Experimental Study of Effects of Fly Ash on the Mechanical Properties of Hybrid Fiber Reinforced Cementitious Composite

Fibers are increasingly used for enhancement of the tensile strength of conventional concrete. using fiber cementitious composite as well as microfiber and pva fibers can be considered to improve the mechanical property of selfcompacting concretes. this study considers the mechanical properties of highperformance hybrid fiber reinforced cementitious composite specimens, which     are reinforced by micro steel fibers, pva, and a combination of them. in order to achieve the study goals, 10 mixture ratios were considered. all mixtures underwent compressive, tensile, and flexural strength tests as well as ultrasonic pulse velocity tests. the compressive strength, tensile, and flexural strength tests were performed on cubes (100x100x100mm), cylindrical (100x200mm) and prismatic beams (320x80x60mm), respectively. also, ultrasonic pulse velocity testing was carried out on cubic (100x100x100mm) specimens. results of these tests exhibit high variability and vary considerably for mixtures containing different fiber contents. microsteel fibers have a great effect on the mechanical strength of the specimens compared to pva fibers. the specimens with a high percentage of microsteel fibers showed higher resistance to the first flexural crack, failure, and final energy absorption compared to those with a high percentage of pva.. in addition, by adding a pozzolanic material like fly ash, the 28day resistance of all the mechanical properties of the specimens were reduced.