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Accelerated Concrete Bridge Decks

Presented by: Robert Rugg

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1 hour mix:- Pre-bagged product mixed on site.- Trial batch should be performed.- Coarse aggregate may be added for application

that exceed 2 inches.

- Pro: 1 hr to achieve 3000 PSI, 5000 PSI at 24 hrs.

- Cons: Limited to areas no larger than 10 SF. and should not be used for long term durability.

Accelerated Concrete Mixes

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2-4 hour mix:- Uses rapid hardening cement (RHC).- 0.37 W/C ratio. - Trial batch should be performed.

- Pro: Can be mixed on site, transit mixed or delivery from a ready mix concrete plant (RMC).

- Con: Mixed results on Freeze/Thaw & long term durability.

Accelerated Concrete Mixes

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4-6 hour mix:- Can be produced from by standard practices at

RMC Plant.- 0.35 W/C ratio.- Trial batch should be evaluated prior to use.

- Pro: Reasonable F/T durability can be expected.

- Con: Type III cement can be limited to certain producers.

Accelerated Concrete Mixes

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24 hour mix:- Mix type used on the I-690 bridge decks.- Class H (modified) mix achieving 3000 PSI in 24 hrs.- Maximum 0.40 W/C ratio.- Slump – 3-5”- Air Entrainment – 5-8%- 24 hour wet cure or until compressive strength is

met.- 10 year minimum service life can be expected.

Accelerated Concrete Mixes

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Case Study – I-690 EB3 Bridge Decks in the City of Syracuse

BIN 1051000, Spans 4 and 5 – Salina St. and Community LotBIN 1050852,

Franklin Street

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- I-690 EB was closed through the City of Syracuse.- 10 day target completion from time of I-690 closure to

the reopening of I-690 EB .- Incentive/Disincentive clauses were used.- Expected service life of deck to be 10+ years.- Bridges are expected to eventually be replaced with

the viaduct project.- Lot of press coverage and public outreach occurred.- Bridges (121’, 110’ & 62’) were re-opened after 8 days.- Parapets remained in place with some spot repairs.

Highlights of Project

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Project Photos

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Project Feedback

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What Went Smoothly- Work was accomplished safely.- Road closure duration was less than 8 days.- Project quality and finished ride quality are good.- Trucks used to catch deck removal made cleanup

easier/quicker avoided repairs to under bridge areas.- Rubber mats placed where trucks could not access

limiting the impact from falling debris.- Traffic was only slightly impacted w/ minimal

complaints. - WZTC was clear, public outreach was good.- Maintenance used closure to work on adjacent decks.

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What Could Have Been Improved?- Placing underdecking after the deck was removed

was cumbersome and time consuming.- Slurry ran down scuppers to under bridge areas

and left a film (later cleaned up). Methods to contain the slurry should could have been detailed.

- Penetrating sealer absorbed very fast. Special specification states 24 hours of air dry after saw cut grooving, manufacturer’s instruction say surface only needs to be clean and dry.

- Contractor’s communication/coordination between day and night crews could have been better.

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Material Observations- 24 hr. mix behaved unusually. Slump seemed to

increase during unloading, but then become unworkable within 30 minutes of discharge from the pump.

- Cylinder strength obtained (3000 psi) around 25 hours.- Pour ran smoother when discharge was at high end of

slump range (5”). Consideration should be given to allowing a higher range slump.

- Placement went well until the sun began hitting, at which point finishing became difficult and concrete began setting up quickly.

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Placement Feedback- Once the deck pour began, rejecting trucks would

have resulted in a cold joint due to the quick setup time.

- Rails were pulled after the deck set, leaving a grease residue in hole, which was grouted. The grout could pop out, but as this area is out of the wheel path and we’re only looking for 10 years it is unlikely to be an issue.

- Leaving a few feet of deck in place (from parapet) would provide a work area and a place to run rails.

- Deck was found to be 9” (8” per plan).

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Other Project Feedback- A 48 hour mix would have delayed the overall work

by only 1 more day. This mix would have given one more day of additional wet cure (longer service life expected) and is a mix that DOT has more experience with.

- With the jack hammering and full deck removal it didn’t seem that pointed tips were a detriment.

- Misting or placement at night would have helped with the deck pour.

- 50% expected camber was used.- 16” development length was calculated (vs. 24”).

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PDH Questions

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Question #1

What is one of the advantages of using Accelerated Concrete Mixes on roadway and bridge repairs?

A. Longer Service Life.B. Quicker reopening of the repaired area.C. Increase resistance to freeze/thaw.D. B & C.

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Question #2

As you significantly accelerate the time required to achieve compressive strength, you (generally) can expect the following:

A. Higher water to cement ratio.B. Higher air voids.C. Decreased durability.D. Easier finishing.

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Question #3Observations from the I-690 Accelerated Bridge Deck Project revealed what?

A. Bridge decks can be removed and replaced in less than 10 days

B. An accelerated mix can create difficulties and challenges in placing bridge decks.

C. Acceptable ride quality can be accomplished with a 24 hour mix.

D. All of the above.