FHWA Resource Center
Date: November 1, 2004
Subject : Minutes of October 28, 2004 Meeting of Prestressed Concrete Committee for
Economic Fabrication (PCEF): Quality Inn - Pottsville, PA.
To: PCEF Members
Self-introductions were made.
· Approval of Minutes from February 10, 2004 Meeting in Dover, DE
Bill Via made a motion to approve the minutes from the last meeting. Claude Napier seconded the motion.
· Phase I Report on the FHWA/MDSHA Delayed Ettringite Formation (DEF)Study.
Paul Finnerty of MDSHA was not present, therefore Lou Triandafilou gave the committee an update. Phase I study of 24 bridges is complete, cores were taken and petrographic analyses were conducted. Findings indicated that there is a definite presence of DEF in varying degrees in the majority of structures studied, whether precast or cast-in-place. This refutes the premise that DEF only exists in precast or prestressed concrete structures subjected to high temperature curing. Phase II funding has been awarded and the study will be underway soon. Its purpose is to enlarge the original bridge population to a statewide effort and to introduce additional testing methodology. Copies of the reports will be posted online for review.
All States are requested to review the reports and determine whether their participation in the study is warranted. Any states interested in participating in the future research may contact Paul Finnerty (410-321-4111).
Lou also mentioned that the Mid-Atlantic Region Technician Certification Program has developed an initial draft of a manual for precast concrete technicians. The manual covers “Best Practices” and will be distributed to the all DOTs in December for their review and comments by end of the year. This certification will be for precast operations only, and will not supercede PCI requirements for prestress concrete plants.
· HPC Project Implementation; PCEF Bulb-T Project Implementation; and Use of Self-Consolidating Concrete.
Each state was asked to provide a status and update concerning all three issues. Lou also mentioned that the FHWA Resource Center had developed a CD summarizing the states HPC implementation efforts to date and indicated that the information is posted on the HPC Website. Copies of the CD were made available at the meeting.
Virginia - Working on an end-result HPC (low-permeability) specification. Currently low-permeability concrete is being used on all NHS and Interstate projects bridge projects and on non-NHS bridges over 500 feet.
Thirteen (13) bridges have used PCEF Bulb-T’s; having proven themselves to be economical, (a reduction from $89/s.f. for all bridges bid in 2002 to $ 81/s.f. for PCEF bridges)
Their innovative bridge program is currently looking into the use of SCC and lightweight concrete in bridge beams. They will also be building a ultra HPC bridge using 24 ksi compressive strength.
Delaware - HPC is being specified on the Indian River Bridge Project.
They have not used the PCEF Bulb-T’s, but are considering them for use on two new projects.
The use of SCC is being made on a project-by-project basis; implementation is slow.
New Jersey - Have had enough experience with HPC now to use it on a routine basis.
No use of the PCEF Bulb-T shapes to date
They are currently using SCC at J&R Slaw, Inc. on a noise barrier project.
Pennsylvania- Penn State is currently on board conducting research for Department on HPC. One HPC deck was poured this year with use on several decks previously; about 2/3 of the 15 decks placed have had some minor problems. Minor problems have slowed the progress. I-99 project will be using HPC next year on bridge decks.
PCEF Bulb-T’s are now included in their standards, but no use of them to date. Design software will be made available to designers soon, and the DOT will be showcasing them to contractors.
Department is currently evaluating a PETA funded project conducted by Lehigh University which is evaluating SCC bridge beams. SCC use in precast area was being considered, but this effort has stalled, largely due to a lack of response to issues raised by the Department in a meeting held in October of 2003. PCAP will be proposing an ultra-high slump (11”) mix using viscosity modifying admixtures and high range water reducers.
N. Carolina - They currently have a prescriptive HPC specification.
PCEF Bulb-T’s are in standards, but with no use of them to date.
They have used SCC on some Type IV AASHTO bridge beams (two projects so far), but there have been problems noted with camber growth (1”). Dr. Paul Zia is doing testing at S&G Prestress.
Maryland - Two HPC bridge decks have been constructed to date with good results. HPC will also be used on the on the Woodrow Wilson Bridge Project.
A PCEF Bulb-T design may be used on a Baltimore City or County project next year.
Limited SCC use reported previously for precast items only
West Va. - No use of HPC reported.
No use of PCEF Bulb-T’s.
No SCC use reported, but a specification will be developed.
DC- Two bridge decks have been constructed using HPC (low permeability) specification, and 2 more are underway.
No PCEF Bulb-T’s used to date.
No SCC use reported.
Joseph Policelli (FHWA, Maryland) indicated that he is aware of three State DOTs that have specifications for SCC – Illinois, Ohio and California, with others looking into its use.
Although representatives were not present, it was noted that NYSDOT is specifying HPC in all new prestressed concrete beams. They allow a 1:1 substitution of PCEF beams for the New England Bulb-Ts. Also, they are allowing Schuylkill Products to develop an SCC mix that will be required on a bridge with congested rebar. RI has a low permeability concrete specification, and MA is interested in the direct substitution of PCEF beams for the New England bulb-Ts (as NY allows).
· Presentation on Completed NCHRP Study on Continuity and Splicing Prestressed Concrete Beams
Reid Castrodale of Ralph Whitehead Associates gave a presentation on NCHRP Project 12-57. The report was distributed in early 2004 and is available on the NCHRP website for download. The report was based on an overview of 252 spliced girder bridges (61 bridges were built since 2000). Most spans have been built in the southeast and Midwest. Current record span is 320’, built over a channel in FL. On a project with alternate bridge designs, spliced concrete girders won over steel girders.
