This paper presents an experimental and a numerical investigation of light-gauge steel box sections filled with concrete made with a combination of natural aggregate (NA), recycled concrete aggregate (RCA), and recycled asphalt pavement (RAP). A total of 47 specimens, including 30 composite beams, 15 plain concrete beams, and 2 bare steel beams were tested. The main variables in the tests were the steel thickness (2 and 2.4 mm), the coarse aggregate type and replacement ratios. NA was replaced by RCA and RAP with replacement levels of 20 %, 40 %, 60 %, 80 %, and 100 % by the total weight of NA. In addition, RCA and RAP were incorporated in the same mixes with four replacement levels of (20 % RCA and 80 % RAP); (40 % RCA and 60 % RAP); (60 % RCA and 40 % RAP); and finally, with (80 % RCA and 20 % RAP). The experimental capacities were compared to the theoretical prediction of EC4, AISC-LRFD, AIJ, and the Rigid Plastic Theory (RPT). Moreover, a finite element analysis (FEA) was performed using ABAQUS software. The experimental results showed that the ultimate capacity of composite beams decreased with the increase of RCA and RAP percentage. However, both RCA and RAP enhanced the capacity of plain concrete beams. Current code provisions predicted lower capacities than the experimental values, and the FEA results showed reasonable agreement with the test results.