HMA Construction ProgramHMA Construction Program

Module 10 – Quality Control / Module 10 – Quality Control / Quality AssuranceQuality Assurance

Module 10 ObjectivesModule 10 Objectives

• Objective of Quality ControlObjective of Quality Control

• Objective of Quality AssuranceObjective of Quality Assurance

• Four Types of SpecificationsFour Types of Specifications

• Population, lot, sample, and specimenPopulation, lot, sample, and specimen

• Random sampling and testing plansRandom sampling and testing plans

• Control chartsControl charts

• Applicable QC/QA testsApplicable QC/QA tests

Quality Trends in ConstructionQuality Trends in Construction

• Customer-driven quality initiativesCustomer-driven quality initiatives

• ISO 9000-based quality systemsISO 9000-based quality systems

• Project-focused quality effortsProject-focused quality efforts

• Focus on customer satisfactionFocus on customer satisfaction

• The definition of “quality”The definition of “quality”

• Senior leadership involvementSenior leadership involvement

Quality Pavements: Don’t Begin Quality Pavements: Don’t Begin and End with Material Inspectionand End with Material Inspection

• Pavement designPavement design

• Subgrade preparationSubgrade preparation

• Base constructionBase construction

• Management philosophyManagement philosophy

Specification EvolutionSpecification Evolution

• Method or Recipe (Past)Method or Recipe (Past)

• End Result (Quasi-Present)End Result (Quasi-Present)

• Quality Assurance (Present)Quality Assurance (Present)

• Performance Based (Future?)Performance Based (Future?)

Method or Recipe (Past)Method or Recipe (Past)

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Department of Transportation LibraryDepartment of Transportation Library

Method SpecificationMethod Specification

• Owner designs project and sets Owner designs project and sets specificationsspecifications

• Contractor identifies material sourcesContractor identifies material sources

• Contractor supplies representative Contractor supplies representative samples samples

• Agency conducts mix designAgency conducts mix design

Method Specification (continued)Method Specification (continued)

• Contractor begins production of mixtureContractor begins production of mixture

• Agency conducts gradation and asphalt Agency conducts gradation and asphalt content tests at plant and makes plant content tests at plant and makes plant adjustmentsadjustments

• Agency checks pavement densityAgency checks pavement density

• Pay adjustments, if any, are madePay adjustments, if any, are made

Problems with Method Problems with Method SpecificationsSpecifications

• Mix design Mix design – plant specificplant specific

• Types of tests inadequateTypes of tests inadequate

• Economic incentive Economic incentive – materialsmaterials

• Adjustments at plant affect densityAdjustments at plant affect density

• Frequent disagreementsFrequent disagreements– Agency makes changes which affect payAgency makes changes which affect pay– Referee testing often requiredReferee testing often required

End Result SpecificationsEnd Result Specifications

• Specifying agency/contractorSpecifying agency/contractor– Sets limitsSets limits– Defines the desired quality of the finished Defines the desired quality of the finished

productproduct

End Result Specifications End Result Specifications (continued)(continued)

• Becoming more prevalentBecoming more prevalent

• Agency or contractor designs project and Agency or contractor designs project and provides expected results for: provides expected results for:

– Materials used, Materials used,

– Volumetrics, Volumetrics,

– Smoothness, and Smoothness, and

– DensityDensity

End Result Specifications End Result Specifications (continued)(continued)

• They typically require the:They typically require the:

– Contractor to do quality control testingContractor to do quality control testing

– Agency to do assurance testing and Agency to do assurance testing and conduct an acceptance program for conduct an acceptance program for paymentpayment

• Consultants can play the role of either Consultants can play the role of either the contractor or the agency in terms the contractor or the agency in terms of testing.of testing.

