Published: Građevinar 77 (2025) 12
Paper type: Scientific research paper
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Orthogonal test-based study on mechanical properties of coal-fired slag concrete

To improve the incorporation of coal-fired slag into concrete, this study investigated the effects of several key factors on the mechanical properties of coal-fired slag concrete using orthogonal testing. The parameters studied included water-binder ratio (0.45, 0.475, 0.5, and 0.525), fly ash replacement ratio (0, 10, 20, and 30 %), sand ratio (37.5, 40, 42.5, and 45 %), and coal-fired slag replacement ratio (0, 33.33, 66.67, and 100 %). The effects of these factors on the seventh, 14th, and 28th-day compressive strengths, as well as the 28th day splitting tensile strength, were examined. A microscopic analysis was performed via SEM to explore the surface characteristics of the concrete. The results revealed a gradual decrease in concrete strength as the water-binder ratio and coal-fired slag replacement ratio increased. The water-binder ratio significantly affected both the compressive and splitting tensile strengths. The optimal concrete mix, consisting of a water-binder ratio of 0.45, fly ash replacement ratio of 10%, sand ratio of 45%, and coal-fired slag replacement ratio of 66.67 %, resulted in a 28-day compressive strength of 42.18 MPa and splitting tensile strength of 3.21 MPa. These values satisfy the C30 strength requirements for structural building applications, enhancing the economic value of coal-fired slag and broadening the potential uses of slag concrete.

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