不同预浸骨料-PVA纤维对再生混凝土力学性能的影响

Effect of different pre-soaked aggregate-PVA fiber on the mechanical properties of recycled aggregate concrete

为研究纳米SiO_(2)溶液和水泥净浆改性再生粗骨料后,掺入聚乙烯醇(Polyvinyl alcohol,PVA)纤维再生混凝土的基本力学性能和动态力学性能,分别对不同浓度的纳米SiO_(2)溶液和不同水灰比的水泥净浆进行再生骨料浸泡预试验,选定浓度为2wt%的纳米SiO_(2)溶液和水灰比为0.5的水泥净浆,对改性后再生混凝土的力学性能进行对比试验。选取再生粗骨料取代率、PVA纤维掺量和应变率为变量,静力学性能采用万能压力机进行,动态力学性能采用霍普金森压杆(Split Hopkinson pressure bar,SHPB)进行。测试试件28天立方体抗压强度、轴心抗压强度和抗折强度,得到了不同应变率条件下试件的应力-应变曲线,分析了试件静力性能、动态抗压强度、动态增长因子(Dynamic increase factor,DIF)、动态峰值应变和比吸能随变量的变化规律。结果表明:随取代率增加,试件基本力学性能降低,增加PVA纤维掺量,试件抗压强度降低而抗折强度提高;随取代率和PVA纤维掺量增加,试件动态峰值应力呈下降趋势,而动态峰值应变呈增长趋势;取代率的增加提升了试件的DIF值,而PVA纤维对DIF值影响并不明显;应变率的提高增强了试件的动态强度和应变,而水泥净浆改性再生混凝土比纳米SiO_(2)改性再生混凝土具备更高的比吸能。

In order to study the basic mechanical properties and dynamic mechanical properties of recycled aggregate concrete mixed with polyvinyl alcohol(PVA)fiber after modified recycled coarse aggregate with nano-SiO_(2) solution and cement paste,recycled aggregate pre-soaking tests were carried out on different concentrations of nano-SiO_(2) solutions and cement pastes with different water-cement ratios.The nano-SiO_(2) solutions with a concentration of 2wt%and the cement paste with a water-cement ratio of 0.5 were selected.The mechanical properties of recycled aggregate concrete were tested for comparison.The replacement percentage of recycled coarse aggregate,the content of PVA fiber and the strain rate were variable.The static mechanical properties were tested by a universal press,and the dynamic mechanical properties were tested by using a split Hopkinson pressure bar(SHPB).The 28 days cube compressive strength,axial compressive strength and flexural strength of the specimen were tested,the stress-strain curves of the specimen under different strain rate conditions were obtained,and the static performance,dynamic compressive strength,dynamic increase factor(DIF),dynamic peak strain and specific energy absorption of the specimen changes with variables were analyzed.The results show that with the increase of the replacement percentage,the basic mechanical properties of the specimen decrease,and the content of PVA fiber increases,the compressive strength of the specimen decreases while the flexural strength increases;with the increase of the replacement percentage and PVA fiber content,the dynamic peak stress of the specimen decreases,while the dynamic peak strain shows an increasing trend;the increase of the replacement percentage increases the DIF value of the specimen,while the PVA fiber has no obvious effect on the DIF value;the increase in strain rate enhances the dynamic strength and strain of the specimen,and the cement paste modified recycled aggregate concrete has a higher specific energy absorption than the nano-SiO_(2) modified recycled aggregate concrete.