Common factors are used in end-result Common factors are used in end-result specifications for acceptance of specifications for acceptance of

materials and finished materials and finished pavementspavements

Quality Assurance SpecificationsQuality Assurance Specifications

• Separates responsibility for process Separates responsibility for process control and product acceptancecontrol and product acceptance

• Ensures that inspectionEnsures that inspectionplays an essential roleplays an essential role

QCPlan

Performance Based SpecificationsPerformance Based Specifications

• Performance of the final, in-place Performance of the final, in-place product, is measured; not how it was product, is measured; not how it was builtbuilt

• Performance-based test methods have Performance-based test methods have not been fully developednot been fully developed

• Superpave TechnologySuperpave Technology• WarrantiesWarranties• Rut TestersRut Testers

Performance BasedPerformance Based

The primary goal of a The primary goal of a

QUALITY ASSURANCE SYSTEMQUALITY ASSURANCE SYSTEM

is to provide CONTROL and is to provide CONTROL and maintain ASSURANCE. This maintain ASSURANCE. This

partnering approach will help to partnering approach will help to maintain program credibility.maintain program credibility.

Objectives of a Quality Control Objectives of a Quality Control SystemSystem

• Produce a quality productProduce a quality product

• Assure that the final product meets job Assure that the final product meets job specificationspecification

• Satisfy the customer’s needs, as Satisfy the customer’s needs, as economically as possibleeconomically as possible

QC is the CONTROL portion of the QC is the CONTROL portion of the inspection system. QC ensures the inspection system. QC ensures the

production of uniform materials that production of uniform materials that meet required specifications through meet required specifications through

periodic inspection and testing. periodic inspection and testing.

QC is the producer’s responsibility!QC is the producer’s responsibility!

QA is the ASSURANCE portion of the QA is the ASSURANCE portion of the inspection system. QA assures the owner inspection system. QA assures the owner

that the producer’s test results are that the producer’s test results are accurate. Random sampling and testing accurate. Random sampling and testing

are at greater intervals than the are at greater intervals than the producer’s process.producer’s process.

QA is the buyer’s responsibility!QA is the buyer’s responsibility!

Testing ResponsibilityTesting Responsibility

• Shifting from agency to contractorShifting from agency to contractor

• Certification training programsCertification training programs

IndependentAssurance

Quality AssuranceOrganization

Quality ControlSupervisor

FacilityForem an

Quality ControlT echnician

Hot M ix FacilityOw ner

Laydow nCrew Chief

SellerContractor

BuyerAgency

Quality Control Work ChartQuality Control Work Chart

Typical QC/QA Sampling and Typical QC/QA Sampling and Testing ProceduresTesting Procedures

• Pre-productionPre-production

• Job Mix Formula approval and Job Mix Formula approval and verificationverification

• QC during production by contractorQC during production by contractor

• Production and in-place acceptance by Production and in-place acceptance by ownerowner

Pre-Production QC/QAPre-Production QC/QA

• Plant ConsiderationsPlant Considerations

• Aggregate, asphalt cement, and additives Aggregate, asphalt cement, and additives for mix designfor mix design

• Consider anticipated process Consider anticipated process adjustmentsadjustments

– Cause and effectCause and effect

– EconomicsEconomics

Job Mix Formula Approval Job Mix Formula Approval and Verificationand Verification

• Aggregate gradationAggregate gradation

• Aggregate physical propertiesAggregate physical properties

• Asphalt contentAsphalt content

• Volumetric analysisVolumetric analysis

• Stability or strength testing, where Stability or strength testing, where applicableapplicable

• Moisture susceptibilityMoisture susceptibility

QC During Production by QC During Production by ContractorContractor

• Aggregate gradationAggregate gradation

• Asphalt contentAsphalt content

• Volumetric analysisVolumetric analysis

• In-place densityIn-place density

QA During Production by AgencyQA During Production by Agency

Random production and in-place acceptance Random production and in-place acceptance testing by the owner is similar to contractor testing by the owner is similar to contractor testing, plus measurements of:testing, plus measurements of:

– ThicknessThickness

– Smoothness Smoothness

– Overall profile and workmanshipOverall profile and workmanship

Independent AssuranceIndependent Assurance

In order for the QC/QA program to In order for the QC/QA program to maintain the highest level of accuracy and maintain the highest level of accuracy and credibility, owners should maintain an credibility, owners should maintain an Independent Assurance Group. Typically Independent Assurance Group. Typically separate, the group randomly reviews both separate, the group randomly reviews both parties’ procedures and addresses parties’ procedures and addresses discrepancies.discrepancies.

