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TRANSCRIPT
Construction QC/QA Background 1
Quality Control / Quality Assurance
Background
Senior/GraduateHMA Course
Construction QC/QA Background 2
What you will learn….
• Types of specifications• An introduction to process control• Sampling• An introduction to acceptance
Construction QC/QA Background 3
Fundamental QuestionsRelated to a Specification
• What do you want?
• How do you order it?
• How do we know we get what we ordered?
Construction QC/QA Background 4
What do we want - what do we specify
Strength Volumetric Properties
Durability Gradation
Density Asphalt content
Smoothness Thickness
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How do we order it - types of specifications
How do we order what we want?
Proprietary product
Method or recipe
End result
Quality Assurance
Warranty
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Proprietary Product Specification
• Brand or manufacturer or equal• Relies on past performance• Relies on the integrity of the producer• Generally not used in the HMA industry
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Method Specification
• Procedural• Prescription• Materials and workmanship - descriptive• Detailed description of the materials and methods
used to prepare the product• Maximum control by specifying agency
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Method Specificationdisadvantages
• Does not allow for innovation
• Inspector intensive
• Contractor - no legal responsibility
• Quality Performance?
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End-result specification
• Minimum requirements for the in-place materials• Does not specify construction methods• Component materials specifications may or may
not be included
SPECIFYING AGENCY SETS THE LIMITS FOR THE
CONTRACTOR
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Disadvantages
• Spec limits based on subjective judgement
• Target + what• Often n = 1• Who has responsibility for process
control?
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Method Specification
+
End result Testing
= DANGER
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Quality Assurance Specifications• A form of end- result specification
Materials properties
Specification
Performance
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Advantages of QA specification
• Can be performance related• Pay factors can be related to performance• Less inspector intensive• Responsibility for process control and
acceptance is separated and clearly defined
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Statistics
IS A TOOL USED IN QA SPECIFICATIONS
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QUALITY ASSURANCE
PROCESS CONTROL
INDEPENDENT ASSURANCE ACCEPTANCE
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PROCESS CONTROL
INDEPENDENT LABORATORY
SUPPLIER
CONTRACTORHIGHWAY AGENCY
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Acceptance function
• Acceptance testing• Monitor testing• Process control monitoring
• INSPECTION
• Performed by the owner or his representative
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Independent assurance
• Provides for an independent third party assessment of the reliability of the results obtained for acceptance
• Must be performed by personnel NOT directly responsible for process control or acceptance sampling and testing
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What Do We Do If We Don’t Get What We Ordered?
Mix Properties/Characteristics:• Density• Strength• Durability• Smoothness• Thickness• Etc.
Decisions:
• Incentives• Penalties• Reject
MixturePerformance
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To be considered in establishing a sampling and testing program
• Frequency of tests
• Location of samples
• Size of samples
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Warranties to the rescue?
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Perceived Advantages
• Decreased construction oversight• Improved quality • Lower maintenance and life cycle cost• Innovation in materials, testing, and
construction
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Types of warranties
• Materials and workmanship – the contractor is responsible for correcting defects in work elements within the contractors control for the warranty period
• Performance – The contractor assumes full responsibility for pavement performance during the warranty period.
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Perceived Disadvantages
• Large contractors emerge• Surety issues• Uncertainty and risk may drive cost up
– contractor involvement in design process
• Definition of performance
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Reasons for sampling materials
• Certification or source approval
• Process/quality control
• Acceptance
• Independent verification samples
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Types of samples
• Judgement
• Quota sampling
• Systematic sampling
• Stratified sampling
• Random sampling
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Number of lots and number of samples in the lot
• Depends on practicality and convenience– Day’s production/time– Tonnage– Length
• Production homogeneity
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Location of samples
• Aggregates– Flowing aggregate stream– Conveyor belt– Stockpiles– Transportation units– Roadway
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Location of samples
• Asphalt mixtures– Conveyor belt (hot elevator)– Truck or paver hopper– Roadway prior to compaction– Roadway after compaction
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Questions?