Russian Engineers Training March 2011

Russian Engineers Training March 2011
Construction Specifications and Quality Control/Quality Assurance for Hot Mix Asphalt Paving Good performing HMA requires a chain of tasks to be done correctly. No single link in the chain guarantees a successful paving project. Proper pavement design and mix design are two important tasks. Construction is the next step and certainly plays a significant role. Construction is controlled by specifications. QC/QA should be a key component of the specifications. This course will define terminology as it progresses. local terminology may vary, but the practices are still the same. Dr. Michael Heitzman, PE Assistant Director National Center for Asphalt Technology Construction Specification & QC/QA for HMA Paving

Outline Session – 1 Specification Session – 2 QC/QA Basics Session – 3 Hot Mix Asphalt QC/QA Session – 4 Summary and Key Points Program is divided into four parts. Session-1 – the basic components of a asphalt paving specification Session -2 – the basic theory and components of QC/QA Session-3 – discussion of HMA paving quality following the spec outline Session-4 – Brief summary and discussion of key HMA quality construction tasks Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Session -1 Specifications
Russian Engineers Training March 2011 Session -1 Specifications Purpose Types of Specifications Common HMA Specification Components Session-1 – the basic components of a asphalt paving specification This session is divided into three parts. Fisrt – what is the purpose of a construction spec -- many agency and contractor staff do not value the purpose of the spec criteria Second – there are different types of specifications – you should know and understand why you are working under a particular type of specification Finally – we will outline the common HMA spec components – most of the components should be in every HMA paving spec Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Purpose of Specifications
Russian Engineers Training March 2011 Purpose of Specifications Vital to performance of HMA pavements Achieve a quality product Vital to successful construction Pay a fair price Focus on HMA, but applicable to many aspects of roadway construction Why do we need a HMA paving spec? What purpose does it serve? Spec defines the level of quality expected. EX--- the level of quality required for a Interstate pavement is different than the quality required for a residential street ---therefore the spec should be different Spec criteria are contractual requirements for the owner to receive the desired pavement and for the contractor to receive fair compensation for his effort EX --- The owner’s spec requires the HMA to be compacted to not more than 8% air voids, the contractor should not expect 100% pay if he (or she) fails to meet the minimum density requirement. All specifications should meet these two basic purposes --- define the level of quality and define the criteria for pay. Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Purpose of Specifications
Russian Engineers Training March 2011 Purpose of Specifications more…. Must have a good production process to achieve a good pavement Having good material and good mix design are not enough There is no single correct QC/QA program. Each program reflects the regional conditions and level of expertise of the owner and industry. The construction process is not always prescribed by the spec, but that does not diminish the importance of the construction process. Simply meeting the material and mix design requirements of a spec does not guarantee a good performing pavement. EX--- Most HMA spec do not prescribe the details of how to place HMA with a paver. Paving is a construction process that is the responsibility of the contractor. The paving operation (if not performed using good industry practices) can diminish the performance of the pavement. The purpose of the QC/QA criteria in a spec is to reflect the level of quality required for the project that is in line with the regional conditions. EX– some areas of the country have very high quality aggregate locally available. In these cases the spec can prescribe a relatively narrow set of limits for the aggregate. In other areas high quality aggregate is not locally available and the aggregate characteristics are more variable. If the owner prescribes the same narrow and/or high quality spec limits, the agency can expect to pay an excessive amount for the project because the contractor must ship in aggregate and assumes a higher risk for product variability. Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Russian Engineers Training March 2011 Session -1 Specifications Purpose Types of Specifications Common HMA Specification Components So the purpose of a spec is to define the level of quality required for the project that reflects the regional capability of the owner and contractor. Spec have evolved over 50+ years of roadway paving after the beginning of the interstate highway system. Although hard surface paving started in the late 1800s, modern paving practices and the need for better spec language did not develop until federal funding for the interstate system required higher standards. Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Types of specifications
Russian Engineers Training March 2011 Types of specifications Method End results Performance related Warranty Proprietary Design / Build / Operate General evolution of spec based on expertise of parties. In general, expertise is moving from DOT to contractor. Risk and responsibility also changing. Method >> End Result >> Performance related spec are the three steps in the development of specs. Each type defines a major shift in the roles and responsibilities. Warranty / Proprietary / DBO are all special types of spec that serve a particular purpose. Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Method Specification Recipe >>> “how to…” Must describe all aspects of the process Must be very detailed Impossible for owner to write Requires 100% inspector observation Method spec are the oldest form of spec. They were developed when the knowledge of HMA paving was still developing and the expertise was predominantly in the hands of the owner agencies. Like using a cooking recipe, a method spec is a recipe that describes “how to” construct a HMA pavement. Paving projects in the 1950s, 60s and 70s were built by contractors under the direct instruction of the agency engineers and inspectors. The contractor operated the equipment, but the agency took on most of the responsibility (and risk) for the quality of the paving. As our understanding of paving improved, the level of detail and complexity increased. It is nearly impossible to write a method spec that encompasses every technical detail require for a modern HMA paving project. Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Method Spec for roller compaction
Russian Engineers Training March 2011 Method Spec for roller compaction mat thickness mat temp base temp air temp roller type roller size roller weight roller speed roller freq/ampl number of passes mix specific Each of the components listed will impact the quality of field compaction. Mat thick – thin / thick / variable Mat temp – influenced by plant production and truck delivery Base temp and air temp – can vary in early and late season paving Roller type-size-weight need to be optimized for the paving conditions Roller speed needs to be balanced with paving production and achieving density Vibratory roller freq/amplitude need to match mixture consistency The number of passes defined by the test strip on a hot Aug day may not be appropriate for paving in October Today we have fine and coarse graded dense mixes, surface, intermediate and base mixes SMA, and OGFC with a range of binders -- each have their own set of paving criteria These are only the variety of conditions for field compaction. To write a method spec to cover all these variable combinations is almost impossible. Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

