ABSTRACT
There are three general types or groups of aggregates depending on their source: primary: which are specifically produced for use in concrete; secondary: by-products of other industrial processes not previously used in construction; recycled: from previously used construction materials, for example, from demolition. These can be obtained either from natural sources, such as gravel deposits and crushed rocks, or specifically manufactured for use in concrete. It is convenient to group them in terms of their density or specific gravity. For fine aggregate, the definition of some intermediate values gives a useful addition to these overall limits when considering their use in concrete. Sieve analysis and grading curves take no account of particle shape, but this does influence the voids content of the aggregate sample – more rounded particles will pack more efficiently and will therefore have lower voids content.
