sementtilimeseokset

Cement-lime mixtures, or sementtilimeseokset, are blends used as binders in mortars and plasters. They combine cement’s early strength with lime’s plasticity and moisture management, producing mortars that are strong yet permeable to water vapor. This makes them suitable for masonry and restoration work where compatibility with historic materials is important.

Composition and variants: The most common form is a cement-lime mortar or plaster made by combining Portland cement with hydrated lime or hydraulic lime and an aggregate such as sand. Lime can be hydrated lime, lime putty, or hydraulic lime, and pozzolanic additives may be used to adjust setting and performance. There are also lime-putty mortars with reduced cement content and cement-lime mixtures with higher lime proportions. The exact ratios vary according to climate, substrate, and performance goals.

Applications: Cement-lime mixtures are used in new construction where some cement strength is desired but permeability must be maintained, as well as in the restoration and conservation of historic structures. They are common in mortar joints, plaster layers, and repointing work on masonry where movement and moisture transfer need to be accommodated without excessive rigidity.

Properties and considerations: Compared with pure cement mortars, sementtilimeseokset offer better workability, improved bonding to traditional masonry units, and greater capillary moisture transfer. They typically develop strength more gradually than pure cement mortars and remain more flexible, reducing cracking in some substrates. However, too much cement can reduce lime’s breathability and cause incompatibilities with older materials, so mix design and curing are important. Proper curing, compatible aggregates, and surface preparation are essential for durability.

See also: historic masonry, lime mortar, hydraulic lime, plastering mortars.