盐冻作用下玄武岩纤维混凝土力学性能损伤研究

针对西北寒旱地区混凝土结构易开裂耐久性降低的问题,选取力学性能优异的玄武岩纤维作为混凝土增强材料,采用室内快速冻融试验,以纤维体积掺量为变量,研究了不同纤维体积掺量(0.05%、0.1%、0.15%、0.2%)混凝土试件分别在清水、质量分数为3%的NaCl溶液、质量分数为5%的Na₂SO₄溶液冻融作用下动弹性模量、抗压强度、抗折强度三个力学性指标的变化。研究发现,玄武岩纤维的掺入能有效提升混凝土的初始抗折强度和抗盐冻能力,纤维体积掺量在0.15%~0.2%时混凝土试件动弹性模量、抗压强度与抗折强度在盐冻作用下的衰减速率减缓明显,玄武岩纤维混凝土在三种冻融介质中力学性能下降速率排序为清水<5%Na₂SO₄溶液<3%NaCl溶液。以动弹性模量为损伤变量,拟合混凝土相对抗压强度、相对抗折强度与损伤度的相关模型,模型相关性良好。研究结果可为玄武岩纤维混凝土的实际运用与后期维护提供理论依据与参考。

Damage of Mechanical Properties of Basalt Fiber Reinforced Concrete under Salt Freezing

Aiming at the problem that the concrete structure is easy to crack and the durability is reduced in the cold and dry areas of Northwest China, basalt fiber with excellent mechanical properties was selected as concrete reinforcement material. The volume fraction of fiber was taken as the variable. The dynamic elastic modulus, compressive strength and flexural strength of concrete specimens with different fiber volume content (0.05%, 0.1%, 0.15% and 0.2%) under freeze-thaw action of clean water, 3%NaCl solution and 5%Na₂SO₄ solution were studied. It is found that basalt fiber effectively improves the initial flexural strength and salt frost resistance of concrete, when the fiber volume content is between 0.15% and 0.2%, the attenuation rate of dynamic elastic modulus, compressive strength and flexural strength of concrete specimens under salt frost action slow down obviously. The descending rate of mechanical properties of basalt fiber reinforced concrete in three kinds of freeze-thaw media is clean water<5%Na₂SO₄<3%NaCl. Taking the dynamic elastic modulus as the damage variable, the correlation model of concrete relative compressive strength and relative flexural strength are fitted, and the correlation of the models are good. The research results provide theoretical basis and reference for the practical application and building maintenance of basalt fiber reinforced concrete.