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. This report was prepared by the working group within RILEM TC 262-SCI, and further reviewed and approved by all members of the RILEM TC 262-SCI.

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This article has been prepared within a framework of RILEM TC 262-SCI. The article has been reviewed and approved by all TC members.

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By monitoring the free induction decay and spin-echo envelope (acquired with the Meiboom-Gill modified Carr-Purcell pulse sequence), during hydration of white cement paste, information about growth patterns of various cements is obtained. In particular, the secondary hydration water is characterized through direct observation, and a relatively immobile, near solidlike water phase, observed for the first time in hydrating cement, is discussed.