关键词: 早期受冻, 冻融循环, 掺玄武岩纤维混凝土, 纤维掺量, 耐久性, 孔隙率

Abstract: To address the problem of rapid durability degradation of early freezing plain concrete in the cold and arid regions of northwest China under the action of salt-freezing coupling effect, based on the indoor rapid freezing and thawing test, the durability deterioration law of concrete with different volume content of basalt fibers was studied using a 3.5% (mass fraction, the same below) NaCl+5.0% Na₂SO₄ composite salt solution as a freeze-thaw medium, and scanning electron microscope, ultrasonic defect detection and nuclear magnetic resonance pore size detection were applied to explore the improvement effect of basalt fibers on the macroscopic properties of concrete under the salt-freezing coupling effect at the micro level. The results show that the addition of basalt fibers in the early freezing plain concrete can effectively improve the compressive strength and reduce the mass loss. With the increase of fiber content, the compressive strength and relative dynamic elastic modulus increase first and then decrease. With the increase of freeze-thaw cycle time, the ultrasonic pulse propagation velocity of different volume content of basalt fibers in the early freezing plain concrete gradually increases, and the total porosity of each group specimens is positively correlated with the freeze-thaw cycle time, and the addition of basalt fibers increases the proportion of harmless pores, reduces the proportion of multi-harmful pores, and improves the durability resistance of concrete. In the tests, the fiber of 0.15% (volume fraction) group of test blocks has the most superior performance among all of test blocks. The research results can provide a reference for the study of durability of early freezing plain concrete in cold and arid irrigation areas and later maintenance.

Key words: early freezing, freeze-thaw cycle, basalt fiber concrete, fiber content, durability, porosity