"Bitumen and the Dark Arts"
Forthcoming Conference at the SCI
Surface Dressing 2012
TRL Reports and Publications
"Highways Maintenance" Websites
Road Accidents in 2011
Important Addition - 27-07-2012
A140 Scole Bypass
Road Pavement Temperature Monitoring
Motto of the month
There is much that I could talk about in this edition, but I am becoming jaded by the need to talk about the same old topics because people keep making the same mistakes by virtue of not having sufficient knowledge and experience to make the correct decisions.
The alternative reason being people are deliberately not embracing correct procedures and and materials because more money can be earned by using inappropriate procedures and poor quality materials, and it does happen, that is the nature of things.
However there are authorities who seem to want to possess an efficient highways department, and are employing proven highway maintenance practices and materials so I will continue to try and provide information that they will find interesting, and which may be of assistance to them.
But if you do not find the necessary comments or information to help you in any current newsletter please review/search previous newsletters where you could well find the comments and information that you are looking for.
The true guidance on various subjects you will find in the main body of the website if you search appropriately, but my recent practice of including actual case studies in newsletters will continue but I will not repeat myself.
I will not adopt the practice of the sales and public relations people that if I tell you something forcefully enough and often enough it must be right, "I will tell you only once, so listen very carefully".
I am becoming more and more disappointed with the quality of the maintenance of trunk roads in my area, especially if the standard of the surface course I see on the A5 in my immediate vicinity is anything to go by.
It is my opinion that the the length between the M69 and Tamworth is in real need of some extensive quality patching in some areas and complete resurfacing in other areas, both forms of resurfacing needing a more durable surface course bituminous mixture, especially around islands.
The bituminous mixture I will of course recommend is hot rolled asphalt and precoats, which unfortunately Highways Agency will not allow the maintenance consultant/contractor to employ as it is not a permitted material, because it is not a proprietary thin surface course system (TSCS).
And to make a further comment, I have never observed any evidence to suggest that putting a complete high friction surfacing covering to a proprietary surface course around an island will make it any more durable.
In fact I am of the opinion that the increased stresses from fixed three axle "super single" tyre configurations on large HGV's "screwing" around on "tight" islands that have an unusually high level of friction will produces stresses that the surface course is unable to cope with, and hence cause early failure of the surface course.
There is evidence of this happening on an island quite close to me, and the surface is only just over two years old.
(On a tight turn the forward and rear tyres on this now typical back axle array pivot around the centre wheel causing considerable sideways "scrubbing" to the road surface, the higher the friction the greater the "scrubbing" action.
And do not forget the pressure on the road surface from a "super single" is considerably more than a "conventional" HGV tyre in the first place.
In my opinion many "new" engineers and certainly "modern management" have no idea what they are doing, very few have the background to be able to think appropriately to each engineering situation. As long as its "innovation" it does not seem to matter if it actually works or not.
Do you know the tyre pressure in a "super single", do you know the "footprint" of a "super single, work out the total load on the road surface of just one tyre, and then imagine you have about a metre of leverage to pull/push this area of load over the road surface. I will leave you to work out the figures, but if you perform this exercise you may start to understand." )
I am certainly not against high friction surface on the straight line approaches to islands, or bends, this is where the deceleration from breaking should be taking place and it is not subject to the damaging action of "screwing" "super single" back axle arrays.
If initial surface course texture depths and the polished stone value (PSV) of the aggregate in the surface course are reduced in the still delayed HD28, as is being indicated by various "releases", the use of high friction surface in any highly stressed area will be almost be obligatory in my opinion if we are to keep these sites safe.
And just in case anyone should take my advice on the use of HRA and precoats of the required PSV, do make sure you get get good quality hot rolled asphalt.
The HRA primarily needs to have a good quality "asphalt sand", some, and only some quarry fines are of the required standard, you need to know which have good stability and can "hold" a high binder content without "fatting up".
A straight run 50pen. bitumen binder is required, and only in really high stressed areas will you need a modified binder, and be careful in your selection, in my experience some binder modifiers are very good, and some can even cause you problems in laying, especially with a consistent embedment of the pre coated chippings.
It is important to be aware that if you are using a modified binder the handling of the binder before and after mixing is critical, this is with regard to temperatures and length of storage at high temperatures, abuse your expensive modified binder and you have wasted your money, the enhance engineering properties that it can impart to the bitumen have been lost.
The 8/10% filler component must be ground limestone because of the hydraulic binding quality the limestone will impart to the mixture, this will provide the required stiffness element of your HRA .
And finally and most importantly if you want durability of your surface course you must have an adequate binder content, my suggestion is that you do not listen to the "sales" advice that suggests you must have a low binder content to provide the stiffness to prevent wheel tracking.
If your supplier has indicated in his design submission that he is using a known good quality asphalt sand and will use limestone filler it is unlikely that you will have a problem with wheel tracking with a 7.5% to 7.8% target binder contents (TBC), remember there is a +/- 0.6% tolerance around the TBC so assuming that you have chosen a 7.8% TBC you are likely to receive material with a binder content between 7.2% and 7.5%, the modern mixing plants are really that efficient. Do not complain, the material is in specification, it is the way of things, just pitch your TBC accordingly.
Your knowledgeable and experienced Materials Engineers may be able to help you in these matters if he/she has not been pre-programmed to only use proprietary thin surface course system bituminous mixtures.
Now, hypothetically, if I were to go looking for a hot rolled asphalt of the nature I have indicated above I feel sure that there are a number of competent production plants in my area that are capable, and more than willing to supply the above material, should they get the opportunity.
I also know that I could go straight to at least three local contracting companies that are able to provided gangs that can lay HRA and precoats to a high standard.
Why do I say this, well I do still keep in touch with a few people, and to the credit of my local authority, perhaps I should say some of the engineers who work for the authority, they do still employ a significant amount of HRA and precoat surfacing, usually in high stressed areas, or difficult sites where they want to do the job once and not do it again for some considerable time, and I mean a considerable time, not five years.
And even longer when you get a good surface dressing on it when it finally starts to surface fret, or indeed surface dress any dense bituminous surface course.
Whether the procurement/partnering arrangement, that your organisation is almost certainly a part of, will allow you to do it is entirely another matter, but for the record you are permitted to use HRA and precoats, or high stone content asphalt, as your surface course bituminous mixtures on any local highway network subject to the usual engineering requirements of any surface course.
And for those in Northern Ireland and Scotland you can still use HRA and precoats on your motorways and trunk roads.
It is just England and Wales that you are not permitted to use HRA and precoats as your surface course, the only surface course option permitted by the Highways Agency being a proprietary Thin Surface Course System (TSCS) approved bituminous mixture as your surface course.
That has nicely led me into my next item.
Forthcoming Conference at the Society of Chemical Industries
There is to be an event at the Society of Chemical Industries on the 18th. of October 2012 at there headquarters in London that relates to many aspects of the properties and use of bitumen in highway construction and highways maintenance.
The event takes place under the title "Bitumen and the Dark Arts", which I think is an extremely appropriate description, because so many highways maintenance engineers are continually using bitumen, in its many forms, in highways maintenance but actually know very little about it, e.g. the sources of road pavement quality bitumen, how it is produced, how it can be adapted and modified for different types of highways maintenance processes, and how to select the appropriate form and grade of bitumen for particular materials, bituminous mixtures and sites.
(I would also include information on how to sample and test bitumen, whether as an individual bitumen item, or after being reclaimed from the mixture/material it has been used in, but the agenda looks pretty full already.)
I totally recommend that all who are actively involved in highways maintenance, and therefore will be heavily into the use of bitumen, that you attend this event in the Autumn.
There are some very knowledgeable speakers presenting papers, even if I detect that there may be a hint of "promotion" of certain products and processes in some of the titles of the papers it does not matter, if you can get to this event I suggest that you do so, they are not expensive, for the quality of the speaker and the indicated content.
