TOPICS
BS
EN 12591 - Bitumen Viscosity
The Role
of the Soils and Materials Engineer
Durham
University, Road Pavement Design Site
"New"
and "Stiff" Bitumen Grades
Motto
of the Month
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Introduction,
to 2002
I do not have a lot to report at the moment but
I thought I would try and get January's newsletter out on
time so I could wish you all a Happy New
Year, may it
be a year where we all continue to learn about the
profession we are employed in. in all its disciplines.
I stress that we all should know, as well as we are able,
what we are responsible for and we should not become a
profession of "suits" buying products on the
basis of glossy brochures and thinking responsibility can
be laid at the feet of organsiations who issue approval
documents.
This is really not the case, and if you think it is, read
the small print, sometimes it is quite large print, just
so the organisation does not pick up any liability for
failure.
For those of you who read this who are in positions of
authority it may be time to reconsider the positions of
Materials Engineers, Materials Technicians and even
laboratory facilities, because I really feel you do not
appreciate the amount of money that is involved, over the
long term, if correct materials are not employed in
highways maintenance.
The amounts of money I refer to are not just related to
actual price of products and their longevity, but also to
claims for liability against authorities where highway
surfaces can be deemed as "not suitable for the
purpose intended", an all encompassing phrase the
lawyers like to use a lot.
In my opinion quietness comes behind safety in order of
importance, give me a good "HRA and precoats"
or a "14mm/racked in 6mm." surface
dressing on a cold frosty morning when I am not sure if
the "gritters" have been out, rather than a
Thin Surfacing, any time.
And if what I write seems gobbledegook and you do not
know what I am talking about, and you are in charge of
highway networks, perhaps you ought to ask a man who does
know, such as a Materials Engineer.
BS
EN 12591 - Bitumen Viscosity
Do
not forget, if everything has gone to plan, binder grades
in BS 4987 bituminous mixtures will change from 1/1/2002,
and this could include BS 594 mixtures as well, although
this was not originally intended at this time.
( Comments on the draft copy of BS594 were not due back
until the end of December. )
But mixing plants only have so many bitumen storage tanks
for distinct bitumen viscosities so that is why it may be
necessary to introduce binder grade change in hot rolled
asphalts.
More about bitumen viscosities can be found in the
September
newsletter.
It is
also interesting to note that binder grades in some of
the proprietary Thin Surfacings will have to change
if the "old" grades are no longer
available.
This will mean the physical properties of the materials
that under went trials to receive HAPAS certification
will change if the grade of bitumen changes, which is
interesting.
It might also be worth noting at this time that in the
draft BS 594 it proposed blending differing
"straight run" grades of bitumen to produce the
appropriate viscosity of binder in accordance with the
new British/European Standard.
I, personally, am not too happy about this as it
introduces another possible source of variability in the
properties of a particular bituminous mixture.
The Role
of the Soils and Materials Engineer
With all this change, and some might say confusion,
taking place in the specifying and manufacture of
bituminous products perhaps readers can understand why I
feel a strengthening of "in-house" highway
materials knowledge is not out of place.
I will not "go on" about my enthusiasm for the
need of more independent soils and materials engineers,
as I am biased, coming from that background.
But I will draw your attention to three reports published
by the County Surveyor's Society, and still readily
available from the CSS,
CSS ENG/2-94 : Materials for
Construction and Maintenance
CSS ENG/4-94 : The Provision of the Soils and Materials
Engineers Service
CSS ENG/6-95 : A Specification for the Provision of the
Soils and Materials Engineering Service
I hope some of you will take the time to obtain and read
these reports, the engineers who prepared them are to be
respected and not ignored.
Durham
University, Road Pavement Design Site
I
have been doing a dis-service to Durham University in not
using the appropriate hyperlink to correctly link in to
the their Road
Pavement Design site for students. I have now
rectified this (on the links page) and suggest this is a
MUST visit site for everybody, not just students, who
wish to have an insight in to all the various aspects
relating to road pavement design
"New"
and "Stiff" Bitumen Grades
I always like to take advantage of
information in articles provided by other parts of the
industry, and therefore I would draw your attention to
the article "Binding Agreement" on page 36 of
New Civil Engineer - 17th. Jan. 2002.
This article gives details on the recent changes to
specifying the binder grades of bitumen, and goes on to
discuss the role of the stiffer (15pen. and 25pen.)
grades of bitumen that have been trialed in High Modulus
Roadbases with questionable success.
I would draw your attention to the views of Chris Rayner,
technical manager with Exxon Mobil, which I would tend to
agree with.
However one has to bear in mind that the article does
state that Exxon Mobil are the largest supplier of hard
grade bitumen so they do have an interest in ensuring
that the stiff roadbases and basecourses are correctly
formulated.
Further information on High Modulus Roadbase and
Basecourse can be found in the June newsletter , and on
the website page,
"NOTES ON HIGH MODULUS
( STIFF ) DENSE BITUMEN MACADAM ROADBASE" .
and information on the
"new" binder grades can be found in the
newsletter of September, see the earlier part of this
newsletter.
Information
can also be found on commissioned research work on the
subject of stiff roadabses and basecourses on the
following website :-
www.civeng.nottingham.ac.uk
I trust
this work will include monitoring the "real"
side of laying stiff bituminous materials on site in all
weathers.
Returning to
the magazine article there is also the opportunity to
obtain a "handy calculator" from RMC Aggregates
for converting the superseded bitumen grades into their
nearest European equivalent, (but remember moving to the
nearest equivalent grade of bitumen may not necessarily
be the way you want to move according to the traffic and
site conditions, however it may be the right way
according to how you are laying the product).
Who said highways maintenance was easy, I did not.
A colleague has already ordered several copies of the
calculator for the office and as other information is
also displayed on the item I will await its arrival with
interest.
Motto of the Month
"To
travel hopefully is often a better thing than to
arrive."
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