History of Bituminous Mixtures
BS 4987 Replacement by BS EN 13108
There's More - BS EN 14023
of the Month
I have started to write this
Summer newsletter because it is raining outside, and I mean raining,
it was raining all night, and again, I mean raining.
Indeed it has been raining, significant amounts most days for the last
fortnight, and on occasions the downpours have been torrential.
Today is the 25th. of June, the first day of Wimbledon, and
the forecast is for a "wet" first week,
(by the way it is still raining on the second Wednesday at Wimbledon,
and the Royal Show has finished a day early because of the wet
My involvement with the highways maintenance industry is not great,
but I have some friends still active in the industry and I am
led to believe there have been some surface dressing failures
"allegedly" attributable to the prolonged and severe wet weather.
But it would still be
interesting to know the dust contents of the chippings used on the
failed sites as it is unusual to lose chippings once they have become
firmly attached to the binder layer.
If there is a layer of dust between chipping and binder then, in my
experience, the chipping attachment is at risk for some time after
dressing, including the following winter.
However this is the UK, and just because it is raining now does not
mean we might not have the hottest August on record. It is the
weather conditions in the UK that contribute to highways maintenance
being so "interesting".
It also means you should not over react to any particular situation,
e.g. increase binder rates of spread, as you will only create further problems
for yourself. If experience tells you that a particular material or
process has been successful over a number of years I would be very
careful before you make any radical changes.
The difficult bit of the last sentence is "if experience tells
I am finding that engineers and technicians with experience in their
relative disciplines are becoming increasingly scarce, and getting
more so, as they seem to be being actively dispensed with as an
(So much for the "skills shortage".)
Allegedly all we need is "Managers" and everything will be fine,
who they are going to manage is going to be the interesting bit.
If they are going to just trust the industry, (bless 'em*),
I think you will be in for a few surprises.
The "suits" had all better sign up for the "Beat the Backlog"
campaign for more money currently being promoted by
"Surveyor" magazine. But perhaps not, they will not want to
be seen disagreeing with the "government", they might not
get the next "step up" managers job, even in a local
It would be nice to see "Surveyor" devoting a little of
their magazine each week to providing some "real" information to
engineers and engineering technicians on the various highways
maintenance disciplines, that is if they have anybody on their staff
capable of overseeing such engineering content.
Perhaps it is more important to provide the sort of
information that the "managers" need.
Is it my perception of the situation, but when did you last read a
technical article written by a "real" engineer rather than a
public relations consultant for the particular company, or authority.
Just to clarify, I have
never had, and do not have a problem with the industry being the way
it is, they are doing their job, and they are doing it particularly
well, i.e. earning money for their shareholders.
The individuals who
do best in this respect will be the most rewarded, and there is strong
competition in the industry to be the most rewarded.
My particular admiration goes to experienced laying gangs and their
supervisors, and the true "day to day" technical guys, who are generally not the
most rewarded but often the most criticised.
However, if you do not make provision for engineers and engineering
technicians to have an overseeing/supervising role in highway works,
giving them the authority to fulfill this function, I
believe you are making it a little too easy for the industry.
Without an "intelligent client" how do you know that you are
following an appropriate course of action to meet your highway
maintenance needs, just trust the "industry", I think not, I
regard that course of action rather unwise, it did not work in
the USA, it is unlikely to work here.
It is not just about asking for more money, how you spend it is just
as, if not more, important.
In looking to find further information on subjects that will follow I
visited the website of the CSS, to find that it had received its
The organisation has re-branded as just CSS, and dropped the title
"County Surveyors Society".
Old timers like myself will recall that this is the second time the
organisation has done this, the previous occasion was about fifteen or
years ago, but it quickly reverted to being known as the County
Surveyors Society again, as what else could CSS represent, and there
did still remain a few County Surveyors.
It will be interesting to follow what happens this time, with all
County Surveyors long gone and replaced by "Strategic Directors".
What was wrong with calling it the SDS (Strategic Directors Society) I
wonder, if that is what they are. There is no shame in being a
Strategic Director, but you do not have the same role as a County
Surveyor. Perhaps the "public relations people" did not feel
that the title SDS projected the desired image.
I also found that it was no longer possible to find any technical
information on current topics, as had often been present on the
previous website, e.g. minutes of recent committee meetings, or
possibly copies of TRL reports commissioned by CSS.
