Articles to Study, No.1

Articles to Study, No.2

Motto of the Month

Hello again, I am back, for at least one more sporadic edition, but I suppose there may be others from time to time, but not on a regular basis..
I stopped writing the newsletters because I was getting tired of repeating myself, that and the fact that few people actually read them, some of you may have missed them, but it is no use deceiving myself they are not widely read according to my website statistics.
But I have decided to come out of Newsletter writing retirement because I felt there was something important to bring to your attention, especially to those of you who work maintaining Local Authority road pavements, especially the surfacing.
Many of you are aware that I work for an organisation that maintains a local authority highway network, and I have done for t h i r t y  f i v e  y e a r s,  (some of you may remember this plaintive cry from "Rambling Sid Rumpo" in "Beyond Our Ken", or possibly "Round the Horne", not the "Navy Lark" as I earlier quoted and have been corrected, whilst listening to the "wireless" sitting round the table with the family eating your Sunday Dinner).
I am quite proud of my past role, of being a "public servant", and having been part of a wide "team" that has maintained the local highway network in good condition with never a big enough budget.
("Any department short of money, take it from the highways maintenance budget", often prevails with local authorities.)
But we have been awarded the much sort after "4 stars" so we must have been doing something right all these years.
And, I do not believe that you necessarily do your  best "engineering" when you have your biggest budget.
I have waffled enough, read the items included, make use of the links provided, make yourself aware of what is happening, make your own decisions. 
You are not purchasing fizzy drinks, snack foods or "designer label" clothing. 
You are spending public money maintaining a public highway network, I believe that is a very important role, be Engineers and Engineering Technicians, take pride in what you do, an old concept I know, but looking at work well done at the end of your career is rewarding, even if that reward is not in your pocket.
I know it is getting more difficult to practice "engineering judgment" but somebody has got to do it or the current problems with early failure, the short life of "new" bituminous surfacings, and indeed whole road pavements will continue to happen in the industry.
Do not let the accountants rule completely, they only know how to move money around and balance budgets. They are hoping the new "machinery" will remove the need for "awkward" people like me, they will not, unless it is accompanied by a significantly increased budget.
You  on the other hand know how to spend that money to best effect in relation to highway needs, or you should do.
The accountants would be in the brown smelly stuff without you, or to be more precise they would be driving over slippery roads, bumping down pot-holes and caught in premature or unnecessary traffic queues, without good highways maintenance engineers and technicians doing their jobs, do not forget that.
One last point in this introduction before getting to the main topic, negative texture surfacing (NTS).
Not all bituminous mixtures retain that initial negative texture present at the time of laying. 
With the passage of traffic the fines in the matrix are slowly worn away and the larger coarse aggregate becomes exposed, and the nature of the road surface changes from a surface that has negative texture to one that can be more accurately described as a positive texture.
I do not ask you to believe me, I would prefer you did not, get out there and look for yourself, at the time of laying and a few years after.
In fact people who employ certain types of bituminous mixture as thin surfacings, on their networks, rely on this process for the surface course to attain its potential skid resistance.
It follows that initial noise readings on newly laid surfaces may be misleading, and not be the level of noise tyres will generate on that particular surface during the majority of its life.

 

Negative Textured Surfacing
After the conference, "Highway Maintenance 2006" organised by the industry journal Surveyor on the 6th. of June at the East Midlands Conference Centre, Nottingham, the document, 
"Best Practice Guidelines for Specification of modern Negative Textured Surfaces (NTS) on Local Authority Highways" 
has been published and is available to download as a .pdf file on the website,

www.roadscodes.org

I suggest that you obtain this document and read it thoroughly, there is contained in it a wealth of good information, and observation on road surfacing practices, you have to look for it but it is there.
However, and there is always a however with my comments, it is my opinion that in order not to cause offence to both the "traditionalists" such as myself with the, "if it ain't broke don't fix it" attitude to the bituminous surfacing of local authority highway networks, and the "modernists" who wish to pursue a more "innovative" "marketing" approach to all bituminous mixtures offered for all road surfacing, the document is almost contradictory in some of its statements.
With the publication of these "Guidelines" we now know what NTS's are, apart from another set of initials we have got to remember, "the NTS family comprises a suite of proprietary surfaces, known collectively as thin surfacings, and generic stone mastic asphalt."
I read this to mean that if a particular proprietary bituminous mixture is laid on a motorway or trunk road it is a thin surfacing (TS), if the same material is laid on a local authority highway it is a negative textured surfacing (NTS).
0r, are the suppliers going to develop two ranges of materials, one for Highway Agency work and another for Local Authority work. 

