Fines in Crushed Sand: How to Control Stone Dust
Crushed sand carries stone dust, which is not the same as clay. Learn the ASTM C33 limit, the methylene blue test and how production controls fines.
Industry developments
Recycled Concrete Aggregate: Properties, Limits and Uses
Crushing old concrete reduces quarrying and waste. Learn the properties of recycled aggregate, its higher absorption, suitable uses and how to control its quality.
Demolishing buildings and pavements produces a great deal of rubble. Crushing old concrete and reusing it cuts extraction from natural sources and reduces waste sent to landfill. These materials do not, however, behave like natural aggregate.
How it differs from natural aggregate
Mortar stuck to the particles is the most important difference. This mortar is porous and leads to:
- Higher water absorption
- Lower density
- Lower abrasion resistance
- More variation between shipments
Common uses
| Use | Status |
|---|---|
| Subbase and fill | Common |
| Base | With suitable quality control |
| Non-structural concrete | Common in some regions |
| Structural concrete | Needs specification and technical approval |
The definition of coarse aggregate in ASTM C33 includes crushed concrete, but its use depends on meeting the same requirements and on approval in the project specification. Use under local specifications should be checked against each project’s references.
Quality control notes
- Removing wood, gypsum, plastic and metal before crushing
- Monitoring sulfate and chloride, especially in material of unknown origin
- Pre-wetting, or correcting mix water, for the higher absorption
- Storing it apart from natural materials and testing each batch
For water correction, Moisture and absorption helps. See the wider picture in New directions in the aggregates industry.
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