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What is No-Fines Concrete?No-Fines Concrete is a lightweight concrete made up of only coarse aggregate, cement and water by omitting fines (sand or fine aggregates) from normal concrete. Advantages, limitations and mix proportions of no-fines concrete is discussed. Very often only single sized coarse aggregate, of size passing through 20 mm retained on 10mm is used. No-fines concrete is becoming popular because of some of the advantages it possesses over the conventional concrete. The single sized aggregates make a good no-fines concrete, which in addition to having large voids and hence light in weight, also offers architecturally attractive look.
Advantages of No-Fines Concrete
- No fines concrete is a lightweight concrete i.e. density is about 25 to 30% less than the normal concrete due to no fine aggregates, thus self-weight of structure is less.
- As it does not have sands or fine aggregates, it has less drying shrinkage compared to normal concrete
- It has better thermal insulating characteristic than normal concrete and thus it is useful for construction of external wall.
- As it has no fine aggregates, the surface area required for cement coating is reduced considerably. So, quantity of cement required gets reduced per cubic meter compared with normal concrete. So, it is economical.
- Lightweight concrete has no effect on quality due to segregation of coarse aggregates as it has no fine aggregates. Thus, it can be dropped from heights.
- No fines concrete can be compacted without the need of any types of concrete vibrators and can be easily done by tamping with rods.
Limitations of No Fines Concrete
- As there is no fine aggregates to fill the voids in this concrete, it has high permeability than normal concrete. Thus, it is not a good idea to construct reinforced concrete with no fines concrete, as the reinforcement can easily get corroded.
- To make this concrete impermeable, extra coat of masonry plaster is required, which increase the cost.
- No fines concrete can not be tested for workability by using tests for normal concrete such as slump or compaction factor test. Values of workability and its test methods are unknown.