What Is Mortar Made Of?

The recipe for mortar has changed through time, having been around for thousands of years in differing regions. Modern mortar is made of either cement powder or lime (or a combination of the two) with sand and water. Additives can be added to mortar such as retardants or accelerants.

Cement

The most common mortar is Portland cement, and is made from heated and powdered limestone mixed either with clay or shale.

Sand

Sand for mortar should not be rounded, but angular. This is so the rest of the ingredients can stick to it.

Water

Water for mortar is made as pure as possible (and therefore as neutral as possible) before being used.

Lime

Slaked lime, calcium hydroxide, is used in mortar to improve the smoothness, water holding capacity and workability of mortar.

Types

There are five main types of mortar, type S, type N, type M, type O and type K. These types vary in ratio depending on how many pounds per square inch (psi) it can stand.

References

• A History of Cement
• Description of Sand Used in Mortar
• Mortar What's Your Type

Resources

• Mortar: What Type Do You Need ?
• Essentials of Masonry