I am always happy to mention relevant courses hosted by the SCI because it is a requirement of those speaking that their papers will subsequently be archived on the SCI website for us all to download and read, an admirable display of bringing information to all who are interested, by this charitable body.
However some speakers do seem to "forget" to place on record what they have presented, and I once again refer to the fact that not all papers presented at the "Pavement Surface Texture - Fact or Fiction" have been lodged with the SCI for downloading and study. I leave you to determine which are missing, but I will give you a clue they seem to have particular reference to possible changes in HD28.
Although I have included a direct link to the brochure for "Bitumen and the Dark Arts" event I hope that you will visit the Society of Chemical Industries website, www.soci.org.
Here you will be able to put yourself on the emailing list for future events, and I certainly suggest that you look at the papers from past events that you will find through the toolbar heading "Publications", and then the left side heading for "Past Conference Papers", happy browsing, you will learn from your study.
But if I may be allowed one further "however" in relation to bitumen, which is of a practical nature.
Perhaps somebody would like to mention the fact that bituminous mixture producers can now "modify" straight run penetration grades of bitumen in their mixing plants to produce penetration grades of bitumen of less viscosity/stiffness, i.e. a straight run 50pen grade of bitumen can be "modified" to become a 100pen. or a 200pen. bitumen by the addition of an appropriate amount of an appropriate flux oil.
(I hope it is not just diesel, and I do know I am not using the correct current terminology for the current referencing of penetration grades of bitumen, but everybody, well everybody in real highways maintenance understands "100" and "200".)
I personally am not happy with this practice which was only introduced in the early 2000's during the later editions of BS594 and has been carried on into the new "European" specifications.
I could look up the precise date this was introduced but it is not that relevant it is the fact that it is now common practice to modify supplied penetration grade bitumens in the mixing plant, whereas previously it was not.
In my opinion this process can result in the lowering of the quality of the bitumen in the mixture, produce more variability in the stiffness of the mixture throughout the supply, and in extreme instances of incorrect blending produce a bitumen viscosity other than that required, usually softer.
Please be aware of what I am talking about, I am referring to the modification of a penetration grade bitumen to a softer, less viscous, penetration grade of bitumen by the addition/blending of a precise amount of of a heavy, non volatile flux oil. The modified penetration grade bitumen will remain/stay at the viscosity/stiffness that has been achieved by the modification process.
I am not referring to the process of the "cutting back" a penetration grade bitumen with a light, volatile, oil to produce small tonnages of a workable bituminous mixture for hand laying in cold weather, usually patching.
Cutback bituminous mixtures, over time, will lose the volatile oils and the penetration grade bitumen will revert to its original viscosity over that time, even if the amount of time is considerable.
And just for the record I do not like bituminous mixtures with cutback binders, but they are sometimes necessary to fill potholes and "top" utility reinstatements during bad weather, even if they frequently give problems later,
The terms "fluxing" and "cutting back" are often used incorrectly and confusion reigns, be sure that you and your supplier, and contractor, are all using the terminology correctly and understand what it means.
The interesting relationship between the producer/supplier of bitumen and the producer of bituminous mixtures, especially hot mixtures is more fully covered in this linked web page.
Surface Dressing 2012
Once again I have been inadvertently drawn into the argument over surface dressing, as the public perceive it, i.e they love to hate the process, even though they know practically nothing about it and the importance it has in keeping the roads safe for them, and relatively free of potholes if the original surface was in sound structural condition.
This outburst from the public is not without cause when there have been a number of reports of surface dressing failure, resulting in exposed areas of bitumen and subsequent pickup of bitumen on vehicles. These public outbursts being of significant importance in the local areas that they occur.
In responding to requests for information, and to suggest reasons for failure I find myself quoted in some of these publications, but I have not said anything I would not have said even if I had known my views would be published.