The minutes I was particularly looking for being recent minutes of the
Southern and Northern Materials Groups.
Unless the website is still a "work in progress" it appears
only visitors who are members of the CSS will be able to know what is being
discussed by these bodies. Therefore "ordinary"
engineers and engineering technicians will just have to trust that the
members have the interests of local authority highway departments, and
the public they serve, at heart, as well as considering the input from
a number of large companies who also have representation on
The "make-over" has included the services of a public
relations company, "daybreak communications", perhaps you
would also like to visit their website, and note who else employs
their services, and the material that they have produced in their
And I am sorry Fiona, I find it necessary to take you off my list of
thinking men's pin-ups.
History of Bituminous Mixtures
It is amazing how quickly the
years pass, it is already ten years since government separated the
motorway and trunk road network from the total highway network in the
UK, and awarded major contracts for the maintenance of large areas of
the network to Consultants, Contractors and Suppliers, sometimes
separately but often as a "combined" operation.
Thus, for all intents and purposes "privatising" this
significant portion of the highways maintenance industry, although
only 5% of the total network, it carries the bulk of the damaging
heavy traffic, and receives a significant slice of the highway
At this same time the decision was taken by Government, well the
Highways Agency (same thing), that all surface course bituminous
mixtures would be proprietary (branded) Thin
Surfacings, and these
materials have continued to be used to the present time.
Similar materials are now being promoted for local authority highway
networks under the description of Negative Textured
again proprietary bituminous mixtures.
The length of time that these materials have been employed,
successfully or unsuccessfully, means that there are now many
established engineers and engineering technicians who have little if
any experience of established generic British Standard hot rolled asphalts and
I find this situation disturbing, especially with the introduction of
the new standard BS EN 13108 for Bituminous Mixtures : Material
Bituminous Mixtures not Asphalts, if we are supposed to be
harmonising with Europe perhaps we should be using the same
It is sad to report that there are even laying gangs, consisting
mainly of younger men, who do not have the expertise/experience to lay
satisfactory surfaces of hot rolled asphalt and precoats.
I do not consider this sufficient reason to no longer specify this
most durable highway surfacing available to engineers, and the
surfacing that will make the best, and most cost effective use of,
scarce resources of premium, high PSV (polished stone value),
It, of course, also permits the economic use of lower PSV (above
45) aggregate in the matrix of the hot rolled asphalt.
& BS 4987 Replacement by BS EN 13108:Bituminous Mixtures -
Material Specifications (or parts of BS EN 13108)
First of all you do not panic,
there really is no need, you will be buying the same aggregate, and
the same bitumen, mixed in the same plants and supplied to you by the
As I understand the situation, if you know the composition of the
mixtures that you are receiving now you will be able to
"construct" a specification that you can place in a contract
that will provide exactly (as near as makes no difference) the same mixture in the future.
Just because the sieve sizes may change a little does not mean the
overall composition has to change.
As long as you have a man or woman who knows about these things there
will not be a problem, if you do not have such a person you may need
to find one quite quickly.
There really should not be any change in the bituminous mixtures you
want to receive, unless suppliers take the opportunity to supply
mixtures that are different in composition to those that you are
familiar with, and that you know perform well for a particular cost.
What may happen is that suppliers may suggest that if material
supplied to you does not meet your particular specification, it has
not actually "failed" but is just a different
"grade", and therefore still complies with BS EN
13108:Bituminous Mixtures - Material specifications.
This is because the combinations of the options in the various tables
means a bituminous mixture has to be rather extraordinary for it not
to meet some combination of options.
I have been telling you for years that you could not dispense with the
services of Materials Engineers, if you no longer have such support
you may need to buy it in.
Hopefully detailed guidance will be provided in PD 6691:Asphalt-Guidance
on the use of BS EN 13108:Bituminous Mixtures-Material specifications , the "interpretation"
document that will provide guidance on the use and application of the
new standards, that is to be published by the British Standards
The fact that this document is late on parade makes me think that what
it may contain is still being argued over, this document could make
the change-over relatively painless if it contains an accurate set of
example specifications for the commonly used bituminous mixtures on
local highway networks.
