Coulis (maçonnerie)

Grout is a dense fluid that hardens to fill gaps or used as reinforcement in existing structures. Grout is generally a mixture of water, cement, and sand, and is employed in pressure grouting, embedding rebar in masonry walls, connecting sections of precast concrete, filling voids, and sealing joints such as those between tiles. Common uses for grout in the household include filling in tiles of shower floors and kitchen tiles. It is often color tinted when it has to be kept visible and sometimes includes fine gravel when being used to fill large spaces (such as the cores of concrete blocks). Unlike other structural pastes such as plaster or joint compound, correctly mixed and applied grout forms a water-resistant seal. Although both grout and its close relative mortar are applied as a thick suspension and harden over time, grout is distinguished by its low viscosity and lack of lime (added to mortar for pliability); grout is thin so it flows readily into gaps, while mortar is thick enough to support not only its own weight, but also that of masonry placed above it. Grout varieties include tiling, flooring, resin, nonshrinking, structural, and thixotropic grouts. The use of enhancing admixtures increases the quality of cement-based materials and leads to greater uniformity of hardened properties. Tiling grout is often used to fill the spaces between tiles or mosaics and to secure tile to its base. Although ungrouted mosaics do exist, most have grout between the tesserae. Tiling grout is also cement-based, and is produced in sanded and unsanded varieties, which affects the strength, size, and appearance of the grout. The sanded variety contains finely ground silica sand; unsanded is finer and produces a smoother final surface. They are often enhanced with polymers and/or latex. Structural grout is often used in reinforced masonry to fill voids in masonry housing reinforcing steel, securing the steel in place, and bonding it to the masonry.