Brick

A brick is one of the most popular exterior materials - it is beautiful and provides a solid well-made structure. A brick is a unit of material used in masonry construction by skilled masons using mortar. Bricks come in many sizes but usually in a width and weight suitable to grasp in one hand while holding a trowel in the other.

Different clays produce different colors. Natural coatings, such as sand and limestone, can be added during the firing process to produce different colors, effects, textures and finishes. In addition, the brick’s position in the kiln can affect the final look.

Clay Brick

The more commonly used bricks are made of clay. They have a natural beauty and do not fade over time. Extruded clay bricks are made with a mixture of finely ground shale and water forced through a die. The result is a long cable of material that is then cut into bricks of any desired length. The introduction of holes or indentations reduces the volume of clay needed, with a consequent reduction in cost but with increased thermal properties. The cut bricks are hardened using waste heat from the kiln. They are then fired in the kiln at temperatures near 1000°C for about 24 hours. The vitrified clay shale produces hard, dense bricks of unparalleled strength, texture and colour.

Concrete/Calcite Brick

Concrete or calcite bricks are denser than clay bricks. The raw materials for concrete or calcium silicate bricks include lime or Portland cement mixed with fine aggregates and mineral colorants. The materials are mixed and then pressed into moulds. The formed shapes are cured in an autoclave or humidity controlled environment. The finished bricks are very accurate and uniform and can be made in a variety of colours. Advantages include their lower manufactured cost from regional production facilities.

Block

A normal block or concrete masonry unit (CMU) is made from Portland cement and sand or fine gravel. Lightweight blocks are produced by using aerated concrete or lighter weight aggregates. The very firm concrete is pressed into moulds under intense pressure and then the formed block is cured in an autoclave or humidity controlled environment.

Blocks are usually produced with hollow centres to reduce weight and improve insulation. These voids also allow rebar and concrete to run vertically through the block to create stronger, load-bearing walls (reinforced concrete). Block is available in many sizes but the standard size is 20cm x 20cm x 40cm (8in. x 8in. x 16in.); the actual size is usually about 1cm smaller to allow for mortar joints. The surface which forms the outside of a wall can be formed using numerous profiles in smooth face or split face and in many colours from pure white through a range of blended colours to almost black.

Stone (natural or manufactured)

Natural stone is usually quarried stone which is sawn or split into regular shapes for interior and exterior architectural use. Colours, hardness and surface texture are as varied as nature can create.

Manufactured stone products are formed using aggregate and either extreme pressure or cement as a binder to create a more consistent stone product. In all other aspects, the two products can look and handle alike complete with subtle variations in colour and texture. Sizes and shapes vary by style and manufacturer, often with numerous different shapes on the same skid.

Masonry Mortar

Masonry mortar is used for bedding, jointing, and bonding masonry units. It is composed of cementitious materials, sand and water.

The cementitious materials essentially include cement and/or lime. In the hardened state, the cement and lime provide compressive strength and mortar/unit bond strength. In the plastic state, the cement accelerates the time to set to facilitate speed of construction, and the lime contributes to the workability, which helps ensure full and intimate contact between units and mortar.

Sand provides colour, texture, and cohesiveness, and reduces drying shrinkage. Water added to the mortar makes the mix workable and hydrates the cement. Other materials are sometimes added to give the mortar particular properties; for example, entrained air improves the workability and resistance to freeze/thaw deterioration.

The requirements for mortar for masonry used in Canada are contained in CSA Standard A179, Mortar and Grout for Unit Masonry.

The properties of mortar in its plastic and hardened states are both important, but for different reasons. Plastic properties such as workability and water retention determine construction suitability while laying the units, and hardened properties such as compressive strength, bond strength and durability affect the performance of the finished masonry.

CSA A179 identifies two mortar Types suitable for use in modern masonry construction, these being Type N and Type S. In the hardened state, Type S mortar has a higher compressive strength and generally higher bond strength than does Type N mortar. However, Type N mortars often show better workability in the plastic state, helping to ensure good bond between mortar and unit.

Because properties vary with mortar Type, and no single mortar Type is best for all purposes, it is important that the mortar Type selected for a particular application is the one that best meets the end-use requirements.

A basic rule for the selection of a mortar is to not to use a mortar with a compressive strength greater than is demanded by the structural and durability requirements of the masonry. A mortar with the lowest compressive strength consistent with the performance requirements should be selected.

Type N mortar is recommended for general use, where high lateral and vertical masonry strengths are not required, such as for interior or exterior non-load bearing walls, as well as for exterior veneers. Type S masonry mortar is recommended for use in all masonry below grade as well as for load bearing masonry walls (typically block), both interior and exterior, where higher vertical and lateral strength is needed.

CSA A179 identifies three mortar mix formulations suitable for use: Portland cement/lime, Masonry Cement, and Mortar Cement. Both Type N and Type S mortar can be manufactured under each mix formulation. However, for each of the three formulations, the constituent cementitious materials differ, and therefore the relative volumes of cementitious materials and aggregate to be combined on the jobsite to manufacture the same mortar Type differ. Under the proportion specification of CSA A179, to produce either a Type N or a Type S mortar as desired, the relative proportions of the materials to be added together by the mason on the jobsite are tabled for each mix formulation. This simplicity in the manufacture of mortar makes the proportion specification the most desirable means to specify mortar for both the mason and the designer.

For further information on mortar selection, mixing   installation procedures and specification requirements please refer to the 2004 edition of CSA A179.