Which One Is Better For Concrete-Rounded or Angular Aggregate
Angular aggregate are superior to rounded aggregate from the following two points of view.
Angular aggregate exhibit a better interlocking effect in concrete, which property makes it superior in concrete used for roads and pavements.
The total surface area of rough textured angular aggregate is more than smooth rounded aggregate for the given volume. By having greater surface area, the angular aggregate may show higher bond strength than rounded aggregate.
The higher surface area of angular aggregate with rough texture requires more water for a given workability than rounded aggregate. This means that for a given set of conditions from the point of view of water-cement ratio and consequent strength, rounded aggregate gives higher strength.
As a conclusion we can say that:-
For a water-cement ratio below 0.4, the use of crushed aggregate has resulted in strength upto 38% higher than rounded aggregate. With an increase in water-cement ratio the influence of roughness of surface of the aggregate gets reduced, presumably because the strength of the paste itself becomes paramount, and at a water-cement ratio of 0.65, no difference in strength of concrete made with angular aggregate on rounded aggregate has been observed.