So this gives us the situation that we can specify bituminous mixtures from, 
BS 4987:Coated macadam for roads and other paved areas,  
Part 1:Specification for constituent materials and for mixtures, 
Part 2:Specification for transport, laying and compaction, 
and 
BS 594 : 2002 : Hot rolled asphalt for roads and other paved areas: 
Part 1 : Specification for constituent materials and asphalt mixes. 
Part 2 : Specification for the transport, laying and compaction of rolled asphalt
that will have the characteristic of negative texture but cannot be regarded as a NTS because they are not proprietary bituminous mixtures, this is the same situation as being able to lay British Standard bituminous mixtures at or less than 40mm. and they cannot be called thin surfacings.
"One" has to wonder if somebody is deliberately trying to confuse the hard working highways maintenance engineer who has a host of other things on his mind other than which bituminous mixture to specify.
Purchasers will be spoilt for choice with "names of mixtures", and will not know what to choose, and this document does say the client is responsible for the selection of material, I think, so if it all goes wrong it is the fault of the engineer/technician not the supplier.
At this present time I believe there are no better documents than BS 4987 and BS 594 for specifying bituminous mixtures for Local Authority roads, and also for advising how they should be selected, transported, laid and compacted.
Already coming "on stream" are similar BS EN (European) specifications for bituminous mixtures and generic stone mastic asphalt (SMA), some are already published, some are long over due with no reason provided why this is so.
I am still not happy about the explanation of what is a HAPAS approved system and how it relates to the production of individual proprietary bituminous mixtures, but I am very pleased that the published "Guidelines" include a revised copy of the CSS, 
"Advice Note for the Specification of Thin Surfacing", (Report Eng/2003).
If you do decide to purchase proprietary materials use this specification, all of it, but especially the sections "Declaration of Design", and "Cold Weather Working".
It would also have been a good opportunity to have included a copy of the BBA document, 
"Guidelines Document for Thin Surfacing Systems", so that you may know the procedure for approving "systems", but I believe it is still in draft form, after nine years, so perhaps this was not possible.
I could continue at length and highlight individual statements in the document that I do not like, such as, "The 0/10 close grade mixture is unlikely to produce a texture depth suitable for areas with a speed limit above 30mph", but I will not.
Perhaps my local suppliers just happen to produce a particularly good 10mm.CGM Surface Course which seems to fill an important role in the maintenance of our rural road network, and use a considerable amount of the embarrassing stockpiles of "fines" left over from producing proprietary thin surfacings.
14mm.CGM Surface Course, and 20mm.DBM Binder Course laid as a "running surface" ( this will be laid thicker to add strength), are both good materials that successfully include large percentages of quarry fines, and are suitable for surfacing local authority rural road networks. 

I am straying from the main theme of the "Guidelines", this is a good document even if I think it is somewhat ambiguous, and it has finally been published after a number of delays. 
I repeat it does contain a lot of good observations and information relating to highway surfacing practices.
Download it and study it thoroughly, all of it, but do not think it will replace a good Materials Engineer, or Road Pavement Engineer, in fact it seems to call upon such a person to make many of the judgments needed in the selection of the appropriate bituminous mixture.

But before I finish, let me try and help you become "uncomplicated" by offering you two tables based on work I do training young engineers and technicians in my "day job".
They are for guidance only, I accept no liability what so ever as to how you interpret them, they are to improve your knowledge on bituminous mixtures used in road surfacing and not to be taken as "working practice", if you decide to use them in that role that is your decision.
Bitumen Macadam Mixtures for Local Road Surfacing
and
Hot Rolled Asphalt Mixtures for Local Road Surfacing

I believe that the bulk of local highway networks could be suitably surfaced with a bituminous mixture from one or other of these two tables, and in doing so you will know the grading of the mixture and the binder content, because they are specified in British Standards.
[Added on the 6th. July 2008 - These bituminous mixtures are still available, or mixtures so similar as to make no practical difference, but you will need to specify to the appropriate part of BS EN 13108 and determine your Target Mixture Composition to replicate the appropriate "recipes" in BS 4987:Part 1 and BS 594:Part 1. Further guidance HERE. ]
(This could be very important in procurement documents.)
You will still need to specify aggregate quality appropriate to the site requirements, i.e. polished stone value, aggregate abrasion value, etc..
Initial surface fretting, simply caused by oxidation through ageing will be dealt with by surface dressing as a preventive maintenance treatment on non stressed lengths of highway, not by immediately resurfacing.
Job done ! All we need now is a regular amount of sufficient funds that we know are ours to keep. 

