BDCS Notes - Aggregate Uses

Aggregate Uses

Aggregates are primarily used as:

1. An underlying material for foundations and pavements

2. Ingredients in portland cement and asphalt concretes

Aggregate underlying materials, or base courses, can add stability to a structure, provide a drainage layer, and protect the structure from frost damage.

Stability – a function of the interparticle friction between aggregates and the amount of clay and silt “binder” material in the voids.

Increasing the clay and silt content will block the drainage paths between the aggregate particles, thereby inhibiting the ability of the material to act as a drainage layer.

% Aggregate in Portland Cement Concrete

1. 60% to 75% of the Volume

2. 79% to 85% of the Weight

How Aggregate Works in PCC:

Aggregate acts as a filler to reduce the amount of cement paste needed in the mix. In addition, aggregates have greater volume stability than cement paste. Therefore, maximizing the amount of aggregate improves the quality and economy of the mix.

% Aggregate in Asphalt Concrete

1. 80% of the Volume

2. 92% to 96% of the Weight

How Aggregate Works in AC:

Asphalt cement acts as a binder to hold the aggregates together, but does not have enough strength to lock the aggregate particles into position. The result is the strength and stability of asphalt concrete depends mostly on interparticle friction between the aggregates and (to a limited extent) on the binder.