Performance of hybrid basalt-recycled polypropylene fibre reinforced concrete

This study investigated the influence of hybrid basalt-recycled polypropylene (PP) fibre reinforcement on the mechanical properties of concrete at various volume fractions. Various volume fractions of basalt micro fibres (0.1 % and 0.3 %) and recycled PP macro fibres (0.3 %, 0.7 %, and 1.0 %) were examined. The results showed significant improvements in compressive strength, flexural performance, and energy absorption capacity compared to plain concrete. The optimal mixture (0.3 % basalt and 0.7 % recycled PP) achieved a 64 % increase in flexural strength. Compressive strength increased by up to 13.2 % with 0.3 % basalt and 0.3 % recycled PP. Hybrid reinforcement also enhanced post-cracking behaviour and energy absorption, with the highest energy absorption reaching 20 J, nearly tenfold that of plain concrete. Virgin PP fibres predominantly failed by rupture, indicating strong fibre-matrix bonding, while recycled PP fibres mainly failed by pull-out. The modulus of rupture of recycled PP reinforced concrete (3.76 MPa) was only marginally lower than virgin PP one (4.52 MPa). Importantly, the post-peak strength of virgin and recycled PP reinforced concrete (B01VP07 and B01P07, respectively) remained comparable at approximately 2.5 kN. This study demonstrated the effectiveness of using the basalt recycled PP fibre reinforcement and highlighted its potential as a sustainable solution for enhancing concrete performance.