The toughness property of coarse aggregates can be assessed by conducting which laboratory experiment?
Impact value test
Assessing Toughness of Coarse Aggregates
The toughness of coarse aggregates is an important property to consider in construction, especially for pavement layers. Toughness refers to the resistance of the aggregate to sudden impact or shock loading. When aggregates are used in roads, they are subjected to dynamic loads from moving vehicles, which can cause impact stresses.
Laboratory Tests for Coarse Aggregate Properties
Various laboratory tests are conducted on coarse aggregates to determine their suitability for different construction purposes. Each test assesses a specific property:
| Test Name | Property Measured | Description |
|---|---|---|
| Crushing Value Test | Strength (resistance to crushing under gradual load) | Measures the resistance of aggregates to compressive stress. Useful for determining suitability for base courses and concrete. |
| Impact Value Test | Toughness (resistance to sudden impact or shock) | Measures the resistance of aggregates to shattering under impact loading. Essential for aggregates used in pavement wearing courses. |
| Abrasion Value Test | Hardness/Wear Resistance (resistance to wear and tear) | Measures the resistance of aggregates to rubbing or grinding action. Important for aggregates exposed to traffic abrasion, like in surface courses. |
| Flakiness Index Test | Shape Property (presence of flaky particles) | Measures the percentage of flaky particles (where the least dimension is less than 3/5th of the mean dimension). Affects workability of mixes and interlocking properties. |
Based on the description of toughness as resistance to sudden impact or shock, the laboratory experiment specifically designed to assess this property is the Impact value test.
Impact Value Test Explained
In the Impact value test, a standard sample of aggregate is subjected to a series of impacts from a hammer of a specific weight falling from a fixed height. The amount of finer material produced after the test indicates the toughness of the aggregate. A lower impact value means the aggregate is tougher and more resistant to impact.
Other Tests vs. Toughness
- The Crushing value test assesses resistance to gradual compressive load, which is related to strength, not sudden impact.
- The Abrasion value test assesses resistance to surface wear caused by friction, related to hardness, not toughness.
- The Flakiness index test assesses the shape of the aggregate particles, which affects workability and packing, not the material's resistance to impact.
Therefore, to determine the toughness property of coarse aggregates in a laboratory setting, the Impact value test is the appropriate experiment.
Important Questions from Highway Materials and Maintenance
The damaged material on the surface of road which is removed by rubbing or chipping action is called:
The bitumen that is obtained as a residue during the distillation of a high-resin petroleum is called:
The Indian Road Congress (IRC) recommends what value of camber for gravel or water bound macadam road surface subject to heavy rains?
In the Aggregate impact value test, as per IS: 2386 (part IV), the test sample should pass and retain through which of the following sieve size?
Flakiness index and Elongation index test is not applicable to aggregate sizes smaller than:
