Forgotten Material History of Historic Concrete

In this paper, an overview is given of the material history of early historic concrete, i.e. the late 19th and early 20th century. As interventions of historic concrete structures are increasing, for both for repair and conservation, more background information is necessary. Whereas the structural appraisal is commonly discussed, the material composition is less addressed. Better information on the historic concrete itself is essential, as the previously used constituents can influence the durability differently. A challenge hereby is that many details of the material history have been forgotten. Especially in the period before the 1940s, many rarities were applied and the pace of technological progress is frequently misconceived. The role of the national context is underestimated. To improve pre-investigations of historic concrete structures, timelines for the binders used and changing perceptions regarding aggregates are presented.