Fair-faced concrete has been enjoying newfound popularity. The artificial “rock” concrete, which can be shaped in the mould at will, is extraordinarily suited to simultaneously perform constructive and creative functions. In this context, the implementation in building practice of the optical appearance of the concrete surface visualised is of paramount importance for the creative objectives of the architect being achieved.

Differences in colour, which cannot be safely avoided in spite of expert planning and execution, have repeatedly given cause for complaint. These include:

• partial discoloration
• intense pore formation
• large-surface “cloud formation” and “marbling”

caused by the action of release agents, excessive compaction, discoloration of the mould and concrete bleeding at leakages of the mould.

The practical experience of the people in charge of building execution and the framework conditions prevailing in each individual case presently still play a major role in accomplishing a fair-faced concrete surface that meets expectations. The considerable number of bungled fair-faced concrete surfaces is also attributable to the fact that the sources of the deficiencies cited above have not been investigated systematically to date.

An investigation programme called “Joint research on fair-faced concrete”, which is sponsored by the Federation of Industrial Cooperative Research Associations “Otto von Guericke” (AiF), is conducted under the joint overall responsibility of the German Cement Works Association (VDZ) and the German Concrete and Construction Engineering Association (DBV). The objective of the programme is to identify the relationships resulting in complaints about fair-faced concrete surfaces. Mechanisms and influencing variables as well as effective control measures apt to avoid colour phenomena will be derived from the results obtained.