Using recycled concrete aggregate (RCA) can offer significant sustainability benefits by reducing waste and lowering the environmental impact on construction. This study presents a series of tests on short partially encased composite (PEC) columns to investigate the effects of RCA on the compressive behavior of PEC columns cast with recycled aggregate concrete. A total of 15 PEC columns and three bare steel columns were tested under concentric axial compression loads. The test incorporated five RCA replacement ratios (0%, 25%, 50%, 75%, and 100%) and three link spacing-to-depth ratios (0.33, 0.5, and 0.67). The failure modes, load-strain behavior, load capacity, and ductility were assessed to evaluate the effects of the RCA replacement ratio and link spacing. The failure mode was similar for all the PEC columns: crushing of concrete, and buckling of steel flanges. The test results indicate that columns become more brittle when the RCA replacement ratio exceeds 50% since RCA contains microcracks. However, under concentric loading, the effects of the RCA replacement ratios on column strength were negligible across different link spacing. Incorporating RCA resulted in a maximum 6% drop in strength. An increase in link spacing reduced the ultimate load for all columns. The initial stiffness was also comparable for different RCA replacement ratios and link spacings. Increasing the RCA replacement ratio increased the strain at peak load, especially for smaller link spacings. The current design guidelines for PEC columns with natural aggregate concrete can be safely used to predict the capacity of the PEC columns incorporating RCA. These findings enhance sustainable building techniques by illustrating that RCA can be utilized efficiently in PEC columns without a considerable decline in strength and stiffness.

partially encased composite columns, recycled concrete aggregate, steel-concrete composite structure, concentric load, transverse link