Assessing the mechanical and microstructural properties of concrete with electric arc furnace slag replacement at 60%, 75%, and 90%

Chang, Shao Hern (2025) Assessing the mechanical and microstructural properties of concrete with electric arc furnace slag replacement at 60%, 75%, and 90%. Final Year Project, UTAR.

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Abstract

Nowadays, reusing the industrial by-products by aiming on sustainable objectives has risen as a important move in reducing the environmental impact by construction field. The objective of this study is to determine the mechanical properties which is compressive strength through evaluating the microstructural properties of elemental and chemical compound composition of concrete with EAF slag replacement for natural fine aggregates at different ratios of 60%, 75% and 90% for acrossing three particle size ranges (R1: 0.8 to 2.36 mm, R2: 2.36 to 4.75 mm and R3: 4.75 to 6.30 mm). Optimal replacement ratio which could provide optimum replacement ratio is also being determined. A total of 30 concrete samples were prepared and tested by using 5 tests which including of Compressive Strength Test, Scanning Electron Microscopy (SEM) Test, Energy Dispersive X-ray Spectroscopy (EDX) Test, X-ray Diffraction (XRD) Test and Thermogravimetric Analysis (TGA) Test. The Compressive Strength Test shows that all EAF slag mixes concrete samples outperformed the control sample with the highest strength of 54.75 MPa. SEM Test had showed visibility of hydration products such as Ettringite, Portlandite and C-S-H gel in the microstructural of concrete samples casted. EDX Test indicated existence of several elements but Calcium and Silicon as the elemental composition which contributes to affect the compressive strength. Results of XRD Test validated the presence of compounds such as Ca(OH)2, CaCO3, SiO2 and CaO and suggest that Ca(OH)2 and CaCO3 could contribute to affect the compressive strength. TGA Test presented the thermal stability of EAF slag replaced concrete for up to approximately 660°C before degradation starts. Overall, the results shows that a 90% replacement of fine aggregate with EAF slag using the R1 particle size range (0.8–2.36 mm) achieved the highest compressive strength of 54.75 MPa. Supported by favorable elemental (Ca and Si) and compound-level (Ca(OH)2 and SiO2) microstructural characteristics, this mix was identified as the optimal replacement ratio in this study. These findings could provide insights for the potential of EAF slag as a sustainable and performing alternative to natural fine aggregates. This also alignes with environmental and structural demands in modern construction practices. Keywords: Electric Arc Furnace (EAF) Slag, Concrete, Fine Aggregate Replacement, Compressive Strength, Microstructure Subject Area: TH1000-1725 Systems of building construction Including fireproof construction, concrete construction

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