Flexural Behavior and Single Fiber-Matrix Bond-Slip Behavior of Macro Fiber Reinforced Fly Ash-Based Geopolymers

Abstract

A study on flexural response and single fiber-matrix bond-slip behavior in fly ash-based geopolymer reinforced with different types of macro steel fibers is presented. Although direct correlations between bond-slip behavior and composites’ flexural response cannot be drawn, investigation of the fiber-matrix bond-slip behavior allows a fundamental understanding of some of the mechanisms involved in the flexural response. Three types of fibers (straight, end-deformed & length deformed), two curing regimes (ambient & heat) under flexural and single fiber pullout conditions are discussed. The performance of geopolymer composites is compared with Portland cement composites. The quantitative effect of fiber geometry is analyzed by introducing the “fiber deformation ratio”. End deformed steel fiber exhibits a better performance than straight and length-deformed fibers both in flexural and pullout tests. In the single fiber tests, steel fibers perform better for lower fiber deformation ratios, where the full fiber pull-out mechanism can be exploited; for higher deformation ratios, the strong bearing forces developed, combined with the high adhesion strength of the geopolymer-steel fiber interface, lead to more brittle failure mechanisms, such as fiber breakage or matrix failure. These mechanisms are partially mitigated in the composite (group effect), where end-deformed steel fibers exhibit the most ductile flexural response.