Influence of alkali-treated and bitumen emulsion-coated sisal fibres on the physical, mechanical, and durability performance of reinforced bricks and paver blocks

This study investigated the influence of untreated, alkali-treated and bitumen emulsion-coated sisal fibres on the physical, mechanical, and durability performance of compressed bricks and paver blocks. Fibre incorporation significantly improved the mechanical performance of both composites, with 0.5% fibre dosage providing the optimum overall performance. Compared with the corresponding untreated fibre composites, alkali-treated fibres enhanced the compressive strength by up to 9.8% for bricks and 8.2% for paver blocks, while the flexural strength increased by up to 15.4% and 13%, respectively. The combined alkali treatment and bitumen emulsion coating produced considerable improvements in compressive and flexural strengths of up to 7.1% and 11.6%, respectively. Surface modification of fibres significantly enhanced wetting–drying durability, with the combined treatment reducing mass loss by up to 50.6% for bricks and 53.1% for paver blocks after 12 wetting–drying cycles, while bitumen emulsion-coated specimens improved residual compressive strength by up to 33.7% and 24.0%, respectively. Overall, alkali treatment provided the greatest enhancement in mechanical properties, whereas the combined alkali treatment and bitumen emulsion coating delivered the most balanced improvement in strength and long-term durability, demonstrating the potential of surface-modified sisal fibres as sustainable reinforcement for masonry and pavement applications.