Building Materials Chapter 3

Bricks

• Bricks are a popular and leading construction material due to their affordability, durability, and ease of handling.
• Clay bricks are commonly used for building exterior and interior walls, partitions, piers, footings, and other load-bearing structures.
• Bricks can be made of burnt clay, a mixture of sand and lime, or Portland cement concrete.

Classification of Bricks

• Based on field practice: • First-class bricks: thoroughly burnt, deep red, cherry or copper color, smooth surface, free from flaws, and have a uniform texture. • Second-class to fourth-class bricks: classified based on physical and mechanical properties.

Physical Requirements for Clay Building Bricks (ASTM C62)

• Compressive strength: not less than 10 N/mm2.
• Water absorption: 12-15% of its dry weight when immersed in cold water for 24 hours.

Classification of Bricks Based on Use

• Common bricks: general-purpose units, manufactured economically, used for filling, backing, and in walls where appearance is not important.
• Facing bricks: made for good appearance, durable, and used in fronts of building walls for a pleasing appearance.
• Engineering bricks: strong, impermeable, smooth, table-molded, hard, and conform to defined limits of absorption and strength.

Classification of Bricks Based on Finish

• Sand-faced bricks: textured surface manufactured by sprinkling sand on the inner surfaces of the mold.
• Rustic bricks: mechanically textured finish, varying in pattern.

Classification of Bricks Based on Burning

• Pale bricks: under-burnt bricks obtained from the outer portion of the kiln.
• Body bricks: well-burnt bricks occupying the central portion of the kiln.
• Arch bricks: over-burnt bricks, also known as clinker bricks, obtained from the inner portion of the kiln.

Types of Clay

• Surface clays: found near the surface of the earth, used for brick manufacturing.
• Shales: clays subjected to high pressures, nearly hardened into slate.
• Fire clays: usually mined at deeper levels, refractory qualities, and used for brick manufacturing.

Phases of Manufacturing

• Mining and storage of raw materials.
• Preparing raw materials.
• Forming the brick.
• Drying.
• Firing and cooling.
• De-hacking and storing finished products.

Manufacturing Process

• Mining: surface clays, shales, and some fire clays are mined in open pits with power equipment.
• Preparation: breaking up large clay lumps and stones, and mixing the raw material.
• Forming: tempering, producing a homogeneous, plastic clay mass, and then forming the brick using stiff-mud, soft-mud, or dry-press processes.
• Firing: tunnel kiln or periodic kiln, divided into five general stages: final drying, dehydration, oxidation, vitrification, and flashing or reduction firing.
• Cooling: important stage, as the rate of cooling has a direct effect on color.
• De-hacking: unloading the kiln or kiln car after the brick has cooled.

Harmful Substances in Bricks

• Lime: excess lime can change the color of the brick from red to yellow and cause disintegration.
• Pebbles, gravels, grits: can spoil the appearance of the brick and cause cracking.
• Organic matter: can make the brick porous, increase water absorption, and reduce strength.
• Alkalis (alkaline salts): can be beneficial as fluxes, but excess can make the clay unsuitable for bricks.

This quiz assesses understanding of building materials, covering topics related to civil engineering. It is part of the course materials for the University of Halabja's Civil Engineering Department.