End Result Specification
Russian Engineers Training March 2011 End Result Specification Process by contractor Acceptance by owner based on measure of end product Burden on contractor to use good practices to achieve “end-result” Does not require 100% inspection As the contractor’s knowledge of HMA paving expanded, it was appropriate that the contractor would have more responsibility for the paving operation. The end result spec made the construction process the contractor’s responsibility. The owner specifies the quality of the paving by the measure (testing) of the end product. Looking at the field compaction – the spec defines the level of compaction required, but it is the responsibility of the contractor to determine the number/size/pattern of rollers to accomplish the compaction. Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Russian Engineers Training March 2011 End Result Specification more…. Used by most highway agencies Specify material properties that impact performance Avoid duplicate AND/OR conflicting criteria. Method criteria added when end result tests are not available. Can be a problem when Method and End Result spec criteria conflict. Example of impact properties >>> field density has greater impact than No 30 gradation Example of duplicate/conflict >>> having both field density and field air voids criteria OR specify rolling pattern and minimum density EX appropriate method criteria – no paving when raining / frozen base Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Russian Engineers Training March 2011 End Result Specification more…. Should apply sound QC/QA practices Agency must use “proper” S/T procedures for acceptance Good End Result spec are not perfect, but suited for current level of testing capability QC/QA does provide for an objective measure of construction. It must also reflect the State’s conditions EXAMPLE if aggr is variable, then QC/QA must reflect material variability that is needed without being too costly. To be objective – the S/T must be done to acceptable standards so it reflects the material/product variability, not the variability due to poor S/T practices. This is the current standard of HMA paving spec – it is not perfect because the level of testing does not guarantee a high level of product confidence. The risk to both the contractor and owner are high. Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Performance Related Specification
Russian Engineers Training March 2011 Performance Related Specification Measure of acceptance is directly related to expected product performance. Requires tight QC/QA Test methods MUST have strong correlation to actual performance Pay is based on predicted performance Growing interest, BUT test methods lack robust correlation and repeatability The third step in the evolution of spec. More responsibility and risk on contractor. There are some spec being described as PRS that are not truly performance related. Our knowledge base to combine construction with actual performance is growing, but very few tests can be defined as performance related. Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Warranty Specification
Russian Engineers Training March 2011 Warranty Specification Specify minimum level of performance over a period of time Often applied as material and workmanship warranties for shorter (3-5 year) period Contractor carries burden for construction Contractor should have control over design decisions Fourth evolution – contractor is responsible Must have good set of performance criteria for end of warranty period Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Warranty Specification
Russian Engineers Training March 2011 Warranty Specification more…. Typically requires a performance bond Can exclude smaller contractors that are unable to “bond” the project for the specified time period Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Proprietary Specification
Russian Engineers Training March 2011 Proprietary Specification Typically product specific Often sole source or patented Minimizes competition May include “…or approved equal.” Needed for particular performance criteria Limited use for public agency projects (must justify) Very common for traffic signal projects – agency can justify need to keep the equipment the same Common problem for specifying a modified asphalt binder -- cannot call-out a specific modifier brand (NO Shell Kraton, YES SBS polymer) Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Design/Build/Operate Specification
Russian Engineers Training March 2011 Design/Build/Operate Specification Common spec for big projects Design-Build is more common Design-Build-Operate might be used for tollway Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Russian Engineers Training March 2011 Session -1 Specifications Purpose Types of Specifications Common HMA Specification Components Typical for HMA spec to be mixture of method and end-result Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

