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The corrosion of reinforcement is one of the major causes of deterioration of reinforced concrete (RC) structures, considerably affecting their durability and reliability. The rate of reinforcement corrosion is governed by, among other factors, the presence of chlorides on the surface of the steel. The assessment of such deteriorating effects necessitates the development of relevant models and the utilization of advanced simulation techniques to enable the probabilistic analysis of concrete structures. In this article an approach for the assessment of the durability and reliability of RC structures under attack from chlorides is introduced. The field of chloride concentration at different locations in the structure (represented in 2D space by chosen longitudinal or cross sections) is modeled as a function of time by a cellular automata (CA) technique. The results of this simulation are then utilized for the assessment of a steel corrosion prognosis using a probabilistic 1D model at chosen points, although the rate of corrosion is based on experimental results. The concentrations of chlorides and pH levels are reflected in this way. The described approach is applied to an illustrative example showing the feasibility of capturing the effect of chloride concentration on the steel corrosion rate and consequently on the assessment of the service life and/or reliability of the structure.

In the production of cement and concrete, mechanical and durable properties are essential, along with reasonable cost and sustainability. This study aimed to apply an evaluation procedure of the level of sustainability of mixtures of high-performance concretes (HPC) with various eco-friendly supplementary cementitious materials (SCM). The major supplementary cementitious materials (SCMs), namely, volcanic pumice pozzolan (VPP), Class C and F fly ash, ground granulated blast furnace slag of grade 120, silica fume, and metakaolin, were included. Twenty-seven concrete mixtures were analyzed using a previously presented comprehensive material sustainability indicator in a cost-effective variant. The results indicated that the rank of the concretes differed at 28, 56, and 91 days after concreting. In addition, the study showed no correlation of strength and diffusion parameters with sustainability indicators. Finally, this study will contribute to the optimal selection of mixtures of HPC with VPP in terms of sustainability, cost, and durability for future implementation in reinforced concrete bridge deck slabs and pavements. The values of sustainability indicators for pumice-based mixtures were compared with those for other SCMs, highlighting the sustainable performance of volcanic ash-based SCM.

Since concrete is one of the most important and useful materials in the construction sector, which, unfortunately, has an adverse impact on the environment, it is evident that correct procedures for designing and/or assessing concrete structures need to be created. Model Code 2020 with the focus to sustainability stated to be one of main aspiration goals, which will have implications for subsidiary performance requirements critical to structural design, integrate life cycle perspective, reliability and performance based concepts and end-of-service-life issues. Evidently the combined impact of the service life and relevant safety level of structures on the economical and environmental aspects desire full consideration of engineers and stakeholders. Consideration is also given to energy and raw material costs, as well as to environmental impact throughout the life cycle – e.g. due to emissions.

In the context of performance-based approaches, sustainability and whole life costing, the concrete structure durability issue has recently gained considerable attention. The present paper deals with service life assessment utilizing Durability Limit States specialized for concrete structures. Both initiation and propagation periods of reinforcement corrosion are considered and a comprehensive choice of limit states is provided. The approach is based on degradation modelling and probabilistic assessment, enabling the evaluation of service life and the relevant reliability level, serving thus to facilitate the effective decision making of designers and clients. For this purpose the selected analytical models for degradation assessment are randomized and appropriate software has been developed. Three numerical examples are presented: a comparison of modelled carbonation depth with in-situ measurements on a cooling tower, and analyses of crack initiation due to corrosion and loss of reinforcement cross section.

Die Sicherstellung eines ausreichenden Zuverlässigkeitsniveaus im Rahmen der Erhaltung von Bauwerken und insbesondere Betonbrücken, welche durch Verkehrs‐ und Umwelteinflüsse einer kontinuierlichen Verschlechterung im Laufe ihrer Lebenszeit unterliegen, ist in der Regel eine komplexe und teure Aufgabenstellung. Besonders in Regionen mit Streusalzeinsatz in der Winterzeit beeinflusst die Chloridbelastung sowohl den Entwurf als auch die Erhaltung der Bauwerke durch ihren Einfluss auf die Dauerhaftigkeit wesentlich. In diesem Beitrag wird eine Bewertungsstrategie für die durch die Chloridbelastung hervorgerufene Zustandsverschlechterung von Betonstrukturen und deren Auswirkung auf das Sicherheitsniveau sowie die verbliebene Lebenszeit an einem Fallbeispiel vorgestellt. Hierbei werden die Entnahme von Proben, deren Untersuchung, die inverse Analyse des Eindringverhaltens und infolge die Prognose der Chloridkonzentration im Bauteil, die Vorhersage der Korrosionsentwicklung über die Zeit und schließlich die Bestimmung des gegenwärtigen und zukünftigen Zuverlässigkeitsniveaus unter Beachtung der normativ festgelegten Grenzzustände für Tragfähigkeit und Gebrauchstauglichkeit behandelt. Schlussendlich werden unterschiedliche Erhaltungsstrategien in Bezug auf die zu erwartenden Lebenszykluskosten verglichen.Approach for the Assessment of Concrete Structures Subjected to Chloride Induced DeteriorationThe maintenance of an adequate safety level of concrete bridges under their gradual degradation due to traffic and environmental actions during service life is an expensive, problematic and questionable task. Chloride ion ingress is an important aspect of durability design and maintenance, especially in regions where winter salt application for traffic safety is common, e. g. for highways. A feasible approach for the assessment of chloride induced deterioration and its consequences on the safety level, remaining service life and thus maintenance planning will be presented by a case study. Steps include the extraction of samples, laboratory test, inverse analysis and prognosis of chloride ingress, prediction of likely corrosion propagation over time and determination of the current and future safety level with regard to code based service limit states and ultimate limit states. Finally different maintenance strategies are compared with respect to the total life cycle costs.

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