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In recent times, with rapid development in the construction sector, the use of enormous amounts of materials is required for the production of concrete. Fire penetrates concrete, leading to chemical contamination, small cracks, and lightening. These effects can significantly change the properties of concrete's structure, reduce its strength and durability, and also change the behavior of the structure and lead to effects on the environment. An attempt was made to study the effects of elevated temperature on the mechanical characteristics of self-compacting concrete (SCC) with by-products including fly ash as a partial replacement for cement and waste copper slag as a partial replacement for fine aggregate at 0%, 10%, 20%, 30%, 40%, 50%, 60%, and 70%. The SCC specimens were subjected to elevated temperatures ranging from 200, 400, 600, and 800 °C, respectively, for a steady-state of two hours in a digital muffle furnace. The residual compressive strength, mass loss, ultrasonic pulse velocity, and residual density along with a visual inspection of cracks and color changes were observed. In this study, with over 400 °C temperatures, surface fractures appeared. The residual compressive strength (R-CMS) of all the individual temperatures of the SCC-WCS% mixes exhibited a gain in strength range from 31 to 34 MPa at 400 °C, 26 to 35 MPa at 600 °C, and 22.5 MPa to 33.5 MPa at 800 °C, respectively. Microstructural analysis of SCC-WCS% mixtures subjected to elevated ambient temperatures is carried out with a scanning electron microscope (SEM) and X-ray diffraction (XRD). [ABSTRACT FROM AUTHOR]

Concrete, the most extensively utilized construction material, maintains its high demand owing to the swift urbanization and population expansion worldwide. However, cement manufacturing consumes considerable energy and emits substantial CO2 into the atmosphere. To ensure the construction industry's sustainability, it is imperative to use eco-friendly and cost-effective products. As an additional cementitious ingredient in concrete, nano-based GGBFS (NGGBFS) is therefore employed to provide sustainable environmental impacts. The main purpose of this study is to assess the compressive strength, tensile strength, and Young's modulus of NGGBFS, considering various replacement percentages (2%, 4%, 6%, 8%, 10%, and 12%) compared to conventional cement. The maximum compressive strength (72.68 MPa) and tensile strength (6.12 MPa) were obtained at 365 days for GB4 concrete. The Taguchi optimisation technique was employed to determine the interaction between mineral admixture and curing days on the mechanical properties of concrete; it reveals that GB4 mineral admixture and 365 days of curing days have good interaction between the factors taken for the study. The ANOVA quadratic regression model provided the optimisation process response. According to principal component analysis, the compression strength and Young's modulus significantly influence the components because their loadings are so close (0.722 and 0.68). As a result, optimal combinations with equivalent strengths can be successfully created by substituting 8% nano-based GGBFS (GB4) in cement, offering an alternative path toward sustainable development. [ABSTRACT FROM AUTHOR]