HMA Specification Description Materials Mix Design Equipment Construction Quality Control Method of Measure Method of Pay Simple and brief description of the type of construction May also state what the spec is not. Generally up to 8 component parts to a spec – these parts should be consistent for most construction activities EX -- May not apply to asphalt treated base construction Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

HMA Specification Description Materials Mix Design Equipment Construction Quality Control Method of Measure Method of Pay Asphalt binder Aggregate Mineral filler RAP Anti-strip agents May refer to material specifications in a separate spec section Should discuss method by which the material will be accepted for use (certified, tested on site) Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

HMA Specification Description Materials Mix Design Equipment Construction Quality Control Method of Measure Method of Pay Lab method Mix criteria Approval process Often you will see a table of required properties for all mixes. The plans will specify what mix to use from the table. Approval process typically has to steps 1) submittal by contractor and 2) review and approval by agency Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

HMA Specification Description Materials Mix Design Equipment Construction Quality Control Method of Measure Method of Pay Calibration Capacity Features Most of the “method spec” language regarding equipment has been removed. The contractor is required to maintain and operator “in accordance with manufacturers guidelines” Equipment spec are often group together for the entire spec book or may be part of the construction section. They are grouped together to avoid duplication or simplify referencing Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

HMA Specification Description Materials Mix Design Equipment Construction Quality Control Method of Measure Method of Pay Restrictions Pavement preparation Stockpiles Plant production Mix storage Hauling Paving Compaction Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

HMA Specification Description Materials Mix Design Equipment Construction Quality Control Method of Measure Method of Pay May be called: Method of Acceptance Lot/sublot size Sampling frequency Test methods Acceptance limits Small quantities Certified materials Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

HMA Specification Description Materials Mix Design Equipment Construction Quality Control Method of Measure Method of Pay Area Weight (tons) Will also state what will not be measured – pay on plan quantity Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

HMA Specification Description Materials Mix Design Equipment Construction Quality Control Method of Measure Method of Pay Separate for asphalt binder? Incidental items not paid separately Incentive / disincentive There are pros and cons for having a separate asphalt binder pay item. Pro – contractor does not minimize binder content (better mix durability) Con – contractor may not optimize the design (EX -better aggregate with lower absorption) Pro – Contractor reduces risk of increased binder cost Con – contractor may not be able reflect Recycle component in bid Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Russian Engineers Training March 2011 Session -1 Specifications Purpose Types of Specifications Common HMA Specification Components Summary comments for session – 1 specs…. Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Specifications and QC/QA for Hot Mix Asphalt Paving Outline Session – 1 Specification Session – 2 QC/QA Basics Session – 3 Hot Mix Asphalt QC/QA Session – 4 Summary and Key Points Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Session -2 QC/QA Basics Terminology Basic Statistics QC/QA components Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