Process Control PlanProcess Control Plan

• Assignment of QC responsibilitiesAssignment of QC responsibilities

• Type and frequency of testsType and frequency of tests

• Record of plant inspections and Record of plant inspections and calibrationscalibrations

• DocumentationDocumentation

• Criteria for actionCriteria for action

Quality ControlSupervisor

FacilityCrew Chief

Quality ControlTechnician

Hot M ix FacilityOw ner

Laydow nCrew Chief

SellerC ontractor

Assigning QC ResponsibilitiesAssigning QC Responsibilities

Type and Frequency of TestsType and Frequency of Tests

• Sampling and testing mix components Sampling and testing mix components (Plant)(Plant)

• Sampling and testing mixture produced Sampling and testing mixture produced (Plant/Field)(Plant/Field)

• Analysis of resultsAnalysis of results

• Evaluation of compliance with Evaluation of compliance with specification limitsspecification limits

HMA Sampling and TestingHMA Sampling and Testing

It is crucial that the producer and It is crucial that the producer and agency use the agency use the same same test methods and test methods and equipment specifications in order to equipment specifications in order to compare test results appropriately.compare test results appropriately.

Analysis of Test ResultsAnalysis of Test Results

• Does the mix comply with specification Does the mix comply with specification limits?limits?

– Current results vs. previous resultsCurrent results vs. previous results

– Job Mix Formula, JMF (+/-)Job Mix Formula, JMF (+/-)

– Single test vs. moving averageSingle test vs. moving average

Sample Process Control ChartSample Process Control Chart

5.3

5.5

5.7

5.9

6.1

1 2 3 4 5 6 7 8 9 10 11 12Test Number

Per

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Upper Control LimitUpper Control Limit

Job Mix Job Mix FormulaFormula

Lower Control LimitLower Control Limit

= Running Average = Individual Test Results

Sample Process Control ChartSample Process Control Chart

5.1

5.3

5.5

5.7

5.9

6.1

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1 2 3 4 5 6 7 8 9 10 11 12Test Number

Per

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UpperUpper

Job Mix Job Mix FormulaFormula

LowerLower

Control Charts Control Charts

• What is plotted?What is plotted?– Control sievesControl sieves

• Max, 4.75 mm, 600 µm, 75 µm Max, 4.75 mm, 600 µm, 75 µm (#4, #30, #200)(#4, #30, #200)

– Asphalt ContentAsphalt Content

– Max. Theoretical Sp. Gr.Max. Theoretical Sp. Gr.

– Laboratory Sp. Gr.Laboratory Sp. Gr.

– Voids and VMAVoids and VMA

– Pavement in-place densityPavement in-place density

Benefits of Control ChartsBenefits of Control Charts

Benefits of Control ChartsBenefits of Control Charts• Early detection of trendsEarly detection of trends

• Establish process capabilityEstablish process capability

• Decrease inspection frequencyDecrease inspection frequency

• Permanent record of qualityPermanent record of quality

• Provide a basis for acceptanceProvide a basis for acceptance

• Instill quality awarenessInstill quality awareness

• Taking corrective measures Taking corrective measures

• Evaluating data for cost savings Evaluating data for cost savings

• Recording and reportingRecording and reporting

Plant Inspections and CalibrationsPlant Inspections and Calibrations

• Control cold feeds and hot binsControl cold feeds and hot bins

• Facility operations and controlsFacility operations and controls

QC / QAQC / QA

• DocumentationDocumentation– Day to day resultsDay to day results– Problems with incoming productsProblems with incoming products– Adjustments made to trend towards JMFAdjustments made to trend towards JMF– OthersOthers

QC / QAQC / QA

• Criteria for actionCriteria for action– Specification tolerancesSpecification tolerances– Timely response for adjustmentsTimely response for adjustments– Adjusted job mix formulaAdjusted job mix formula– OthersOthers

