Mechanical properties of high volume flyash concrete reinforced with hybrid fibers

Abstract: Flyash substitution to cement is a well-recognized approach to reduce CO2 emissions. Although flyash concrete is prone to brittle behavior, researchers have shown that addition of fibers could reduce brittle behavior. Previous research efforts seem to have utlised a single type of fiber or two types of fibers. In this research, three types of fibers - steel, polypropylene and basalt as 0%, 0.50%, 0.75% and 1% by volume of concrete were mixed in varying proportions with concrete specimens substituted with 50% flyash (Class F). All specimens were tested for compressive strength, indirect tensile strength and flexural strength over a period of 3 to 56 days of curing. Test results showed that significant improvement in mechanical properties could be obtained by a particular hybrid fiber reinforcement combination (1% steel fiber, 0.75% polypropylene fiber and 0.75% basalt fiber). The observed strength values were observed to exceed previous research results. Workability of concrete was affected when the fiber combination exceeded 3%. Thus a limiting value for adding fibers and the combination to achieve maximum strengths have been identified in this research.