Compressive performance of underwater concrete columns strengthened by nondispersive mortar and stainless steel tubes

Abstract

A novel type of underwater pier reinforcement technology was proposed. A non-dispersive mortar (NDM) and stainless steel tube (SS) were adopted to strengthen an underwater concrete column. The strengthened column takes advantage of the good adhesion of NDM and the corrosion resistance of SS. The NDM pouring and curing processes were both conducted in an underwater environment, which simulated the environment of underwater bridge pier reinforcement. An axial compression test was carried out on 16 strengthened columns and 3 unconfined concrete columns to explore the reinforcement effect of SS thickness and NDM type, including the 2–6 mm thickness of SS, the epoxy-based NDM, and the cement-based NDM. The test results indicated that all the specimens showed extrusion expansion failure. The increase in the thickness of SS resulted in a significant improvement in the load capacity of the specimens, and the stress-strain curves showed the strengthening stage and softening stage according to the confinement factor of the SS thickness. After adding cement-based NDM and epoxy-based NDM, the strength of the specimens increased by 6.2–21.4 % and 8.8–31.5 %, respectively. In the case of the same thickness of SS, cement-based NDM showed a better reinforcement effect. The stress-strain curves for the strengthened columns can be divided into three stages. Calculation models were proposed to predict the full stress-strain curves, including the calculation method of the capacity. The calculated results are in good agreement with the experimental data.