QC/QA Terminology Owner / Engineer / Inspector Contractor / Foreman / QC Technician Material Supplier Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

QC/QA Terminology Quality Control Contractor’s actions Tests performed to determine the quality of the material and consistency of the process Quality Assurance Owner actions Inspection and testing to determine spec compliance and factors in the decision for acceptance Independent Assurance Program to assure the precision and accuracy of the testing by comparing test results with an independent lab Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

HOT MIX ASPHALT QUALITY ASSURANCE PROGRAM CONTRACTOR QUALITY CONTROL INDEPENDENT ASSURANCE OWNER / AGENCY ACCEPTANCE MATERIAL PRODUCTION AND DELIVERY SAMPLING & TESTING SAMPLING & TESTING SPECIFICATION CRITERIA MATERIAL HANDLING SAMPLING & TESTING SAMPLING & TESTING MIXTURE PRODUCTION SAMPLING & TESTING SAMPLING & TESTING PAY FACTOR MIXTURE STORAGE SAMPLING & TESTING SAMPLING & TESTING MIXTURE DELIVERY SAMPLING & TESTING SAMPLING & TESTING MIXTURE PLACEMENT SAMPLING & TESTING SAMPLING & TESTING MIXTURE COMPACTION SAMPLING & TESTING SAMPLING & TESTING Construction Specification & QC/QA for HMA Paving

QC/QA Terminology Lot / Sublot Quantity of production to be grouped for pay. Impact of lot size What are the minimum tests per lot? based on statistics Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

QC/QA Terminology Accreditation Quality of the sampling and testing equipment Knowledge of the test protocol Certification Critical to getting “good” test results Parts of Independent Assurance Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Basic Statistics Sample - less than 10 tests Population - more than 50 tests Normal Distribution No. of Samples Asphalt Binder Content Construction Specification & QC/QA for HMA Paving

Basic Statistics Mean - average Standard Deviation - measure of the variability No. of Samples Asphalt Binder Content +/- 1 std dev +/- 2 std dev Construction Specification & QC/QA for HMA Paving

Basic Statistics Precision and Bias Precision: poor good good Bias: low high low Construction Specification & QC/QA for HMA Paving

Basic Statistics Spec target USL (upper spec limit) LSL (lower spec limit) No. of Samples Asphalt Binder Content Construction Specification & QC/QA for HMA Paving

Basic statistics IMPACT of sample size Basic statistics based on 95% confidence that 90% population data falls within +/-2 standard deviations SAMPLE SIZE LEVEL OF CONFIDENCE PERCENT OF POPULATION STD DEV MULTIPLIER 50+ 95% 90% +/- 2.0X 4 +/- 5.3X 75% +/- 2.9X 7 Construction Specification & QC/QA for HMA Paving

QC/QA Components Sampling and Testing SAFETY MUST BE STRICTLY ENFORCED Asphalt binder is hot and under pressure Aggregate feed belts are mechanical systems Heavy construction equipment Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

QC/QA Components Sampling and Testing more…. Very important Poor sampling and testing impacts performance. Use certified technicians, accredited labs, and good test protocols Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

QC/QA Components Sampling and Testing more…. When/where/how to sample the material How many samples? More samples reduce risk. More testing & smaller lot size reduces contractor’s exposure. Test frequency based on “per day” or “per ton” basis. More tests should be done at the beginning of production Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

QC/QA Components Sampling and Testing more…. Where sample is taken is critical for absorptive aggregate Random sample versus representative sample Stratified random sampling Random sample – when the sample is taken (and where) – often a single sample Representative sample – how the sample is taken – may be a combined sample Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

QC/QA Components Quality Control Charts Used on all projects Shows production consistency Shows production trends Displays test results test values running average target and limits Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

QC/QA Components Make a change? Construction Specification & QC/QA for HMA Paving

