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Asphalt Quality Assurance Program
Rob Crandol, P.E. – Statewide Asphalt Program Manager Asphalt Regional Meetings
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INDEPENDENT ASSURANCE (IA)
QUALITY ASSURANCE PROCESS CONTROL (QC) INDEPENDENT ASSURANCE (IA) ACCEPTANCE (VST) In order to be effective, QA must include the functions of process control, acceptance and independent assurance. All three of these QA functions provide measurement data on the quality of the materials or construction under consideration. Measurement is an important component of the continuous management functions in a total quality management (TQM) system. The value of measurement results depends entirely on how well conceived and executed is the measurement in the first place. Since the specifications stipulate the procedures to be followed and the tests to be run, well thought out, rationally developed specifications are important ingredients for quality improvement. The relationship among process control, acceptance and independent assurance varies from agency to agency, primarily depending on their experience in QA specifications. The one constant that must be present is the necessity for clearly stating which party is responsible for each function.
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Contractor – Performs QC VDOT – Performs IA & VST
Asphalt QA Program Contractor – Performs QC VDOT – Performs IA & VST Asphalt Certification schools for contractors, inspectors and testing personnel. Plant Certification Field Certification
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Quality Control (QC) All activities performed to control the quality of the asphalt mixture during production and placement to fulfill the contractor requirements. Section 211 Mix Design Contractor provides QC testing Section 315 Mix Placement Contractor provides Field Control - Equipment Density Testing
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Independent Assurance (IA)
Activities that are an unbiased and an independent evaluation of all Operations, sampling and testing procedures, and equipment used in the acceptance program. VDOT provides IA during production and placement Inspection – observations Split sample tests Evaluations of Technicians AASHTO Materials Reference Laboratory
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Verification Sampling and Testing (VST)
Validate the quality of the product Performed by VDOT VST should determine if the material is acceptable per specification. VDOT uses split samples plus a statistical process of examining Contractor QC test data to verify the accuracy of sampling and testing used in the acceptance decision. Plant VDOT uses independent samples Field
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Mix Design Approval Process
Contractor submits mix design laboratory data and forms to VDOT for initial approval. Limited production - contractor can produce up to 500 tons or one day’s production. Gyratory samples taken and analyzed by both VDOT and Contractor for compliance with Specification requirements and conformance to submitted mix design. Full production approval granted after a successful limited production trial.
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Asphalt Plant Quality Control
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Random Truck Sampling Critical to the integrity of QA program
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Sample Splitting
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Asphalt Plant QA VDOT uses the Contractor’s test data (QC) in the acceptance of plant produced Asphalt mixtures
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Producer Samples and Tests (QC)
Perform Gradation and Asphalt Content testing randomly every 500 tons Temperature Measurements 1st and 5th load then at least once an hour Volumetric SUPERPAVE tests every 1,000 tons Air Voids (VTM) Voids in Mineral Aggregate (VMA) Voids filled with Asphalt (VFA) Rice test – Maximum Specific Gravity (Gmm)
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VDOT Responsibilities, Samples and Tests
Inspect Plant equipment and lab for compliance with specifications – IA Split sample tests for gradation and Asphalt Content are used for system wide IA and VST purposes Volumetrics SUPERPAVE tests used for verification purposes. Air Voids (VTM) Voids in Mineral Aggregate (VMA) Voids filled with Asphalt (VFA) Rice test – Maximum Specific Gravity (Gmm)
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Independent Assurance
3 IA1 2 1 4 Lot 2 Lot 3 Lot 1 Lot 4 IA3 IA2 IA4 Matched Comparison Analysis QC Sample Comparison IA
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VST 3 IA1 2 1 4 Lot 2 Lot 3 Lot 1 Lot 4 IA3 IA2 IA4 QC
System Comparison Non Matched Comparison VST
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4.4 4.6 4.8 5.0 5.2 5.4 5.6 Asphalt Content f(x) Comparison Reports
Lab #1 Lab #2 4.4 4.6 4.8 5.0 5.2 5.4 5.6 Asphalt Content f(x) Populations of data can have different means or averages but have the same standard deviations.
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4.4 4.6 4.8 5.0 5.2 5.6 5.8 Asphalt Content f(x) Comparison Reports
Populations can have different standard deviations or variabilities and have the same mean (average)
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Asphalt MITS - PLAID Reports
Statistical Tests are performed on both Split Comparison and IA Samples. Any non comparison must be investigated, resolved and documented.
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Assessment of Random Samples
Is this random?
