Preliminary Study on the Self-Healing of Steel, Resulting from the Presence of Nano-Aggregates in Cement Extract

This work presents results from a preliminary investigation on the corrosion behavior of carbon steel in cement extract (CE) in the presence of very low concentration polymeric nano-aggregates (PEO113-b-PS70 micelles). The steel electrodes were investigated in Cl-containing CE as corrosion medium, compared to chloride-free solution as a reference case. Electrochemical measurements (EIS, Potentio-dynamic and Potentiostatic Polarization (PDP, PSP)) and surface analysis (SEM, XRD, XPS) were employed for evaluating the corrosion performance at different time intervals. The results so far indicate that a very low concentration of the micelles (0.024 g/l) improves the corrosion resistance of steel in Cl-containing cement extract at early stages. The investigation is on-going. Materials and methods: Steel electrodes (low-carbon steel 37) with surface area of 0.65 cm were used. All electrodes were equally treated prior to electrochemical measurements i.e. they were grinded with no.500 to no.4000 grinding papers and polished; further, just before immersing in the relevant solution, they were cleaned with acetone. Cement extract: Ordinary Portland cement CEM I 42.5 and tap water were mixed in the ratio of 1:1; the suspension was filtrated after 24h and thus a simulated pore solution (CE) received. The pH of CE is 12.6 – 12.8. Polymeric nano-aggregates: Used in this study were PEO113-b-PS70 micelles, received as stabilized aggregates, concentration 0.5 g/l (demi-water). For this experiment, part of the so received solution was added to the CE (groups CN and CNC below), thus 0.0024 wt% of the micelles were present in both chloride-free and chloride containing CE. Sample designation: For the EIS and PDP measurements, four solutions are relevant: CE with micelles; CE without micelles; CE with micelles and NaCl; CE without micelles with NaCl. Thus the samples designation is: control groups “C” (without micelles) and “CN” (with micelles) and corroding groups “CC” (without micelles) and “CNC” (with micelles), where Cl was added to the CE in concentration 10 g/l.