What is aggregate?

Aggregate is a key component of concrete. It is a range of rock fragments going by different names, depending on their size (between 0 and 125 mm, as determined by the smallest size of the square mesh of the sieves through which each fragment passes): filler, fine sand, coarse sand, gravel. A distinction is made between natural aggregate derived from loose or massive rock that has undergone nothing more than simple mechanical processing, and artificial aggregate that results from more elaborate thermal or mechanical processing of rock or minerals. Natural aggregate can be rounded alluvium or sharp-edged fragments of crushed quarry rock. The types of bonding between the different aggregates and the cement paste are determining factors in the strength of concrete.