READY Floor Guidelines

READY Floor Pour Foundation slab - Allied Concrete

Follow these guidelines when placing and finishing an Allied READY Floor as per CodeMark certificate conditions.

Subbase/Subgrade
It is important that the support provided to a slab from the subgrade/sub base is as assumed in the design.
It is essential that the subgrade and any sub base always be prepared in accordance with the recommendations of a qualified geotechnical engineer or soils consultant in order to achieve the values for CBR or modulus of subgrade reaction used in the slab design.

The prepared subgrade/sub base should also extend past the edge of the formed slab and the finished levels selected such that water drains away from the slab edges. 
For domestic or other slabs designed in accordance with NZS3604, the slab should be supported on ‘good ground’ (as defined in NZS3604) and prepared in accordance with this standard.

 

Placing
Good practice needs to be followed for any concrete placing if cracking is to be avoided and a durable ground slab is to be provided. Particular attention should be paid to the following:

  • Ensuring the concrete is vibrated and well compacted, placed, finished and cured to give a high quality surface finish that is not prone to dusting.
  • Eliminate thickenings at slab joints and edges to reduce shrinkage restraint or alternatively select joint locations to accommodate them. 
  • Isolate internal shrinkage restraining elements such as columns, pedestals, etc. by using isolation joints or advantageously locating control joints.
  • Install saw cuts as early as possible, ensuring the concrete has sufficient strength to avoid ravelling to the edges of the joints or pulling out of fibres and/or aggregate.
  • Avoid early drying by applying evaporation retarders (aliphatic alcohol) and straight after finishing apply effective curing using water or membranes.
 

Finishing
When finishing READY Floor the only real difference is timing. If you are going to achieve a relatively fibre free surface follow these steps:

  • Screed off concrete to finished levels using normal screeding tool.
  • Bull float to push down aggregates and fibres left at surface during screeding operation. An extra pass or two with the bull float is recommended with SFRC in order to get 2-3mm of paste at the surface of the concrete to cover the fibres and coarse aggregates.
  • Finish the edges of the placed concrete with a steel trowel and the internals with power floats or by hand where access is limited.
  • Squeegeeing surface water from concrete prior to finishing may lead to increased incidence of fibre on the surface.
Please Note:
  • The timing when stage three is started will determine the number of fibres at the surface of the concrete.
  • Do not finish too early to acheive a fibre free surface.
  • Undertake saw cutting at the right time to avoid random cracking


Saw Cutting
Where saw cuts are to be provided to control cracking the type of saw cutting to be used should vary with the location of the slab.

Indoors: Concrete slabs cast indoors are typically not subjected to sudden and significant changes in the prevailing ambient conditions, so it is quite normal to wait between 24-48 hours before saw cutting when a conventional wet blade is undertaken. Cutting should always be undertaken prior to the commencement of any random cracking. The stronger the concrete is when cut, the less likely will be the occurrence of any ravelling to the edges of the joints or pulling out of fibres and/or aggregate.

Outdoors: Concrete slabs cast outdoors can experience sudden changes in ambient conditions, potentially causing random cracking. This is most likely to occur when cold nights follow mild sunny days and the placed concrete has delayed setting times and a slow rate of strength gain. It is recommended that slabs cast outdoors are cut the same day using saws specifically designed for cutting “Green” concrete. For steel fibre reinforced concrete it is recommended that the “softer free cutting” blades such as the Series 2000 or Series 1000 blades with a new skid plate be used and that the concrete be left about one hour longer than normal before cutting.