Bending behavior of engineered cementitious composites (ECC) with different recycled and virgin polymer fibers

Abstract

This study evaluated Engineered Cementitious Composites (ECC) with polyvinyl alcohol (PVA), polypropylene (PP) or recycled polyester (POL) fibers inserted in a matrix with elevated silica fume content. Several PP (2.2–2.6%) and POL (2.3–2.7%) contents were tested and compared to a compound containing 2.0% PVA. Flexural bending strength tests, the bending rupture modulus, number and width of cracks and deformation were measured at 5 different curing ages (7, 14, 28, 56 e 84 days). The test results also showed that in the fresh state, ECCPVA2.0 presented the best result with an average spread of 255 mm, followed by ECCPP2.4 and ECCPOL2.3. All Γ values obtained confirmed that all composites attained plastic consistency. In the hardened state, composites with POL fibers had tensile strength performance similar to PVA fibers with regards to deformation, deflection, rupture modulus, average crack width and number of cracks. In addition, ECCPOL2.7 demonstrated mechanical properties superior to ECCPVA2.0. So, the use of 2.7% POL content resulted in strengths higher than the reference PVA compound and demonstrated the potential of POL fibers in ECC development at ages over 28 days. The use of recycled POL fibers, at a content of 2.7%, resulted in an increase in the ductility of the composite, reaching the values of ECC-PVA at 28 and 84 days. On the other hand, PP composites did not present the expected behavior of an ECC. More specifically, the matrix had high tensile strength, modulus of elasticity and tenacity, which limited crack formation and overloaded the reinforcement fibers. Thus, PP fibers were deemed incompatible for ECCs with rich matrices.