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Summary – Asphalt Plant QA
Statistics is the tool that VDOT uses to verify the quality of asphalt mixtures.
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Asphalt Field Quality Assurance
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Contractor Field QC Testing
Depth Checks Cross Slope Straight Edge Transverse Joints QC Density testing either by Thin Lift Nuclear gauge or through cores/plugs Joint Density Test and Test frequency will be determined by Road & Bridge Specifications, Special Provisions or as directed by the Engineer Cut plugs for VST at direction of Materials QA technician.
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VDOT Project Staff Responsibilities IA
Verifies Paving equipment meets specifications Verifies materials being used are from approved sources Take Temperature measurements of AC at least every hour Verifies that contractor personnel are performing QC operations correctly Verifies Density testing being performed Joint Density
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VDOT/Materials VST and IA
Perform VST testing on plugs IA testing Verify method of random selection Marking of test locations Observe QC testing at control strip Observe test sections. Obtain samples of cores from control strip to reweigh in laboratory. Depth Control tests
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Asphalt Density Virginia Test Method VTM-76
Stratified Random Locations - QC Control Strip Test Sections Cores for Control Strips - IA 6 cores for new mixes 2 cores per site 2 cores
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STRATIFIED RANDOM LOCATIONS
1000 ft. 5000 FEET 1000 FOOT SECTIONS TEST SECTION
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ROLLER PATTERN CONTROL STRIP NUMBER OF PASSES TARGET DENSITY 75 ft. 300 ft.
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ORIENT GAUGE IN SAME DIRECTION
TEST THREE LOCATIONS 50 FEET 1 3 2 75 FEET MARK TEST LOCATIONS ORIENT GAUGE IN SAME DIRECTION
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DENSITY vs NUMBER OF PASSES
144.0 143.0 142.0 141.1 140.0 138.0 137.0 139.0 136.0 135.0 DENS I TY (lb/ft3) NUMBER OF PASSES
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Locations of nuclear readings are marked by contractor.
VTM-76
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TAKE READINGS AT LEAST 1 FOOT FROM EDGE OF PAVEMENT
CONTROL STRIP 1 5 9 3 7 2 10 6 8 4 300 FEET TAKE READINGS AT LEAST 1 FOOT FROM EDGE OF PAVEMENT Using 5 roller passes
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Core locations are marked for cutting.
VTM-76
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Cores are cut … VTM-76
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…and carefully removed.
VTM-76
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MINIMUM DENSITY REQUIREMENT
(Bulk Specific Gravity / Max Specific Gravity) * 100 (Table III-3)
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TABLE III-3 Density Requirements
Mixture Type Min. Control Strip Density (%) SM-9.5A, 12.5A 92.5 SM-9.5D, 12.5D 92.2 SM-9.5E, 12.5E IM-19.0A IM-19.0D BM-25.0 92.2 Note: The control strip density requirement is the percentage of theoretical maximum density at the job-mix formula as determined by Superpave Mix Design.
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Nuclear Gauge Calibrated Same gauge used at Control Strip
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QC Density Test Section
1 J 2 J 3 J 4 J 5 J 6 J 7 J 8 J 9 J 10 J 5 9 1 3 7 2 10 4 6 8 1 J 2 J 3 J 4 J 5 J 7 J 9 J 10 J 6 J 8 J 5000 FEET TAKE READINGS AT LEAST 1 FOOT FROM EDGE OF PAVEMENT Average of 10 readings (98 – 102% of control strip) Density Readings 4 or 6 inches from the Joint
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QC Density Test Section
1 J 2 J 3 J 4 J 5 J 6 J 7 J 8 J 9 J 10 J 5 9 1 3 7 2 10 4 6 8 5000 FEET TAKE READINGS AT LEAST 1 FOOT FROM EDGE OF PAVEMENT Average of 10 readings (98 – 102% of control strip) Density Readings 4 or 6 inches from the Joint
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Contractor must cut 2 cores for VST at the direction of VDOT
Select one Test Section for VST Lot 1 Lot 2 Lot 3 Lot 4 Lot 5 Contractor must cut 2 cores for VST at the direction of VDOT
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VST Density Test Section
1 5 9 3 7 VST R-VST VST 2 10 R-VST 6 8 R-VST 4 5000 FEET CUT 2 CORES Referee Procedure - Cut 3 more Cores use average of all 5 for final decision
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Determine Limits Lot 13 Lot 14 Lot 15 Lot 16 Lot 17 Preceding After
Failing
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Asphalt Quality Assurance Program
Rob Crandol, P.E. – Statewide Asphalt Program Manager Asphalt Regional Meetings
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