Multiscale and multidimensional analysis of coarse aggregate morphological characteristics for road-used steel slag

Steel slag has emerged as a promising coarse aggregate for pavement construction, offering a pathway toward green and sustainable infrastructure. However, insufficient multi-scale particle morphology characterization limits the accurate matching between material properties and pavement functional requirements, restricting its efficient utilization. This study investigates the aggregate morphological characteristics and develops a refined multidimensional evaluation framework encompassing macroscopic, mesoscopic, and microscopic scales. Two-dimensional analysis and three-dimensional scanning were employed to quantify morphological parameters of three steel slags, with basalt and limestone as references. Seven digital indices were used to access particle shape. Surface texture was characterized using orientation distribution, arithmetic mean roughness, fractal dimension, and SEM images, while pore structure using mercury intrusion porosimetry. Furthermore, grey relational analysis quantified the association degree between digital morphological parameters and empirical performance metrics. Results indicate strong correlations between the indicators. Steel slag exhibits the shape index of 1.1 – 1.3, shape factor of 0.04 – 0.07, aspect ratio of 1.0 – 1.6, flatness ratio of 1.5 – 1.8, polygonal perimeter ratio of 0.6 – 0.7, elliptical perimeter ratio of 1.02 – 1.12, and sphericity of 0.45 – 0.85, reflecting a balance between angularity and flowability. The orientation entropy of three steel slags is 6.33 % – 6.47 % higher than that of basalt, with values of 4.1546, 4.1526, and 4.1490, indicating more complex textures. Distinct morphology supports function-oriented applications of different steel slags. Basic oxygen furnace slag, with favorable morphology, texture, low porosity, and stable performance, is suitable for high-skid-resistance pavements. Open-hearth furnace slag, featuring coarse texture and abundant mesopores and micropores, also demonstrates strong skid-resistance potential. Electric arc furnace slag, with the highest porosity of up to 10.22 %, is recommended for drainage or noise-reducing pavements. This study clarifies the relationship between multi-scale particle characteristics and pavement functionality, providing theoretical support for non-destructive evaluation and function-driven application of steel slag in various pavements. • Non-destructive coarse aggregate evaluation methods had been proposed. • Multi-scale and multi-dimensional evaluation system for road-used steel slag was updated. • The applicability in pavement engineering of steel slag under different scenarios was analyzed. • 3D scanning technology was applied and the results were analyzed. • The particle shape characteristic differences between steel slag and natural aggregates were compared.