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.[1] Grout is generally a mixture ofwater,cement, andsand, and is frequently employed in efforts such aspressure grouting, embeddingrebar inmasonry walls, connecting sections of precastconcrete, filling voids, and sealing joints such as those betweentiles. 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 asplaster orjoint 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[2] 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.[1] Grout is also similar toconcrete, but grout is distinguished by having only very fineaggregate (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 buildingmaintenance to a significant degree, the former is usually made up of afluidsilicone orpolyurethane type ofchemical 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 bothdirt andmoisture from getting under tiles.[3]
Cementitious grout can be classified into two types: ordinary grout and improved grout. They can be further divided into three types based on their additional performance characteristics:[4]
Grout varieties includetiling,flooring,resin,nonshrinking, structural, andthixotropic grouts.[5] The use of enhancing admixtures increases the quality of cement-based materials and leads to greater uniformity of hardened properties.[6]
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 thetesserae. Tiling grout is also cement-based, and is produced in sanded and unsanded varieties, which affects the strength, size, and appearance of the grout.[7] The sanded variety contains finely ground silica sand; unsanded is finer and produces a smoother final surface. They are often enhanced with polymers and/orlatex.[8]
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.[2] Nonshrinking grout is used beneath metal bearing plates to ensure a consistent bearing surface between the plate and its substrate, which adds stability and allows for higher load transfers.[9]
Portland cement is the most common cementing agent in grout. However, the utilization ofthermoset polymer matrix grouts based onthermosets such asurethanes andepoxies are also popular.[10]
Portland cement-based grouts include different varieties depending on the particle size of the groundclinker used to make the cement, with a standard size around 15microns, microfine from 6–10 microns, and ultrafine below 5 microns. Finer particle sizes let the grout penetrate more deeply into a fissure. Because these grouts depend on the presence of sand for their basic strength, they are often somewhat gritty when finally cured and hardened.
From the different types of grout, a suitable one has to be chosen depending on the load. For example, a load up to 7.5 tons can be expected for a garage access [two-component pavement joint mortar (traffic load)], whereas a cobbled garden path is only designed for a pedestrian load [one-component pavement joint mortar (pedestrian load)]. Furthermore, various substructures determine whether the type of grout should be permanently permeable to water or waterproof, for example, by concrete subfloor.
Tools associated with groutwork include:
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