Decay Patterns and Damage Processes of Historic Concrete: A Survey in the Netherlands

Abstract

Historic concrete buildings (end of 19th century -1960s), because of their "experimental" character, require a specific approach to both survey and conservation. Although they were built with empirical approaches, some buildings show a fair state of conservation and resilience -even though they have already exceeded the 100-year threshold-while others of comparable age are in severe need of restoration.As part of the European project CONSECH20, aimed at contributing to the conservation of cultural-heritage concrete buildings, this paper investigates what are the most common types of damage and hypothetical causes, and what direct and non-direct parameters can lead to a faster or slower deterioration of historic concrete in the Netherlands. The research is based on an initial screening study, which will be used as a basis for a larger research among the participant countries.The current research is divided in three phases. Firstly, a selection of 15 case studies from the Netherlands are investigated; the selection was based on criteria of age, state of conservation and type of ownership. Secondly, the history and materials of the buildings are examined. Thirdly, an on-site visual survey is performed per each building, with predesign templates, to identify types of damage, extent and severity. The data is then analysed combining different factors with a calculated index of severity. Results are discussed and contrasted to provide further clarification of the degradation of historic concrete. A fourth phase, not discussed in this paper, will use this methodology in a broader context, with a larger number of case studies in different countries.The results indicate that the majority of types of damage are related to corrosion, being the hypothetical cause carbonation-induced corrosion. The outcomes of the investigation point out that the factors with a higher impact on the durability are the environment, the use and maintenance of the buildings, the existence of a sacrificial plaster in exposed elements, and the type of ownership.Considering the limited number of buildings, the conclusions presented in this paper will be further contrasted with a larger number of case studies.