Grout

Grout is a dense substance that flows like a liquid yet hardens upon application, often used to fill gaps or to function as reinforcement in existing structures. Grout is generally a mixture of water, cement, and sand, and is frequently employed in efforts such as 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 is also similar to concrete, but grout is distinguished by having only very fine aggregate (sand) and by generally containing a higher ratio of water to achieve the low desired viscosity.

The materials "caulk" and "grout" may be confused for each other or otherwise subject to misunderstandings. While each are used in building maintenance to a significant degree, the former is usually made up of a fluid silicone or polyurethane type of chemical substance while the latter consists of a specific mixture based on many fine particles, with the aforementioned household use of grout relying on its basis in cement being important. In addition, caulk remains flexible after it dries, which contrasts with the utilization of grout. Projects involving a lot of work involving grout frequently take place with the goals of preventing both dirt and moisture from getting under tiles. Provided by Wikipedia