The increasing generation of industrial and plastic waste has encouraged the development of sustainable construction materials. This study investigates the mechanical properties of zero-cement paving blocks utilizing Polypropylene (PP) plastic waste as the sole binder and fly ash as a sand substitute. A direct thermo-mechanical melting process at 180°C–200°C was employed without the use of water or chemical activators. To ensure sufficient binder volume, the PP ratio was fixed at 4 parts. Specimens were tested for compressive strength and water absorption according to the Indonesian National Standard (SNI 03-0691-1996). The results demonstrated a clear dependency between the filler ratio and mechanical performance; a 25% substitution of sand with fly ash achieved the optimal performance, yielding a maximum compressive strength of 11.59± 0.84 MPa and a remarkably low water absorption rate of 0.75 ± 0.31%, while the lowest water absorption of 0.62 ± 0.07% was achieved by the control mixture. However, increasing the fly ash substitution to 50% resulted in a strength reduction due to the inability of the fixed PP matrix to completely encapsulate the high surface area of the fine fly ash particles. Although classified as Quality D paving blocks, this purely waste-derived composite presents a highly viable, eco-friendly solution specifically targeted for light-duty infrastructure applications, such as pedestrian walkways and city parks.
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