No-Fines Concrete and Its Mix Proportion

No-fine Concrete is a type of concrete in which fine aggregate in concrete is eliminated. This concrete is made of only coarse aggregate, cement and water.

Mix Proportion of No-fine concrete

• Coarse aggregate which passes 20mm sieve and retained on 10mm sieve is used for production of these concrete.
• The cement to aggregate ratio should vary from 1:6 to 1:10.
• The water to cement ratio vary from 0.38 to 0.52. The ratio should be choose very carefully. If amount of water is less then the bonding between cement and coarse aggregate is very poor. But if amount is high then cement paste flow downward and the paste cover the voids of aggregate completely at lower portion of concrete. Hence Concrete will be dense at lower portion.
• The density of concrete with normal aggregate vary from 1600 to 1900 Kilogram per cubic metres but with light weight aggregate help to reduce density upto 300 kilogram per cubic metres. 
• The compressive strength of no fine concrete   lies between 4 MPa to 14 MPa. 
• No fine concrete will easily compacted by simple rodding. There is no need of compactors or vibrators.
• The bond strength is very low and used in conjunction. For providing reinforcement, the reinforcement should cover with a cement paste as it help to create better bond between aggregate and reinforcement and also prevent corrosion. 

Advantages of No-Fines concrete

• The shrinkage of these concrete is very less as compared to ordinary concrete. 
• The capillary action is very negligible than ordinary concrete.
• The thermal insulation is higher than ordinary concrete.
• It reduces the cost of production as construction material like sand or fine aggregate is not used.
• The density of no fines concrete is of 25- 30% of ordinary concrete density. Thus it produces lesser pressure on formwork. 
• It is light weight in nature. Thus it is used in light weight construction work.
• Segregation of aggregate is very low in these concrete. Thus concrete can be laid from any considerable height without any fear of segregation.

Limitation of No-Fines concrete

• Reinforcement is not recommended for these concrete.
• There is not any particular or standard test (workability/ compaction factor) for checking the consistency of concrete. It is done only by observation. 
• It is more permeable than ordinary concrete. A layer of cement mortar is required for increasing the durability of concrete.
• No-Fines Concrete has less cohesiveness in plastic stage. It increases the time required to remove formwork.

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