喷射混杂纤维混凝土抗冻性及损伤模型

Frost Resistance and Damage Model of Sprayed Hybrid Fiber Reinforced Concrete

目的为提高高寒地区喷射混凝土耐久性,改善冻融环境下普通喷射混凝土易开裂、抗冻性能差等问题。方法在喷射混凝土中掺入混合纤维,通过冻融循环试验、超声波检测、压拉性能试验以及气孔结构测试等方法,研究不同冻融循环次数下喷射混杂纤维混凝土的相对纵波波速、相对压拉强度以及试件内部气孔结构变化规律。通过压拉性能损伤量对试件冻融损伤进行多项评价,分析钢纤维和聚丙烯纤维贡献率与喷射混凝土抗压强度之间的关系,并根据钢纤维和聚丙烯纤维贡献率公式建立喷射混凝土冻融损伤模型。结果与单掺钢纤维和聚丙烯纤维试件相比,混合掺入1%钢纤维、0.1%聚丙烯纤维喷射混凝土试件的抗压强度损失分别降低了7.5%、33.3%,劈裂抗拉强度损失分别降低了15.6%、35.0%。在弦长尺寸0.1mm<d<1mm处,混合掺入0.1%聚丙烯和1%钢纤维喷射混凝土气泡弦长频率比单掺1%钢纤维喷射混凝土和单掺0.1%聚丙烯喷射混凝土分别降低了24.9%和27.3%。钢纤维和聚丙烯纤维对抗压强度的贡献率呈现先增长后下降趋势。基于冻融损伤与钢纤维和聚丙烯纤维贡献率建立冻融损伤模型。结论喷射混杂纤维混凝土力学性能损伤量低,不易开裂,抗冻性能好,可为高寒地区喷射混凝土结构提供理论参考。

Objective To improve the durability of shotcrete in high-altitude and cold regions and to address issues such as cracking and poor frost resistance of ordinary shotcrete in freeze-thaw environments.Methods With the method of adding mixed fibers to shotcrete,the relative longitudinal wave velocity,relative compressive tensile strength and changes in internal pore structure of sprayed mixed fiber concrete under different freeze-thaw cycles were studied by combining freeze-thaw cycle experiments,ultrasonic detection experiments,compressive tensile performance tests and pore structure tests.Multiple evaluations were conducted on the freeze-thaw damage of specimens based on their compressive and tensile performance damage levels.The relationship between the contribution rates of steel fibers and polypropylene fibers and the compressive strength of shotcrete was analyzed and a freeze-thaw damage model of shotcrete was established based on the formula for the contribution rates of steel fibers and polypropylene fibers.Results Compared with the single steel fiber and polypropylene fiber specimens,the compressive strength loss of shotcrete specimens mixed with 1%steel fiber and 0.1%polypropylene fiber decreased by 7.5%and 33.3%respectively,and its splitting tensile strength loss decreased by 15.6%and 35.0%respectively.At the chord length dimension of 0.1mm<d<1mm,the frequency of bubble chord length in the mixed addition of 0.1%polypropylene and 1%steel fiber shotcrete decreased by 24.9%and 27.3%respectively,compared to the single addition of 1%steel fiber shotcrete and 0.1%polypropylene shotcrete.The research found that the contribution rates of steel fibers and polypropylene fibers to compressive strength showed a trend of first increasing and then decreasing.The freeze-thaw damage model was established based on the contribution rates of steel fibers and polypropylene fibers.Conclusion The mechanical properties of sprayed hybrid fiber reinforced concrete are low in loss and less prone to cracking and have good frost resistance,providing a theoretical reference for shotcrete structures in high-altitude and cold regions.