To summarise what I said, I like surface dressing, it is an excellent process and I will continue to support it when performed correctly. It is a very cost effective means of maintaining the integrity of an existing surface course and when engineered correctly will improve safety of the treated roads by improving the surface texture of the road, and it will present the opportunity to spread chippings from an aggregate source which has a high polished stone value (PSV) on difficult sites, further increasing skid resistance.
This allows scarce, and expensive, high PSV aggregate resources to be used very effectively.
Therefore it really does infuriate me when those involved, that is sub-contractor, main contractor and client all get their heads together and say, "It's the weather". In my opinion that is a professional "cop out".
There have been plenty of surface dressing contractors around the country who have been undertaking surface dressing contracts who have not had any trouble, and must be pretty annoyed at the process they earn their living at once again getting a bad press.
I am not saying that 2012, so far, has not been a difficult year for performing surface dressing, it has, but with the correct attention to detail there should not have been any serious problems, and I will list some precautions that good contractors will have been taking.
I hope I have given a bit of an
insight, by no means complete, in to how a good surface dressing
contractor, and there are many, should be operating in the weather
conditions we have/are experiencing in 2012.
It is more than likely that programmes will not be completed this year, do not be tempted to extend the surface dressing season by increasing binder rates and dressing into late September and October, you are only storing up problems for any hot weather you may have next year.
To sum up I like surface dressing and will continue to support it, but I will also criticise those who give it a bad name by virtue of bad practice, or taking "short cuts" to increase profits, and then try to blame the weather, poor weather, and even hot weather from time to time, is not unknown in the UK, work accordingly.
Should you require a fairly full "picture" of the surface dressing process, and it seems many people do, visit my "Practical Guide to Surface Dressing".
The "Practical Guide to Surface Dressing" is now available as a .pdf download, in association with Rainbows, click the logo, and please donate, details on the last page.
TRL Reports and Publications
I thought that I would just add an item on TRL and their publications "old" and "new".
The information that can be gained from reading TRL publications has been a big part of my education in the field of highways materials, and I have been reading various TRL (and TRRL) documents ever since I entered the profession 40 years ago, and I continue to read them now.
I do miss "my" (well, the Highway Department's) materials technical library that I inherited from my predecessors and to which I added as various documents were published.
"My" technical library basically consisted of an extensive range of TRL reports, British Standards, Volume 1 of the Specification for Highway Works, with accompanying Notes for Guidance, and the various relevant "Design Guides" from the Design Manual for Roads and Bridges, a good example being HD/28 Skid Resistance.
Supplemented of course by a number of the classic text books on highways maintenance, usually based on the physical properties of aggregate and/or bitumen, e.g. the the "Shell Bitumen Handbook".
There were a few extra relevant publications from a few other bodies, but with the range of documents from the sources already mentioned around my desk I was pretty much able to help the engineers and technicians in the department that required particular information on various highways materials, this was part of my job.
How many Highways Departments, and Highways Consultants have access to a similar resource these days, lamentably few if their continued accessing of my website is any indication.
I like to think that "my" (the Departments) technical library still exists, but it is unlikely, everything has to be accessed "on line" these days, and I know that I am preaching against m own website.
It seems these days that anything that takes up valuable floor space has to be trimmed out for "efficiency" and "cost savings", and that quite often means experienced people.
My argument is that how can people access items "on line" when they do not even know they exist, whereas when you had a technical library contained on a relatively few shelves the engineers and engineering technicians could browse the shelves for the relevant documents that would provided the knowledge/specification that they needed.
And for the trainee graduates and trainee technicians that the department did have up until the early 1990's the term "read an engineering book" was often heard when there was not any gainful employment for them, and where did they fine these "engineering books" but in the technical library.
It can be a long and difficult job finding the correct information/document when searching the internet, hence my website that provides basic highways maintenance information, and reference to the more relevant technical documents.