(examples of frequently
used bituminous mixtures as .pdf documents can be found on this linked
It is my feeling that the industry may take this opportunity to subtly
alter the nature of bituminous mixtures supplied, that may not be to
the benefit of local highway networks.
It may be wise to take up the opportunity offered by the QPA (Quarry
Products Association) of a place at one of a series of "briefing meetings"
during July, across England.
I hope a good proportion of practicing (and practical) Engineers and
Engineering technicians can find seats at these meetings, asking the
right questions, if there is an opportunity to ask questions.
Engineers and Engineering technicians will need to consider how such
not adjusting binder and filler contents to aggregate gradings,
binder adjustments according to the density of the aggregate,
and how and where will aggregate properties, e.g. PSV (Polished Stone
Value) and AAV (Aggregate Abrasion Value) be specified, will be
Do not be afraid to ask the obvious questions as it is answers to such
basic items that are important, especially with regard to local
authority highway networks.
A couple more points of importance before I finish.
A new laying standard is to be published, it should have already been available
but it too is late, so again we do not yet know what it contains.
This laying standard is BS 594987, a "catchy" title, this
document is said to replace the Part 2's of
BS 4987 and BS 594.
However, I am a little confused, as the document appears to have the
title of a British Standard, yet, as I understand it, it was produced
as a result of a research programme run by QPA, the Highways Agency
and the Refined Bitumen Association (RBA).
I am not aware of any direct input from Engineers in local authorities, where
this document is likely to have the most impact.
(No mention of it on the CSS website, but then I am not a member, and
could not get access to most of the website.)
If one was prone to conspiracy theories, one could start to imagine
all sorts of things.
Finally, I am not sure why the January 2008 date is being stressed so
highly, it may be due to "legislation" reasons, I am trying
to keep to practical aspects.
As I understand it BS 4987 and BS 594 will not be superseded, at the earliest,
until the end of March 2008.
This appears completely sensible as most of you will have yearly contracts
in relation to bituminous mixture supply until this date, to change
the method of specifying mid contract could cause all sorts of
Some of you may well have longer contracts that will pass the March
2008 date, I am unsure as to whether these will be binding or will
need to be re-negotiated, that will be for the legal boys and girls.
So you still have time, to wait for the forthcoming documents and
study them, and also make sure that the "new" specification
you need to put in place will ensure that you receive the same actual
bituminous mixtures that you know work for you, on your network, and
at a similar price.
I would have thought this would be a brilliant opportunity for a
supplier to do some seriously good public relations, if anybody
responds to the challenge it is likely to be R.J.
Maxwell & Son Ltd.,
in Northern Ireland, so it might be worth monitoring the "education" section of
IMPORTANT UPDATE (8th. July)
P.D. 6691:2007:Guidance on the use of BS EN
13108 Bituminous mixtures. Materials specifications,
was published on the 29th. of June, and it is able to be purchased
"on line" from the BSI website,
£154:00 to none members, £77:00 to members.
BS 594987:2007:Asphalts for roads and other
paved areas - Specifications for transport, laying and compaction and
type testing protocols,
was published on the 29th. of June, and it is able to be purchased
"on line" from the BSI website,
£142:00 to none members, £71:00 to members.
The QPA have also recently published a bulletin, i.e.
QPA Asphalt Group Bulletin 3:Impact on Standards
for laying asphalt on their website.
This document is able to be downloaded and gives an indication of what BS 594987 contains,
and its purpose.
However it is the detail of BS 594987 that needs to be studied, so I
feel you do need to spend some money and obtain a copy of the actual
The bulletin appears to indicate an emphasis on "resistance to
permanent deformation" and "stiffness" of bituminous
mixtures, admirable qualities for heavily trafficked roads, but
probably not for local and rural networks.
These properties tend to have associated with them reduced binder
contents and increased stiffness (high viscosity) bitumen binders,
modifications to a bituminous mixture that may affect the property of
durability, especially on rural roads with "moving" pavement
Also I cannot help but continue to notice the complete avoidance of
the the term "bituminous mixture" by the author in the whole
of the text of this bulletin. That is except in the
"References" section at the end where the actual document
that is causing all these changes is listed, i.e. BS EN
13108:Bituuminous Mixtures-Material specification.
