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.
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