Mörteladmixtures

Mörteladmixtures, or mortar admixtures, are chemical or mineral additives incorporated during mixing to modify the properties of cementitious mortars. They are used to improve workability, reduce water demand, control set characteristics, increase bond to substrates, and enhance durability. They enable masonry mortars, renders, and screeds to meet performance requirements while allowing lower cement contents, more consistent workability, and better resistance to cracking and moisture.

Common classes and functions include: plasticizers and superplasticizers to improve flow and reduce water content; air-entraining agents to create a microscopic air void system that improves frost resistance and shrinkage control; accelerators to shorten initial set in cold conditions; retarders to extend working time in hot weather or complex pours; bonding agents to enhance adhesion to old masonry or substrates; water repellents to reduce capillary moisture uptake; and set-control or pozzolanic admixtures to tailor hydraulic set and durability.

Usage and compatibility are important. Dosage is specified by product data and must suit the cementitious system (cement type, lime content, aggregates). Incompatible combinations can cause segregation, excessive air voids, reduced strength, or poor bonding. Applications include masonry mortars, plaster renders, and screeds where predictable workability, cracking resistance, and long-term durability under moisture and weathering are desired.

Standards and guidance vary regionally. In Europe, mortar admixtures are covered by the EN 934 family, with EN 934-2 addressing admixtures for mortar.