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<p>This study investigates the mechanical, durability, microstructural, and structural performance of silica-fume-modified normal-strength concrete incorporating steel slag (SS) and slag aggregate as sustainable replacements for natural fine and coarse aggregates. Replacement levels of 25, 50, 75, and 100% were evaluated under identical mix design and curing conditions. The silica-fume reference mix (NSC–SF REF) achieved the highest 28-day compressive strength of 42.79&#xa0;MPa, representing a 35% improvement over conventional concrete (31.65&#xa0;MPa). Among slag-modified mixes, 25% steel slag replacement (SS25) demonstrated the most balanced performance, retaining 86.3% compressive strength, 92.8% tensile strength, 81.7% flexural strength, and 93% elastic modulus relative to the silica-fume reference system. At the structural level, SS25 retained 84% peak load capacity with stable ductility behavior. Coarse slag replacement at 50% (SA50) maintained acceptable mechanical performance but exhibited increased durability sensitivity beyond this threshold. Durability results showed controlled permeability at moderate replacement levels, with water absorption increasing from 1.108% (NSC–SF REF) to 2.329% (SS50) and significant degradation observed beyond 50% replacement. SEM–EDS analysis revealed reduced Ca/Si ratios (~1.15 for SS25), indicating silica-rich C–S–H formation and matrix densification, which directly correlated with strength retention behavior. Statistical evaluation confirmed high experimental reliability, with COV values below 5%, R<sup>2</sup> &gt; 0.95, and RMSE &lt; 1.8&#xa0;MPa for compressive strength trends. Since the investigation is experimental rather than predictive-model-based, bias metrics such as PBIAS were not applicable; instead, dispersion-based reliability measures were employed. The study establishes a clear performance threshold near 50% slag replacement, below which silica-fume-induced densification compensates for slag porosity. The findings provide experimentally validated replacement limits for sustainable aggregate utilization in structural concrete applications.</p>

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Mechanical, Physical and Micro-structural Studies on Silica-Fume Modified Concrete with Sustainable Aggregates

  • 期刊论文

  • 发表日期：

    2026年6月29日

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  • S. Vinoth,
  • V. Rajesh Kumar,
  • S. Deepika,
  • E. Prabakaran

摘要

This study investigates the mechanical, durability, microstructural, and structural performance of silica-fume-modified normal-strength concrete incorporating steel slag (SS) and slag aggregate as sustainable replacements for natural fine and coarse aggregates. Replacement levels of 25, 50, 75, and 100% were evaluated under identical mix design and curing conditions. The silica-fume reference mix (NSC–SF REF) achieved the highest 28-day compressive strength of 42.79 MPa, representing a 35% improvement over conventional concrete (31.65 MPa). Among slag-modified mixes, 25% steel slag replacement (SS25) demonstrated the most balanced performance, retaining 86.3% compressive strength, 92.8% tensile strength, 81.7% flexural strength, and 93% elastic modulus relative to the silica-fume reference system. At the structural level, SS25 retained 84% peak load capacity with stable ductility behavior. Coarse slag replacement at 50% (SA50) maintained acceptable mechanical performance but exhibited increased durability sensitivity beyond this threshold. Durability results showed controlled permeability at moderate replacement levels, with water absorption increasing from 1.108% (NSC–SF REF) to 2.329% (SS50) and significant degradation observed beyond 50% replacement. SEM–EDS analysis revealed reduced Ca/Si ratios (~1.15 for SS25), indicating silica-rich C–S–H formation and matrix densification, which directly correlated with strength retention behavior. Statistical evaluation confirmed high experimental reliability, with COV values below 5%, R2 > 0.95, and RMSE < 1.8 MPa for compressive strength trends. Since the investigation is experimental rather than predictive-model-based, bias metrics such as PBIAS were not applicable; instead, dispersion-based reliability measures were employed. The study establishes a clear performance threshold near 50% slag replacement, below which silica-fume-induced densification compensates for slag porosity. The findings provide experimentally validated replacement limits for sustainable aggregate utilization in structural concrete applications.