<p>The mechanical properties of recycled brick-concrete aggregate (RBCA) concrete are weaker than those of traditional concrete and recycled concrete aggregate concrete (RAC). On the basis of the well-known fact that confinement of concrete by steel tubes can increase both the axial compressive strength and ductility of the concrete, this research experimentally investigated the axial compressive behaviour of RBCA concrete confined by steel tubes. The experimental variables are the replacement ratio of the recycled brick aggregate (RBA), the strength of the concrete, and the shape and thickness of the steel tubes. The test results indicated that steel tubes and circular and/or square confinement could effectively increase the axial compressive strength and ductility of the RBCA concrete. When the concrete strength was nearly identical, the axial strength and deformability slightly decreased with increasing RBA replacement ratio. The test results also indicated that the thickness of the steel tubes had a positive effect on the axial compressive strength, peak strain, stiffness and ductility and that square steel tubes exhibited a lower confinement effect than circular steel tubes did. The axial stress‒strain behaviours of RBCA concrete confined by steel tubes were compared with the predictions of current well-known stress‒strain models for confined concrete. In this study, new stress‒strain models for RBCA concrete confined by circular and square steel tubes were developed, and the proposed models could trace the experimental stress‒strain curves well up to high strain. The coefficients of variation between the predicted peak strain and peak stress were not less than 3.0% and 17.0%, respectively, verifying the good predictive accuracy of the model.</p>