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FHWA
High Performance Concrete
Research Program
FHWA HPC Program
• Section 5202(b)(3)(B) of SAFETEA-LU
-- RT&E on HPC bridges
-- Fiscal 2006 through 2009
-- = $2.9M per year after adjustments, etc.
• R&D at TFHRC
• D&D at Headquarters
• TT through Resource Center
FHWA HPC Research Program
• FHWA "Bridge of the Future" initiative
-- 100-year service live w/ little or no maintenance
-- Significantly reduced construction time
-- Easily widened or adapted to new demands
-- Significantly reduced life-cycle cost
-- Significantly improved resistance to typical and extreme natural and man-made hazards
-- Integrated substructure and superstructure design and construction
-- Elimination of vertical and lateral clearance problems

FHWA HPC Research Program
• Program developed by FHWA in consultation with stakeholders and industry
• Primary topics to be addressed
-- Lightweight Structural Concrete
-- Shear of Non-Prestressed Elements
-- HPC Deck Behavior (Cracking, Durability, etc.)
-- NDE Methods for Void Detection in PT Ducts

Lightweight Structural Concrete
• AASHTO LRFD allows lightweight
-- Includes arbitrary definitions
-- Based on dated research from a limited compressive strength range
Lightweight Structural Concrete
• NCHRP 18-15
-- Parallel effort ongoing with proposals due today
-- Effort focused on equilibrium densities less than 125 pcf
-- RFP focused on material characterization with limited structural testing for verification of behaviors

Lightweight Structural Concrete
• Research Objective
-- Address perceived shortcomings in LRFD with regard to equilibrium densities less than 140 pcf
• Are across-the-board resistance factor modifications correct?
• Are predictor equations acceptably accurate?
• What about equilibrium densities between "normal weight" and "sand lightweight"?

Lightweight Structural Concrete
• Focal Areas
-- Structural behavior research focusing on higher strength girders and higher durability decks
-- Material characterization research focusing on strength, serviceability, stability, and production issues

Lightweight Structural Concrete
• First Steps
-- Synthesis of existing research results and the state-of-the-practice regarding the use of lightweight concrete in highway bridges
• Currently underway
• Scheduled for completion in January 2007

Lightweight Structural Concrete
• Phase 1: Material Property Characterization of Structural Lightweight Concrete
-- Literature Search
-- Identification of Mix Designs
• Range of equilibrium densities
• Range of lightweight coarse aggregates
• Mixes representative of normal/intended use
• At least 3 mixes for superstructures
• At least 3 mixes for decks

Lightweight Structural Concrete
• Phase 1: Material Property Characterization of Structural Lightweight Concrete (continued)
-- Test Program
• Strength (Compressive, Tensile, Modulus)
• Stability (Creep, Shrinkage, CTE)
• Durability (Freeze-Thaw, Scaling, Chloride Pen)
-- Compile Results
• Develop predictor equations
• Prepare final report

Lightweight Structural Concrete
• Phase 2: Behavior of Structural Lightweight Concrete Bridge Components
-- Literature Search
-- Identification of Mix Designs
• Use mix designs from Phase 1

Lightweight Structural Concrete
• Phase 2: Behavior of Structural Lightweight Concrete Bridge Components (continued)
-- Test Program
• Shear capacity in superstructure members
• Transfer and development length of strands
• Development length of rebar
• Prestress losses
• Confinement requirements for anchorage regions
• Punching shear capacity

Lightweight Structural Concrete
• Phase 2: Behavior of Structural Lightweight Concrete Bridge Components (continued)
-- Test Program (continued)
• Testing completed on full-scale components
-- Compile Results
• Develop predictor equations for relevant behaviors
• Prepare final report

Shear Capacity of Non-Prestressed High-Strength Concrete Members
• AASHTO LRFD Shear Provisions
-- High-strength concrete use restricted to situations where physical tests have demonstrated applicability of relationships
-- NCHRP 12-56 focused heavily on prestressed girders
-- Other members composed of HSC have not been thoroughly addressed
Shear Capacity of Non-Prestressed High-Strength Concrete Members
• Research Objective
-- Extend applicability of shear provisions for normal weight concrete to 18 ksi compressive strength without any restriction on structural applications
Shear Capacity of Non-Prestressed High-Strength Concrete Members
• Research Plan
-- Perform literature search for relevant prior work
-- Develop practical HPC mix designs with the desired properties
-- Perform full-scale component tests to determine the relevant behaviors
-- Report results
HPC Deck Behavior
• HPC Deck Issues
-- HPC deck cracking is an ongoing concern
-- Early age and longer term behaviors
-- HPC may exacerbate issues due to potential higher strengths & stiffnesses
-- Mix designs, construction practices, lack of oversight, etc. may all be underlying causes

HPC Deck Behavior
• Research Objective
-- Identify the primary root causes of underperformance of HPC bridge decks
-- Develop and/or verify remedies

HPC Deck Behavior
• Research Plan
-- Compile experiences and best practices from around the U.S.
-- Establish, verify, develop, and/or compile:
• good mix designs
• effective construction practices (e.g., curing duration and equipment, limiting weather factors)
-- Perform full-scale laboratory testing as necessary
-- Report findings and disseminate results

NDE Methods for Detecting Voids in Post-Tensioning Ducts
• Strand Deterioration Resulting from Voids
-- Detailing and construction practices can lead to voids in tendon ducts
-- Voids already exist due to past practices
-- Future voids are likely even with better detailing and better construction practices
-- Locating voids can allow for remediation prior to strand deterioration
NDE Methods for Detecting Voids in Post-Tensioning Ducts
• Research Plan
-- Synthesize existing practice and recent research regarding void and deteriorated strand detection
-- Compile a state-of-the-research report
-- Develop experimental research plan based on synthesis results and availability of funds

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