No Fines Concrete

No fines concrete may be defined as concrete mixtures containing little or no fine aggregate.

No fines concrete

The fine aggregate is not added in this concrete so that there are voids left in the coarse aggregate. The coarse aggregate may be any of the usual type or the light weight aggregate. The coarse aggregate used should be finer than 20 mm size and not more than 10% should pass the 10 mm sieve. The usual proportion of cement to aggregate is 1:10 in case of heavy aggregate and 1:6 in case of light aggregate. The amount of water should be just sufficient to give a coating of cement paste on all particles. Too little water may leave loose aggregate inside the concrete and too much of water may cause the cement paste to flow and segregate. It is better to wet the aggregate before adding cement and water. The concrete should then be mixed thoroughly till all the particles are coated. Properly prepared concrete will not segregate during placing. It does not need any water tight forms also. It should be rammed but only rodded to remove large cavities. This concrete cannot be easily cut away afterwards and all fixtures etc. should be placed in the green state. It has no resistance t penetration of water and suitable rendering may be applied on its external surface.

Properties of No Fines Concrete

  • It does not segregate
  • The density varies with the grading of aggregates
  • Water cement ratio of this concrete varies from 0.38 to 0.52
  • Its strength increases with time
  • There is very little cohesiveness, necessitating longer duration of form work removal.
  • Shrinkage of this concrete is lower than normal concrete and its thermal expansion is about 0.6 to 0.8 of normal concrete.

Limitations Of No Fines Concrete

  • It disintegrates rapidly
  • It is unsuitable for foundations and in places continuously in touch with moisture, because of its high absorption quality.
  • It is also not suitable for reinforced concrete.

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