Recycling Bituminous Materials
of the Month
I do not have a great deal to relate at this time because if I
were to mention things that are concerning me I would be repeating
topics I have included in the past.
So I can only say if you are
looking for topical items and this is the first page you have happened
upon read the newsletters for the last twelve months, all the subjects
covered in them are still relevant to highways maintenance at the
Having said I have little to say, information has just been released
on particular methods of recycling bituminous materials, and other
materials, by the Aggregates Information Service, so I will include an
item on the subject.
Just to clarify how I regard inclusion of
entries into the newsletter, it is this, I may well continue to add
items to any particular newsletter during the course of the month in
question, so the content could be added to during that time. At the
end of the month it will be left unchanged for future reference unless
a true error or spelling mistake is found which will be rectified.
I have created a few new pages even though it is the summer here and I
spend less time at the computer, this is probably because they are
pages consisting mainly of photographs and take less time to prepare,
not that they are any less useful, in fact some of you prefer
You will find these new pages on the "Fast
Loading Photographs" menu, I have tried to keep all the pages
on this menu to about one minute download time, according to your
modem speed and internet connection.
This item is probably only relevant
to U.K. roads, but possibly Europe as well, where roads have evolved
over the centuries and will have included a period where they had to
withstand trafficking from the iron clad wheels of carts and
The photographs above go a long
way to illustrating my point about the inherent road pavement strength
of some evolved roads, and the fact that this strength must be
recognised and allowed for in road pavement refurbishment and overlay.
The failure to recognise this strength and incorporate it in the new work
will not only incur increased expense but could also introduce fresh problems if a total road pavement reconstruction is decided upon.
When total reconstruction is decided upon in urban environments this very often has to be
undertaken as a number of small areas of construction so that traffic
will still have access to the road under reconstruction and other roads and premises leading from the
This in turn can often mean there has to be many vertical joints
included in the construction of the road.
Every one of these joints will be a potential failure of the road
pavement because it is practically impossible, even with the best of
intentions, to fully compact the areas around the joint between
different sections of construction.
It has to be a considered option to "plane off" the failed road pavement layers
in one operation, leaving the large aggregate pitchings in as undisturbed manner as
possible. The removed material to be replaced with "premium" base (roadbase), binder course (basecourse)
and surface course (wearing course).
This option allows material to be removed and replaced
quickly with only a brief road closure, usually a Sunday, and few if any
poorly compacted joints.
My personal preferred material options in these situations are Hot
Rolled Asphalts, wearing courses and basecourses, this is because they
have stiffish binders (50pen.) and high binder contents relative to
Each site has to be considered on merit after good site investigation
that includes a number of decent size trial holes to be able to obtain
a clear picture of the nature of the road pavement construction.
But it has to be noted well seated
"pitchings" (known by other names in various parts of the
country) provide an extremely strong load distributing layer as a foundation
to subsequent road pavement layers.
One also has to remember that 95% of roads in this country are NOT
motorways or trunk roads, and a large portion of the 95% will be
evolved roads carrying only moderate amounts of mixed traffic.
Although over designing these lesser
roads may be one option to providing a long road pavement life it is
probably not the best use of
inadequate budgets, and not what I regard as true highways maintenance
To those of you out there who already employ this procedure I apologise,
but there are a large number of young engineers and technicians, and
those more familiar with "green field" road construction, who are lacking experience in maintaining road pavements of
a more unorthodox nature, these notes are so that they might ask a few
more questions before deciding on a course of action.
Information Service has just published a number of new
digests on various subjects relating to recycling in road pavement
construction and maintenance.
These are in addition to the considerable number of excellent digests
already present on the site.
Copies of these digests can be obtained from their website in .pdf
format, well I am sure they will be able to be downloaded when one or
two gremlins have been sorted out that is preventing the download of
particular digests, especially "Digest 68 :
Road Maintenance, Small Scale Road and Footway Maintenance Using In-Situ
Recycling Technologies", which I am keen to get a look at,
hopefully this will be sorted by the time you access them.
The Aggregate Information Service (AIS) is operated by Viridis, the
sustainability and waste management research arm of the Transport
AIS is funded by the RMC Environment Fund under the land fill tax
credit scheme, with third party funding from the Department for
Transport, Local Government and the Regions.
It is my opinion that if a bunch of people sat down to create a user
friendly totally recyclable road making material they would be hard
pushed to create a product better than bituminous material, i.e. a
mixture of good quality aggregate and bitumen.
Providing this material, of whatever particular type, is treated with
the care that comes from knowledge of the material, ( do not over heat
it in the recycling process ) it is able to be recycled many times.
However, there is a very important point to make, which is that we are
talking about bitumen based bituminous materials, although the word
tarmac is used quite commonly to describe bituminous materials there
has been very little tar used in general road making in the thirty
years I have been involved in the industry, for the simple reason that
as soon as natural gas replaced "town gas" there was not the
large source of tar available to be used as a cheap bituminous
(A bit of history for all the "youngsters".)
I mention this because tar has a few health problems associated with
it which bitumen does not have. I would regard it as quite unlikely to
come across tar based materials when recycling any bituminous
materials that is less than thirty years old, which is likely to be
the the bulk of material you will be dealing with.
If this is not the situation in the area you work it is something you
must be aware of and make provision for.
If you wish to know a little more about recycling
bituminous materials may I suggest you visit the page on
this website that offers some relevant information, and links to other
sites involved in various recycling processes.
Motto of the Month
fool some of the people all the time, and all of the people some of the
time, but you cannot fool all of the people all of the time"