Good Quality Brick Specifications Based on ASTM, IS, and CSA

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Bricks 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 specifications

Good quality brick specifications based on American Concrete Society for Testing and materials (ASTM), Indian Standard (IS), and Canadian Standard Associations (CSA) include:

1. compressive strength of bricks
2. shape of bricks
3. brick construction materials
4. brick size
5. brick color
6. brick appearance
7. water absorption
8. brick cracks
9. brick soundness
10. efflorescence

1. compressive strength of bricks 

According 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
Severe weather	20.7	17.2
Moderate weather	17.2	15.2
Normal weather	10.3	8.6

2. Shape of bricks

Brick 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 materials 

Bricks 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 size 

Good 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

The size of the modular bricks shall be 190 x 90 x 90 mm or 190 x 40 mm. As per ASTM C62, the size of Solid brick shall be as specified by the purchaser. The maximum permissible variation in dimensions of individual units shall not exceed those given in Table 2.  Table 3 provides different sizes for hollow bricks. Table 2 variations of dimensions of solid bricks

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)

Table 3 Hollow Brick Minimum Thickness of Face Shells and Webs

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
152	25.4	38	25.4
203	32	38	25.4
254	35	41	29.5
306	38	50	29.5

5. Brick color 

Good quality brick needs to have uniform color. According to IS, good quality brick has deep cherry red and copper color.

6. Brick appearance

According 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 absorption

After 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 (---)

8. Brick cracks

Good quality bricks shall be free from cracks, flaws and nodules of free lime as per Indian standard. With regard to ASTM C62, brick unit shall not develop a crack that exceeds, in length, the unit’s least dimension

9. Brick soundness

They shall give a clear metallic ringing sound when struck by a mallet and shall not break when dropped on the ground on their flat face in a saturated condition from a height of 600 mm.

10. Efflorescence

Efflorescence in bricks shall be within limits prescribed in (Not more than 10% of the exposed area of the brick shall be covered with a thin deposit of salts) IS:3495 (Part-3). According to ASTM standard, bricks are not required to be tested for efflorescence unless requested by specifier.