Articles to Study, No.1
I will be brief because I would prefer that you draw your conclusions from the article, rather than what I say.
The "Technical Paper", "In pursuit of efficient local highway services", is relevant to the current changes taking place, and proposed, with regard to the buying of materials and services that are needed to maintain a local highway network.
Within the text is reference to "uniform (across all authorities) specifications" to allow "the effectiveness and efficiency of local highway procurement".
But there is also an "however" in the paper, this saying, "However the adoption of uniform outcome specifications would also deal effectively with this issue - as well as encouraging continual improvement."
This paper is to be found in June 2006 edition of the journal "Transportation Professional".
If you are a member of IHT you can access a copy via the "members lounge" of the website www.iht.org, if not you will need to find a copy of the journal, there should be one in any decent size office dealing with highways maintenance. 
I urge you to obtain a copy of this article and study it so that you may have an opinion on the way forward.
But I will have the last word. 
Whichever method you choose for governing the quality of the materials you purchase, it does not seem very "local" to me, and in adopting grand strategies local knowledge could be ignored. 
Also long serving satisfactory local suppliers and contractors may no longer be able to make their significant contribution to the quality of what is also their local highway network.

Articles to Study, No.2
Again this article, "Harmonised standards explained", can be found as a "Technical Paper" in "Transportation Professional", in the May 2006 edition of the journal.
This a truly technical paper from a well established, knowledgeable, senior figure in the field of bituminous materials.
The paper comprehensively covers the history and introduction of the harmonised European Standard for Bituminous Mixtures, i.e.,
BS EN 13108 : Bituminous Mixtures. Material Specification, and its many sub-parts covering the various differing types of bituminous mixture
There is little need for me to add anything to this paper, this gentleman's knowledge is far greater than mine, other than to list the various parts of the specification that are now available, as it is likely that at the time of writing the paper the British Standards Institute (BSI) had not made them available.
BSI now list the following standards on their website, www.bsonline.bsi-global.com

BS EN 13108-1 : 2006:Bituminous mixtures. Material specifications. Asphalt Concrete
BS EN 13108-2 : 2006:Bituminous mixtures. Material specifications. Asphalt Concrete for very thin layers
BS EN 13108-3 : 2006:Bituminous mixtures. Material specifications. Soft asphalt
BS EN 13108-4 : 2006:Bituminous mixtures. Material specifications. Hot rolled asphalt
BS EN 13108-5 : 2006:Bituminous mixtures. Material specifications. Stone mastic asphalt
BS EN 13108-6 : 2006:Bituminous mixtures. Material specifications. Mastic asphalt
BS EN 13108-7 : 2006:Bituminous mixtures. Material specifications. Porous asphalt
BS EN 13108-8 : 2005:Bituminous mixtures. Material specifications. Reclaimed asphalt
BS EN 13108-20 : 2006:Bituminous mixtures. Material specifications. Type testing
BS EN 13108-21 : 2006:Bituminous mixtures. Material specifications. Factory production control

Although the above have now been published, there are periods of time before they will be implemented, e.g. implementation for BS EN 13108-1 : 2006:Bituminous mixtures. Material specifications. Asphalt Concrete, that will replace BS 4987 is stated as 2008, although sometimes these dates have a habit of sliding back.
I have read some of these standards in draft form and it was my opinion that they were well thought out, well presented documents for specifying the various bituminous mixtures available.
But you will still need the knowledge and experience of selecting the appropriate mixture for the site in question and the budget available.
This paper, in fact a longer version, is available on the Institute of Highways and Transportation website, www.iht.org  but you need to be a member to access it, and make comments.
I would urge you to read this paper if you are in any way involved in the specifying and use of bituminous mixtures.
And, if you are wandering whether to purchase any of these standards may I suggest you start with, 
BS EN 13108-5 : 2006:Bituminous mixtures. Material specifications. Stone mastic asphalt,
if it has remained the same as the original draft I think you will find it a very useful standard.
It has taken over five years for it be published after a "finished" draft copy was available, I hope it is still in its original form.

Motto of the Month

" If it ain't broke don't fix it ! "