Grout

Summary

Grout is a fluid mix of water, cement, and fine sand, or of urethane or epoxy resin, used to fill joints, voids, and cells. It fills tile joints, grouted masonry cells, and bearing plate voids, so the grout type must match the load, joint width, and exposure.

Cols

Image

Sanded grout: contains finely ground silica sand
Unsanded grout: finer particles, smoother surface
Non-shrinking grout: fills gaps under bearing plates
Thixotropic grout: resists flow until agitated
Microfine cement: particles 6 to 10 microns; ultrafine below 5 microns

Composition and production

Raw materials

Water, cement, and fine sand; Portland cement is the most common binder
Thermoset polymers such as urethanes and epoxies as alternative binders
Higher water ratio than concrete to reach low viscosity

Grades and types

Tiling: cementitious, classed ordinary or improved, with add-on traits F (fast setting), W (reduced water absorption), A (high abrasion resistance)
Flooring: pavement joint mortar rated up to 7.5 tons for garage access
Resin: epoxy or urethane
Nonshrinking: supports metal bearing plates
Structural: reinforced masonry
Thixotropic

Properties

Physical

Cement particle size: standard about 15 microns; finer particles penetrate deeper into fissures

Uses in buildings

Building elements

Ceramic and Porcelain Tile: tile and shower joints
CMU Walls: grouted cells with reinforcing steel
Precast Concrete: joining precast units

Pros and cons

Pros

Flows into narrow joints and cells
Epoxy and urethane grout resist stains

Cons

Higher water ratio than concrete
Type must match joint width and load

Manufacturing and cost

Main manufacturers and suppliers

Trade association: Tile Council of North America.

Sources

Wikipedia: Grout, https://en.wikipedia.org/wiki/Grout
Wikimedia Commons: Applying grout.jpg, photo by unknown (Public domain), https://commons.wikimedia.org/wiki/File:Applying_grout.jpg