Each part of the standard will then refer to a particular defined
mixture, e.g.'s Hot Rolled Asphalt, Asphaltic Concrete, Stone Mastic
I do not like calling everything "asphalt", in my opinion it
is a "dumbing down" of engineering terminology and will only
cause confusion, educate yourselves to know what you are talking about
and what you wish to specify and receive. I believe this is one of the
functions of the new standard.
The above standards may seem expensive but it is absolutely insignificant compared to
the amount of money that you will be spending on bituminous mixtures, you do need
these documents, purchase them and study them.
In my opinion it is very important
for you to
do so if you want to specify the bituminous mixtures that you want to
Just a couple of further points that I will bring to your attention,
and then I will leave you to get studying, ready for those QPA
It appears that PD 6691 does not give guidance on,
BS EN 13108-2 : Asphalt concrete for very thin
BS EN 13108-3 : Soft Asphalt
stating they are "either little used in the UK or covered
by other guidance", it would be nice to have all the guidance in
one volume though, would it not.
I would have thought guidance on BS EN 13108-2 is important as this document covers mixtures with aggregate particles up
to 12.5mm. size. I believe that guidance relating
to this specification is important to ensure appropriate
specifications to replace bituminous mixtures for "0/4 fine graded
surface course" up to
10mm. close grade macadam currently specified in Part 1 of BS 4987,
and very widely used.
Perhaps there is a "conflict" here with the word
"thin", what was I saying earlier about conspiracy theories.
Although in fairness there is a degree of "overlap" in
relation to the aggregate sizes of bituminous mixtures between BS EN
13108-2 and BS EN 13108-1:Asphalt concrete,
for which you will be able to find guidance.
It will be in the grading
of the "fines", for smaller aggregate size mixtures, where I
believe any difference may occur.
Similarly I would have thought guidance on BS EN 13108-3 was
important, because as I understand it this specification will cover
mixtures with low viscosity and cutback binder from 250/330pen down,
(meaning less viscous).
Specifying bituminous mixtures with cutback binders can be a
"minefield" and any document that can bring some clarity and
conformity to these mixtures is to be embraced, as the information,
and method of specifying in current specifications does need
improvement, in my opinion.
However, may I point out that although you are not being given
guidance on the use of these particular parts of BS EN
13108:Bituminous Mixtures-Material specifications, they are
still current BSI specifications and you can use them to specify the
material you wish to receive.
Once you have got you head around how to use them.
With regards to the publication of BS 594987 it is the inclusion of
the wording "and type testing protocols" in its title that I
find intriguing, what does it mean, all will be revealed in the course
It appears those of you who are technically interested in the changes
relating to the specifying of bituminous mixtures have some
considerable study to undertake before attending the QRP Briefing Meetings on
the 17th., 19th., 26th., 27th. and 31st. of July.
I bet some of you wish you had a Materials Engineer to sort it all out
for you, or perhaps you are glad you have not, it is easier to
One Engineering Consultancy is already offering a training course on the introduction of the new standards, perhaps you had better do
some "Googling" and sign up, just try "PD 6691" or
"BS EN 13108", or both as your keywords.
Do not just trust me, or anybody, . . . . . . . . . it is not that sort of
"world" any more.
Trust me I am a Materials Engineer.
just one last point, as a retired local authority Materials Engineer,
a bit of advice, never forget the basics, sample and test, you will soon know if you are
receiving the same mixture that you were receiving before specifying
to the appropriate part of BS EN 13108. That is assuming you are
sampling and testing now, if you are not perhaps you ought to start
while you are still receiving bituminous mixtures supplied to BS 4987
and BS 594, so that you can make a comparison.
If you no longer have your own Materials Engineer and materials
laboratory there are still many competent, independent, UKAS approved
soils and materials laboratories who you can employ.
Training your own people to do the sampling, and supplying the samples
to the laboratory for testing considerably reduces the cost, which has
remained remarkably constant over a number of years while the cost of
bituminous materials has escalated.
By the way, the testing you will be using could well be included
BS EN 12697
Bituminous mixtures - Test methods for hot mix asphalt,
to which there is over forty parts, however there are only a small
number where frequent use is necessary. But all parts are useful and
required in some capacity
Guidance for the use of
BS EN 12697
is to be found in,
Asphalt : Guidance on the use of BS EN 12697 - Bituminous mixtures.