QC/QA Components Quality Control Charts more… Assist with determining production changes When are control charts restarted? significant change in the mix not just adjustments to stay on target Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

QC/QA Components Quality Control Charts more… Common control charts Gradations (P200, P30, P8) measure of material input Binder content Lab voids measure of mix consistency Field voids measure of construction consistency Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

QC/QA Components Acceptance Limits & Production Tolerances Tolerance = test measurement range about a target value Tolerance reflects allowable variability. Must be reasonable for both the owner and contractor (level of risk) Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

QC/QA Components Acceptance Limits & Production Tolerances more… V data = V constr + V matl + V cond + V sample + V test Must reflect the typical variability Industry construction capability Materials Paving conditions Sampling Testing Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

QC/QA Components Acceptance Limits & Production Tolerances more… Setting specification tolerance should consider statistical boundaries material performance engineering judgment Tolerance range for average vs individual tests. tests tolerance for field density based on lot average tests tolerance for lab air voids based on 4-pt moving average also have a spec tolerance for individual values. Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

QC/QA Components Acceptance Limits & Production Tolerances more… Low production variability allows contractor to set production targets closer to a spec limit without increasing risk of failing material tests Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Minimum Specification Limit Avg = 93.5 Std Dev = 0.75 Avg = 95.0 Std Dev = 2.0 No. of Samples In-Place Density (%Gmm) Construction Specification & QC/QA for HMA Paving

QC/QA Components Incentives and Disincentives Public regulation of low bid award for roadway construction is counter-productive to achieving quality paving Low bid award encourages cutting corners, using marginal material, and minimal QC Agencies need to reward contractors for exceptional work AND discourage contractors from marginal/poor work Minimize construction variability Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

QC/QA Components Incentives and Disincentives more… Pay based on ability to achieve spec criteria Incentive for higher quality (consistency) 100% pay for normal quality Dis-incentive for poor quality PWL – pay for quality – applies statistics and confidence levels to pay factors Larger data sets are better Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

QC/QA Components PWL and PD Concept PWL = (PDU + PDL) PDL PDU PWL % AC Construction Specification & QC/QA for HMA Paving

Percent Within Limits ± 0.4 Limits 5.0 Target Value 67 0.40 5.0 2 100 0.20 1 PWL s X Lot target Lot 1 Lot 2 Upper limit Lower limit Asphalt Binder Content Construction Specification & QC/QA for HMA Paving

Percent Within Limits ± 0.4 Limits 5.0 Target Value 84 0.20 4.8 2 100 5.0 1 PWL s X Lot target Lot 2 Lot 1 Upper limit Lower limit Asphalt Binder Content Construction Specification & QC/QA for HMA Paving

QC/QA Components HIGH Quality 110 100 90 80 70 60 NORMAL Quality Pay Factor (%) LOW Quality P W L Construction Specification & QC/QA for HMA Paving

