proper placement of concrete decks
TRANSCRIPT
Proper Placement of
Concrete Decks
Some Rules for Being a
Good Inspector
• Know the goal
• Enforce the specification
• Understand the contractor’s position
• Make sure the contractor understands
your position
Stiff Mixture
Wet mixture
• Know your technical limits—particularly on
bridge projects
• Develop a strategy for getting information
when you need it
• 3 major goals for any project:
1. Schedule
2. Budget
3. Quality
Some Rules for Being a
Good Inspector
Long after people forget the schedule and
budget, they will remember the quality.
This is your legacy and contribution to
our infrastructure.
Concrete Deck Construction
Three Parts to Deck Inspection:
1. Pre-placement Inspection
2. Placement Inspection
3. Post-placement Inspection
If the checklist below were followed on all
deck construction, we could have avoided
the vast majority of our deck problems.
Part 1: Pre-placement Inspection
Chairs: tipping, slippage, stacking,
consolidation
Forms: sturdy, clean
Reinforcement: size and type, clean
Shear Studs: spacing, height
Joints
Concrete Deck Construction
Deck Forms: Continuous Chairs
Are the bar size and spacing correct?
Typical transverse bar spacing is in the 5”- 7” range.
This deck is missing every other bar for a 14” spacing,
which should be a red flag that a problem exists.
Are the joints formed with
compressible material?
Use rigid foam or rubber rather
than timber
(Part 1)
Trucks
Screed set properly
o Vibrating unit
o Burlap drag
Backup vibrators
Clean lines for pump
Mobile mixer calibration
Concrete testing equipment
o Specs and calibration
Curing box with recording
thermometer
o Continuous temperature data
that can be printed
Concrete Deck Construction
Checklist
Is the concrete deposited using a chute?
(Aluminum chutes or lines are not permitted)
Is the screed set properly to provide
the specified crown and grade?
Check before placing concrete
Tachometer
(Part 1)
Aggregate Storage
Contingency Plan
o Equipment breakdown and inclement weather
Trial Batches
o Completed and results submitted and approved
Concrete Deck Construction
Checklist
(Part 2)
Forms are pre-warmed in cold weather
Aggregates kept from freezing
Ingredients cooled in hot weather
Use flaked or shaved ice
Monitor rate of evaporation
Concrete Deck Construction
Checklist
Part 2: Placement Inspection
Light availability
Certified Personnel
Formwork
Proper documentation
o Form TL-28a
Concrete protected against the elements
Concrete Deck Construction
Checklist
(Part 2)
Added water
Concrete delivery within time limit
Placement against fresh batch
Placement as close as possible to the final location
Even distribution
Concrete free from segregation
Concrete Deck Construction
Checklist
Place concrete as close as possible
to the final location in the structure
Chute outlet does not reach entire pour
(Part 2)
Avoid concrete contact with reinforcing bars
Dropping concrete
o Distance < 5’
o Drop chutes or tremie to direct the fall, no free fall
Avoid time delay
Concrete covered if delay
Moved by vibrators: NO
Concrete Deck Construction
Checklist
Is concrete moved by vibrators?
(Unacceptable Practice!)
(Part 2)
Vibrator inserted vertically and in grid pattern
Proper consolidation conducted even along the
edge and joints,
Over vibration may cause segregation
Concrete Deck Construction
Checklist
Are vibrators inserted in a grid pattern?
Consolidation
Is vibration causing segregation? (excessive mortar brought to the surface)
Excessive mortar at surface
Segregation
(Part 2)
Sufficient screed support
Sufficient concrete rolling in front of the rollers
Moderate amount of paste or mortar on the surface
of the concrete after screeding?
Concrete Deck Construction
Checklist
Is there enough concrete rolling in
front of the rollers?
Concrete in Front of the Rollers and the Auger
Is there only a moderate amount of paste or mortar
on the surface of the concrete after screeding?
Excessive mortar at surface
(Part 2)
Apply fog mist to concrete surface immediately after
screeding. Do not use a hose or pressure washer.
Do not spray water on the concrete before the screed
Only moderate hand finishing
Low areas
Wet burlap application
Specimen box immediately after casting
Concrete Deck Construction Checklist
Do NOT spray water on the
concrete surface before the screed
Fog Misting (Correct Procedure)
Water applied to
concrete surface
after screeding
should use a fog
mist. Do not use
hose nozzle.
Is any hand finishing
moderate?
Excessive hand finishing
Is the burlap wet and applied in a timely manner? (Surface drying! )
Is the burlap wet ? (but not dripping!)
Wet burlap
Proper Application of Wet Burlap?
Place Blankets Immediately After
Screeding
Proper Application of Wet Burlap
Burlap marks indicating timely
application of burlap.
Plastic Cover to Prevent Loss of
Moisture
Ties & Weights
help keep plastic
in place
Part 3: Post-placement Inspection
Daily checks on wet burlap
Freeze protection
Proper use of curing compound
Monitor concrete temperature
Checking joints
Alignment, formwork removed, workmanship
Low spots
Concrete Deck Construction
Checklist
Cold weather - Concrete Temperature
Cracks should be kept to less than .10mm. Cracks greater
than .20 mm (.01”) will allow intrusion of water & chlorides
& should be repaired either with epoxy or sealant
Cracks over .20 mm
should be repaired
Plastic shrinkage cracks – usually appear within the first
week or two
Plastic shrinkage cracks – usually appear within the first
week or two
Plastic shrinkage cracks – usually due to improper curing
and should be the responsibility of the contractor
Drying shrinkage cracks – may occur up to 6 months after
pour. Often transversely oriented and deep.
Checking for Low Spots:
Is the surface checked for low spots?
Checking for Low Spots:
Is the surface checked for low spots?
Checking for Low Spots:
Is the surface checked for low spots?
Conclusion
Proper attention to details will result in
quality construction. Structures built
with quality are safe, durable, and
cost effective.
Thank you.