Dear reader we have discussed many aspects of aggregates and some advance application of aggregates; but we have not defined yet aggregate. Let’s try to define them.
This definition is quoted from ACI C125 and ACI committee 116. ACI 125 provides standard definition of terms related to concrete and as well as concrete aggregate. ACI committee 116 provides a glossary of terms in the field of cement and concrete technology.
Aggregate is a granular material which is mixed with cementing medium or compounds to produce either mortar or concrete. The usual examples are
-crushed blast-furnace slag
-or demolition or construction waste
Depending on size we can group aggregate as coarse aggregate and the fine aggregate. Coarse aggregate are those that have particle size greater than 4.75 mm (or No. 4 standard sieve).
On the other hand fine aggregate are those that have particle size range > 75µm to <4.75 mm. 75µm is stand for retaining on No.200 sieve.
But some aggregate containing substances that can check hydration process, deviate hydration products and some produce expansion that results serious problem to concrete and compromising durability.
We have provided deleterious substances that can remain in aggregate, their effect and volume fraction to limit harmful reaction, workability or durability problems.