Understanding Materials: Masonry

Brick manufacturing today follows fundamental procedures pioneered centuries ago. However, better knowledge of raw materials and their properties, better control of firing and improved kiln designs have resulted in a superior product. The production of bricks centers around the type of clay that is used. Clays occur in three forms (Surface Clays, Fire Clays & Shales). Although they share similar chemical compositions, they will differ in their physical characteristics. All properties of brick are affected by the composition of the raw materials and the manufacturing processes. Essentially brick are produced by: (1) mixing ground clay with water, (2) forming them into desired shapes, (3) then drying and firing them. Establishing a homogeneous blend is necessary before subjecting the mixture to one of three forming processes (Stiff–Mud, Soft–Mud or Dry–Press). Next, the process continues with drying, firing and cooling. Kiln firing temperatures during manufacturing graduate from 400°F to 2400°F.

Hardness of Bricks

  • There are many different types of brick (Building, Facing, Hollow, Paving, Ceramic Glazed and Thin Brick), and different scales of hardness. The strength of a unit is used to determine its durability and cutability. Both compressive strength and absorption are affected by properties of the clay, method of manufacturing and degree of firing. Most bricks have a strength ranging from 3,000 PSI to over 20,000 PSI, with the average being around 10,000 PSI.
  • Brick may also include different size, type and volume of aggregates to further strengthen the mix.