Field tests of bricks

The following tests are done at the site to check the quality of bricks.

1. Colour: should be uniform, bright and cherry red (or as required).
2. Shape and size: bricks should be rectangular with sharp edges and straight faces. The Nepal Standard size is 240 × 115 × 57 mm (the IS modular brick is 190 × 90 × 90 mm). Size is checked by measuring 20 bricks laid in a row.
3. Soundness test: two bricks are struck together; a clear metallic ringing sound shows good quality, while a dull sound shows a poor brick.
4. Hardness test: a scratch with a fingernail should leave no impression on a good brick.
5. Structure: a broken brick should show a uniform, compact, fine-grained structure without voids, lumps or cracks.
6. Water absorption test: a dry brick is weighed, soaked in water for 24 hours and weighed again. Absorption should not exceed 20% of its dry weight for first class bricks (15% for facing bricks).
7. Efflorescence test: a brick is kept in a dish of water for 24 hours and then dried; white patches should be no more than slight.
8. Drop test: a brick dropped from about 1 m onto a hard surface should not break.
9. Compressive strength: done in the laboratory; minimum 3.5 N/mm² for common bricks as per NBC.