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Construction QC/QA Background 1

Quality Control / Quality Assurance

Background

Senior/GraduateHMA Course


What you will learn….

• Types of specifications• An introduction to process control• Sampling• An introduction to acceptance


Fundamental QuestionsRelated to a Specification

• What do you want?

• How do you order it?

• How do we know we get what we ordered?


What do we want - what do we specify

Strength Volumetric Properties

Durability Gradation

Density Asphalt content

Smoothness Thickness


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


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


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


Method Specificationdisadvantages

• Does not allow for innovation

• Inspector intensive

• Contractor - no legal responsibility

• Quality Performance?


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


Disadvantages

• Spec limits based on subjective judgement

• Target + what• Often n = 1• Who has responsibility for process

control?


Method Specification

+

End result Testing

= DANGER


Quality Assurance Specifications• A form of end- result specification

Materials properties

Specification

Performance


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


Statistics

IS A TOOL USED IN QA SPECIFICATIONS


QUALITY ASSURANCE

PROCESS CONTROL

INDEPENDENT ASSURANCE ACCEPTANCE


PROCESS CONTROL

INDEPENDENT LABORATORY

SUPPLIER

CONTRACTORHIGHWAY AGENCY


Acceptance function

• Acceptance testing• Monitor testing• Process control monitoring

• INSPECTION

• Performed by the owner or his representative


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


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


To be considered in establishing a sampling and testing program

• Frequency of tests

• Location of samples

• Size of samples


Warranties to the rescue?


Perceived Advantages

• Decreased construction oversight• Improved quality • Lower maintenance and life cycle cost• Innovation in materials, testing, and

construction


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.


Perceived Disadvantages

• Large contractors emerge• Surety issues• Uncertainty and risk may drive cost up

– contractor involvement in design process

• Definition of performance


Reasons for sampling materials

• Certification or source approval

• Process/quality control

• Acceptance

• Independent verification samples


Types of samples

• Judgement

• Quota sampling

• Systematic sampling

• Stratified sampling

• Random sampling


Number of lots and number of samples in the lot

• Depends on practicality and convenience– Day’s production/time– Tonnage– Length

• Production homogeneity


Location of samples

• Aggregates– Flowing aggregate stream– Conveyor belt– Stockpiles– Transportation units– Roadway


Location of samples

• Asphalt mixtures– Conveyor belt (hot elevator)– Truck or paver hopper– Roadway prior to compaction– Roadway after compaction


Questions?

block 21 background 13

Technology

process control sampling

contractors control

process control andacceptance

independent assurance

end result testing

product maximum control

past performance

place materials