Investigation on compressive strength of fiber reinforced concrete subjected to the coupling effects of freeze-thaw cycling and loading utilizing fractal theory
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摘要: 为了研究持续荷载与冻融循环耦合作用下纤维混凝土的抗压性能与分形维数值之间的关系,开展了不同压应力水平(0、0.3、0.5)作用下的纤维混凝土冻融循环试验。对冻融前后纤维混凝土裂缝进行分形特征研究,并基于分形理论研究了不同耦合作用下试件的抗压强度变化规律,建立了裂缝分形维数与抗压强度的演化方程。结果表明:随着冻融循环次数的增加,试件抗压强度逐渐减小。当冻融循环次数增加到160次,不同耦合应力水平下试件抗压强度损失率差异显著,其中在耦合应力水平为0.3时损失率最小为21.59%,耦合应力水平为0.5时损失率最大为33.58%。裂缝的分形维数与耦合作用有明显的线性关系,能够定量反映纤维混凝土的劣化规律,裂缝分形维数的数值越大,纤维混凝土冻融损伤越大,抗压强度越低。Abstract: This study explores the correlation between the compressive attributes of the fiber reinforced concrete and the fractal dimension value under the combined influence of continuous loading and freeze-thaw cycling. Freeze-thaw cycling tests were conducted on the fiber reinforced concrete with varying compressive stress levels (0, 0.3, 0.5). The fractal characteristics of the concrete cracks pre and post freeze-thaw were examined, and the alteration in the compressive strength of the samples under different coupling effects was analyzed using the fractal theory. An evolution equation was established between the fractal dimension of the cracks and the compressive strength. Findings indicate that as the number of freeze-thaw cycles increases, the compressive strength of the sample progressively decreases. When the number of freeze-thaw cycles increases to 160, the loss rates in the compressive strength of the specimens under different coupling stresses exhibit the significant differences, the smallest loss rate of 21.59% is observed at a coupling stress of 0.3, while the maximum of 33.58% is noted at a coupling stress of 0.5. A clear linear relationship is found between the fractal dimension of the cracks and the coupling effect, quantitatively reflecting the deterioration pattern of the fiber reinforced concrete. A larger fractal dimension value of the cracks indicates greater freeze-thaw damage to the fiber reinforced concrete and a lower compressive strength.
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表 1 各组试件耦合应力
Table 1. Couple stress of each group
Specimen set F-0 F-0.3 F-0.5 Stress level 0 0.3 f 0.5 f Stress magnitude/MPa 0 13.56 22.6 Notes: F-0 and F-0.3 and F-0.5 represent the different compressive stress levels and f represents the compressive strength of concrete specimens after 28 days. 表 2 纤维混凝土抗压强度
Table 2. Compressive strength of the fiber reinforced concrete
Number of
freeze-thaw
cycles/timesCompressive
strength
of F-0/MPaCompressive
strength
of F-0.3/MPaCompressive
strength
of F-0.5/MPa0 45.20 45.20 45.20 20 44.18 45.13 44.94 40 43.04 44.27 44.46 60 41.99 42.56 42.28 80 39.90 41.42 40.85 100 38.29 39.81 38.57 120 35.91 38.48 35.34 140 33.73 36.96 32.87 160 31.16 35.44 30.02 表 3 各组纤维混凝土试件分形维数值的参数
Table 3. The parameter values of fractal dimension for the fiber reinforced concrete specimens in each group
Specimen set a/10-3 b F-0 3.49 1.19 F-0.3 3.31 1.16 F-0.5 4.12 1.15 Notes: a and b are parameter values of the fractal dimension -
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