Study on the dispersibility of modified basalt fiber and its influence on the mechanical properties of concrete

With the aim of improving the dispersion property of basalt fibers in concrete, its surface was modified using hydrochloric acid (HCl) solution. The distribution characteristics of fiber were quantitatively evaluated by the dispersal degree test with response surface method and cutting plane image analysis technique. Besides, the effect of modified basalt fiber on the mechanical properties of concrete was investigated. The results show that the surface roughness of basalt fiber was increased, the toughness of the fiber did not significantly degrade after being modified by the hydrochloric acid solution. When the concentration of hydrochloric acid was 4 mol/L, the modification time was 15 h and the modification temperature was 50 °C, the fiber dispersion degree in cement suspension paste reached 84%, the fiber dispersion coefficient reached a higher level of 0.9 in the harden concrete matrix. The splitting tensile and flexural strength of modified basalt fiber-reinforced concrete are improved. In contrast to untreated basalt fiber-reinforced concrete, a higher splitting tensile strength and greater flexural strength were obtained after curing for 28 days. Furthermore, the pull-out load, average bond strength and pull-out work of concrete with modified fiber were 128%, 129% and 71% higher than concrete with neat fiber. Surface modification method by HCl solution demonstrates great potential for large scale production of basalt fiber-reinforced concrete.