Aggregates PDF

Aggregates: These are broad categories of coarse- to medium-grained particulate material used in construction, including sand, gravel, crushed stone, etc. Characteristics of Aggregates Aggregates generally make up the bulk of the concrete. These are available in fine and coarse grades. For morta...

Aggregates: These are broad categories of coarse- to medium-grained particulate material used in construction, including sand, gravel, crushed stone, etc. Characteristics of Aggregates Aggregates generally make up the bulk of the concrete. These are available in fine and coarse grades. For mortar the size of aggregates is very small ranging from 0-4mm, and for general concrete work the size varies from 5-20mm. Requirements of Aggregates All aggregates should be: clean free from sediments sound strong – not easily crushed well graded well shaped Types of Aggregates 1. Coarse Aggregate Gravel – This consists of small pieces of stone which are somewhat rounded in shape. It makes good coarse aggregate because it is hard and closed textured. (Source= gravel banks, river beds). Crushed Stones – Trap rock is the hardest and most durable stone that can be crushed and used for making concrete. This stone is dark, heavy and close-grained. Granite makes good crushed stone and is less expensive than trap rock. The stone should be graded in sizes 6mm-20mm. 2. Fine Aggregates For concrete work these are sand, crushed stones or gravel screening. The most important of these is sand. Sand is a fine divided material of rock which will pass through a standard 5mm sieve. Sand is not subjected to disintegration, decay or expansion.