纳米SiO_2/PVA纤维复合改性HVFC的断裂性能实验研究

Bending Fracture Toughness of Nano-SiO_2/PVA Fiber Modified High-Volume Fly Ash Concrete

研究了纳米二氧化硅(NS)及聚乙烯醇(PVA)纤维对高掺量粉煤灰混凝土(HVFC)弯曲断裂性能的影响.通过对5组质量掺量分别为0%,0.5%,1.0%,1.5%与2.0%的纳米二氧化硅和4组体积掺量分别为0%,0.08%,0.1%与0.2%的PVA纤维实验配比进行了研究.结果表明,单掺适量NS能提高HVFC的初裂荷载、初裂挠度,但是不能改善混凝土的脆性特征.单掺PVA纤维能提高混凝土的断裂韧性,其荷载-挠度曲线出现应变硬化现象.少量NS可以显著提高PVA纤维的增韧效果.当PVA纤维体积分数掺量为0.08%时,NS质量分数掺量为0.5%时,使得HVFC的弯曲韧性指数I_5、I_(10)、I_(20)比单掺PVA纤维混凝土分别高28%,43%和60%.

The effect of nano-SiO2 and PVA fibers on the 28-days fracture toughness of high-volume fly ash concrete, with a constant fly ash/binder ratio of 50% by weight, was investigated through a comparative experimental study under four-point bending loading. Five nano-particles/ binder weight ratios of 0%, 0.5%, 1.0%, 1.5% and 2.0%, and four PVA fiber volume fractions of 0%, 0.08%, 0.1% and 0.2% were adopted. The test results showed that an increase in the toughness index of concrete could be found with incorporating of proper content of nano-SiO2 and PVA fibers. The combined addition of 0.5% wt. NS with 0.08% vol. PVA fibers resulted in an increase of 28%, 43% and 60% in the toughness index of I5, I10, I20 as compared to concrete containing 0.08% PVA alone, respectively.