Aggregates are immobile granular materials such as sand, gravel, or crumble stone that, along with water and Portland cement, are an indispensable ingredient in concrete.
If you want a good concrete mix, you need to make sure that the aggregates you use are clean and hard, with strong particles free of absorbed chemicals or coatings of clay and other thin materials that could cause the disintegration of concrete.
Around 60 to 75 per cent of the total volume of concrete is aggregate. They are divided into two different groups: