🕑 Reading time: 1 minuteBricks are widely used in building construction because of their adequate strength, durability, availability and low cost. They can be made in desired shape and size. Bricks which are used for construction purposes shall poses good qualities otherwise the safety and serviceability of masonry structure would be compromised. Hence, this article presents qualities of good bricks based on the IS 1077, IS 2180, ASTM C62, ASTM C216, and CSA A288 in the cases where it is different from ASTM.
Good quality brick specificationsGood quality brick specifications based on American Concrete Society for Testing and materials (ASTM), Indian Standard (IS), and Canadian Standard Associations (CSA) include:
- compressive strength of bricks
- shape of bricks
- brick construction materials
- brick size
- brick color
- brick appearance
- water absorption
- brick cracks
- brick soundness
1. compressive strength of bricksAccording to ASTM C62, compressive strength of good quality brick shall be not smaller than those provided in Table 1. CSA A288 provides the same result for compressive strength but only for severe and moderate exposure conditions. The crushing strength of the brick to be used in all types of works shall not be less than 7.356MPa unless otherwise specified when tested according to IS:3495 (Part-1). Table 1 minimum compressive strength of bricks
|Grade of bricks||Minimum Compressive Strength gross area, MPa|
|Average of 5 Brick||Individual brick|
2. Shape of bricksBrick are shaped during manufacture by molding, pressing, or extrusion using hand or machine. Ordinary bricks are rectangular solids. But sometimes bricks are given different shapes to make them suitable for particular type of construction. They shall have regular and uniform size, sharp straight and right-angled edges.They shall have smooth rectangular faces with parallel sides and sharp corners.
3. Brick construction materialsBricks shall be constructed from suitable soil and kiln burnt. They shall be well burnt throughout but not over-burnt. Similarly, ASTM standard specify that, brick shall be of clay, shale, fire clay, or mixtures thereof, and burned properly to meet good quality brick requirements. If the bricks are burnt excessively or under burnt, they lose equality of color on the surface and strength.
4. Brick sizeGood quality bricks shall have uniform size. The size of the conventional bricks shall be 225 x 110 x 75 mm. Only bricks of one standard size shall be used in one work unless specially permitted by the Client / Consultant. The following tolerances are permitted in the standard conventional size adopted on the particular work.
- Length plus or minus 3.0 mm
- Breadth plus or minus 1.5 mm
- Depth plus or minus 1.5 mm
|Specified dimension, mm||Maximum Permissible Variations from Specified Dimension, plus or minus, mm (CSA A288)|
|Up to 76, inclusive||2.4 (2.4)|
|Over 76 to 102, inclusive||3.2 (3.2)|
|Over 102 to 152, inclusive||4.8 (4.8)|
|Over 152 to 203, inclusive||6.4 (6.4)|
|Over 203 to 305, inclusive||7.9 (7.9)|
|Over 305 to 406, inclusive||9.5 (9.5)|
|Nominal Width of Units, mm||Face Shell Thicknesses, mm||End Shells or End Webs|
|Solid||Cored or Double Shell|
|76 and 101||19.05||---||19.05|
5. Brick colorGood quality brick needs to have uniform color. According to IS, good quality brick has deep cherry red and copper color.
6. Brick appearanceAccording to Indian standard, bricks shall show a fine-grained, uniform, homogeneous and dense texture on fracture and shall be free from lumps of lime, lamination, cracks, air holes, soluble salts causing efflorescence or any other defect which may impair their strength, durability, appearance and usefulness for the purpose intended. They shall not have any part under-burnt.
7. Water absorptionAfter immersion in cold water for 24 hours, absorption by weight shall not exceed 15 percent of the dry weight of the brick when tested according to IS:3495 (Part-2). According to ASTM C62, maximum saturation shall conform to the values provided in Table 4. This requirement can be neglected If the brick are intended for use exposed to weather where the weathering index is less than 50 but compressive strength shall not be less than 17.2MPa Table 4 Maximum water absorption of bricks
|Grade of bricks||Maximum Water Absorption by 5-h Boiling, %|
|Average of 5 Brick (CSA A288)||Individual brick (CSA A288)|
|Severe weather||17 (---)||20 (17)|
|Moderate weather||22 (22)||25 (25)|
|Normal weather||No limit (---)||No limit (---)|