Development of an optimized mixing method and analysis of the synergistic effects of HMPE fiber addition in UHPC

Ultra-high-performance concrete (UHPC) exhibits enhanced characteristics compared to conventional concrete (CC), most notably its high compressive strength due to low porosity, a high fine content, and a low water-to-binder ratio (w/b). However, the toughness of UHPC remains an area requiring improvement. Incorporating high-modulus polyethylene fibers (HMPE) into UHPC is a promising alternative for enhancing the composite's toughness. This study developed an optimized methodology for adding HMPE fibers to UHPC, comparing the performance of a reference UHPC (H0) with UHPC mixtures containing 0.10% and 0.15% HMPE fibers (H10 and H15). Workability, volume and mass variation, compressive and tensile strengths, toughness, and accelerated crack propagation were analyzed. Complementary analyses were performed using optical and scanning electron microscopy. Results demonstrated the feasibility of fiber insertion without composite expansion. The minimum normative compressive and tensile strengths required for classifying the composite as UHPC were achieved with fiber addition. Furthermore, reduced shrinkage and crack formation, as well as increased toughness, were observed, highlighting the potential of high-modulus fibers in ultra-high-performance matrices.