1.12 Testing Materials(1)

7/27/2019 1.12 Testing Materials(1)

1/29

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


2/29

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.


3/29









4/29

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.


5/29

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)


6/29









7/29

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


8/29

TYPES OF REFERENCES

Journal Papers

Conference Papers

Light Weight Journals

Company Literature

Books Web sites


9/29


10/29

Journal

Publication

Dates


11/29

The future of

Journal

Publishing??

Coventry

University has

an Athenssubscription


12/29

JournalRankings


13/29

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.


14/29

TYPES OF REFERENCES

Journal Papers

Conference Papers


Company Literature

Books Web sites


15/29

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.


16/29

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


17/29

Company

Literature


18/29

TYPES OF REFERENCES

Journal Papers

Conference Papers


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


19/29

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.


20/29






1.12.5 Choosing a method

1.12.6 The null hypothesis



21/29

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.


22/29










23/29

Choosing a method

The three objectives are:

1. Make it realistic

2. Make it fast

3. Make it cheap

These three are conflicting.


24/29

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.


25/29

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.


26/29










27/29

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.


28/29










29/29

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.

1.12 Testing Materials(1)

Documents

Transcript of 1.12 Testing Materials(1)