Historically, bricks have been used on the Tower of Babel through to modern times.
The first brick building in Australia was Government House, Sydney. It was a substantial building that was officially opened in 1789, just six months after the first fleet's landing at Sydney Cove.

Durability of Brickwork

Brickwork has a long record as one of the most durable and versatile building materials. However, as with all such materials, there are a few essential considerations to ensure satisfactory performance:

• Correct selection of the brick for the site conditions.
• Proper mortar mixing.
• Suitable design and detailing.
• Correct installation of fittings and connections to adjacent building materials and components.

The Australian standard for masonry units and segmental pavers (including clay bricks and pavers), AS/NZS 4455:1997, states that they may be classified according to their durability in three categories:

• Exposure
• General Purpose
• Protected

Seven points must be considered when designing and constructing durable brickwork:

1. the exposure condition at the site;
2. the durability classification of the bricks;
3. selection of the appropriate mortar mix;
4. correct and accurate batching of mortar;
5. suitable wall ties;
6. separation of the brickwork exposed to the weather from concrete or other uilding elements;
7. good advice to the prospective client on landscaping practices.

Clay Brick and Paver Institute [1].

Mortar

Australian Standard Masonry Structures specifies two essential properties of mortar:

1. Adequate workability to permit the masonry units to be properly placed.
2. The ability, in conjunction with the masonry units, to provide the structural properties and appropriate durability required for the given situation.

Mortars are classifid by their proportions of cement, lime and sand. There are definite advantages in using lime in a mortar:

• Increased workability,
• Increased cementitious material content,
• and Increased durability because of self-healing of small cracks in mortar joints.

The use of plasticisers is often abused by bricklayers trying to obtain a fatty mix that "feels good on the trowel". Most plasticisers dramatically increase the air content of mortar. The bond between mortar and bricks is achieved by coating the face of the brick with cement paste. If air bubbles are present at the point where brick and mortar meet, the area of cement paste coating is reduced and therefore bond is reduced. Moisture absorption will also be greater, increasing the likelihood of salt attack in Exposure classification sites. If plasticisers are used they must be in the proportions recommended by the manufacturer.

Mortar cannot be batched consistently and accurately by shovel. This batching technique leads to a lower than required cement content and colour variation (when colouring additives are used). Using a gauge box is the simplest accurate method of batching mortar. Any convenient sized container on the site can be used. This is the right way to go!

The selection of sand is important. Many 'brickies sands or loams' have fine sand particles and contain significant amounts of clay. Some clay assists workability but too much eventually weakens the mortar leaving it prone to salt attack. Sand with very fine or uniform grain sizes may give problems in laying-up rates. A 50/50 mixture of brickies loam and washed sharp sand will generally give the best all-round results. And don't forget the lime!

Clay Brick and Paver Institute [1].

Mortar joints

The use of open or raked and recessed joints is a common practice that can expose more brick area to the elements, wind abrasion and water penetration. The ledges formed by the joints allow the collection of pollutants and may lead to streaking or staining after rain. They also allow the build-up of salt. In many cases the joints are not ironed, presenting an uncompressed surface to the elements. These joints should be restricted to low-pollution, no-exposure areas and interior face brickwork.

Important: The most durable joint finish is the shallow round-ironed joint. The effect of ironing a mortar joint is similar to 'helicoptering' a concrete floor slab. The joint face is compressed and a cement-rich layer is brought to the surface.

Clay Brick and Paver Institute [1].

The following hyperlinks provide great resources for teachers and students.

The Austral Brick and Paver website includes a range of technical information.

The Clay Brick and Paver Institute website has a section on "Story of brick" and also a "How bricks are made" section.

Return to >> Concrete

Glossary

Brick: first produced at least 6,000 years ago and the forerunner of a wide range of structural clay products used today, is a small building unit in the form of a rectangular block and fired in a kiln, or oven, to produce strength, hardness, and heat resistance [2].

Mortar: is cement mixed with sand or crushed stone that must be less than approximately 5 millimetres in size. Mortars are used for binding bricks, blocks, and stone in walls or as surface renderings [2].

Citations

[1] Clay Brick and Paver Institute (CBPI) (1998). CBPI Techniques 04, September 1998 ["Durability of Brickwork"] [WWW Journal/Online Series - Adobe pdf file]. URL www.claybrick.com.au/downloads/cbpi_techniques_04.pdf

[2] Britannica.com Inc (2001). ENCYCLOPÆDIA BRITANNICA ["Brick and Tile"] [WWW document]. URL www.britannica.com/

Note: This page is under construction, and will be added to as time permits.

Copyright D. L. Christiansen [Last updated Sept 2002] Images: respective copyright owners noted/cited.