Investigation of the effect of ecological inhibitors added to concrete mixing water and pore solution on the corrosion of reinforcing steel

Corrosion is the biggest problem of reinforced concrete structures. Organic and inorganic inhibitors are added to the cement to prevent corrosion. Today, due to the toxicity of some inorganic and organic compounds, more attention is paid to the use of natural inhibitors. The aim of this study; To investigate the corrosion mechanism of reinforcement steels exposed to concrete mixing water and concrete pore solution for 2 hours, 7, 28, 56 and 90 days. Corrosion resistance of reinforcement in mixing water and concrete pore solution was determined using Dynamic Electrochemical Impedance Spectroscopy (DEIS), Electrochemical Impedance Spectroscopy (EIS) and Tafel Extrapolation (TP) methods. In addition, ecological inhibitors (50 ppm caffeine and 50 ppm L-Arginine) have been used to increase the corrosion resistance of the steels exposed to the specified environment and conditions. The changes on the metal surface after electrochemical experiments were examined by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Atomic Force Microscopy (AFM) and Optical Profilometer (OP) analysis, and the correlation between them was revealed with all the methods applied. In addition to these, compressive strengths of reference and inhibitor added cement pastes were determined for 2, 7 and 28 days according to TS-EN 196-1. Changes in the hydration mechanism of samples on the 28th day, which is critical period, were examined using SEM, Differential Thermal Analysis (DTA), Thermogravimetric Analysis (TGA), X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR) analysis techniques. According to the obtained results, it was observed that the corrosion resistance of reinforcement steel increased with the waiting time of the solution. It has also been determined that the corrosion resistance of the reinforcement steel in the concrete pore solution is higher than the mixing water. It was determined that the inhibitors used had an effect on increasing the corrosion resistance of the reinforcement steel in parallel with the waiting time and L-arginine had a higher inhibition effect than caffeine. The compressive strength of mortars containing 75 ppm caffeine and L-arginine showed higher strength than all the cement mortars on the 28th day. It has been scientifically proven that the inhibitors used to contribute to the cement hydration can also be used as a corrosion inhibitor in concrete pore solution and mixing water mediums.