Structural Behaviour of Hollow One-way Slabs of Recycled Concrete Aggregate with Rectangular Longitudinal Cavities for Sustainability: An Experimental and Numerical Study

Abstract Widespread usage of concrete and increasing construction waste have negative environmental impacts. Therefore, reducing concrete consumption and recycling construction waste has become essential for improving the environment and promoting sustainability. This study adopts a sustainability approach by reducing concrete consumption in slabs, the largest structural elements, and reusing recycled concrete. Five identical slab specimens were cast. One was solid, and four were longitudinally hollow. Results of comparing longitudinal and transverse voids' direction showed that the longitudinal voids achieved the highest load and the least deflection. Four proportions of recycled concrete aggregate (RCA) for replacing the normal coarse aggregate (NCA) at 0, 25%, 50%, and 75% was adopted. Test results show that the solid slab failed in flexural, while hollow-core slabs failed in shear. The high reinforcement ratio of the hollow-core slab increased its loading capacity and decreased deflection. The cracking and peak loads of the hollow slab with no RCA were approximately 13% and 23.5% lower than those of the solid slab, while the deflection was identical. Replacing 25% and 50% of the NCA with RCA did not significantly affect the hollow-core slab's peak load. A 75% RCA content had a more significant impact on loading capacity, resulting in a 25% decrease. Therefore, the weight reduction compared to the loading capacity reduction was economical and more sustainable. The numerical analysis results showed that when the reinforcement ratio was reduced by 60%, the failure mode of all hollow-core slabs shifted from shear to flexure, and the cracking load decreased by 10% to 16% compared to slabs with a high reinforcement ratio. The analysis reveals that increasing the ultimate load by shortening the void length shifts the failure mode from shear to flexure, with higher ductility and energy absorption.