Impact of cracks on distribution of chloride-induced reinforcement corrosion

Surface crack width is regulated in codes to limit corrosion of reinforcement bars in concrete. However, the influence of surface crack width on corrosion damages is not directly inferable from previous research.In this work, data on corroded cracked concrete specimens in chloride environments was compiled. Detailed information was included, such as crack and pit locations, local corrosion pattern, etc. Five hypotheses on the influence of transversal cracks on corrosion damage were formulated, and statistical methods were used to test them on the dataset.Transversal cracks were good indicators of the position of corrosion pits. The corrosion rate of the pit increased in proximity of a crack. With time, pits grew in depth at a slower rate but increased in number. No clear correlation between surface crack width and corrosion damage was found. Results point out discrepancies in the collected data, arguing for the need of well-defined procedures for assessing crack and corrosion damage.Further, the statistical treatment allowed for identification of bias in existing data, which was used as a research planning tool to provide guidance on the design of additional experiments. Thus, recommendations for future experimental work required to reduce the bias are given

Concluding destructive investigation of a nine-year-old marine-exposed cracked concrete panel

This study undertaken on a nine-year-old cracked concrete panel further investigates the impact of cracks on the corrosion performance of conventional steel reinforcement in marine-exposed concrete to explain observed monitoring data. The present data covers seven 1.80 m long (12.6 m) reinforcing bars embedded in good quality concrete (w/b = 0.40 and cover >75 mm). Each bar was crossed by two horizontal cracks (surface crack widths 0.20–0.30 mm). The investigation showed no corrosion on the surface of the reinforcing bars, in either cracked or uncracked areas. Two of the seven reinforcing bars were instrumented in the vicinity of the cracks. Extensive corrosion was found in the interior of all instrumented parts of these bars. This may explain the monitoring data despite the lack of corrosion on the exterior surface of the two instrumented rebars. However, with no other weaknesses, the remaining conventional rebars showed no impact from the cracks

The steel–concrete interface

Although the steel–concrete interface (SCI) is widely recognized to influence the durability of reinforced concrete, a systematic overview and detailed documentation of the various aspects of the SCI are lacking. In this paper, we compiled a comprehensive list of possible local characteristics at the SCI and reviewed available information regarding their properties as well as their occurrence in engineering structures and in the laboratory. Given the complexity of the SCI, we suggested a systematic approach to describe it in terms of local characteristics and their physical and chemical properties. It was found that the SCI exhibits significant spatial inhomogeneity along and around as well as perpendicular to the reinforcing steel. The SCI can differ strongly between different engineering structures and also between different members within a structure; particular differences are expected between structures built before and after the 1970/1980s. A single SCI representing all on-site conditions does not exist. Additionally, SCIs in common laboratory-made specimens exhibit significant differences compared to engineering structures. Thus, results from laboratory studies and from practical experience should be applied to engineering structures with caution. Finally, recommendations for further research are made

Durability-based design: the European perspective

In Europe, design for the durability of new reinforced concrete structures is currently based on a prescriptive approach. The design, execution (construction) and planned maintenance of a concrete structure have to lead to the intended level of safety and serviceability throughout its entire service life. This requires numeric models based on a sound scientific background of mechanistic understanding as the basis for design and management tools and for the further development of standards and regulations. Designers must understand the basic deterioration mechanisms and the potential types and rates of damage development. For example, different types of corrosion cause very different damage developments, some of which reduce structural safety. We propose that the next generation of service life models should either explicitly include the propagation period or implicitly include it by selecting an accepted probability of depassivation that reflects the type of corrosion and its structural implications.ISSN:2378-9697ISSN:2378-968