Surface-engineered in-situ fibrillated thermoplastic polyurethane as toughening reinforcement for geopolymer-based mortar

Geopolymer composites often exhibit severe brittle failure when subjected to tensile and flexural loads, mainly owing to their inherently ceramic-like structure. Therefore, this study aims to overcome the previously mentioned weaknesses by introducing 2 wt% of surface-modified, in-situ fibrillated Co-PP (copolymer of polyethylene (PE) and polypropylene (PP))/thermoplastic polyurethane (TPU) blend to produce fiber-reinforced geopolymer mortars. The fiber-in-fiber Co-PP/TPU was first fabricated using spunbond, then functionalized using a mild, two-step, one-pot chemical surface modification process. A comprehensive and detailed study of the fibers' chemical structure, morphology, and mechanical properties has been conducted. As well as their impact on the geopolymer mortars' mechanical performances. Moreover, incorporating the modified fibers dramatically increased the flexural toughness and strength at failure of the composite, reaching up to 1600 % and 280 % compared to the control sample, respectively. Furthermore, the flexural modulus was improved by 2 folds. Additionally, the split tensile and compressive strength were improved by 84 % and 17 %, respectively. These findings and the SEM images of the fractured samples indicate the presence of several toughening mechanisms, associated with an improved matrix-fiber interface and an enhanced growth of geopolymer products around the fiber's surface. [Display omitted] •The mechanical response of surface-modified fiber-reinforced geopolymer mortar (FRGM) was investigated.•The FRGM's flexural toughness and strength improved significantly, up to 1600% and 280% over the control sample.•The flexural modulus of the FRGM was enhanced by 2 folds compared to the control sample.•The surface-modified FRGM's split tensile strength increased by 85% compared to the control sample.•Incorporating hydroxyl polar groups to the fiber surface enhanced the fiber/geopolymer interface.