Flexural behaviour of partially encased composite beams with recycled aggregate concrete

Research on recycled aggregate concrete (RAC) has grown in response to the need for sustainable management of construction and demolition waste. However, applications in partially encased composite beams (PECBs) remain limited. This study investigates the flexural behaviour of PECBs with RAC through material characterisation, a four-point bending test and numerical modelling using the Abaqus v6.16. A parametric analysis assessed the effects of steel profile geometry, concrete type and steel yield strength on the load capacity of the beam. Concrete mixtures with 0%, 30%, 50% and 100% natural coarse aggregate replacement were characterised, and one PECB with 50% replacement (RAC-50) was tested in bending. The RAC-50 beam reached a peak load about 5% higher than the natural aggregate concrete specimen, showing greater ductility, slightly larger deflections and similar failure modes. Numerical results reproduced peak loads within 5% error and indicated that RAC replacement up to 50% has minimal influence on flexural behaviour. Parametric studies showed that steel profile height was the dominant geometric factor, affecting capacity by up to 74%, while yield strength influenced it by up to 18%. Overall, the results highlight the structural viability of using RAC in PECBs and support its adoption in sustainable composite construction.