highwaysmaintenance.com
NEWSLETTER
Summer Edition 2007

Recent History of Bituminous Mixtures

BS 594 & 
BS 4987 Replacement by BS EN 13108

And There's More - BS EN 14023

Motto of the Month

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 you". 
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 unnecessary expense.
(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

CSS "Make-over"
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 "make-over".
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 twenty 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 committees.
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 service.
And I am sorry Fiona, I find it necessary to take you off my list of thinking men's pin-ups.  

Recent 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 budget. 
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 Surfaces, but 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 bitumen macadams.  
I find this situation disturbing, especially with the introduction of the new standard BS EN 13108 for Bituminous Mixtures : Material Specifications.
Note Bituminous Mixtures not Asphalts, if we are supposed to be harmonising with Europe perhaps we should be using the same terminology.

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), aggregate.

It, of course, also permits the economic use of lower PSV  (above 45) aggregate in the matrix of the hot rolled asphalt.

BS 594 & 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 same suppliers.
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 Institute (BSI). 
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 page) 
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 changes as,
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 addressed.
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 problems.
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 their website.

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 standard.
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 construction.
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 Asphalt, etc.,  
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 receive.

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 briefing meetings.

It appears that PD 6691 does not give guidance on,
BS EN 13108-2 : Asphalt concrete for very thin layers
or
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 of time.

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 "accept" stuff.
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.

And 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 in, 
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,
PD 6692 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 paved areas,
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 to.
Information on the various parts of the above standards can be found in, 
BS EN (European) Specifications, relevant to Highways Maintenance and Construction
and 
British Standards,  relevant to Highways Maintenance and Construction 

And There's More - BS EN 14023 : 2006 : Framework Specification for Polymer modified Binders
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 bituminous mixtures.

There are also tests and procedures for monitoring the use of PMB's in the,
900 Series - Road Pavements - Bituminous Bound Materials, of Volume 1:Specification for highways Work, Manual of Contract Documents for Highways Works
Examples :-
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 mixture.
General guidance on polymer modified bitumens can be found on the page,
"MODIFIED 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 heat. 
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 Urban Drainage. 
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

"Trust, but verify"