Concrete Industrial Pavements - Allan Cockerell... · Concrete Industrial Pavements • Client...

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Concrete Industrial Pavements Client Requirements Pavement Guidelines Subgrade & Sub-base Design Methods Flatness & Levelness Floor Finishes Joint Design

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

“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 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

• Flatness & Levelness.

Specifications

- Gap under straight edge / No

- FF & FL 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 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

“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 Screeduse 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

• 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

“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

- 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

“The Get Cracking System”

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