Q. Why is it important for a highway engineer to study the properties and behavior of aggregate? State their desirable properties.

Q. What are the desirable properties of aggregate? Explain any one with permissible limits.

Following are the various desirable properties of good aggregate.

1. Shapes of aggregate should be rounded, cubical, angular, flaky or elongated.

2. Surface texture of aggregate is generally preferable to smooth aggregate.

3. It should be chemically insert.

4. It should have sufficient toughness to resist the impact load and vibratory loads.

5. The aggregate should be sufficiently strong such that it resist the stresses developed due to the wheel loads of the traffic.

6. It should have sufficient hardness so as to resist scratching and abrasion in the hardened concrete.

7. The aggregate should be reasonably hard enough so as to resist abrasion and attrition.

8. It should able to take compression load as well as normal tensile load in ordinary concrete.

9. The aggregate should be free from any impurities, dust, inorganic and organic matter, oil etc. because such impurities effects on the quality of concrete.

10. The aggregate should be easily workable when it combines with cement and water.