Stevenson No Fines concrete is a specially designed concrete with a specified void content that allows large volumes of water to quickly fill the voids between the aggregate particles. It is formed by eliminating the fine material from the regular concrete mix. Single-sized coarse aggregates are surrounded and held together by a thin layer of cement paste, which gives strength of concrete.

No Fines concrete has large uniformly distributed interconnected voids (up to 30%) between the aggregate particles. This structure makes it ideal as a free-draining medium. It is available in two aggregate sizes – 19mm and 10mm. No Fines (pervious) concrete is made from carefully controlled amounts of water and cementicious materials used to create a paste that forms a thick coating around aggregate particles. Unlike conventional concrete, the mixture contains little or no sand, creating a substantial void content – between 15% to 30%.

Using sufficient paste to coat and bind the aggregate particles together creates a system of highly permeable, interconnected voids, which drain quickly. Both the low mortar content and the high porosity reduce strength compared to conventional concrete, but sufficient strength is readily achieved for many applications.

No Fines concrete allows large volumes of water to pass through each square metre of the material. By allowing rainwater to seep into the ground, pervious concrete can be instrumental in recharging groundwater and reducing stormwater runoff. This capability can reduce the need for retention ponds, swales, and other stormwater management devices. Pervious pavement integrates hardscape surfaces with stormwater management.

Typical features:

  • Ease of placement from a concrete truck
  • No compaction required
  • Hardens to maintain the form it is placed in
  • Consistent quality of the finished product
  • Is environmentally friendly

Benefits:

  • Cost benefit – No Fines is delivered from the back of a concrete truck.
  • Lower cost due to lower cement content.It is easy to screed and hardens to the shape in which it is poured.
  • No compaction is required.
  • The resulting concrete has an open texture that provides a free-draining concrete.
  • Enables more efficient use of residential land.
  • Local bodies require a maximum impermeable area.
  • Lower density.
  • Relatively low-drying shrinkage.
  • Better insulating characteristics than regular concrete due to the presence of large voids.
  • We can modify the strengths, aggregate size, shape and void contents to suit many applications, filtration and sedimentation requirements.
  • (Please refer to the relevant local regulatory body requirements. NZ standards specification for concrete production – NZS3104:2003)
 

Suitable for:

  • Fill behind retaining walls to dissipate water pressure
  • Drainage layers in reservoirsSite concrete to provide a dry working base
  • Foot traffic areas
  • Beneath pavements to channel water away
  • In situations where water run-off is undesirable
  • For landscaping

Frequently asked questions:

What is the typical strength of No Fines concrete? Typical strengths are in the range 5 to 13 MPa. (Mega-Pascals).

What is the shrinkage rate of No Fines concrete? Much lower than conventional concrete, e.g. in the range 0.0002 – 0.0003 microstrain.

What is its permeability? High. Water and air flow easily through it, but no quantitative data is available. Blocking of the pores is more likely to occur the smaller the aggregate size.

What is the aggregate size? 10mm to 20mm are the most common.

What are the applications for No Fines concrete? Used as drainage behind walls, paving, tennis courts, drainage layer levelling courses.

What are the advantages of No Fines concrete? Lower cost due to lower cement content, lower thermal conductivity, no segregation and, better insulating characteristics than conventional concrete because of the presence of large voids.