A study on end-anchorage and bond behavior of steel-fiber reinforced cementitious matrix composites externally bonded to a concrete substrate

Fiber reinforced cementitious matrix (FRCM) composites are a strengthening material consisting of continuous fibers embedded in an inorganic matrix that have the potential to provide additional flexural and shear strength to concrete and masonry members. When used for external strengthening, however, debonding of the material is often observed due to slippage of the fiber with respect to the matrix, causing loss of composite action and a reduction in load carrying capacity. The composite utilized in this study consisted of continuous steel fibers embedded in an inorganic cementitious matrix bonded to a concrete prism. Additionally, an end-anchorage system was implemented with the goal of limiting or preventing fiber slip by anchoring the free end of the steel fibers into a pre-drilled hole in the concrete prism. A total of 33 single lap direct shear specimens were tested with varying composite bonded length, anchor depth, and anchor material to study the effectiveness of an end anchorage system on bond performance. Also, strain data was collected from 12 of the 33 specimens to better observe the bond behavior of anchored and unanchored specimens. The results from the experimental analysis found minimal contribution of the end-anchorage system for specimens with a bonded length longer than the assumed effective bond length. However, the end-anchorage did have a considerable effect on the bond behavior (both peak load and absorbed energy) for specimens with a relatively short composite bonded length. Finally, based on the results of a strain distribution analysis, a preliminary bond-slip model for steel-FRCM composites was determined from nonlinear regression analysis of the steel fiber strain at debonding --Abstract, page iii