But to return to my original topic of TRL documents, I have undertaken a little exercise to produce a simple .pdf list of many interesting and useful TRL publications, for you to download and browse so you will know what is available for study, a little coffee time reading, I hope that you find it useful.
Here is a similar list of older, but still very useful, TRRL publications, a simple .pdf list of many interesting and useful TRRL publications, for you to download and browse so you will know what is available for study, a little more coffee time reading, that I hope that you find useful.
I am not saying that all of the reports are as totally informative as they could be, especially in more modern times, but I have found the majority of them worthy of study, often it is the "additional" information that is included in a report that can be of real interest.
A report such as I describe is the the report, TRL Published Project Report PPR148 - Surface Texture Measurement on Local Roads.
This is a 90 page document published in 2006, and although primarily related to surface texture results from the use of SCANNER. It includes interesting sections on skid resistance and road noise associated with differing levels of surface texture, including some data relating skidding resistance to surface texture depth and speed of vehicles.
I only recently became aware of this report, but I have found that it is available for download from the internet, the easiest way to find it being to enter the full title in a "search" and you will find the .pdf document on the first page.
The document is actually lodged on the website of the Pavement Condition Information Systems (www.pcis.org.uk), the organisation that promotes and supports the use of SCANNER, and it is interesting to note that the website is managed by TRL.
The SCANNER as a means of indicating the strength of of a road pavement, or even differentiating between surface cracking/deterioration that does or does not need major maintenance does not impress me, but it does seem that it is building up significant information with regard to the relationship between surface texture, skid resistance and speed of vehicles.
The importance of high texture depth and skidding resistance at high speed is referred to in this document, something that is relevant to proposals affecting possible changes in HD/28.
Perhaps people have lost sight of the fact that skid resistance surveys are performed at 50kph, which I think is 31mph, and although this may be the pragmatic speed to be able to carry out a fairly quick appraisal/comparison of the the skid resistance characteristics of a highway network, it does raise the question as the whether this data is applicable to the skid resistance of a road surface with a vehicle applying its brakes at 70mph, or above.
Lots of things to think about, but read TRL PPR148 if you have a real interest in this topic, even if you do not agree with all its comments it is likely that you will be gaining more knowledge on the subject of road surface texture.
Other "Highways Maintenance" Websites
I thought that I would mention two other websites that have a highways maintenance involvement, certainly in their titles, and I suggest that you visit these sites to see what they offer.
The fairly recent "official" website relating to highways maintenance is that found under the title of the Highways Maintenance Efficiency Programme, www.dft.gov.uk/hmep/, which as you will see is under the DfT umbrella.
I really do think that you should visit this website and have a thorough browse, I am not going to say anything else, except that I recommend that you download and read the recently posted .pdf copies of the "Standardised Specification and Standard Details, Stage 2 Report, Progress Report on Local Authority Specification Variations", only published in June 2012.
A lot of words, but not a lot of "meat" in it yet. I am not going to do a detailed appraisal, not my job any longer but my old bosses would have wanted a full report on what I and other practical engineers thought of it , however I do not like "942SR Thin Surface Course Systems" where it proposes that the, "Surface integrity guarantee has been reduced to 3 years", no comment.
It is my opinion that all those who have a real interest in maintaining local highway networks must keep up with what is happening or you may find yourself in a situation where it will be a budget requirement that you must comply with a forthcoming new DfT specification for Local Authorities that will limit your ability to maintain your highways networks in a safe and serviceable condition at a reasonable cost.
While on the subject of HMEP you should visit YouTube and enter HMEP, you will find several short videos explaining the "official" purpose of HMEP, some pretty impressive tailoring.
The second, again fairly recent, website I think you should visit is, www.highwaysmaintenance.org, this being the website of the All Parliamentary Group on Highway Maintenance.
The purpose of this group is, and I quote, "The All Parliamentary on Highway Maintenance aims to promote understanding and awareness of the fundamental importance of the highway network, and to promote the environmental economic, and social case for a properly maintained sustainable network in the UK."
