Ultra-high performance rubberised concrete slabs cast in stay-in-place formworks: Enhancing shear strength and vibration characteristics

This study investigated innovative bridge slabs using ultra-high-performance rubberized concrete (UHPRuC) combined with special square hollow stiffeners (SHS) or Y-shaped stiffeners. The newly developed UHPRuC was prepared using crumb rubber, silica sand, hooked-end steel fibers, cement, silica fume, and superplasticizer. Four slabs were prepared: two measuring 1400 mm× 600 mm x 75 mm without glass fiber-reinforced polymer (GFRP) SIP formwork, and another two measuring 1400 mm× 600 mm x 65 mm with GFRP SIP formwork. The results showed that incorporating 20 % crumb rubber into UHPRuC increased the damping ratio by 1.5 times and the maximum strain by 3.5 times compared to reference slab. Furthermore, the Y-shaped stiffener significantly enhanced the ultimate loading capacity and resistance to shear stress, and the UHPRuC slabs cast on GFRP SIP formwork demonstrated a 60–91 % improvement over normal-strength concrete slabs. Slabs without GFRP SIP formwork experienced a flexural-shear failure, while slabs with GFRP SIP formwork exhibited predominantly shear failure. Finally, a comparison between experimental data and theoretical predictions revealed that the punching shear strength of the SHS slab closely matched the experimental results, with a 4 % difference. However, the Y-stiffened slab exhibited an experimental value that was 44 % higher than predicted. • UHPRuC enhances vibration characteristics of bridge slabs. • 20 % rubber crumb in UHPRuC improves damping ratio by 1.53 times. • UHPRuC slabs show 60–91 % capacity increase on FRP SIP formwork. • Y-stiffened SIP formwork slab exhibits 38 % higher ultimate strength. • SH-stiffened SIP formwork slab offers a lightweight solution.