Properties Research For Polyvinyl Alcohol And Basalt Hybrid Fibers Reinforced Concrete

The hybrid effect of hybrid fibers can improve the performance of concrete through synergy and superposition. High-strength and high-modulus polyvinyl alcohol fiber and basalt fiber are two kinds of new fibers, so the influence of their hybrid on the performance of concrete is rarely studied. In this paper, the author systematically explores the hybrid effect produced by these two fibers and discusses the regularity of influence of fiber hybrid on the performance of concrete in an attempt to better improve the performance of ordinary concrete.In terms of these two fibers, three lengths (5mm,10mm and 15mm) and four volume contents (0,0.05%,0.10% and 0.15%) are selected to formulate single or hybrid fiber reinforced concrete of two strength grades:C30 and C60; then, compressive and flexural strengths, bending and toughness are tested to study the respective influence of length, type and content of fibers on strength and toughness of concrete; range and variance analyses are adopted to quantify the influence of various factors on performance of fiber concrete; mathematical statistical methods are used to investigate the changes in slump retention value, flexural and compressive strengths of concrete with length, type and content of fibers; scanning electron microscope is employed to study the microstructure of concrete and discuss the reasons for the changes in performance of fiber concrete.The results show that, the slump retention value of concrete decreases with the increase of content and length of fibers; in terms of the influence on the performance of concrete, hybrid fiber is less than basalt fiber; the variance analysis suggests that fiber content is a factor that influences the performance of concrete most. The compressive strength of concrete first increases and then decreases with the increase of fiber content, and increases with the increase of fiber length; hybrid fiber can improve the compressive strength more significantly than basalt fiber concrete; type and content of fibers are major factors that affect the compressive strength of concrete. Fiber content exerts the greatest influence on flexural strength, followed by fiber type and fiber length in sequence; flexural strength increases with the increase of content and length of fibers, and the flexural strengths of these two kinds of fibers both increase a bit; when other factors remain unchanged, the flexural strength of hybrid fiber concrete is superior to that of basalt fiber concrete. Fiber type is the most important influencing factor of the toughness of fiber reinforced cement concrete, and deformation and hardening phenomena are more easily found in hybrid fiber concrete than single-doped fiber concrete. In the meantime, it can be concluded that, the greater the content and length of fiber are, more significant the deformation and hardening phenomena of fiber concrete will be, and the greater the toughness index value will be.The toughening mechanism analysis shows that, hybrid fiber will form a three-dimensional chaotic distribution network in the concrete, curbing the emergence of initial defects of concrete; when bending cracks occur, polyvinyl alcohol fiber and basalt fiber will play different roles. The latter mainly plays a bridging role in the cracks, while the former will be able to absorb a lot of energy through self-deformation in the crack expansions due to its excellent deformation performance. These two fibers work together to curb the expansion of cracks, thereby significantly increasing the toughness of the base.