This document outlines the key functions and requirements of a good mortar mix. It explains that mortar cements bricks together to provide stability and seal gaps to resist weather penetration while accommodating irregularities. Good workability, resilience to movement, adequate bond strength, and resistance to water are important. Proper mixing and workmanship can improve sealing. The document also provides information on calculating mortar quantities for wall areas.

1. •Explain the main functions of a
good mortar mix
• State how good workmanship will
improve the sealing properties of a
mix
• Calculate mortar quantities for
walling areas
Lesson Objectives

2. Mortars Generally
Mortar fulfills a number of functions. These include:
It cements the bricks together to provide stability -
and solidity, while holding them apart to spread loads
evenly.
It compensates for irregularity between units when
straight, level and plumb walling is laid.
It also seals any gaps to resist wind or rain
penetration.
As well as its gap-filling adhesive function it is
required to have durability and strength to suit the
application.
It also contributes to the aesthetic qualities of the
wall.

3. Three important Functions
Mortars should have:
1. good workability
2. sufficient resilience to accommodate long term thermal
movement of the masonry
3. adequate bond strength
4. good resistance to water penetration

5. Mortar is made from fine aggregate (usually sand) and a binding agent
(nowadays usually cement). When mixed with water a chemical
reaction, called hydration, occurs and the mortar sets. Early mortars
were usually based on lime and sand but they were very slow to set
and readily absorbed rain water (the mortar set through a process
known as carbonation where the lime gradually hardened by absorbing
carbon dioxide from the atmosphere).
Mixing On Site

6. Requirements of a Good MortarRequirements of a Good Mortar
• Adequate compressive
strength
• Adequate bond strength
• Durability:- resistance to
frost and chemical attack
•Joints sealed against, wind
driven rain
LONG LIFE REQUIREMENTS WORKABILITY
Bricklayers require a “fatty”
mortar which hangs on the
trowel without being sticky,
spreads easily and stiffens
neither too quickly nor too
slowly.

12. Modern mortars use cement as the main binding agent although
hydrated lime (ie bagged lime) is often introduced into the mix to
give it a more plastic feel and to make it more ‘workable’.
Lime also improves the mortar’s ability to cope with thermal and
moisture movement.
Mixed Ready for Use