength and pulse velocity through concrete were not affected on the use of coal bottom ash in concrete. Water absorption and initial rate of absorption of water by capillary action increased on incorporation of coal bottom ash in concrete manufacturing. However, the secondary rate of absorption of water was constant for all concrete mixtures. Water absorption varied between 4.68 and 5.56% for all concrete mixtures at curing period of 28 d. With increasing age, bottom ash concrete mixtures showed significant reduction in permeable pore space and water absorption. Abrasion resistance was measured in terms of average depth of wear. Bottom ash concrete mixtures displayed marginally lesser resistance to abrasion than control concrete. All the concrete mixtures showed decrease in the average depth of wear with increasing age, in other words increase in resistance to abrasion. [ABSTRACT FROM AUTHOR]

Sewage sludge (SS) management has been regarded as a serious environmental and health issue around the globe, especially in developing countries like India, mainly due to the lack of proper regulatory criteria, and appropriate engineering infrastructures. The present research work demonstrates the utilization of Fly Ash (FA) in varying percentages (with an interval of 10%) with SS as brick for sustainable building material with special emphasis on dimensional Effect. The impact of dimensional effect is measured using compressive strength behaviour for a stress rate of 14 MPa/min of two different sizes of brick i.e. D1 and D2 of sizes 7 × 7x7 cm3 and 2 × 2x2 cm3, respectively. Owing to the sintering effect, the maximum strengths of 4.02 MPa and 7.6 MPa are noticed for a composition of 60% SS+40% FA for D1 and 40% SS + 60% FA for D2, respectively. According to the Indian Standards (IS) 13757: 1993, an exhibited strength of more than 3.5 MPa by any brick composition enables it to be used as a common building brick. In general, due to the formation of triangular wedges, the D2 bricks exhibited better strength for any mixing ratio of FA and SS. The added benefit in our study was lower thermal conductivity (0.48 Wm−1K−1) of the prepared fired brick implying its better insulation property. Our study uniquely highlights the possible utilization of FA for stabilizing SS for sustainable substitution of natural clay fired brick. Future study may further investigate the compositional effect of FA on the thermal and thermodynamic attributes of the bricks. Image 1 • Pioneer study on bricks that visualizes dimensional effect along with mechanical properties. • 40–60% fly ash with sewage sludge satisfies Indian codal provisions as construction material. • Thermal conductivity of synthesized brick is lower than conventional fired clay bricks. • Dimensional effect significantly influences the compressive strength behaviour. [ABSTRACT FROM AUTHOR]

The mining of natural material such as sand on large scale for use in construction of infrastructure in developing countries like India is posing threat to the environment. To save the environment, therefore, it becomes obligatory on the part of researcher to explore the utilization of industry by-products in place of natural material. In this study utilization of saw dust generated by wood industry in concrete has been explored. This article presents properties of concrete using different percentage of water and sodium silicate treated saw dust as replacement of sand. Saw dust passing through 4.75 sieve was treated with water and sodium silicate for 24 h before using in concrete. Natural sand was replaced with 5, 10,15 and 20% water treated saw dust in concrete mixture. The effect of silica fume on properties of concrete containing 5% water treated saw dust was also studied by replacing 4, 8 and 12% cement with silica fume in concrete. It was observed that concrete made with 5% water or sodium silicate treated saw dust displayed compressive strength comparable to that of control concrete. However, for 10% replacement level, compressive strength and split tensile strength decreased by 30.30% and 32.19% respectively, at 28 days. Total charge passed, water penetration and capillary water absorption increased by 224%, 153% and 117.4%, respectively, on use of 10% treated saw dust. The concrete mixture modified with sodium silicate treated saw dust showed remarkable improvement in respect of resistance to chloride ion penetration. As expected, the results showed considerable decrease in density of concrete with the use of saw dust as replacement of sand. Addition of sodium silicate treated saw dust resulted in ettringite formation in large quantity in concrete. • Sand in concrete was replaced with 5, 10, 15 and 20% water treated saw dust. • The optimum quantity of water or sodium silicate treated saw dust is 5%. • Density of concrete decreased on use of saw dust. • Strength properties of concrete modified with 5% saw dust is comparable. • Chloride ion permeability improved on silica fume in saw dust modified concrete. [ABSTRACT FROM AUTHOR]