No-Fines Concrete - Properties and Features

No-fines concrete (NFC) is a concrete without fine material i.e. sand in the mix. So, its microstructure will be, the coarse aggregates surrounded by the thin layer of cement paste. This mix structure imparts strength to the concrete. 

No-Fines Concrete - Properties and Features

It is not recommended for R.C.C , but in unique cases, the rebars need a thin layer coat of 3mm paste to improve the bond with concrete and to prevent corrosion. But, its high end application is as a backfilling material, especially in areas with negative sight conditions.

Structure of No-Fines Concrete
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The concept of NFC was derived back in 1800s in Europe, with an objective to bring cost savings by reducing the cement and sand requirements for concrete construction. The first known application of NFC was for the construction of segmental retaining walls, over 25 years ago.

How To Make No-Fines Concrete (NFC)?

The preparation of NFC is simple. It mainly involves the following procedure:

1. Decide to prepare a NFC of mix ratio 1:6 (cement : coarse aggregate).
2. Take coarse aggregate with average size 20 mm and no aggregates with size less than 10 mm.
3. Mix the cement and the aggregates in 1:6 ratio.
4. After mixing thoroughly, add water in the required consistency and amount.
5. The paste must be such that it coats the aggregates.
6. The external surface of NFC must be plastered or rendered in both sides to reduce the permeability to air.
7. When NFC is used for acoustic applications, one side only require rendering, or else its sound absorbing properties reduces.

Properties of No-Fines Concrete (NFC)

1. No-fines concrete is quite porous as it do not have fine aggregates, and are sometimes referred as pervious concrete or permeable concrete.
2. Due to the presence of large voids, NFC have high insulating properties compared to conventional concrete.
3. NFC has lower density and low cost due to no fines and less cement content.
4. It possess low thermal conductivity and relatively low drying shrinkage.
5. NFC undergo no segregation
6. NFC is highly resistant to frost due to the absent of capillaries in it, given that the pores are not saturated.

Advantages of No-Fines Concrete (NFC)

1. NFC are used as a backfill material mainly in retaining wall construction, which can be performed quickly and with less excavation work.
2. NFC masses are permeable, that helps to be a superior wall drainage.
3. NFC backfill eliminates the need for compaction and compaction testing of the reinforced soil.
4. NFC have high frost resistance

Disadvantages of No-Fines Concrete ( NFC)

1. NFC has less strength compared to other concrete types due to the presence of voids.
2. Due to lack of strength and permeability, it is not a good option for R.C.C.
3. Small quantity production of NFC is difficult.
4. The consistency of NFC is difficult to measure.
5. It let water drain to it, hence improper design and planning for NFC can cause moisture penetration and related issues.

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