Total VariabilityTotal Variability

• Variability – Everything variesVariability – Everything varies

• Assignable variability can be eliminated Assignable variability can be eliminated IFIF we identify the cause we identify the cause

Scientific Tools to Use in the Scientific Tools to Use in the Treatment and Analysis of DataTreatment and Analysis of Data

• StatisticsStatistics

• Random sampling Random sampling

StatisticsStatistics

• Central tendency or averageCentral tendency or average

• Dispersion or rangeDispersion or range

• Standard deviation or variabilityStandard deviation or variability

• Degrees of freedom (n-1)Degrees of freedom (n-1)

• OutliersOutliersNormal Distribution is Normal Distribution is

most important for most important for highway materialshighway materials

Statistics (continued)Statistics (continued)

• Sampling vs. complete enumerationSampling vs. complete enumeration– PopulationPopulation– SampleSample– DataData

• Controlled conditionsControlled conditions

Population or LotPopulation or Lot

Sample from theSample from thePopulation or LotPopulation or Lot

Sample #1Sample #1

Sample #3Sample #3

Sample #2Sample #2

Random SamplingRandom Sampling

• Any portion of the population has equal Any portion of the population has equal chance of being selectedchance of being selected

• Bias is introduced when judgment is usedBias is introduced when judgment is used

• Use random number tablesUse random number tables

Lots and Sublots Lots and Sublots

LOTLOT

SUBLOTSUBLOT

Random Random SamplingSampling

Stratified Stratified Random Random SamplingSampling

QC / QA Sampling ExampleQC / QA Sampling Example

• Lot size: 1,000 metersLot size: 1,000 meters

• Pavement width: 3.6 metersPavement width: 3.6 meters

• 5 cores per lot5 cores per lot

• Lot begins at Sta. 100+000Lot begins at Sta. 100+000

LOTLOT

100+000100+000

5 equally sized sub-lots5 equally sized sub-lots

Random Number TableRandom Number Table

0.740.74 0.600.60 0.010.01 0.270.27 0.430.43

0.290.29 0.210.21 0.780.78 0.010.01 0.430.43

0.280.28 0.370.37 0.000.00 0.490.49 0.970.97

0.730.73 0.080.08 0.870.87 0.320.32 0.970.97

0.720.72 0.140.14 0.090.09 0.700.70 0.410.41

X (longitudinal)X (longitudinal)

Y (transverse)Y (transverse)

QC / QA Sampling Example (QC / QA Sampling Example (cont’d)cont’d)

• Sub-lot #1Sub-lot #1– Length = 200 metersLength = 200 meters– Random numbers: 0.74 and 0.29Random numbers: 0.74 and 0.29

• Measure up from Sta. 100+000Measure up from Sta. 100+000– X = 0.74 x 200 meters = 148 metersX = 0.74 x 200 meters = 148 meters– Y = 0.29 x 3.6 meters = 1.0 metersY = 0.29 x 3.6 meters = 1.0 meters

QC / QA SamplingQC / QA Sampling

• Participant Example:Participant Example:

– Lot size: 2,000 metersLot size: 2,000 meters

– Pavement width: 3.6 metersPavement width: 3.6 meters

– 5 cores per lot5 cores per lot

– Lot begins at Sta. 200+000Lot begins at Sta. 200+000

Random Number TableRandom Number Table

0.740.74 0.600.60 0.010.01 0.270.27 0.430.43

0.290.29 0.210.21 0.780.78 0.010.01 0.430.43

0.280.28 0.370.37 0.000.00 0.490.49 0.970.97

0.730.73 0.080.08 0.870.87 0.320.32 0.970.97

0.720.72 0.140.14 0.090.09 0.700.70 0.410.41

X (longitudinal)X (longitudinal)

Y (transverse)Y (transverse)

QC / QA SamplingQC / QA Sampling

• Participant Example (cont’d.):Participant Example (cont’d.):– Sub-lot #1Sub-lot #1

