Aggregates
from the viewpoint of durability in aggressive media, should prefer the arid type (gravel and sand quarries rivers) siliceo.
gravel
is called gravel or dry bulk the fraction greater than 5 mm. And sand or dry thin to less than 5 mm. The resistance of the gravel is linked to its hardness, density, and module of elasticity.
sand
the arid greater liability in contrast to the gravel, water, and even the cement is the sand, you can say that it is not possible to make a good concrete without sand quality. The best sands are the River.
particle aggregates
the distribution of the sizes of the grains that make up an arid, were of critical importance in the characteristics of the concrete
COBOCE IRPA-IRPA provides the following aggregates:
taxes 1 1/2 "
taxes 3/4 "
sand