Oil Palm Kernel Shell (OPKS or commonly OPS) is one of many agricultural wastes from the extraction of palm oil. Existing disposal methods includes landfill for decomposition and incineration for energy recovery, which does not fully utilise the inherent material properties and strength of OPS. Study on granite replacement with OPS as coarse aggregate in concrete is on the rise, owing to its low density. Oil Palm Kernel Shell Concrete (OPKSC or commonly OPSC) is classified as Light Weight Aggregate Concrete (LWAC), and functions similarly albeit at a slight compromise in performance as regular Normal Weight Concrete (NWC). The structural performance of LWAC is heavily influenced by the properties of aggregates it is batched from. Consequently, a deeper understanding on OPSC structural performance and existing design provision is necessary to aide its application within the industry. As accidents involving punching shear failure have been relatively unpredictable and sudden relative to failures in compression or flexural, studies on punching shear mechanism of flat slabs have been done under rigorous scrutiny. Therefore, the punching shear performance of OPSC as flat slabs is regarded as vital for adoption of OPSC in industrial practices. This study investigates the punching shear mechanism of reinforced concrete flat slab cast with OPSC through experimental and analytical methods. A total of 27 flat slabs, 5 NWC and 22 OPSC, were constructed and tested under concentrated load until punching shear failure. Mix designs for required concrete strengths were formulated which is able to achieve 100 mm concrete cube compressive strengths ranging from 15. 0 Nmm-2 to 27. 5 Nmm-2 for OPSC and 20. 0 Nmm-2 to 25. 0 Nmm-2 for NWC. In general, collected data indicates that OPSC flat slabs performed at approximately 75. 1% of their NWC counterparts under similar conditions, with ratios ranging from 66. 2% to 99. 4%. Punching shear resistance of OPSC flat slabs develops better than NWC flat slabs at higher concrete compressive strength, fewer rebars, steeper shear angle, and larger columns. OPSC punching shear resistance correlates directly to concrete strength (fc) raised to the power of 1/3. Pairing higher concrete strength with higher reinforcement ratio (ρ₁) leads to enhanced punching shear resistance. The effect of column shape (Sc) is minimal whilst punching shear resistance increases with increasing column perimeter (Γc). OPSC flat slabs perform less effectively at higher shear span (dᵥ) and but better with higher slab thickness (h). Prediction of OPSC flat slab punching shear resistance using Eurocode 2 (EC2) NWC provisions and LWAC provisions yield a prediction ratio of 1. 032 ± 0. 125 and 0. 800 ± 0. 097 respectively. Prediction using concrete plasticity yields prediction ratio of 1. 324 ± 0. 305. Modified models successfully produced unity mean with standard deviations within ± 0. 118 to ± 0. 208 across all models. Overall, OPSC flat slabs behaves similarly to NWC flat slabs with a slight reduction in performance in punching shear. It is confirmed that present design codes were configured to generally underestimate punching shear resistance, at about 80. 0% of maximum shear capacity, even in absence of safety factors when used according to its provisions. Plastic theory further demonstrates that OPSC flat slabs perform about 83. 6% of NWC flat slabs by its own provisions. Modifications proposed are recommended as a frame of reference if one were to attempt to design and adopt OPSC flat slabs in real world construction. This study aligns with and contributes to Sustainable Development Goals (SDG) set out by the United Nations, particularly SDG 11: ‘Sustainable Cities and Communities’, SDG 12: ‘Responsible Consumption and Production’ and SDG 13: ‘Climate Action’. By promoting the use of agricultural waste as a viable structural material, this research supports the transition towards a more sustainable construction practice by providing technical support for the use of OPSC as flat slabs under punching shear load.
Daryl Ng Chun Pinn (Sat,) studied this question.