Structural performance of lightweight fibre-reinforced oil palm shell concrete subjected to impact loadings under varying boundary conditions

Lightweight concrete produced from recycled agricultural waste, has been used for decades as an eco-friendly product. This innovative approach aims to mitigate environmental pollution and promote sustainable practices in managing industrial waste. Despite these benefits, there is a limited study on the structural behaviour of lightweight oil palm shells (OPS) concrete with varying boundary conditions. This study conducted a series of low-velocity impact loading tests to investigate the structural performance of lightweight fibre-reinforced OPS concrete slabs, in which the natural aggregate is completely replaced with OPS. The slab specimens sized 300 mm x 300 mm x 40 mm were used. The control sample contained polypropylene fibre (PPF) mesh at mid-layer, in addition, other specimens contain 1%, 2% and 3% PPF content. For each PPF content in the experimental specimens, the boundary conditions were varied from 2, 3 and 4 including the control case. The recorded experimental results for impact and crack behaviour under service and ultimate loading were analysed using response surface analysis. Regression models were developed to predict responses for specimens with up to 8 boundary conditions and 5% PPF. The results demonstrated the effectiveness of OPS as a coarse aggregate in lightweight concrete, showing substantial enhancements in impact energy absorption (up to 20 times at ultimate loading), crack resistance (up to 29 times at ultimate loading) and reduction in crack propagation with increased PPF and varying boundary conditions. Furthermore, the incorporation of PPF also enhanced the OPS concrete’s resistance to cracking relative to its compressive strength. However, these only had a minimal influence on controlling crack length and width, and did not result in reasonable improvement of the residual strength. These findings highlight the limitations as well as the potential of utilising OPS in fibre-reinforced lightweight suspended concrete slabs and other impact-resistant constructions.