4.3 AGGREGATES

Aggregate

An inert material mixed with cement and water to form mortar, plaster or concrete.

Aggregate

Composed of approximately 75% of a concrete mix.

coarse aggregates

fine aggregates.

Categories of aggregates

Coarse aggregates

Particles retained by sieve #4 (4.76mm Ø).

• natural gravel deposits which are formed by water, wind or glacial action,

• manufactured by crushing rocks, stones, boulder and large cobble stones.

Sources of coarse aggregates

• limestone or calcium-bearing minerals

• basalts, granite and related igneous rocks

• sandstones and quartzsites

• rock such as opal and chert composed mainly of amorphous silicon dioxide.

Kinds of coarse aggregates

• it should fit easily into the forms and in between the reinforcing bars

• it should not be larger than 1/5 of the narrowest dimension of the forms or 1/3 of the depth of the slab nor ¾ of the minimum distance between the reinforcing bars.

Conditions on what maximum size of aggregates to be used

pea gravel

crushed stone

quarry process gravel.

Types of gravel and their uses

Pea gravel

Composed of small round stones. Used in walkways in parks, backyards, asphalt driveways.

Crushed stone

Typically made from limestone or granite using a stone crusher. Usually used in

residential landscaping, commercial landscaping.

Quarry process gravel

Contains a mix of stone dust and crushed stone. Used in asphalt driveways.

Fine aggregates

The product of the natural disintegration of silica-bearing or calcium-bearing rock.

Sand

Name a Fine aggregate.

Fine aggregates

Pass sieve #4 and retained by sieve #200 (74 micron Ø).

Fine aggregates

Can also be manufactured from large aggregates by crushing, grinding or roll