Not much price information is available yet on spliced girder bridges. On the average, there is a 10% increase in span length just by using high strength/high performance concrete, and a 17% increase by using 0.6” diameter prestressing strands. A decked bult-T can achieve a 33% span length increase.
The study proposed LRFD revisions that were adopted in June 2004. The ductility of spliced girders is beneficial for seismic areas. Reid suggested that standard details were needed for this concept, and that issues related to lifting capacity and hauling need to be addressed. It was noted that there are 2 post-tensioning suppliers in the Mid-Atlantic region.
Reid will email his presentation to Lou T. so it can be placed on the FHWA Resource Center website (attached)
· Design Parameters & Standardization Subcommittee Report
Claude Napier of FHWA-VA Division office provided a status report. They have developed recommendations for steel diaphragm use. If the steel diaphragm is being used on a concrete beam bridge their recommendation is to “snug” the bolts. For steel diaphragms on steel beam/girder bridges, the standard ½ turn of the bolt would apply.
AASHTO is coming out with a new LRFD debonding recommendation using 25%.
The subcommittee is looking for guidance from the committee on how they should proceed with spliced prestressed girders. This use would allow them to be competitive with steel for longer spans. The recommendation of committee was to have them review the NCHRP report and provide feedback at the February 2005 meeting. These and other action items were discussed as follows:
· The subcommittee will re-issue the steel diaphragm standard drawing at the next PCEF meeting, deleting diaphragm spacing.
· The subcommittee will review NCHRP Report 517 and evaluate appropriate standard details that can be presented at the next PCEF meeting.
· Troy Jenkins volunteered to contact the PCEF member suppliers and develop a list of industry standardization issues that will be presented at the next PCEF meeting.
The issue of pre-paying for material (i.e. steel and strand) was discussed and referred to the Contracting Practices Subcommittee.
Hank Bonstedt agreed to convene the Subcommittee before the next full PCEF meeting in order to discuss options for materials on-hand payment to suppliers for such items as prestressing strand, rebar, bearing plates, etc.
· Presentation on Lehigh University Study on SCC for PennDOT
Dr. Clay Naito of Lehigh University presented current information and data on this study. Lehigh, in conjunction with Schuylkill Products, constructed two PCEF Bulb-T’s using SCC. Final report is due out by end of year, but preliminary results indicate that the beams performed well when compared to the test beams made with a conventional concrete mix. Material properties of SCC were comparable to conventional high early strength concrete (HES) mix designs. It achieved greater than 6800 psi compressive strength in 24 hours; 7-day compressive strength and tensile and rupture strengths were greater than the values for HES. Modulus of elasticity for the SCC beams was less than the HES modulus but still within AASHTO estimates. Creep and shrinkage values for SCC were less than ACI values.
SCC chloride permeability and plastic air content limits also met DOT requirements. Hardened air content was greater than 3.5%, and high freeze-thaw resistance was achieved along with moderate to low chloride permeability. There was no improvement in voids that appeared on the top on bottom flanges.
In destructive testing of SCC beams, it was noted that transfer length values were less than PCI, strand bond strength was borderline based on direct pullout tests, and there was no appreciable slip at ultimate load. Beams achieved about 105% of design strength.
Dr. Naito was asked to provide a copy of his presentation for distribution or placing on the resource center web site (attached).
· Materials & Construction QC/QA Subcommittee Report
Serge Ter-Arakelov of PENNDOT provided a status update of this subcommittee. Two meetings have been conducted since the last general committee meeting, once in July and once in October (minutes attached). The subcommittee is in the process of creating a matrix to illustrate each state’s QC material testing and testing frequency requirements. Hard copies of the initial draft were distributed to those DOT representatives we haven’t received responses from for their input and comments. A matrix is also being developed to demonstrate the SCC requirements for those State’s who have developed specifications and for other organizations (ASTM, PCI, etc.). The subcommittee would like to meet in January 2005 to review the matrices and make recommendations at the February 2005 general committee meeting.
The Subcommittee will report at the next PCEF meeting regarding common regionwide materials and testing frequency requirements, and on common SCC specification requirements.
· Presentation on FHWA HPC Technology Delivery Team’s (TDT) Nationwide Survey on HPC Implementation
Claude Napier made a presentation on the TDT survey findings. The findings were distributed on CD nationwide to FHWA and State DOT offices, as well as to LTAP Centers. The findings are also posted on the Team’s website. Claude stated that they were able to get 100% participation in the Survey. A future survey will be conducted with more detail/specific questions.
· Miscellaneous Topics
Lou T. asked the committee if they had any experience with prestressed members cured at high temperatures. Apparently a New Hampshire project had several beams cured at over 210 F for 14 hours. The only State with a similar experience was VDOT, which stated they found it had no adverse effects on the members.
Tom Drda of FHWA- NC Division wanted to know if anyone was aware of screed rail supports causing problems by being embedded in the relatively thin top flanges of bulb-T beams. No one was aware of any problems.
Lou T. asked Hank Bonstedt of the PA Prestress Concrete Association to give a brief presentation on a PENNDOT project that had several beams fall during construction. Five beams, approximately 120’ in length, fell on an I-80 project near Clearfield, PA. Early conclusions were that wind loads had caused the beams to fall before they were properly braced and secured. PCAP is currently working on recommendations for erection to avoid this from happening in the future.
· Next Meeting
The next PCEF Committee meeting will be held on February 7, 2005, from 1 – 5 pm. This will precede the Mid-Atlantic QA Workshop at the Clarion Inn and Convention Center in Carlisle, PA. The meeting adjourned at approximately 5:00 PM.