To date, many studies can be found in the literature attempting to explain the effects of temperature and humidity on the rate of corrosion processes. However, it is difficult to analyze the results of these studies and draw unambiguous conclusions due to the different test conditions as well as different electrochemical test methods for corrosion rates. Most of these studies concern concrete reinforced with ordinary steel. However, there is a lack of research and analysis conducted on prestressed elements. The purpose of this study was to evaluate the effect of temperature and humidity changes on the development of corrosion processes in prestressed concrete beams. Tests were performed both under conditions of increasing temperature and humidity, which were reproduced in a climatic chamber, as well as in an environment exposed to chloride ions. The process of migration of chloride ions into the concrete was accelerated by the application of an electric field. In addition, selected beams were subjected to prolonged loading to sustain the induced scratching. Corrosion rate tests were carried out using the non-destructive linear polarization method (LPR). Strength tests of the beams were also carried out, as well as displacement and deformation measurements using the Aramis system's digital image correlation technique. The beams without chloride addition had a fairly stable low level of corrosion current density throughout the test period, indicating the passive state of the reinforcement, regardless of the environment in which they were placed and the additional loading. In an environment with a humidity of 30% and a temperature of 20 °C, the corrosion current density increment was much faster than for beams with chloride additives in an environment with a humidity of 90% and a temperature of 30 °C. A smaller increase in corrosion current density could be observed in beams that were scratched, compared to non-scratched beams. The results of the strength tests indicated that in beams subjected to accelerated migration of chloride ions, the deflection at scratching was significantly lower than in beams without chloride addition. Also in these beams, milder strains were registered on the surface of the elements at the time of scratching.

• Klíčová slova
• LPR method, chloride migration, corrosion rate, digital image correlation, humidity rise, long-term loading, prestressed concrete beams, scratching, strength of beams, temperature rise,
• Publikační typ
• časopisecké články MeSH

In this work, two methods were used to accelerate the corrosion of concrete. In the first method, chloride ions were injected into the concrete using the migration method. The moment of the initiation of the corrosion process was monitored using an electrochemical method of measuring polarization resistance. In the next step, the corrosion process was accelerated by the electrolysis process. Changes on the sample surface were also monitored using a camera. In the second method, the corrosion process of the reinforcing bar was initiated by the use of the electrolysis process only. Here, changes occurring on the surfaces of the tested sample were recorded using two web cameras placed on planes perpendicular to each other. Continuous measurement of the current flowing through the system was carried out in both cases. It was assumed that in conditions of natural corrosion, a crack would occur when the sum of the mass loss of the reinforcing bar due to corrosion reached the same value in tcr(real) (real time) as it reached in the tcr (time of cracking) during the accelerated corrosion test. The real time value was estimated for C1 concrete with cement CEM I. The estimated value was tcr(real) = 1.1 years and for C2 concrete with cement CEM III, tcr(real) = 11.2 years. However, the main difference that was observed during the tests was the nature of the concrete cracks. In the case of the C1 concrete sample, these occurred along the reinforcing bar, while in the C2 concrete, the failures occurred on a perpendicular plane transverse to the direction of the reinforcing bar.

• Klíčová slova
• accelerated corrosion, concrete cover, corrosion initiation time, corrosion products, cracking time, mechanical impact, time of activation,
• Publikační typ
• časopisecké články MeSH