Functions and properties of mortar

Functions of mortar

1. Binds bricks or stones together into a single unit.
2. Spreads the load evenly over the bedding of the units.
3. Fills the gaps between units, so wind and rain cannot enter.
4. Gives a level bed so that the masonry is straight and plumb.
5. Gives a decorative effect in plaster and pointing, and protects the wall surface.
6. Takes up small movements and gives bond strength.

Properties of good mortar

• Workability: easy to mix and spread; remains plastic long enough to lay the unit.
• Water retentivity: keeps its water long enough, so bricks do not suck it out.
• Adhesion: good bond to bricks and stones.
• Strength: adequate compressive strength (cement mortar 1:4 about 7.5 N/mm² at 28 days).
• Durability: resists weather and chemical attack.
• Setting: should set neither too fast nor too slow.
• Low shrinkage: no cracks on drying.
• Impermeability and low cost.