Joint free slabs: construction checklist

Building Platform Preparation:

1. Maintain slab thickness – Ensure that the slab throughout is the specified thickness "10mm
2. Set out internal ground restraints to suit the set out of the crack inducer grid, and thereby avoid positioning crack inducer grid junctions over ground restraints. Note that the crack inducer grid should be set out as indicated on the drawings to avoid cutting in around the perimeter.
3. Remove all loose material from the building platform, especially from the ground restraints. Any crusher dust or the like used to level the building platform must be compacted.
4. Loosely fit the membrane to all ground restraints and other surface depressions to ensure the concrete will be in full and continuous contact with the excavated surface. A light duty membrane is preferred – 100 micron recommended.

JFS Grid Installation:

1. Set out the crack inducer grid as shown on the drawing to avoid cutting in around the perimeter.
2. Do not install the grid upside down – The flat base of the crack inducer grid junction is to lay directly on the ground and the projections on the top are provided to restrain the reinforcement mesh – refer to the detail on the back.
3. Install the grid in straight lines to ensure the junctions are positioned to provide proper support for the reinforcement mesh. Note that the tubes are cut to length for a one metre spacing of the junctions.
4. Spike the junctions to the ground every so often as necessary to prevent the grid being inadvertently moved. Intermittent sheets of mesh placed onto the junctions can also be used for this purpose.

Placing of Reinforcement:

1. Adjust laps in the reinforcement mesh – Install the specified mesh reinforcement using the lap details and staggered placement shown on the drawing – refer also to the detail on the back.
2. Support mesh on grid junctions – Ensure the sheets of mesh are supported throughout on the grid junctions – refer to the detail on the back. Note that the bars in the mesh should always cross on the junctions if the sheets are installed correctly. Marginally adjust the end and side laps in the mesh as necessary to compensate for any manufacturing discrepancies in the mesh sheets.
3. Tie all end and side laps in the mesh reinforcement.
4. Install HD12 trimmer bars as detailed on the drawings – refer also to the detail on the back. Ensure all slab perimeters in each pour, and all re-entrant corners and penetrations are trimmed. Install bar chairs as necessary around the perimeter and penetrations to ensure all trimmers are adequately supported at the correct height.

Concrete Placement and Curing:

1. 56 day drying shrinkage – Order concrete with a 56 day drying shrinkage of 600 microstrain U.N.O.
2. Dampen the ground immediately prior to placing concrete in situations where there is no membrane.
3. Super plasticiser – the use of super plasticiser is highly recommended to increase workability and to assist with the control of drying shrinkage.
4. Prohibit the addition of water to the concrete mix after any truck has departed the batching plant.
5. Compact all concrete using mechanical vibrators.
6. Cure all concrete for seven days after placing and use aliphatic alcohol as and if necessary during placing.

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