Bricks used in the construction industry may have the following defects. Therefore before using bricks, it should be properly inspected for the presence of any of the following defects.
Different types of defects found on bricks
1. Excessive burning of bricks
Bricks must be burned at the temperature at which initial, complete and viscous vitrification occurs. However, if the bricks are burned, a soft molten mass is produced and the bricks lose their shape. Such bricks are not used in construction works.
2. Under burning bricks
When bricks are not completely burned for vitrification, the clay does not soften and the pores do not close due to insufficient heat. This results in a high level of water absorption and low compressive strength. Such bricks are not recommended for construction works.
This defect was observed as a spongy swollen mass on the surface of the burnt bricks. This is due to the presence of excess carbonaceous material and sulphur in the brick-soil.
4. Black Core
The presence of bituminous material or carbon in the brick soil is the cause of this defect. When these substances are not completely removed by oxidation, due to improper burning, the brick results in a black core.
The presence of soluble salts is the primary cause of this defect. When bricks come into contact with moisture, the water is absorbed and the salts crystallize. On drying, brown or white powdery spots appear on the surface of the brick. This can be reduced by applying any of the following methods, such as
- Selection of proper clay material for brick making
- preventing moisture from coming into contact with the masonry,
- by providing waterproof combat and
- By using water repellent material in mortar and providing damp proof course.
The deformation of the shape of bricks due to rain water falling on heated bricks is known as chaffs.
7. Checks or Cracks
This defect may be due to lump of lime or excess of water. In the former case, when bricks come into contact with water, the absorbed water reacts with the lime lumps, causing the bricks to expand and result in disintegration, whereas shrinkage and burning cracks occur when brick construction. There is an excess of water during
Iron sulfide, if present in brick clay, causes dark spots to form on brick surfaces. Such bricks, although not harmful, are unsuitable for exposed masonry work.
Broken blisters are usually caused by air trapped on the surface of sewer pipes and drain tiles during their molding.
These are caused by air trapped in the voids of the soil. Laminate produces thin laminae on brick faces that weather out upon exposure. Such bricks are weak in structure.