Development and performance evaluation of nano-modified polypropylene fiber-reinforced concrete using GNMPs

The growing demand for high-performance and durable concrete has increased interest in nano-modified fiber-reinforced composites capable of overcoming the limitations of conventional concrete, such as brittleness, crack propagation, and reduced long-term durability. This study investigated the influence of graphite nano/micro platelets (GNMPs) and polypropylene (PP) fibers on the mechanical, microstructural, and durability properties of M20 grade concrete and identified the optimum combination of these constituents using response surface methodology (RSM). Concrete mixtures incorporating GNMPs at 0.1%, 0.3%, and 0.5% (by weight of binder) and PP fibers at 0.5%, 1.0%, and 1.5% (by volume) were prepared and evaluated through compressive, splitting tensile, flexural, density, workability, freeze–thaw, and scanning electron microscopy (SEM) analyses. The results demonstrated that the incorporation of GNMPs and PP fibers significantly enhanced matrix compactness, resulting in improved mechanical strength and durability. The optimum mixture containing 0.3% GNMPs and 1.0% PP fibers achieved the highest overall performance, including a 28.8% increase in compressive strength compared with the control mix, while also exhibiting superior tensile strength, flexural strength, and freeze–thaw resistance. However, increasing the GNMP content beyond 0.3% reduced performance because of nanoparticle agglomeration, despite further improvements in durability. Although workability and density decreased with increasing GNMP and PP fiber contents, RSM-based optimization confirmed that an appropriate combination of GNMPs and PP fibers effectively maximizes the mechanical and durability performance of nano-modified fiber-reinforced concrete, providing a promising and sustainable material for advanced construction applications.