- 2080 Chaitra · 2 marks
Descriptive tests of aggregate
Short answer
Descriptive tests include flakiness and elongation indices, specific gravity, water absorption, bulk density, surface texture, colour, petrographic examination, gradation, adhesion and cleanliness. They describe physical character rather than strength and are used alongside mechanical tests for aggregate acceptance.
Discuss descriptive tests of aggregate.
Descriptive tests of aggregate are simple (visual or physical) tests that describe the character of the aggregate rather than its strength.
- Particle shape tests - flakiness index, elongation index and angularity number; show the proportion of flat, long and angular particles.
- Specific gravity and water absorption - show the density and porosity of the aggregate.
- Bulk density and voids - used for mix proportioning.
- Surface texture (smooth, rough) and colour - indicate the skid resistance and the affinity for bitumen.
- Petrographic examination - rock type and mineral content, including alkali-silica reactive minerals.
- Gradation (sieve analysis) - particle size distribution.
- Stripping/adhesion test and cleanliness tests (clay, silt and organic content).
These tests are descriptive in the sense that they give a physical description of the aggregate; they are used together with the strength tests (crushing, impact, abrasion) for acceptance.
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