The aggregates most commonly used in concrete are gravel, crushed stone, crushed slag, and pumice. Cement and water are mixed with aggregates to produce concrete. Concrete contains both fine and coarse aggregates. Cement paste coats the aggregates, binding them together and curing to form concrete.
Aggregates add strength to concrete and reduce its potential for shrinkage. “Aggregates actually make up 60 to 80% of the volume of hardened concrete, so their properties and characteristics are very important” (Beall, 2004). The coarse aggregates most commonly used in residential concrete are gravel and crushed stone. Aggregates must be sound, volume stable, nonreactive, abrasion resistant, suitably shaped, rough textured, well graded, and clean. Each characteristic of the aggregate has an effect on the resulting concrete. Unsound aggregates produce unsound concrete which is weak, has poor appearance, low durability, and may experience cracking.
Chemical reactivity, especially with the alkalis in cement, causes internal expansion, cracking, and disintegration of the concrete. Low abrasion resistance results in low strength and excessive wear in floors and pavements.
Aggregate that is too absorptive produces concrete that has low durability and may suffer from scaling excessive shrinkage. Dirty or contaminated aggregate bonds poorly with the cement paste, can increase mixing water requirements, delay setting and hardening of the concrete, cause stains, lower strength and durability, and increase shrinkage.
Aggregates add strength to concrete and reduce its potential for shrinkage. “Aggregates actually make up 60 to 80% of the volume of hardened concrete, so their properties and characteristics are very important” (Beall, 2004). The coarse aggregates most commonly used in residential concrete are gravel and crushed stone. Aggregates must be sound, volume stable, nonreactive, abrasion resistant, suitably shaped, rough textured, well graded, and clean. Each characteristic of the aggregate has an effect on the resulting concrete. Unsound aggregates produce unsound concrete which is weak, has poor appearance, low durability, and may experience cracking.
Chemical reactivity, especially with the alkalis in cement, causes internal expansion, cracking, and disintegration of the concrete. Low abrasion resistance results in low strength and excessive wear in floors and pavements.
Aggregate that is too absorptive produces concrete that has low durability and may suffer from scaling excessive shrinkage. Dirty or contaminated aggregate bonds poorly with the cement paste, can increase mixing water requirements, delay setting and hardening of the concrete, cause stains, lower strength and durability, and increase shrinkage.
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