Band 37, Heft 1 - Special issue: Environmental degradation of reinforced concrete structures / Issue editors: Antonio Bossio and Francesco Bellucci

In Europe, stainless steel rebars have been used since the mid-80s, whilst in North America, their use has been progressively growing only since the mid-90s. Due to their higher resistance to corrosion in comparison to ordinary black steel bars, they have been employed in a wide number of applications worldwide to achieve the durability performance of reinforced concrete structures, especially in extremely corrosive marine environments or when long service lives are required. In this paper, a state of the art on the corrosion resistance of stainless steel bars is reported. In particular, the contribution of Professor Luca Bertolini in this research field is considered. Initially, different testing methods are presented to point out their advantages and limitations and then the results on corrosion behaviour of different grades of stainless steel bars (i.e. austenitic, ferritic and duplex), obtained especially with tests in concrete, are analysed. Afterwards, some of the recent applications of stainless steel bars are illustrated.

In chloride environments, reinforcement stress limits, intended to control flexural cracking, are one of the most important requirements for service limit state (SLS) design. However, concrete damage at the steel-concrete interface between bending cracks, so called cover-controlled cracking, is always correlated to areas of severe steel reinforcement corrosion. Based on the assumption that cover-controlled cracking should be limited, a model has been developed to provide alternative reinforcement stress limits in marine exposure conditions such as concrete in sea water, including permanently submerged, spray zone and tidal/splash zone, as well as coastal constructions located within 1 km of the shoreline. In this paper, the new reinforcement stress limitation is compared to the Australian Standards AS3600 concrete building code and AS5100.5 concrete bridge code provisions. Analysis shows that the new model is very sensitive to the reinforcement percentage of the cross-section. As a result, the existing AS3600 and AS5100.5 code provisions are more conservative than the new limitation for lightly to normally reinforced concrete cross-section. In this case, crack width control governs the SLS design. However, for normally to heavily reinforced concrete cross-section, the new model provides more conservative results suggesting that cover-controlled cracking governs the SLS design.

This article presents the results of an extensive experimental program containing 22 beams with tension lap splices in the central region. The beams were preconditioned under simulated corrosion up to specific levels of bar section steel loss and cover cracking in the lap region. They were subsequently tested under four-point loading so as to place the corroded lap splice zones in tension. To prevent corrosion outside the study region, the beams were wrapped with fiber-reinforced polymers outside the laps – this also served to protect them from premature shear failure as the objective was to study failure in the lap zone. The objective of the experiment was to assess the residual anchorage capacity of such zones. The parameters of the experimental study were the extent of corrosion and the available length of lap splicing of longitudinal tension reinforcement. Corroded bond strength was determined from the short-length lap splices, where it may be assumed that stresses are uniformly distributed over the lapped zone; longer specimens were considered in order to examine how the redundancy provided by the longer contact length may improve the resilience and deformation capacity of the corrosion-damaged component prior to bond failure.

Recently, corrosion prevention and monitoring of reinforced concrete (RC) structures became an important issue for seismic assessment of such kind of structures. Therefore, it is important to develop adequate models to represent material degradation into seismic behavior simulation of RC structures. Because of its effects, corrosion represents the most important form of degradation for materials and structures, both for wide diffusion and the amount of danger it presents. To understand the corrosion process is critical in order to design RC structures that are able to guarantee the required service life and in order to understand the residual service life and strength of an existing structure. The seismic behavior of a corroded framed RC structure is analyzed by means of push-over analyses, which allow understanding the development of the global behavior of the structure. Three different degrees of corrosion penetration were simulated, by means of the reduction of bars and stirrups’ diameters and concrete cover cracking and spalling, and three different configurations of corrosion, depending on the number of corroded frames and sides of the structural elements.

This paper presents the results of a series of investigations that were performed on a reinforced concrete bridge structure exposed to marine environment in subtropical weather. Data were obtained by assessing the structural conditions using visual observations, nondestructive evaluations, and laboratory testing in order to define the cause and the level of concrete deterioration due to corrosion. In addition, a probabilistic methodology was used to compute the time of corrosion initiation focusing on reinforced concrete subjected to a similar chloride environment. The initial service life was predicted with a method that employed the use of statistical models of the governing parameters obtained from field data. Results show that this approach could be utilized for assessment of existing and new constructions and/or as a tool for decision-making process during the structural design phase.