The characteristics that decide whether an aggregate produce good, workable, strong as well as durable concrete, were discussed in previous post. These characteristics are derived from three factors as follows:
a. Mineral composition of rock from which aggregate are derived whether from it or from a weathered form of rock. Thus geologic process of rock formation is important.
b. As stated above rock may be weathered to form modified rock. These modification or degree of modification of rock depend on exposure conditions under which they are subjected before mining work.
These mean rock formation,description and classification of minerals and rocks and factors involved in industrial processing are of great importance.
Consider silicious rocks like
They are generated by geological process of weathering. Though they formed from parent hard rocks-minerals but weathering process makes them smooth and round surface are available in these aggregate.
Laminated limestone, shales and sandstones have tendency to produce flaky and elongated fragments while crushing predominantly when jaw crushers is used for crushing to provide workable sized aggregate.