Efflorescence today still repeatedly presents a problem for the acceptance of concrete products. Stone surfaces with light discolouring or grey to yellowish-brown surfaces are still frequently encountered, particularly on earth-moist manufactured concrete products such as e.g. concrete paving stones. While these do not have a negative influence on the quality of the paving stones, they still often lead to complaints from the purchaser (see Fig. 1). As a result, almost all larger manufacturers of concrete products point out in their General Terms & Conditions that efflorescence on cement-bonded building materials can technically not be reliably prevented and that it therefore does not substantiate grounds for complaint. A similar wording can also be found in the relevant technical standards (e. g. DIN EN 1338 or DIN EN 1339). The customers then claim that they purchased “black” and not “grey” paving stones. Such disputes are frequently brought to court, which however rarely leads to a satisfactory solution for the parties involved.
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