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South Dakota Department of Transportation
Project Synopsis
SD1998-06


Title: Evaluation of High Performance Concrete in Four Bridge Decks as well as Prestressed Girders for Two Bridges
Project Researcher: V Ramakrishnan, SDSM&T
Project Manager: Dan Strand
Research Period: - 8/15/2001
Status:
Cost: $200,000.00

Problem Statement: Due to tightening budget constraints, transportation engineers are challenged to construct transportation facilities economically with an increase in performance. However, simultaneous improvements in cost and performance are unlikely unless material properties or construction methods can be enhanced. High performance concrete (HPC) may be utilized to enhance the desired properties for a given application. Recently, HPC was redefined and, although this definition is several pages long, may be summarized as the enhancement of certain desired concrete properties for a given application beyond the properties for plain concrete.

There are times when bridge designers are concerned with overhead clearances for highways beneath bridges, the need for increased span lengths without increasing girder depth, or may desire to reduce the number of girders for a bridge, all of which could require HPC. For states in the colder regions of the United States, de-icing chemicals are used for removing ice from driving surfaces. These chemicals pose problems on pavements and bridge decks. Due to the concrete's permeability as well as any cracking, chemicals can penetrate the concrete causing rebar corrosion and concrete deterioration over time in bridge decks shortening deck life.

Understanding the possible benefits of HPC, SDDOT's bridge designers have a desire to construct and evaluate four bridge decks as well as prestressed girders for two bridges. While HPC may appear to have higher initial costs, these higher costs may be offset through reduced girder depths, reduced number of girders, reduced number of substructure units, or reduced concrete deck thickness. HPC in concrete deck surfaces can result in a higher resistance to chloride intrusion, less surface cracking and greater resistance to freeze-thaw deterioration. Therefore, where HPC is utilized, there is a potential to reduce repair and replacement costs.

SDDOT has the opportunity to incorporate HPC into two bridge decks on I-229 in Sioux Falls as well as the decks and prestressed concrete girders for two additional bridges on I-29 north of Sioux Falls. However, trial HPC batches should be prepared and the necessary fresh and hardened concrete property testing must be conducted to ensure that the desired concrete properties are achieved. Some of the fresh and hardened concrete properties for each HPC mix are unknown and need to be determined prior to the construction of the girders and decks. Also, instrumentation may be needed to monitor the performance of the decks and girders. Some properties in question for HPC's are: 28 day compressive strength, obtaining strand release strength in a specified time, thermal properties, creep, shrinkage, and elastic shortening for high strength concrete with limestone and quartzite aggregates; permeability and crack potential of concrete utilizing fly ash, silica fume, or a combination of fly ash and silica fume with limestone and quartzite aggregates; etc.



Findings: The South Dakota Department of Transportation constructed two three span high performance concrete (HPC) bridges in the summers of 1999 and 2000. The twin prestressed girder bridges are located along Interstate 29 near Sioux Falls, South Dakota. In each bridge instrumentation was installed in two end span girders and in the deck of an end span of these structures. This report presents the results of the laboratory trial batches and testing to optimize HPC mix designs for the girders and the decks. Detailed strain histories in the girders and in the decks, and deflections of the girders prior to installation in the bridge and after they were installed in the bridge over the two year period are also reported. For the high performance bridge deck concrete two different coarse aggregates were used (quartzite and limestone) and ten mixes were cast with each aggregate. In each mix the percentage replacement of cement by weight with silica fume and fly ash was varied, keeping the w/c ratio constant. For the high-strength bridge girder concrete, twelve mixes were cast varying both the percentage replacement of cement with silica fume and the w/c ratios. The percentage replacements of silica fume investigated were 7%, 10% and 12% and the w/c ratios investigated were 0.28, 0.30, and 0.32. All concretes were tested for compressive strength, static modulus, modulus of rupture and chloride permeability. The addition of fly ash and silica fume reduced the chloride permeability of concrete significantly while increasing the compressive strength. Based on the analysis of results obtained, one mix was chosen, as the best mix having all the properties required for a high performance bridge deck. Another high strength HPC mix was selected for the girders to satisfy the strength requirements for the early release of prestress strands and at 28 days. Detailed compressive strength time histories out to ages of one year were developed for the concrete used in the structures. Tests to determine the modulus of elasticity for both the girder and deck concrete were conducted at selected ages out to one year. Shrinkage blocks were cast and instrumented in order to monitor the development of shrinkage strains in the girders and the bridge decks. The total cost of the HPC bridges and the standard SDDOT present design bridges is almost the same. However the life-cycle cost may be cheaper because of the anticipated longer life and reduced maintenance costs for the HPC bridges. Conclusions and recommendations are included in the report.

Research Objectives:
1  To recommend HPC mix designs for use in bridge decks and prestressed girders.
2  To evaluate the constructability and performance of HPC in bridge decks and prestressed girders.

Research Tasks:
1  Review and summarize literature relevant to HPC’s use for bridge decks and prestressed girders as well as instrumentation methods used to monitor them.
2  Meet with the Technical Panel to review the research topic and work plan.
3  Determine the HPC mix design which best improves the desired properties for the bridge decks and prestressed girders by testing trial batches.

  • Reduced permeability and low crack potential are the properties w
    4  Prepare and submit a field sampling and testing program for determining the deck and girder HPC fresh and hardened concrete properties to the technical panel for approval.
    5  Prepare and submit instrumentation and evaluation plans for the HPC decks to the technical panel for approval by April 1, 1998 and for the HPC girders by October 1, 1998.
    6  Attend preconstruction meeting(s) to ensure the HPC mixes, sampling and testing, instrumentation, curing methods, and monitoring are understood by all.
    7  Purchase and install the approved bridge deck and prestressed girder instrumentation for the trial as well as actual HPC plaecements.
    8  Attend the construction of a trial slab on grade utilizing the recommended HPC mix for the bridge decks. Conduct the sampling and testing for the trail placement as approved in Tasks 4 and 5 above. As a result of the trial, recommend necessary HPC
    9  Attend the construction of the HPC bridge decks and prestressed girders. Conduct the sampling and testing as approved in Task 5 above. In addition, record weather conditions, and observe and record construction methods.
    10  Review and evaluate two curing methods on the two bridge decks on I-229. One deck will use SDDOT‘s standard method of curing and the second will utilize a soaked 1” cotton blanket backed with polyurethane in lieu of the burlap. Based on the findings
    11  Conduct performance tests of hardened concrete on the collected field samples for the bridge deck and the prestressed girders as approved in Task 5.
    12  Periodically collect the data from the instrumentation and conduct visual condition surveys of the constructed HPC bridge girders and decks as approved in Task 6.
    13  Based on the data collected from the instrumentation as well as the condition surveys, evaluate the performance of the HPC bridge girders and decks.
    14  Determine the cost difference for the HPC decks and girders as compared to costs for SDDOT present designs.
    15  Recommend mix design, testing, and construction guidelines for using HPC in prestressed girder and bridge deck applications based on results observed from this study.
    16  Submit a final report summarizing relevant literature, research methodology, test results, specifications, design standards, conclusions, and recommendations.
    17  Determine the HPC mix design which best improves the desired properties for the bridge decks and prestressed girders by testing trial batches.

  • Reduced permeability and low crack potential are the properties w

    Documents Available:
    sd1998_06_Final_report.pdf

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