Session -2 QC/QA Basics Terminology Basic Statistics QC/QA components Summary slide - Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Hot Mix Asphalt QC/QA Aggregate RAP Binder Mixture Paving Segregation Compaction Thickness Smoothness Talk about nine components of HMA that have an impact on the quality of the performance Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Hot Mix Asphalt QC/QA Aggregate Consensus Properties (CAA, FAA, F&E, SE, LA Abr, Soundness) Sample location Properties established during quarry production Aggregate Gradation Washed gradation vs dry gradations Variability Processing at the quarry Sample size and splitting Improper handling and stockpiling Contaminated stockpiles Aggregate RAP Binder Mixture Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Hot Mix Asphalt QC/QA Aggregate RAP Binder Mixture Component Properties Aggregate gradation Binder content Binder properties Chemical Extraction testing Ignition Oven Extraction testing Variability Source(s) of RAP Processing Stockpiling Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Hot Mix Asphalt QC/QA Typically certified by the supplier Full set of tests at terminal One test, one temperature for QC/QA Variability Switching crude oil source Refinery blending Contaminated shipping tanks Contaminated holding tanks Aggregate RAP Binder Mixture Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Hot Mix Asphalt QC/QA Mixture Binder Content “wet” mix can be tender “dry” mix can be stiff May be adjusted based on initial production Ignition oven commonly used Simple yield checks Variability Damaged binder pump or aggr weigh belt Uncalibrated binder pump or aggr weigh belt Incorrect aggregate moisture adjustment Varying aggregate Gsb Aggregate RAP Binder Mixture Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Hot Mix Asphalt QC/QA Mixture Volumetric Properties Sample taken from: truck, paver hopper, behind the paver. Based on lab compacted samples Measurement of Gsb is critical Measurement of Gmm is critical Lab Air voids VMA Variability Incorrect material property measurements Fluctuating plant production Bias from compactor Aggregate RAP Binder Mixture Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Hot Mix Asphalt QC/QA Aggregate RAP Binder Mixture Mixture Temperature Not a direct QC item Specification: minimum delivery or placement temp Critical to uniform placement and compaction Variability Aggregate moisture RAP moisture Exhaust gas control Haul distance Air temperature Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Hot Mix Asphalt QC/QA Paving Segregation Compaction Thickness Smoothness Paving Uniformity (Balance) Not a direct QC item Spec will call for uniform continuous operation Critical to achieving density and ride Variability Unbalanced production / delivery / paving Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Hot Mix Asphalt QC/QA Types of Segregation Aggregate segregation Thermal segregation Paver segregation Variability Improper loading of trucks Untarped trucks allow mix to cool Incorrect paver hopper and screed operation Paving Segregation Compaction Thickness Smoothness Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Hot Mix Asphalt QC/QA Paving Segregation Compaction Thickness Smoothness Gradation and binder content not enough Density for dense graded mixes (8% voids) (92% of Gmm) METHOD-1 Percent of lab density METHOD-2 Percent of Gmm METHOD-3 Percent of control strip How to measure density Cut cores Nuclear gauge Electro-magnetic gauge Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Hot Mix Asphalt QC/QA Paving Segregation Compaction Thickness Smoothness “Set it and forget it?” Uniformity is the key Variability Malfunctioning grade controller Non-uniform paving speed Varying mix temperature Varying amount of HMA at the screed Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Hot Mix Asphalt QC/QA Paving Segregation Compaction Thickness Smoothness Profilometer Ride-meter Incentive / Disincentive pay item Pavement design Paving operation Compaction process Variability Existing pavement conditions Faulty grade control Not continuous paving Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Hot Mix Asphalt QC/QA Aggregate RAP Binder Mixture Paving Segregation Compaction Thickness Smoothness Summary slide Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Hot Mix Asphalt QC/QA Special Conditions Small quantities Special mixtures Longitudinal joints Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Summary & Key Points Reasonable specifications with QC/QA Level of quality required and achievable QC and QA Reduce variability Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Summary & Key Points Reasonable specifications with QC/QA Achieve a quality paving product Within the capability of the industry Allow the contractor to be fairly paid Level of quality determined by the owner End Result Spec with some Method Spec Poor specification, particularly conflicting or unattainable QC/QA criteria, are counter-productive and lead to litigation. Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Summary & Key Points Level of quality required and achievable S/T frequency directly impact owner and contractor risk Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Summary & Key Points Quality Control and Quality Assurance Important QC items extend beyond sampling and testing QA criteria do not include all of the QC items Key QA items are P200, Binder Content, Lab Voids, Field Voids, and Smoothness All QC and QA components are important to achieve a good performing HMA pavement Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Summary & Key Points Reduce variability Well-trained workforce (technicians and equipment operators) Properly calibrated and operated plant and paving equipment Balanced, uniform and continuous production and paving operation Proper sampling and testing Commitment to Quality Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Construction Specifications and Quality Control / Quality Assurance for Hot Mix Asphalt Paving Attention to detail and good practices minimize variability Good practices do not cost extra, but can achieve bonus Final slide Construction Specification & QC/QA for HMA Paving Construction Specification & QC/QA for HMA Paving

Russian Engineers Training March 2011

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