Hybrid effects of basalt and polyvinyl alcohol fibers on the mechanical properties and macro-microscopic analysis of low-heat portland cement concrete
Yu Zhang, Yuanxun Zheng, Chaowei Du, Shaowei Hu, Zhi Wang
Abstract
In this study, the pattern of the effect of hybrid basalt fibers (BF) and polyvinyl alcohol fibers (PVAF) on low-heat Portland cement (LHPC) concrete was investigated through mechanical properties and microstructural tests. The compressive stress-strain relationship law for hybrid fiber-reinforced LHPC-C is also summarized by the test data. The test results showed that BF reduced the slump of LHPC-C more significantly than PVAF, and hybrid fibers were better than individual fibers for the strength enhancement of concrete. When the total fiber content was less than 0.4%, the two fibers showed a positive hybrid effect. The optimum hybrid fiber contents for 28 d compressive, splitting tensile, and flexural strength of concrete were 0.15% BF and 0.1% PVAF, 0.2% BF and 0.1% PVAF, and 0.15% BF and 0.3% PVAF, respectively. Compared with the control group, the three mechanical strengths were increased by 30.05%, 56.79%, and 43.51%, respectively. Meanwhile, the toughness of LHPC-C became more apparent as the fiber contents grew. Concrete with BF contents of 0.2% and PVAF of 0.3% had the highest toughness index. At the microscopic level, the components in LHPC-C were mainly SiO2, Ca(OH)2 and C–S–H gels. The surfaces of BF and PVAF were well-bonded to the hydrated cement matrix, and appropriate amounts of hybrid fibers can effectively reduce the porosity of LHPC-C.