Development and Mechanical Performance of Sustainable Concrete with Partial Replacement of Coarse Aggregate by Agri-waste Oil Palm Kernel Shell and Coconut Endocarp

Concrete is one of the most widely used construction materials in civil engineering due to its strength, durability, and versatility. However, the excessive utilization of natural aggregates in concrete production has resulted in depletion of natural resources and environmental degradation.. The cost of making concrete is going up because the prices of cement, sand and big rocks are rising. Using much sand and rocks is also causing worries about running out of these resources and harming the environment. So finding other waste materials to use of these rocks is an important area of research. In view of sustainable construction practices, the present study focuses on the utilization of OPKS and Coconut Endocarp as partial replacement materials for conventional coarse aggregate in M25 grade concrete. In this investigation, Oil Palm Kernel Shell was used as partial replacement of coarse aggregate at replacement levels of 10%, 20%, 30%, and 40%, along with a constant addition of 3% Coconut Endocarp. The experimental program was carried out to evaluate both fresh and hardened properties of concrete. Fresh concrete properties were studied using slump test and compaction factor test, while hardened concrete properties were evaluated through compressive strength, split tensile strength, and flexural strength tests at curing periods of 7, 14, and 28 days. The compressive strength results demonstrated that the strength increased with curing age for all mixes. The conventional concrete achieved a 28-day compressive strength of 31.98 MPa, whereas the OPKS20% + 3% CEP mix attained the highest strength of 34.11 MPa, showing an increase of approximately 6.66%. Similarly, the split tensile strength increased from 3.42 MPa for conventional concrete to 3.56 MPa for the OPKS20% + 3% CEP mix, indicating an improvement of about 4.09%. The flexural strength also improved from 4.56 MPa to 4.82 MPa, corresponding to an enhancement of approximately 5.70%. Among all mixes, OPKS20% + 3% CEP was identified as the optimum replacement level for achieving improved strength and satisfactory workability. The study concludes that OPKS and Coconut Endocarp can be effectively utilized as sustainable alternative aggregate materials for the development of eco-friendly concrete suitable for structural applications.