• Length = 400 metersLength = 400 meters• Random numbers: 0.73 and 0.72Random numbers: 0.73 and 0.72

– Measure up from Sta. 200+000Measure up from Sta. 200+000• X = 0.73 x 400 meters = 292 metersX = 0.73 x 400 meters = 292 meters• Y = 0.72 x 3.6 meters = 2.6 metersY = 0.72 x 3.6 meters = 2.6 meters

Process Acceptance CriteriaProcess Acceptance Criteria

• MaterialsMaterials

• Thickness toleranceThickness tolerance

• Pavement densityPavement density

• Pavement smoothnessPavement smoothness

MaterialsMaterials

• Process control by contractorProcess control by contractor

• Assurance sampling and testing done Assurance sampling and testing done randomly, and less frequently, by ownerrandomly, and less frequently, by owner

Thickness ToleranceThickness Tolerance

• Can be checked with coresCan be checked with cores

• Yield checks during pavingYield checks during paving

• Use of stringlineUse of stringline– Initial HMA courseInitial HMA course– Ski used on subsequent coursesSki used on subsequent courses

• Smooth surface to pave onSmooth surface to pave on

Pavement DensityPavement Density

• Types of density specificationsTypes of density specifications– Laboratory densityLaboratory density– Maximum theoretical densityMaximum theoretical density– Control stripControl strip– Method specification (ordinary compaction)Method specification (ordinary compaction)

Laboratory DensityLaboratory Density

• Compares cores to field-produced mix Compares cores to field-produced mix densitydensity– Field mix compaction same as mix designField mix compaction same as mix design– Mix design properties verifiedMix design properties verified– End result specification End result specification

Percent Density = In-Place DensityPercent Density = In-Place Density Laboratory DensityLaboratory Density

x 100x 100

Maximum Theoretical Density Maximum Theoretical Density (Rice)(Rice)

• Unit weight of mix in “voidless” stateUnit weight of mix in “voidless” state

• Core density is compared to MTDCore density is compared to MTD

• Relative density is in-place air voidsRelative density is in-place air voids

Percent of MTD = In-Place Density Percent of MTD = In-Place Density

Max. Theor. DensityMax. Theor. Densityx 100x 100

Control Strip DensityControl Strip Density

• Requires control strip at start of each liftRequires control strip at start of each lift

• Minimum tonnage or areaMinimum tonnage or area

• After constructed, density tests takenAfter constructed, density tests taken

• Test results compared to lab or MTDTest results compared to lab or MTD– Number of tests is specifiedNumber of tests is specified– Is compaction adequate?Is compaction adequate?

• Field density is the reference target Field density is the reference target

• 100% of target is desired100% of target is desired

Control Strip PrecautionsControl Strip Precautions

• These factors can affect density:These factors can affect density:

– Mix temperatureMix temperature

– Asphalt contentAsphalt content

– GradationGradation

– Rolling techniqueRolling technique

Reference Density ComparisonReference Density Comparison

In-PlaceIn-PlaceAirAir

VoidsVoids

00

11

22

33

44

55

66

77

88

999191

9292

9393

9494

9595

9696

9797

9898

9999

100100% of% ofMaximumMaximumTheoreticalTheoreticalDensityDensity

100100

9999

9898

9797

9696

9595

% of% ofLaboratoryLaboratory

DensityDensity

100100

9999

% of% ofControl StripControl Strip

DensityDensity

For 4% VoidsFor 4% VoidsMix DesignMix Design

Method SpecificationMethod Specification

• No reference densityNo reference density

• Spells out rolling operationSpells out rolling operation– Number of rollersNumber of rollers– Types of rollersTypes of rollers– Number of passesNumber of passes– Temperature measurementsTemperature measurements– ““Free of roller marks”Free of roller marks”

• Very subjective specificationVery subjective specification

Pavement SmoothnessPavement Smoothness

• Provide better rideProvide better ride• Less damage to pavementLess damage to pavement• Measurements must be accurate, repeatable, Measurements must be accurate, repeatable,

and hopefully related to what we feel when we and hopefully related to what we feel when we drive the roaddrive the road

• Specifications should be set to how much we can Specifications should be set to how much we can realistically improve the smoothness of a roadrealistically improve the smoothness of a road

• Corrections?Corrections?

