1.12 testing materials(1)
TRANSCRIPT
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1.12 MATERIALS TESTING
1.12.1 The Experiments
1.12.2 Defining the general objectives
1.12.3 Reviewing previous work
1.12.4 Resources and time limits
1.12.5 Choosing a method 1.12.6 The null hypothesis
1.12.7 The detailed method
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The need for new experiments
There are often no methods for calculating materialproperties.
Materials are continually changing. (e.g. cements) New materials (e.g. pultruded plastics for beams) must
be tested.
Unexpected problems (e.g. delayed ettringite formation)
occur with some materials and must be researched. There are generally no complete answers from these
experiments.
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1.12 MATERIALS TESTING
1.12.1 The Experiments
1.12.2 Defining the general objectives
1.12.3 Reviewing previous work
1.12.4 Resources and time limits
1.12.5 Choosing a method 1.12.6 The null hypothesis
1.12.7 The detailed method
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Defining Objectives
It is quite rare to carry out an experimentsimply to see if one material is adequate for
an application (radioactive waste disposalresearch is an exception to this).
In general durability experiments are aimedat improving a material or method.
Thus the aim is to see if the new methodworks better than the old one.
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Possible objectives
will this paint last longer than the usualone
will this change to the concrete miximprove its durability.
will this change to the concrete mix make
its susceptibility to sulphate attack moresensitive to poor curing (this requiresmulti-variate analysis)
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1.12 MATERIALS TESTING
1.12.1 The Experiments
1.12.2 Defining the general objectives
1.12.3 Reviewing previous work
1.12.4 Resources and time limits
1.12.5 Choosing a method 1.12.6 The null hypothesis
1.12.7 The detailed method
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Where to find references
Library index systems.
References from other documents.
Commercial data-bases which are available on line.
Many organisations (e.g. the British CementAssociation) have large data bases on which theywill do keyword searches (for a fee).
If you have one paper on the subject a system calledthe citation index may be used to find others whichhave cited it as a reference. (science only)
The internet... Google Scholar
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TYPES OF REFERENCES
Journal Papers
Conference Papers
Light Weight Journals
Company Literature
Books Web sites
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Journal
Publication
Dates
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The future of
Journal
Publishing??
Coventry
University has
an Athenssubscription
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JournalRankings
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Changes in journal publishing
Worldwide there are 24,000 journals
publishing 1.3 M papers per year.
50 M papers already published. The bulk
have now been scanned.
New journals being set up using open
sourceauthor pays model.
Great emphasis on citations. Can be
tracked with ISI or Google Scholar.
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TYPES OF REFERENCES
Journal Papers
Conference Papers
Light Weight Journals
Company Literature
Books Web sites
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Conference Papers
The review process for these is often
minimal.
Authors pay to attend conferences.
Conference proceedings are normally
published in book form.
There is often a "supplementary volume"
which has even less review.
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TYPES OF REFERENCES
Journal Papers
Conference Papers
Light Weight Journals e.g. New Civil Engineer.These should be treated with caution but they willoften give you references to work from
Company Literature This is basically advertising
and is not externally reviewed Books
Web sites
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Company
Literature
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TYPES OF REFERENCES
Journal Papers
Conference Papers
Light Weight Journals
Company Literature
Books Text books are normally based onpublished research. They often have a few errorsin them. Some books are more like researchmonographs and the contents may be new and
unchecked Web sites: Generally useless as references
because they keep changing
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References
The essential point is never to rely on
references from a single source, always look
for independent confirmation of results. You must remember that most researchers
are under considerable commercial pressure
to publish papers and, in particular, resultsthat will help them to obtain funding.
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1.12 MATERIALS TESTING
1.12.1 The Experiments
1.12.2 Defining the general objectives
1.12.3 Reviewing previous work
1.12.4 Resources and time limits
1.12.5 Choosing a method
1.12.6 The null hypothesis
1.12.7 The detailed method
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Resources and time limits
Note that many materials are like concrete
in that they take several weeks to achieve
their design properties. This time must beallowed for.
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1.12 MATERIALS TESTING
1.12.1 The Experiments
1.12.2 Defining the general objectives
1.12.3 Reviewing previous work
1.12.4 Resources and time limits
1.12.5 Choosing a method
1.12.6 The null hypothesis
1.12.7 The detailed method
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Choosing a method
The three objectives are:
1. Make it realistic
2. Make it fast
3. Make it cheap
These three are conflicting.
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The samples
In a real construction environment materials are
never in optimum condition..
The difficulties with simulating site conditions arethat all sites are different and that all scientific
experiments must be designed to be repeatable.
One solution is to try to simulate both best and
worst conditions.
The geometry of the sample may affect durability.
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The Environment.
In general real exposure experiments are notvery useful because they are too slow.
Deterioration may be accelerated with, for
example, heat, pressure, applied voltages, orpre-contaminating the samples.
Each of these methods must be used with
care. Heat slows down sulphate attack.Mixing chlorides into wet concrete makes it
less permeable.
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1.12 MATERIALS TESTING
1.12.1 The Experiments
1.12.2 Defining the general objectives
1.12.3 Reviewing previous work
1.12.4 Resources and time limits
1.12.5 Choosing a method
1.12.6 The null hypothesis
1.12.7 The detailed method
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The null hypothesis
This is a statement such as "treatment X
makes no difference to the durability of this
product". The experimental data are thenused to show that there is a probability of
less than 5% of this being true.
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1.12 MATERIALS TESTING
1.12.1 The Experiments
1.12.2 Defining the general objectives
1.12.3 Reviewing previous work
1.12.4 Resources and time limits
1.12.5 Choosing a method
1.12.6 The null hypothesis
1.12.7 The detailed method
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Multivariate or Bi-variate
Bi-variate means change just one variable and
measure another - for example vary the w/c ratio
and measure the strength. Multivariate experiments involve changing several
variables and testing whether they interact, i.e.
whether changing one makes the result more
sensitive to changes in another. They are difficultto analyse but can be very powerful.