The impact of multi walled carbon nanotubes on the mechanical properties of polypropylene fibre reinforced concrete

This study investigates the effects of incorporating multi-walled carbon nanotubes (MWCNTs) on the mechanical properties of polypropylene fibre reinforced concrete (PPFRC). The MWCNTs were dispersed in water using sonication and incorporated at three dosages (0.05%, 0.10%, and 0.15% by weight of cement), each combined with varying polypropylene fiber dosages (0.5%, 1.0%, and 1.5% by volume of concrete mix). Specimens were prepared and subjected to comprehensive mechanical testing, including compressive strength, flexural strength, tensile strength, modulus of elasticity, rebound number and ultrasonic pulse velocity. The control concrete without polypropylene fibre (PPF) and MWCNTs exhibited a compressive strength of 38.7 MPa, flexural strength of 5.4 MPa, split tensile strength of 4.0 MPa, modulus of elasticity of 29000 MPa, rebound number of 37.4 and ultrasonic pulse velocity of 4255 m/s. The addition of 0.10% MWCNTs and 1.0% PPF resulted in optimal performance, with compressive strength reaching 49.4 MPa, flexural strength increasing to 6.4 MPa, split tensile strength improving to 4.9 MPa, modulus of elasticity improved to 33000 MPa, rebound number increased to 47.0 and ultrasonic pulse velocity enhanced to 4757 m/s. Results indicate that the addition of MWCNTs significantly improved the mechanical properties of PPFRC, with optimal performance observed at 0.10% MWCNTs and 1.0% PPF combination. The study also examines the microstructure of the nanocomposite using scanning electron microscopy (SEM) to elucidate the mechanisms behind the enhanced properties. Scanning electron microscopy (SEM) analysis revealed improved interfacial bonding between the cementitious matrix and fibres in the presence of MWCNTs. This research contributes to the development of high-performance concrete materials for construction applications, potentially leading to stronger, more durable infrastructure.