Investigation on pull‐out behavior and interface critical parameters of polymer fibers embedded in concrete and their correlation with particular fiber properties

Abstract

A crucial problem in concrete engineering is the corrosion of steel reinforcements. Polymer fibers as alternative reinforcement material can prevent corrosion; however, high adhesion to concrete and good fiber mechanics are necessary for polymers to be considered as an alternative reinforcement. This study tested different thermoplastic polymer materials to evaluate their level of adhesion to concrete. The adhesion properties of different self‐drawn polymer fibers were analyzed by extracting the fibers from concrete using single fiber pull‐out test (SFPT). To determine the adhesion mechanism, different polymer properties were analyzed and correlated to SFPT. Strong evidence was found that the fibers mechanical properties correlate with SFPT. Roughening the fiber surface increases the SFPT results significantly. While highly polar materials can support the adhesion process, a clear correlation could not be found. This study identifies high stiffness and roughness as the crucial properties of polymer fibers used in concrete engineering. If these factors can be engineered into the fiber, polymer fibers can present an alternative to steel in concrete reinforcement.

Pull‐out behavior of polymer fibers in concrete

“…As shown in a previous study, the bond strength increases for roughened fibers 28 as the resulting undercuts improve the mechanical anchoring of the fibers in the cementitious matrix. Mechanical anchoring is also improved by crimping or embossment as shown by Kaufmann et al 59 These geometrical or surface defects increase the force needed to pull-out the fiber from the matrix as a slightly thicker part of the fiber must be pulled through a thinner fiber channel of the hardened matrix.…”

“…In the reactive extrusion, the peroxide decreases the molecular chain length. A low molecular weight leads to lower tensile strength and Young's modulus as reported by Flood et al, 53 Misra 54 and Capaccio et al 55 It was shown in a previous study 28 that the Young's modulus correlates with the bond strength calculated from SFPT. Hampe et al 51 propose that a mismatch in the elastic moduli between the fiber and the matrix decreases the force distribution.…”

“…Polyether ether ketone (PEEK) is a high-performance polymer with good mechanical properties as well as a good bond behavior to the cementitious matrix as shown by a previous study. 28…”

“…The mechanical properties correlate with the fiber-matrix adhesion. 28 A universal testing machine (Zwick Z100) equipped with 90 deflection grips and a 10 kN load cell was used to test the mechanical properties of the fibers. The tests were performed according to DIN EN 14889-2 15 and DIN EN ISO 2062.…”

“…25,26 Physical anchoring of the fiber by crimping, embossment or surface roughness in the concrete matrix is another method to establish a good fiber-matrix adhesion. 5,27,28 The characterization of the fiber-matrix adhesion is difficult, due to a multi mechanism-based fiber debonding. In literature, various methods to evaluate the micro-mechanical composite properties are mentioned.…”