Experimental Investigation on the Impact of Micro-Steel Fibers on the Flat Slabs' Punching Shear Resistance

Abstract

This research examined the effects of micro-straight steel fiber percentage and column form on the punching shear of SFRC slabs. Fibers made of micro steel with a diameter of 0.2 mm and a length of 13mm with an aspect ratio equal to 65 were used. The fiber content varied between 0.5%, 1%, and 1.5% by volume. Four different types of concrete mixes were adopted and tested. Experimental results showed that when the percentage of steel fibers in SFRC increased, its compressive strength, flexural strength, splitting tensile strength, and direct tensile strength improved. This investigation applied a monotonic load to eight cast slabs (two each of conventional concrete of square and circular column sections of the equivalent area while the other six slabs were made with steel fiber concrete. The dimensions of each slab were  (920 x 920 x 80 ) mm. Each slab specimen had essential, edge-based support with square and round column sections. It has been demonstrated that slabs with square column sections endured a relatively higher ultimate load than slabs with circular column segments when the steel fiber dosage was 0.5% or 1.0%. Still, at a steel fiber dosage of 1.5%, circular column segment slabs approached the ultimate load of square column segment slabs. The heterogeneous behavior in concrete can be attributed to the random and unequal distribution of steel fibers throughout the material. There were only flexural fractures visible on the tensile face of the slab. New fractures emerged in the center of the slab as the load increased.