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STRUCTURES TEAM


PRESTRESSED CONCRETE COMMITTEE FOR ECONOMICAL FABRICATION MEETING
SEPTEMBER 3, 2003
MDSHE DISTRICT 7 OFFICE
BUCKEYSTOWN, MARYLAND

MEETING MINUTES

A. Introduction and opening Remarks/Approval of Minutes from February Meeting.

Mr. Lou Triandafilou of the FHWA was not able to attend the meeting due to illness. In his absence, Paul Finnerty from MDSHA and Robert Horwhat from PennDOT conducted the meeting. The meeting was convened at 9:00 am and the participants were welcomed and were asked to give a self-introduction. A current mailing list was not distributed and will be updated and verified at the next meeting. The minutes from the February 2003 meeting in Charleston were adopted as written by a motion from Claude Napier, FHWA and a subsequent second to the motion.

B. Update on MDSHA’s Field Survey of Delayed Ettringite Formation

Dr. Richard Livingston, Senior Research Scientist, from the FHWA Turner-Fairbank Highway Research Center gave a presentation to update the DEF research project currently underway in cooperation with the University of Maryland. Paul Finnerty is MDSHA’s technical liaison for this study. Dr. Livingston gave a brief but concise overview of the findings to date since the beginning of the project in the spring of 2001. He outlined the preliminary steps that were taken to set up the laboratory program at the FHWA facility and at the College Park Campus. Additionally, the structures chosen for the field cores were identified as well as the equipment used to obtain data from each of the bridge sites.

Dr. Livingston stated that of the structures that were studied to date, the majority showed evidence of secondary ettringite formations. He further indicated that in order to expand the number of structures to be studied, he and Dr. Amde will be developing a proposal for a second phase to the study and will hopefully begin work in the Spring of 2004.

A brief discussion with some questions followed and it is anticipated that we will have Dr. Livingston update the group as to the future findings at an upcoming meeting.

C. Status reports From the States on Implementation of PCEF Bulb-T Shapes and Implementation of HPC.

MDSHA has a new representative from their Bridge Development Division on this committee. He did not have information as to any upcoming projects at this time using the bulb-t design. He will have a more in- depth report at the next meeting. As reported at the meeting in Charleston, WV, Maryland had one project in the design phase using bulb-T at that time. Current efforts with HPC are limited to bridge decks using lightweight HPC. Hopefully, there will be some projects using HPC for AASHTO girders or Bulb-T shapes.

DelDOT is still looking for their first bulb-T application. As of this date, there have been two bridges constructed and one superstructure using HPC. Microsilica was used as the pozzolan. No evidence of early shrinkage cranking at this time. The permeability of the mixes was less than 1000 coulombs.

VDOT is using all bulb-t beams and is planning to do a project using a 93” high bulb-t shape. Since they are a lead state in HPC they have used these mixes extensively for bridges and decks including some 10,000-psi applications and some lightweight concrete.

PennDOT has not used bulb-t’s to date. They have concerns with redecking i.e. thin top slabs may be an issue. They are currently reviewing continuity issues. The use of HPC on decks is increasing. They have developed standard specification criteria using rate of strength gain and a maximum compressive strength of 6000 psi. They have also recently eliminated the shrinkage criteria.

WVDOT has no bulb-t applications to date. Their prestress producers are located primarily in Kentucky. Still evaluating use of this shape for future construction. Nothing to report on use of the HPC.

NCDOT has nothing to date on the PCEF Bulb-T’s. They have used the PCI shape. North Carolina minimizes the volume of pozzolanic material for deck mixes in certain districts. US 64, a five mile long bridge structure with HPC and a 100 year service life will be developed using a corrosion model. Each element of the bridge will be based on a chloride concentration estimate. The air is not specified.

District of Columbia was not able to report on the bulb-t issue. As for HPC, Kwabena indicated that they used this mix on approximately 60% of their structures with a 4500-psi strength and a maximum permeability of 1500 coulombs. The North Capitol Street Bridge will be a HPC Design.

