a) Desirable properties of road aggregates:
Durability: The aggregates should be able to resist the adverse effects of weather and climatic changes.
Wear and tear: The aggregates should be able to resist wear and tear due to traffic loads.
Shape and texture: The aggregates should have a good shape and texture. They should not be too flat or too elongated.
Size: The size of the aggregates should be such that they can be easily compacted and can provide good stability. Generally, the size of aggregates varies from 2.36mm to 75mm.
Bonding strength: The aggregates should have good bonding strength with the asphalt binder and should not detach from it easily.
Polishing resistance: The aggregates should have good resistance to polishing and should not become slippery when wet or smooth due to traffic loads.
b) Variations in temperature that generally affect the pavement
Thermal cracking: Due to temperature variations, the pavement tends to expand and contract. This leads to thermal stresses which cause cracks in the pavement.
0joints: In hot weather, the longitudinal joints expand and may become wavy or corrugated which can lead to roughness in the pavement.
Blistering: In hot weather, the air trapped in the pavement tends to expand and come out of the pavement in the form of blisters which can weaken the pavement.
Rutting: In hot weather, the asphalt binder in the pavement becomes soft which can lead to rutting or depression in the pavement.
Thermal stripping: In hot weather, the asphalt binder may lose its adhesive properties and the aggregates may get separated from the binder. This is known as thermal stripping.