Deleterious Materials In Aggregate
The materials whose presence in aggregates may adversely affect the strength, workability & long-term performance of concrete are termed as deleterious materials.
These are considered undesirable constituents. The total amount of deleterious materials in aggregate should not exceed 5% as per IS 383-1970.
The Deleterious Materials Found in The Aggregates
The deleterious substances found in the aggregates are as follows:
a) Organic matter consisting of decayed vegetable matter
b) Coal & Lignite
c) Clay lumps
Deleterious material present in the aggregates may affect the concrete as follows:
a) The organic matter interferes with the chemical reaction of hydration.
b) The clay & other fine materials present in the form of surface coating interfere with the bond between the aggregate &cement paste.
c) Presence of shale & other particles of low density adversely affects the strength of concrete.