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Quality Assurance
Quality
has become one of the most important consumer decision factors in the selecting
among competing products and services. This is true not only for individual
consumers but also for large corporations, government organizations and the
taxpaying public as a group. In its
broadest sense, quality is a degree of excellence: the extent to which something
is fit for its purpose. In the narrow sense, product or service quality is
defined as conformance with requirement, freedom from defects or contamination,
or simply a degree of customer satisfaction.
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| Figure 1: Checking Mat Density |
Figure 2: Truck Sampling During Night
Paving |
AASHTO and the
FHWA subscribe to definitions that designate “quality assurance” as an
all-encompassing term, to include “quality control”, “independent assurance” and
“acceptance” as its three key components (TRB, 1999):
- Quality assurance.
All those planned and
systematic actions necessary to provide confidence that a product or
facility will perform satisfactorily in service. Quality assurance
addresses the overall problem of obtaining the quality of a service,
product, or facility in the most efficient, economical, and satisfactory
manner possible. Within this broad context, quality assurance involves
continued evaluation of the activities of planning, design, development of
plans and specifications, advertising and awarding of contracts,
construction, and maintenance, and the interactions of these activities.
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Quality control. Those quality assurance actions and
considerations necessary to assess production and construction processes
so as to control the level of quality being produced in the end product. This concept of quality control
typically includes sampling and testing by the contractor to monitor
the process but usually does not include acceptance sampling and
testing by the agency/owner. Also called process
control.
- Acceptance. Sampling,
testing, and the assessment of test results to determine whether or not
the quality of produced material or construction is acceptable in terms of
the specifications.
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Independent assurance. A management tool that requires a third party, not directly responsible
for process control or acceptance, to provide an independent assessment of
the product and/or the reliability of test results obtained from process
control and acceptance testing. The results of independent assurance
tests should not be used as a basis of product acceptance.
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WAPA Pavement Note on
Quality Assurance |
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On State jobs
WSDOT performs acceptance testing, while the contractor may choose to
sample and test at any level for their own quality control. Acceptance
testing is not always used on local or private jobs. If used, it is often
performed by an independent consultant working for the agency or owner.
Typical quality control and acceptance tests are: in-place density (see Figure
1), asphalt content and aggregate gradation in relation to the
JMF, and mat smoothness. |
Quality control, acceptance and independent assurance are wholly
separate components of quality assurance.
It is difficult, if not impossible, to influence one component, solely
through actions within another component.
For instance, acceptance procedures are essentially monitoring
methods used to determine whether or not a particular process is meeting
quality standards. As such, they can
be used to accept or reject material based on its quality but they should never be used as
a method to control or improve quality; quality will not necessarily improve
based on increased or stricter monitoring alone. In short, no amount of inspection changes the quality
of a product or service (IQA, 2001). Quality
control (process control) is used to control and systematically improve
quality. Furthermore, independent
assurance test results should not be used for acceptance or quality control. If they are, the tests are no longer
independent and should not be used as if they were.
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