Concrete Aggregates

Concrete Aggregates

Gravels, stone and sands form the granular structure, which must have its voids filled as completely as possible by the binder glue. They make up approximately 80% of the weight and 70–75% of the volume. Optimum use of the aggregate size and quality improves the concrete quality. Aggregates can occur naturally (fluvial or glacial); for high quality concrete they are cleaned and graded in industrial facilities by mechanical processes such as mixing together, crushing, screening and washing (mechanical preparation).

Suitable as concrete aggregates are materials which do not interfere with the cement hardening, have a strong enough bond with the hardened cement paste and do not put the resistance of the concrete at risk.

Standard and special aggregates

Standard aggregates	Density2.2–3 kg/dm³	From natural deposits, e.g. river gravel, moraine gravel etc. Material rounded or crushed(e.g. excavated tunnel)
Heavyweight aggregates	Density> 3.0 kg/dm³	Such as barytes, iron ore, steel granulate. For the production of heavy concrete (e.g. radiation shielding concrete)
Lightweight aggregates	Density< 2.0 kg/dm³	Such as expanded clay, pumice, polystyrene. For lightweight concrete, insulating concretes
Hard aggregates	Density> 2.0 kg/dm³	Such as quartz, carborundum; e.g. for the production of granolithic concrete surfacing
Recycled granulates	Density approx. 2.4 kg/dm³	From crushed old concrete etc.