Behavior of recycled aggregate concrete-filled basalt and carbon FRP tubes

Abstract

This paper presents the results of an experimental study on the axial compressive behavior of concrete-filled FRP tubes (CFFTs), prepared using different amounts of recycled concrete aggregate (RCA). Thirty-six CFFTs were tested under axial compression. The effects of the RCA replacement ratio, specimen cross-sectional shape, FRP type, and concrete strength were studied. The results suggest that the axial stress–strain behavior of CFFTs is affected by the amount of RCA, which particularly affects the ultimate axial strain and FRP hoop rupture strain. For a given in-place concrete strength, an increase in RCA content leads to a decrease in compressive strength and an increase in ultimate axial strain of FRP-confined concrete. The results also indicate that the increased RCA content leads to a decrease in the hoop rupture strain of CFFTs. CFFTs manufactured with carbon FRP tubes instead of basalt FRP tubes and CFFTs with circular cross-sections instead of square cross-sections develop a higher compressive strength and lower ultimate axial strain. The effects of specimen cross-sectional shape and FRP type on the axial compressive behavior of CFFTs vary with RCA content.