Influence of Synthetic and Natural Fibers on Mortar Frost and Abrasion Resistance

The durability of cementitious mortars exposed to freeze–thaw (F/T) cycles and abrasion remains a challenge in sustainable infrastructure, motivating the exploration of alternative fiber reinforcements with lower environmental impact. There is a notable gap in understanding the behavior of natural-fiber-reinforced composites, particularly their response to freeze–thaw cycles and abrasion. Additionally, data on the physical and mechanical properties of mortars that use sheep wool and Spanish broom fibers as cement composite reinforcement remain limited. This study investigates the influence of industrially produced fibers (polypropylene and glass) and natural fibers (sheep wool and Spanish broom, with different treatments) on the F/T cycles and abrasion resistance of cement mortars. Six mixtures were prepared, including a reference and five fiber-reinforced mortars (FRM) with 0.5% fiber content by binder mass. The workability of fresh mortar, abrasion resistance, flexural strength, compressive strength, and specific fracture energy were evaluated at the age of 56 days and after 56 F/T cycles. Results indicate that fiber addition reduced workability and compressive strength and no FRM has increased flexural strength at 56 days. Polypropylene- and NaOH-treated Spanish broom fibers improved flexural performance after FT exposure, exceeding the reference mortar flexural strength by up to 23%. All FRMs have significantly enhanced fracture energy, with increases up to 2.6 times compared to the reference mortar, and maintained improved values after F/T cycling. For the selected amount of fiber, abrasion resistance remained within the same performance class for all mixtures. Polypropylene and hydroxide treated Spanish broom FRMs demonstrated the highest potential for improving F/T resistance and toughness, while FRM with untreated or seawater-treated natural fibers require further optimization for durability in alkaline environments. Understanding the behaviour of local natural fibers under extreme conditions is essential for developing durable, sustainable construction materials.