Concrete Industrial Pavements - Allan Cockerell... · Concrete Industrial Pavements • Client...
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Transcript of Concrete Industrial Pavements - Allan Cockerell... · Concrete Industrial Pavements • Client...
Concrete Industrial Pavements
• Client Requirements
• Pavement Guidelines
• Subgrade & Sub-base
• Design Methods
• Flatness & Levelness
• Floor Finishes
• Joint Design
• Pavement Guidelines.
C & CA Guidelines / last update 1999.
AS3600 Concrete / confusing.
ACI Guidelines / regularly updated.
UK Concrete Society Technical Report TR34
• Subgrade & Sub-base.
Uniformity of subgrade strength.
Sub-base - uniform strength- increase effective subgrade
strength- construction platform- use of sand for sub-base
• Design Methods.
Simplified thickness design / light loads.
Rigorous thickness design / Coffey Partners International.
Other design considerations.
• Other Design Considerations.
Role of Steel Mesh
- Does not prevent concrete cracking- Restricts opening of concrete cracks- Does not increase load carrying
capacity
• Other Design Considerations.
Design of Steel Mesh- Length over which mesh is continuous- Subgrade friction- Thickness of pavement- Small pours 0.15%- Pours > 80 metres 0.6% to 0.7%
• Other Design Considerations.
Design of Steel Mesh- Length over which mesh is continuous- Subgrade friction- Thickness of pavement- Small pours 0.15%- Pours > 80 metres 0.6% to 0.7%- Cutting of every 2nd bar in mesh
Thicker pavement cheaper than more steel
• Other Design Considerations.
- Tilt-ups tied to concrete pavements.- Unplanned cracking of pavement.- In fire tilt-ups must not fall outward.
> Portal Frame Buildings with tilt-ups• Knee Ties
> Roof Braced Buildings with tilt-ups• Roof Frame / Tilt-up connection
• Floor Finishes.
Critical to life of pavement.
- don’t add water when steel troweling
- use of ride-on trowel machines
Joint Design / Pavement Problems
• Joint failure unlikely to kill anyone.
• Joint repair cost = construction cost.
Joint Problems are on the Increasedue to use of:
• Early Sawcutting.
• Laser Screeds.
• Small diameter, hard wheeled forklifts.
Early Sawcutting
• Timing of sawcut important- difficult to control
• Avoid problems by:-- not sawcutting too early- use cardboard spacers at joint
intersections
Laser Screed Advantages
• Workers with strongest back no longer critical.
• Speed of slab construction.
• Accuracy of finished surface.
Laser Screed Pavement Problem
1. Slab curling if joints too widely spaced.
- Solution – reduce sawcut spacing to about 5 metres
2. Sawcut that cracks first becomes “dominant”- No Solution to date
Laser Screed Pavement Problem
• Steel edging cast in at perimeter joints.
Has been offered as a solution for “dominant” perimeter joints.
Can create more problems than they solve.
Laser Screed Pavement Problem
• Unable to match accuracy of Laser Screed.
• Movement of steel during construction.• Gap between steel edges.• Expensive to do properly.
Difficulties with use of steel edging:-
Laser Screed Pavement Problem
Laser Screeds allow big concrete pours.
Big concrete pours create “dominant” joints.
Forklift Pavement Problem
• Joint damage slow with rubber tyred forklifts.
• Joint damage fast with hard wheeled forklifts.- Damage faster with wider joint opening
Forklift Pavement Problem
• Semi-rigid materials used to fill joints.
• Semi-rigid materials allow only small joint opening.
• Semi-rigid materials no good for “dominant” joints.
Laser Screed/Forklift Pavement Problems
- Eliminate all “dominant” joints.by cracking all sawcuts mechanically.
- Space sawcuts at 4.5 to 5m centres to minimise concrete curling at joints.
Common Sense Solution