Proper Placement of Concrete Decks

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.