Effects of Polyethylene Fiber Dosage and Length on the Properties of High-Tensile-Strength Engineered Geopolymer Composite

This paper presents a high-tensile-strength engineered geopolymer composite (EGC) reinforced by polyethylene (PE) fibers. The influences of fiber dosage (1.5%, 1.75%, and 2.0%) and length (6, 12, and 18 mm) on the mechanical properties and strain-hardening performance of EGCs were examined. The results indicated that increasing either fiber dosage or length decreases the flowability of EGC due to the skeleton formed by fibers. The increase of fiber dosage from 1.5% to 2.0% enhanced the fiber bridging effect in the EGCs with 12-mm PE fibers and subsequently enhanced their compressive and tensile strengths by 9.0% and 12.7%, respectively. Differently, the increase of 18-mm fiber dosage from 1.5% to 2.0% introduced more voids inside the EGCs, which decreased their compressive and tensile strengths by 3.8% and 3.6%, respectively. Fiber clusters were more likely to occur in EGC with a higher dosage of longer fibers, which reduced its tensile strength. A higher fiber dosage improved both tensile strain capacity and crack control capacity of EGC. On the other hand, increasing the fiber length from 6 to 18 mm increased the tensile strength by 42.0%, strain capacity by 148.0%, and crack control ability of EGC by enhancing the fiber-bridging effect, although it was detrimental to the compressive strength of the EGCs with 18-mm fibers due to the magnified air-entrapping effect. In addition, a prediction model modified based on the test results can accurately predict the tensile strength of PE fiber–reinforced EGCs. The environmental assessment indicated that the developed EGCs exhibit dramatically lower environmental impacts than the conventional engineered cementitious composite.