Pavement Smoothness Pavement Smoothness MeasurementsMeasurements

• Straight edgeStraight edge

• ProfilographProfilograph

• ProfilometerProfilometer

• Mays MeterMays Meter

• LISALISA

Pavement Smoothness Pavement Smoothness Measurements (continued)Measurements (continued)

• Straight edgeStraight edge– Typically 3 meters longTypically 3 meters long– Measure deviations > 6 mmMeasure deviations > 6 mm– Some have wheels (rolling straight edge)Some have wheels (rolling straight edge)

• Local requirements?Local requirements?– 3 mm in 3 meters 3 mm in 3 meters – 6 mm in 3 meters (sidestreets)6 mm in 3 meters (sidestreets)– 5 mm in 5 meters5 mm in 5 meters

Pavement Smoothness Pavement Smoothness Measurements (continued)Measurements (continued)

• ProfilographProfilograph– Most common is “California Style”Most common is “California Style”

• 8 meter long aluminum truss8 meter long aluminum truss

• Center mounted measuring wheelCenter mounted measuring wheel

– Standard testing distance = 0.15 kmStandard testing distance = 0.15 km– Blanking band (5 mm)Blanking band (5 mm)– Measurement in mm/kmMeasurement in mm/km– Manual -vs- computer outputManual -vs- computer output– Local requirements?Local requirements?

Pavement Smoothness Pavement Smoothness Measurements (continued)Measurements (continued)

• ProfilometerProfilometer– Self contained truck or trailerSelf contained truck or trailer– Uses accelerometers and distance measuring Uses accelerometers and distance measuring

equipmentequipment– Computer processed informationComputer processed information– Used at highway speedsUsed at highway speeds– High initial investmentHigh initial investment

• Not easy to correlate different methodsNot easy to correlate different methods

Pavement Smoothness Pavement Smoothness Measurements (continued)Measurements (continued)

• Mays Meter – trailer device for Mays Meter – trailer device for measuring roughnessmeasuring roughness

• LISALISA– LLightweight ightweight iinertial nertial ssurface urface aanalyzer or nalyzer or

quick response profilometerquick response profilometer– Laser sensor and an accelerometerLaser sensor and an accelerometer– Travels at 15 to 30 kphTravels at 15 to 30 kph

QC / QA ReviewQC / QA Review

The primary goal of a The primary goal of a

QUALITY ASSURANCE SYSTEMQUALITY ASSURANCE SYSTEM

is to provide CONTROL and is to provide CONTROL and maintain ASSURANCE. This maintain ASSURANCE. This

partnering approach will help to partnering approach will help to maintain program credibility.maintain program credibility.

QC / QA ReviewQC / QA Review

Implementing a Quality CONTROL Implementing a Quality CONTROL ProgramProgram

• Management commitmentManagement commitment

• Quality statementQuality statement

• Developing a Quality Control Developing a Quality Control manualmanual

QC / QA ReviewQC / QA Review

Implementing a Quality ASSURANCE Implementing a Quality ASSURANCE ProgramProgram

• Process Quality ControlProcess Quality Control

• Acceptance sampling, testing and inspectionAcceptance sampling, testing and inspection

• Independent AssuranceIndependent Assurance

Quality Control with Quality Control with Quality AssuranceQuality Assurance

Credibility is another way of saying, Credibility is another way of saying,

““You can believe me!”You can believe me!”

Module 10 Objectives ReviewModule 10 Objectives Review

• Objective of Quality ControlObjective of Quality Control

• Objective of Quality AssuranceObjective of Quality Assurance

• Four Types of SpecificationsFour Types of Specifications

• Population, lot, sample, and specimenPopulation, lot, sample, and specimen

• Random sampling and testing plansRandom sampling and testing plans

• Control chartsControl charts

• Applicable QC/QA testsApplicable QC/QA tests