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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 Highways Agency Specification for Highway Works, clause 2603.

Note that from 1 April 2015, Highways Agency has changed name to Highways England.

 
Acknowledgement: The Concrete Society
 

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No fines concrete