Extended Open Time - the need for standardization of an important characteristic of tile adhesives

The EN 12004 defines the characteristics of ceramic tile adhesives. Because these materials are applied as pastes which undergo reactions to be turned into hard bodies the norm defines the characteristics of both, the initial fresh stage and the final hardened stage. A recent reworking of the EN 12004 targets to delete the fresh mortar characteristics and parts of the strength characteristics. Only the classifications of normal cementitious adhesives (CD and fast-setting adhesives (F) will be kept in the norm. Deleting the classification E for Extended Open Time bears the risk that the number of failures will increase. The reason is that a standard Open Time of 20 min is good enough for normal conditions. But for warm temperatures and/or windy conditions an Extended Open Time of 30 min provides better security for good wetting of the tiles, which is a precondition for a durable adhesion. © 2021 Bauverlag BV GmbH. All rights reserved.