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No-fines concrete
This form of lightweight concrete is generally a crushed rock or gravel of 20 mm single size aggregate (10/20) coated in a cement slurry with no fine aggregate addition. Strength is between 5 and 15 N/mm2 at 28 days. It has good drainage properties due to its open texture. The ratio of aggregate to cement by volume is generally 8:1 or 10:1 by mass.
Because it does not contain any fine aggregate the mix cannot segregate and consequently it can be dropped from a height. Formwork pressures are lower than for normal concrete so shutters can be lighter and pour height lifts greater.
No-fines concrete has been used in large in-situ panel construction (Wimpey housing) and for drainage channels etc. It is specified in the National Highways Specification for Highway Works, clause 2603.
Acknowledgement:
The Concrete Society
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No fines concrete
