PVA纤维、减缩剂和轻烧氧化镁对水工衬砌混凝土性能影响对比研究

Comparative study on the effects of PVA fiber,shrinkage reducing agent and light-fired magnesium oxide on the properties of hydraulic lining concrete

依托于滇中引水工程,研究了掺入聚乙烯醇纤维(PVA纤维)、减缩剂和轻烧氧化镁对衬砌混凝土性能的影响。结果表明:掺入0.9 kg/m^(3)PVA纤维和1.5%减缩剂对混凝土坍落度影响不显著,掺入5%轻烧氧化镁后,混凝土拌和物坍落度下降了36.8%;掺入0.9 kg/m^(3)PVA纤维、1.5%减缩剂和5%轻烧氧化镁后,混凝土7 d、28 d龄期的抗压强度和劈拉强度差异不明显;掺入1.5%减缩剂和5%轻烧氧化镁对混凝土7 d、28 d龄期的极限拉伸值影响不显著,但掺入0.9 kg/m^(3)的PVA纤维后,混凝土28 d龄期的极限拉伸值提高了18×10-6;掺入0.9 kg/m^(3)的PVA纤维对混凝土120 d龄期内的干缩率影响不显著,掺入减缩剂和轻烧氧化镁后,混凝土120 d龄期的干缩率分别降低了100×10-6和33×10-6;掺入PVA纤维、减缩剂和轻烧氧化镁后,混凝土裂缝降低率分别为44.1%、31.9%和25.0%,可以有效减少裂缝的产生。

Based on the Dianzhong Water Diversion Project,the effects of adding polyvinyl alcohol fiber(PVA fiber),shrinkage reducing agent and lightly burned magnesium oxide on the performance of lining concrete were studied.The result showed that the effects of adding 0.9 kg/m^(3)PVA fiber and 1.5%shrinkage reducing agent on the slump of concrete was not significant,and the slump of concrete mix decreased by 36.8%and the viscosity of concrete increased significantly after adding 5%light burnt magnesium oxide.There was no significant difference in compressive strength and split tensile strength of concrete at 7 d and 28 d age after adding 0.9 kg/m^(3)PVA fiber,1.5%shrinkage reducing agent and 5%light burnt magnesium oxide.The effects of adding 1.5%shrinkage reducing agent and 5%lightly burnt magnesium oxide on the ultimate tensile value of concrete at 7 d and 28 d age were not significant,while the ultimate tensile value of concrete at 28 d age was increased by 18×10-6 after admixture of 0.9 kg/m^(3)of PVA fiber.The effects of adding 0.9 kg/m^(3)PVA fiber on the dry shrinkage of concrete at 120 d age was not significant,and the dry shrinkage of concrete at 120 d age was reduced by 100×10-6 and 33×10-6 after adding shrinkage reducing agent and light burnt magnesium oxide,respectively.Finally,the crack of concrete was reduced by 44.1%,31.9%and 25.0%after mixing PVA fiber,shrinkage reducer and light-fired magnesium oxide,which could effectively reduce the cracks.