聚甲醛纤维增强砂浆的力学性能和干燥收缩试验研究

本文研究了不同长度聚甲醛(POM)纤维单掺和混掺对砂浆流动度、抗折强度、抗压强度、弯曲韧性及干燥收缩的影响,并通过扫描电镜观测了其微观结构。研究发现,砂浆流动度随POM纤维长度和掺量增大而下降,混掺纤维比单掺对砂浆流动度的影响更小。POM纤维能有效提高砂浆的抗折强度,但掺量超过0.6%(体积分数,下同)时增强效果减弱,与未掺纤维试样相比,0.6%掺量的6 mm纤维对试样28 d抗折强度提升最高,为14.67%,抗压强度随纤维掺量增加而降低。12 mm纤维比6 mm及混掺对试样弯曲韧性提升更明显,最大提高49.43%。纤维的掺入可显著降低试样的干燥收缩率,且随纤维掺量增加,试样90 d干燥收缩率先减小后增大。与未掺纤维试样相比,0.6%掺量的6 mm纤维试样90 d干燥收缩率下降最多,为27.39%。混掺POM纤维在掺量0.6%以上时仍可显著提升砂浆的抗折强度并减小干燥收缩率。

Mechanical Properties and Drying Shrinkage of Polyoxymethylene Fiber Reinforced Mortar

The effects of single adding and mixing polyoxymethylene (POM) fibers with different lengths on fluidity, flexural strength, compressive strength, flexural toughness and drying shrinkage of mortar were studied in this paper, and the microstructure of mortar was observed by scanning electron microscope. The results show that mortar fluidity decreases with the increase of POM fiber length and content, and the influence of mixed fiber with different lengths on the fluidity of mortar is less than that of single fiber. POM fiber effectively enhances the flexural strength of mortar, but the strengthening effect is weakened when the content is more than 0.6% (volume fraction, the same below). Compared with the sample without fiber, the 6 mm fiber with 0.6% content has the highest increase of 28 d flexural strength, which is 14.67%. The compressive strength decreases with the increase of fiber content. The flexural toughness of 12 mm fiber is improved more significantly than that of 6 mm fiber and mixed fiber, which increases of 49.43% at most compared with the sample without fiber. The addition of fiber greatly reduces the drying shrinkage of the sample, the 90 d drying shrinkage of the sample decreases first and then increases with the increase of fiber content. Compared with the sample without fiber, the 90 d drying shrinkage rate of 6 mm fiber sample with 0.6% content decreases the most, which is 27.39%. The hybrid POM fiber still significantly improves the flexural strength and reduces the drying shrinkage when the content is more than 0.6%.