Research Projects

In recent years, coated steel bars like galvanized steel (GS), plasma coated (PC) steel, fusion bonded epoxy coated (FBEC) steel, and cement polymer composite coated (CPCC) steel have been used to improve the corrosion-free service life of the reinforced concrete structures, especially at marine exposure. Although coated steel rebars are available and used in India, information on their physico-chemical requirements and standard test methods is still lacking. Since the half-cell potential test (ASTM C876) is unsuitable for evaluating the corrosion behavior of these rebars, advanced techniques like linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) are the only way to assess their performance. However, the coatings on these rebars complicate the interpretation of electrochemical responses, and common electrical equivalent circuits like Randel’s and 3R-CPE are proved to be inadequate. Thus, developing an appropriate electrical equivalent circuit is critical for assessing their corrosion behavior. Additionally, the impact of corrosion on residual tensile and bond strength remains unknown, and the corrosion products formed on these rebars need further investigation to understand the corrosion propagation phase and residual service life. Currently, there is no Indian standard for PC and CPCC steel rebar, and the existing standards IS 12594 and IS 13620 fail to provide strong technical specifications and qualifying test criteria for GS and FBEC rebars, respectively, making it challenging for engineers to identify the good quality product available in the Indian market. Therefore, the proposed work assesses the physico-chemical, morphological, and mechanical properties of galvanized steel, FBEC steel, and CPCC steel available in the Indian market by conducting X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), coating thickness test, tempered martensite (TM) ring test, 135° bent/re-bend test, tension test, and bond strength tests. Corrosion resistance will be evaluated using ASTM G31 and ASTM G180 tests in solutions. The chloride threshold and pH threshold will be determined through the macro-cell corrosion test (ASTM G109) and accelerated chloride threshold (ACT) test. Key assessment parameters will include corrosion rate, linear polarization resistance, and impedance. Equivalent electrical circuit models will be developed for each type of coated steel to understand their electrochemical responses and identify corrosion initiation. The impact of corrosion on the residual mechanical properties of the coated rebars will be determined through tensile and bond strength tests. Corrosion products will be characterized using Raman spectroscopy, SEM, and XRD analysis. A nomogram will be created to design corrosion-free service life for RCC structures with coated steel reinforcements exposed to chlorides/CO₂. Finally, performance specifications will be developed for the coated steel rebars.