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

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-SiO₂ solution and cement paste, recycled aggregate pre-soaking tests were carried out on different concentrations of nano-SiO₂ solutions and cement pastes with different water-cement ratios. The nano-SiO₂ 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-SiO₂ modified recycled aggregate concrete.