For checking the length of bricks as per Indian standards how many bricks are to be taken :
📏 Understanding the Dimensional Tolerance Test
To ensure uniformity in brickwork, it's crucial that the bricks from a given batch are consistent in size. The Indian Standard IS 1077 specifies a "dimensional tolerance test" to check this. This test doesn't just measure one brick; it measures a group of them to check the average size and ensure the variation is within acceptable limits.
🔬 Detailed Analysis of the Options
C. 20
This is the correct answer. According to IS 1077, for the dimensional tolerance test, a sample of 20 bricks is selected at random from the stack. These bricks are then laid end-to-end (for length), side-by-side (for width), and stacked (for height). The total dimension is measured and compared against the permissible limits to ensure the batch is of standard size.
A, B, and D
These are incorrect. The standard explicitly states that a sample size of 20 bricks must be used for this particular test. Using a smaller or larger number would not conform to the standard procedure.
📊 Summary: Sample Sizes for Common Brick Tests
| Test Type | Standard Sample Size | Purpose |
|---|---|---|
| Dimensional Tolerance | 20 Bricks | To check for uniformity in size. |
| Compressive Strength | 5 Bricks | To determine the load-bearing capacity. |
| Water Absorption | 5 Bricks | To determine porosity and durability. |
| Efflorescence | 5 Bricks | To check for the presence of soluble salts. |
💡 Study Tips
- 20 for Dimensions, 5 for Properties: This is a simple rule of thumb. The test for physical size (dimensions) uses a larger sample of 20, while tests for material properties (strength, absorption) typically use a smaller sample of 5.
- Why 20?: A larger sample size for the dimensional test helps to average out any minor, acceptable variations between individual bricks, giving a more accurate assessment of the entire batch.
- Know the Code: Remember that these procedures are laid out in the Indian Standards, primarily IS 1077 and IS 3495.