Behaviour of fibre-reinforced lightweight aggregate foam concrete-based precast hollow core slabs at different shear span-to-depth ratios

Sustainable and affordable housing remains a critical challenge for the global construction sector. To address this, the present study develops and evaluates the performance of fibre-reinforced lightweight aggregate foam concrete-based precast hollow core slabs (FR-LAFC PHCS) for residential applications. Lightweight aggregate foam concrete (LAFC) is a hybrid material incorporating sintered fly ash porous aggregates (SFA) as coarse aggregates and preformed foam to produce a cellular cementitious matrix. Owing to the porous nature of both aggregates and the matrix, LAFC tends to exhibit brittle failure. To mitigate this, synthetic polypropylene (PP) macrofibres (0.2%, 0.4%, and 0.6%) in combination with PP microfibres (0.1%) are incorporated to enhance post-cracking ductility and energy absorption. A total of 15 full-scale LAFC-based PHCS specimens, with and without PP fibres, are tested at shear span-to-effective depth (a/d) ratios of 10, 7, and 3.5 to investigate flexural, flexure-shear, and shear behaviour, respectively. Crack propagation is monitored using the digital image correlation (DIC) technique to measure the full-field strain evolution and crack development. The experimental results are further evaluated against the provisions of ACI 318–2019 and fib Model Code -2010 to assess the applicability of conventional design formulations . The specimens exhibited flexural, flexure-shear, and shear modes at a/d ratios of 10, 7, and 3.5, respectively. The inclusion of PP fibres of 0.6% showed approximately 1.26, 5.28, and 2.61 times higher energy absorption than the control specimens tested at a/d ratios of 10, 7, and 3.5, respectively, along with notable improvements in peak load capacity. Despite the superior energy absorption achieved with 0.6% PP fibres, a 0.4% dosage provided the optimum balance between structural performance and serviceability and is therefore recommended for practical applications. The provision of ACI318–2019 underestimated both flexural and shear capacities, whereas fib Model Code -2010 tends to overestimate the shear capacities of FR-LAFC PHCS.