Performance of Cinchona Industrial Waste Ash and Pulverized Plastic Waste as Concrete Aggregate Materials for Production of Concrete Culvert

The global construction sector is undergoing a paradigm shift toward sustainable material utilization due to increasing environmental and resource constraints. In Kenya, culvert construction continues to rely heavily on conventional materials like cement and river sand, contributing to high carbon emissions and resource depletion. This study investigates the potential of incorporating Cinchona Industrial Waste Ash (CIW) and Pulverized Plastic Waste (PPW) as partial replacements for cement and sand, respectively. The objective was to optimize mix designs that achieve an acceptable balance between strength, durability, and workability. A total of 13 mix combinations were tested for compressive, tensile, and flexural strength, as well as water absorption and slump. CIW and PPW replacements ranged from 2% to 3.5%. The results revealed that the L2 mix (2.5% PPW and 2.25% CIW) provided the best performance across all parameters. Theoretical validation was supported by the pozzolanic reactivity of CIW and the micro-filler effect of PPW, in line with BS EN testing standards. The study concludes that moderate dosages of CIW and PPW can enhance performance and sustainability of concrete used in culverts. It recommends wider adoption in Kenyan infrastructure projects, subject to further long-term durability studies under field conditions to confirm these promising laboratory results.