Bond properties of bimetallic steel bar in seawater sea-sand concrete at different ages

The bimetallic steel bar (BSB) consisting of stainless steel (cladding) and carbon steel (substrate) exhibits outstanding mechanical properties and high corrosion resistance and has a wide application in reinforced concrete (RC) structures with seawater sea-sand concrete (SWSSC). A metallurgical bonding layer exists between the cladding and substrate. The bond properties between the BSB and SWSSC with different concrete ages and c/ d ratios were investigated experimentally. Polyoxymethylene (POM) fibre, which has exceptional alkali resistance and tensile properties, was selected to improve the bond properties. The effects of the concrete age, POM fibre, and c/d ratio on the failure mode of bond test specimens are discussed. The scanning electron microscope (SEM) method was selected to clarify the connection between the POM fibre and SWSSC. After the bond test, there was no crack or broken area in the stainless-steel cladding of the BSB. Based on the test results, the variation trends of the key parameters of bond properties between the BSB and SWSSC are discussed. A timevarying bond-slip model is suggested to quantify the bond properties between the BSB and SWSSC effectively. A comparison of the peak bond stress tau u variation trend between SWSSC and ordinary concrete specimens was conducted. The variation trend of tau u,t/tau u,28 of the test specimens without POM fibre was similar to that of ordinary concrete specimens. The test results indicated that the POM fibre had an adverse effect on the growth rate of bond properties between the BSB and SWSSC.