mørtler

Mørtler, or mortar, is a workable paste used in masonry to bond bricks, stones, or blocks and to seal joints between them. It is typically composed of a binder material, aggregates such as sand, and water. The binder provides cohesion and strength, the aggregate provides bulk and reduces shrinkage, and the water enables plasticity and hydration.

Common binders include cement-based mortars (Portland cement), lime-based mortars (hydrated lime or hydraulic lime), and mixtures such as cement-lime mortars. Lime mortars are more breathable and flexible, often favored in historic or traditional masonry; hydraulic lime mortars gain strength through a hydraulic set. There are also plastering mortars for wall surfaces and specialty mortars for tile or repair work. The choice of mortar depends on the masonry units, climate, and desired durability and breathability.

Mortars are used for bedding units, filling joints (pointing), and sometimes as plaster bases. Bedding mortars must have appropriate workability and adhesion, while pointing mortars are designed to allow movement and shed water. Cement-rich mortars tend to be stronger and less permeable, whereas lime-rich mortars are more flexible and breathable, which can be important for historic buildings.

Curing behavior varies: cement mortars cure by hydration and set relatively quickly, while lime mortars cure more slowly by carbonation and often require sustained moisture and moderate temperatures. This difference affects compatibility with existing materials and long-term performance.

Standards and testing exist in many regions, such as EN 998 (specifications for masonry mortars) and related national standards; in North America, ASTM standards address mortar for unit masonry. Mørtler continue to be selected to balance strength, workability, compatibility, and durability for specific applications.