sandlime

Sandlime, commonly referred to as sand-lime brick or calcium-silicate brick, is a building material made from a mixture of silica-rich sand and lime binder, sometimes with cement additives. The mixture is formed into bricks or blocks and cured to develop strength. In many cases the curing is steam-based, including autoclaving, which promotes the formation of a calcium-silicate matrix through the reaction of lime with silica.

Historically, sand-lime bricks were widely used in Europe, especially in Germany and neighboring countries, from the late 19th century into the mid-20th century. They were valued for their uniform size and appearance, good fire resistance, and lower energy use in production compared with fired clay bricks. Demand declined as other masonry units, such as fired clay bricks and concrete blocks, became more common.

Composition and properties vary, but the units are generally dense and strong with uniform color. They offer good dimensional stability and fire resistance, while providing modest to low thermal insulation compared with some other masonry materials. They can be more susceptible to efflorescence if moisture moves through the wall and lime leaches to the surface, and their performance depends on proper jointing and moisture management.

Production methods include molding the sand-lime mix into bricks followed by curing, often under steam or in autoclaves to ensure complete reaction. Non-autoclaved variants exist but are less common. Sandlime bricks are still encountered in restoration and in regions with historic construction, where appropriate detailing and finishes help address moisture and aesthetic considerations.