Investigating the Confining Effect of Steel Reinforced Polymer and Grout Composites on Compressive Behavior of Square Concrete Columns

The compressive behavior of short concrete columns with square cross sections confined with steel fiber reinforced polymer and grout composites, named SRP and SRG composites, was investigated experimentally in this paper. Comparing the loading capacity and ultimate strain of confined specimens to those of unconfined samples was used to assess the confining effect. The influential parameters such as the density of steel fibers, cross section geometry at corners, surface preparation, and the number of confining layers were studied. The results showed that the general failure mode of SRP- and SRG-confined concrete columns was the detachment of overlapping faces of fibers, and separation between the core concrete and the composite, respectively. The average compressive strength and strain at maximum load, respectively, were 7.9% and 9.8% higher in sharp-cornered specimens compared to rounded-cornered specimens. The treatment of specimen surfaces caused a 5.1% and 13.4% increase in compressive strength and strain at maximum load, respectively. The effect of fiber density on increasing strength and strains did not match with density increments. Furthermore, in SRG-confined concrete columns, increasing the number of overlapping faces improved axial strength.