NJDOT was unable to report on the bulb-t issue at this time. HPC will be used on their Long Port project for piles, piers caps and girders. Their Victory Bridge project will use HPC for segmental box columns and footings. A full battery of qualification tests will be run, including creep, shrinkage, permeability and a minimum 8000-psi compressive strength.

NYDOT currently uses New England Bulb-T shapes. They allow the substitution of PCEF shapes w/o calculations. They are in the process of developing new standards. They have used HPC on decks for the last 10 years. The main problem with the decks is cracking even with 14-day wet cure. They have been using fibers recently but the results have not been quantified. Next year all decks will be HPC. Bridge beams will use 10,000 psi concrete.


D. Study of Self-Consolidating Concrete-Presentation by Dr. Celik Ozyildirim, VTRC

Dr. Celik Ozyildirim of the Virginia Transportation Research Council gave a presentation on the VTRC/VDOT work with SCC to date (attached). Based on recent experiences in the precast industry, Celik gave an overview of the mix design with the specific parameters and usage of plasticizers and viscosity modifiers to achieve the desired properties which enable the concrete to have an increased ability to fill forms, pass through very tight steel patterns w/o the use of pencil vibrators and finally, an increased stability of the concrete mix.

Celik stated that three of the major benefits of SCC were faster construction turn around, reduced noise at the time of casting and decreased labor cost.

Testing included the slump flow test which is a measure of the flow separation resistance, the j-ring test, the L- Box and the U-Box which basically measure the passing ability of the mix. Additionally, to measure the ability of the mix to maintain consistency and not to segregate, a method known as the column test has been proposed to ASTM. This test uses a 4” diameter PVC pipe approximately 4’ long to measure the amount of segregation, if any. The tube is filled with the SCC and and the top 4” and bottom 4” are separated from the rest of the sample. The specimens are weighed and graded to check the aggregate distribution from top to bottom of the tube.

Celik indicated that there are some concerns with the use of self-consolidating concrete, regarding the formwork integrity, loss of stability, the air void system and increased shrinkage.

Current applications are in areas of dense steel placement and thin walls. Virginia DOT’s first project using SCC was a BEBO arch bridge in the Frederickburg,VA area and was cast by Old castle-Rotondo Precast. Also, a pretressed concrete bulb-t girder from Bayshore Concrete Products was fabricated with some bug holes at the bulb end of the beam.

E. Materials, QA/QC, Construction and Production Subcommittee Update

The subcommittee met in Hagerstown,MD on August 28, 2003 to discuss the future endeavors of the group and the inclusion of the Construction and Production subcommittee to form one active subcommittee. Attending the meeting on the 28th were: Paul Finnerty of MDDOT, Robert Horwhat of PennDOT, Joe Policelli of FHWA and Paul Ramsburg representing Oldcastle-Rotondo Precast.

Some of the discussion focused on what the committee should adopt as their next task to accomplish. One suggestion was to create a guideline for Q/C plans for use in prestress plants. Another potential topic was the use of self-compacting concrete in the prestress industry. It was finally decided that a survey be developed and sent to the full committee so that a discussion could take place at the next meeting of the full committee in February. Additionally, the sub-committee will carry on with the above mentioned topics as well.

Representatives from the former Construction and Production sub-committee were not in attendance at the meeting on the 28th. We need to discuss with Lou some possible strategies in order to get this sub-committee combined. The next meeting of our group will be scheduled at the gathering in Dover. It is anticipated sometime in March.


F. NCHRP Study on Splicing Haunched Girders.

Due to a scheduling conflict, Reid Castrodale was unable to give this presentation. Rodger Rochelle from NCDOT presented material on the State’s research program.

G. Design Parameters and Standardization Sub-committee Update.

Claude Napier, FHWA, gave a presentation on the responses to a questionnaire on design considerations (attached). There were 13 states surveyed with 7 of the responses included on the formal presentation. PA and NY responded on the day of this meeting and will be added to the CD as an update version. DC will submit a response subsequent to the meeting and be added later to the CD.

NOTE: The next meeting will be held prior to the beginning of the QAW sessions in Dover, DE on Monday Feb. 9th 2004.

Meeting adjourned at 1:30 pm

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