Test methods for hot mixed asphalt
But some parts of,
BS 598 :
Sampling and examination of bituminous mixtures for roads and other
may still be appropriate,
according to which test you may be using and/or existing contractual commitments.
Of course, for comparison purposes, as long as you use the same
sampling and testing procedures it will not matter which document you adhere
Information on the various parts of the above standards can be found
BS EN (European)
Specifications, relevant to Highways Maintenance and Construction
Standards, relevant to Highways Maintenance and
There's More - BS EN 14023 : 2006 : Framework Specification for Polymer
Just when I thought I had finished
this newsletter I become aware of yet another recently published BS
EN standard being implemented on the 1st. of January 2007.
Yes, that is correct, 2007.
The implementation of this document, I was aware that it had been published, had completely slipped my attention,
so I can only say thank you to the Road Bitumen Association (RBA) who
provide guidance on the content and use of this standard.
The guidance document can be downloaded from their website, it is to
be found by selecting "Bitumen" from the toolbar at the top
of the homepage and then selecting "Testing and Standards"
from the list of items in the drop down menu.
The download link is at the bottom of the page, or it was. I could of
course put a direct link to this download but I think you would miss
out on the other useful information that is present on this website.
I am going to say little more on this topic, because you now know as
much, if not more than I do.
I will mention that I like the item in the document that states, The
Standard is a 'Framework' specification based on empirical tests which
have been used previously in (some) European countries. It is not a
Performance-Related binder specification."
May I point out that there is already a wealth of testing that can be
performed on bitumen and polymer modified bitumen (PMB) with existing
standards, if you specify them in your contract document.
e.g.'s : BS EN 1425 --> BS EN 1431 Methods of
test for petroleum and its products,
also the associated, and often the same,
BS 2000 range of standards, Bitumen
and bituminous binders, they tend to come as one standard.
There are others, BS EN 12594, 13398, 13399, 13588, 13589, 13614,
13632, 13702, 14769, 14770 and I am sure I have not listed them all.
These various standards cover most engineering aspects of bitumen and
polymer modified bitumen both before and after the production of
There are also tests and procedures for monitoring the use of PMB's in
900 Series - Road Pavements - Bituminous Bound
Materials, of Volume 1:Specification for highways Work, Manual of
Contract Documents for Highways Works
Clause 923:Binder Recovery using the Rapid Recovery Test
Clause 939:Determination of Cohesion of Bitumen and Bituminous Binders
("Vialit Pendulum Test")
Clause 941:Modified Binder Storage Stability Test
This document can be downloaded from the Standards
for Highways website.
As a retired engineer who played a part in maintaining a local highway
network I would suggest that PMB's will only be necessary on that very
small percentage of the network that is particularly highly stressed
with numbers and/or weight of traffic.
But where you are going to be using them you do need to know what you
are specifying, and receiving, to obtain maximum benefit to the road
pavement, for the significant increase in cost of the bituminous
General guidance on polymer modified bitumens can be found on the
BITUMEN AND BITUMINOUS MATERIALS",
of this website.
Also bear in mind that there are other successful bitumen modifiers
other than synthetic polymers, some of which can be added at the time of
mixing, allowing a much longer, for practical purposes many months, storage
period of the modifier.
Indeed with Trinidad Lake Asphalt (TLA) almost indefinitely.
Any degradation not occurring until after mixing, i.e. exposure to
This factor can be very useful if you only wish to mix,
purchase, small tonnages of modified bituminous material.
An aside - In reading the guidance document
from the Refined Bitumen Association I could not help noticing the
address for further information at the bottom of the page, i.e.
Crowthorne House, Nine Mile Road, Wokingham, Berkshire.
If I am not mistaken the Transport Research Laboratory (TRL) must
practically be neighbours, if not closer.
Hopefully this newsletter is now finished, as it is becoming
"over long" with too much to take in all at once.
I will get back to retirement, unless of course it keeps raining, more
substantial amounts forecast for tomorrow, the 20th. of July.
Perhaps now is the time to become more interested in SUDS, not the
kind that keeps your hands soft while washing up, but Sustainable
Just a thought, as the materials and mixtures already exist to provide
basic "sponge" effect drainage on new housing estates and
car parks, for the shorter length downpours.
Motto of the Month