Grout and Mortar

• The main difference between grout and mortar is the ratio of water in the mixture, according to the Masonry Magazine website. Grout must contain enough water so that it can be applied to the surface, yet not separate. Mortar requires only enough to give the material a buttery consistency for application. In addition, mortar may contain aggregate materials for greater density, as well as hydrated lime for flexibility.
  
  

Information About Grout

• Grout consists of sand, cement and water. Sometimes, other ingredients are used to provide additional properties for the grout in special situations. Fly ash may be added, which is made from burnt coals crushed and ground, then passed through a sieve. Bentonite, a clay material, may also be added to provide water retention. The water in grout is often absorbed by the surrounding materials. Most problems with grout are related to too little water rather than too much.
  
  

Grout Mixture Ratios

• A number of premixed grout compounds are available on the market. Mix these according to package directions to provide the best consistency for your use. For use on walls, the consistency should not be too thin, which can run outside of grout lines creating a mess. The simplest grout mixture ratio for projects such as mosaic tiling is 1 part cement to 3 parts sand, according to the Joy of Shards website. Mix with water to a pourable but not loose consistency. Then, fill in the areas between tiles, removing the grout from the tile surface as you go, and allow the grout to dry. This ratio can be adjusted to provide a thicker or thinner mixture to suit your project’s needs.
  
  

Grout Problems

• Occasionally, problems can arise with grouted materials. Cracking, looseness or uneven coloring can occur. Using an excessive amount of water in the grout mixture ratio can cause pinholing in the grout as it dries, which then creates an overall weakness in the material. Uneven coloring can also be caused by too much water in the grout mixture, as well as insufficient mixing. Adding additional water to the grout mixture after it has already been mixed can cause weakness and crumbling. Uneven packing of grout into the joint can also create weakness when it does not reach completely to the back surface of the joint. This problem often occurs on wall tiles.