مشخصات پژوهش

This study investigates the combined effects of silica fume addition and variable steam-curing durations on concrete mechanical properties. Unlike most prior research, which typically used fixed steam durations and focused mainly on compressive strength, this work directly compares multiple steam-curing intervals (4–48 h at 66 ±2 °C) with conventional water curing (3–28 days), enabling clear one-to-one comparisons of compressive, splitting tensile, and flexural strength development. Four mixtures were tested: control mixes at w/c 0.6 and 0.35 (no silica fume), plus mixes with silica fume added at 10% and 15% by cement weight (w/c 0.6). A total of 396 specimens were evaluated. Under steam curing, the low w/c mix (no silica fume) achieves 70–80% of its 28-day water-cured compressive and tensile strengths within 16–24 h. In contrast, silica fume mixes initially develop strength more slowly but accelerate markedly after 24 h, reaching up to 87–88% of 28-day tensile strengths and ~79–80% of flexural strengths by 48 h — outperforming low w/c mixes in normalized later-age gains. Strong linear correlations (R² ≈ 0.97–0.99) among compressive, tensile, and flexural strengths (validated by partial correlation and residual analysis) enable reliable prediction of non-compressive properties from standard compressive tests. These results demonstrate the potential of controlled steam curing combined with silica fume to accelerate early-age strength gain, reduce early cracking risks, and enhance performance stability in precast production and rehabilitation of high-performance structural elements, although findings are based on laboratory conditions without chemical admixtures, limiting direct field applicability.