Experimental Investigation of Flexural Performance of Prestressed Precast Hollow-Core Slabs with Foam Inserts and Wet Joints

This study introduces a novel prestressed precast hollow-core slab system with integrated polystyrene foam inserts and a spliced design utilizing cast-in-place wet joints, aiming to resolve the inherent trade-off between self-weight reduction and load-bearing capacity in precast floor systems. An experimental investigation was conducted on three individual slabs with varied foam geometries and four jointed slabs with different foam configurations and joint concrete types. All specimens were tested under four-point bending. The experimental program meticulously assessed failure modes, load–displacement characteristics, and load–strain relationships of the proposed slab systems. Results reveal that the hollow-core slabs exhibited failure mechanisms similar to conventional cast-in-place slabs, with cracking initiating in the pure bending region and then propagating along the slab edges. Specifically, specimens with square and circular foam inserts achieved weight reduction rates of 24.57% and 19.78%, respectively. Concurrently, their ultimate loads increased by 32.39% and 46.46% compared to the cast-in-place control. The prestressing tendons remained elastic at ultimate load, confirming that failure was governed by concrete crushing in the compression zone rather than tendon rupture, which represents a ductile failure mode providing sufficient warning prior to collapse. For the jointed specimens, while cracks fully penetrated the foam inserts in the pure bending zone, no cracking occurred at the wet joint interfaces, signifying robust composite action. The load capacity of these jointed specimens surpassed that of the equivalent cast-in-place slab by 19.1% to 50.7%. Based on an evaluation of material cost, structural efficiency, and flexural performance among the tested configurations, the combination of square foam inserts and conventional C40 concrete in the wet joint is recommended. This research provides a critical experimental foundation for the development of lightweight, high-performance precast floor systems in prefabricated concrete construction.