Concrete Industrial Pavements Client Requirements Pavement Guidelines Subgrade & Sub-base Design Methods Flatness & Levelness Floor Finishes Joint Design
Concrete has a mind of its own. It will crack where it wants to
Las Vegas Convention Centre home to World of Concrete
Client Requirements. Developer Clients / Tenants unknown. Client s existing pavements / Inspect.
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.
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 2 nd 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
Flatness & Levelness. Specifications - Gap under straight edge / No - F F & F L numbers / Yes
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 Increase due 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
Sawcut Damage from Early Cutting
Sawcut Damage from no cardboard spacer
Laser Screeds
Laser Screeds SXP
Laser Screeds Copperhead
Laser Screeds Mini Screed
Laser Screed Advantages Workers with strongest back no longer critical. Speed of slab construction. Accuracy of finished surface.
Laser Screed Limitations Edge of Pours must be hand finished
Laser Screed Limitations Edge of Pours must be hand finished
Laser Screed Limitations SXP Laser Screed on Bridging
Laser Screed use is on the Increase.
Laser Screed Pavement Problem 54m x 36m single pours
Laser Screed Pavement Problem 20 dia bars at 150 crs
Laser Screed Pavement Problem Mesh stops at sawcuts & dowels used
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 Dominant Sawcut crack width after 3 months
Laser Screed Pavement Problem Perimeter joints are also Dominant
Laser Screed Pavement Problem No easy repair for Dominant Construction Joint
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 Difficulties with use of steel edging:- Unable to match accuracy of Laser Screed. Movement of steel during construction. Gap between steel edges. Expensive to do properly.
Laser Screed Pavement Problem Steel edging to Construction Joint after 3 months
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
Hard Wheeled Forklift
Forklift Pavement Problem Failed Sawcut Joint
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 Common Sense Solution - Eliminate all dominant joints. by cracking all sawcuts mechanically. - Space sawcuts at 4.5 to 5m centres to minimise concrete curling at joints.
The Get Cracking System
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