<p>Hybrid fiber-reinforced slag-fly ash geopolymer concrete has emerged as a sustainable and high-performance alternative to conventional cement-based materials. However, its fatigue response under external loading remains complex due to material heterogeneity and the multi-scale crack resistance provided by hybrid fibers. In this study, fatigue damage evolution and fatigue life were systematically investigated under varying stress levels, stress ratios, and loading frequencies using four-point bending fatigue tests. A hybrid system incorporating modified basalt fiber and polyvinyl alcohol fiber was employed to analyze the evolution of deflection, crack mouth opening and crack propagation height. The results show that fatigue behavior is governed by the combined effects of loading parameters. Increasing stress level accelerates crack propagation. Fatigue life exhibits a non-monotonic dependence on stress ratio, with maximum at <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$R \approx 0.2$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>R</mi> <mo>≈</mo> <mn>0.2</mn> </mrow> </math></EquationSource> </InlineEquation>. At <InlineEquation ID="IEq2"> <EquationSource Format="TEX">$S = 0.75$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>S</mi> <mo>=</mo> <mn>0.75</mn> </mrow> </math></EquationSource> </InlineEquation>, the fatigue life at <InlineEquation ID="IEq3"> <EquationSource Format="TEX">$R = 0.2$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>R</mi> <mo>=</mo> <mn>0.2</mn> </mrow> </math></EquationSource> </InlineEquation> is 1.11 times that at <InlineEquation ID="IEq4"> <EquationSource Format="TEX">$R = 0.1$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>R</mi> <mo>=</mo> <mn>0.1</mn> </mrow> </math></EquationSource> </InlineEquation>, but decreases to 41% at <InlineEquation ID="IEq5"> <EquationSource Format="TEX">$R = 0.3$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>R</mi> <mo>=</mo> <mn>0.3</mn> </mrow> </math></EquationSource> </InlineEquation>. Fatigue life also increases with loading frequency, reaching 0.38 and 0.61 times that at 1 Hz for 3 Hz and 5 Hz, respectively. From a mechanistic perspective, increasing stress level accelerates crack propagation due to intensified stress concentration, whereas stress ratio and loading frequency affect fatigue behavior through the interaction between fiber bridging, crack closure, and stress redistribution. Furthermore, a two-parameter Weibull distribution was employed to establish probabilistic relationships, enabling fatigue life prediction and reliability-based evaluation.</p>

Fatigue crack evolution and life prediction of hybrid fiber-reinforced slag-fly ash geopolymer concrete: influences of stress level, stress ratio, and loading frequency

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发表日期：

2026年5月14日

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Jin Xia,
Yen-yi Hoo,
Wan-lin Min,
Ke-yu Chen,
Khant Swe Hein

摘要

Hybrid fiber-reinforced slag-fly ash geopolymer concrete has emerged as a sustainable and high-performance alternative to conventional cement-based materials. However, its fatigue response under external loading remains complex due to material heterogeneity and the multi-scale crack resistance provided by hybrid fibers. In this study, fatigue damage evolution and fatigue life were systematically investigated under varying stress levels, stress ratios, and loading frequencies using four-point bending fatigue tests. A hybrid system incorporating modified basalt fiber and polyvinyl alcohol fiber was employed to analyze the evolution of deflection, crack mouth opening and crack propagation height. The results show that fatigue behavior is governed by the combined effects of loading parameters. Increasing stress level accelerates crack propagation. Fatigue life exhibits a non-monotonic dependence on stress ratio, with maximum at $R \approx 0.2$ $R \approx 0.2$ . At $S = 0.75$ $S = 0.75$ , the fatigue life at $R = 0.2$ $R = 0.2$ is 1.11 times that at $R = 0.1$ $R = 0.1$ , but decreases to 41% at $R = 0.3$ $R = 0.3$ . Fatigue life also increases with loading frequency, reaching 0.38 and 0.61 times that at 1 Hz for 3 Hz and 5 Hz, respectively. From a mechanistic perspective, increasing stress level accelerates crack propagation due to intensified stress concentration, whereas stress ratio and loading frequency affect fatigue behavior through the interaction between fiber bridging, crack closure, and stress redistribution. Furthermore, a two-parameter Weibull distribution was employed to establish probabilistic relationships, enabling fatigue life prediction and reliability-based evaluation.