I absolutely embrace these ideals, but I have to be cautious because these words were spoken by politicians, their words seem to have different meanings to ordinary mortals, and I do not know who is funding this group.
But one thing I am fairly sure of, there will be a whole lot of "lobbyists" who will want "meetings" with them.
However I still think it is worth visiting this website to see what is being discussed, it is often quite interesting, and I personally form the impression that they do seem to support local input, and locally made decisions regarding the maintenance of local highway networks, but visit the website yourself and form your own opinion.
The list of members does provide a route to politicians that should have an interest in your views on highways maintenance practice if you choose to send them appropriate information.
An Increase in Road
Accidents in 2011
Whilst browsing around t'internet using highways related keywords I came across the item, "Road deaths up for the first time in a decade", the title of an article in the Daily Mail of the 28th. of June 2012, and picked up by many other publications and blogs.
In engineering terms you must understand that skidding accidents in relation to the road surface are almost always concerned with the road surfaces being wet, not always but mostly.
To realise that there can be a difference in skidding resistance of dry road surfaces you only have to look at the extreme example of the skidding resistance of a high friction (calcined bauxite aggregate) surface compared to a "normal" aggregate surface to realise that there can be a considerable difference even in dry conditions.
But broadly speaking all roads surfaces, whatever the permitted aggregate in whatever the road surface course will provide more than enough friction for vehicle tyres at normal driving speeds to allow a diligent driver to stop in time should a "situation" arise.
However when the road is wet, and especially if there is "standing water" on the road surface the situation changes dramatically.
This is when you must have sufficient texture to allow the instant dispersal of water by the tyre, and an aggregate that has a naturally high micro texture (PSV) to allow the rubber of the tyre to grip the aggregate once excess water has been removed.
Allow a reduction in these two important factors (and a reduction in one of the factors has already occurred quite recently) and you will reduce the skid resistance of a road surface in wet conditions.
So, it was much to my annoyance the road surface does not get any sort of a mention in this article, the reporting crowd, and the politicians, do not know enough to even mention it, but in my opinion it is likely to be a factor in the increase in road accidents.
It is a good, high texture, high friction, road surface that keeps you on the road in the wet, even if you are driving a tad too fast, and helps you to stop in a shorter distance, without skidding, in an emergency, so reducing the possibility of the vehicle driver killing himself or his passengers, or cyclists and pedestrians that have put themselves in his/her way.
You may want a "quiet surface", I would much prefer a safe surface, and there are surfaces that do a pretty good job of providing both, one of them being 6mm. surface dressing but I digress.
You only have to miss by an inch, you have still missed, that extra bit of texture/skid resistance makes all the difference.
It is my belief that local highway authorities need to be cautious in allowing the possible reduction in both the PSV and initial texture depth of bituminous mixtures used for surfacing high speed roads, and my definition of a high speed road is a road where people drive fast, not what the sign says, drivers do not always take any notice of them, and it is not always the people driving too fast that are injured, or even killed, in the accidents.
As I understand it, and I have not driven in France, that in France when roads are wet drivers are required by law to reduce speeds, at least on the main roads.
This policy may need to be introduced in the UK if current talked about proposals come to pass in the still waited for HD 28, that is if you want to continue the general continual reduction in road accidents that was taking place until this recent set of figures.
Perhaps when "they" increase the speed allowed on motorways and trunk roads, presumably on dry roads, as is proposed, "they" can include a reduction in the speed limit for when the roads are wet.
Driving faster on wet roads is just not a good idea, and that is not an opinion, it is a fact.
Be interesting to see if there is a break down of these figures related to road surfaces.
I would have thought, with a bit of education and training, this is something the police accident investigation boys could get involved in, they are the ones who always attend the accident scene.
A few "pendulum tests", and texture depths, of the actual surface, and a quick core of the road surface for later study, would quickly build up a wealth of data for a suitable research institute to get their teeth into, and such a body springs readily to mind.
A "pendulum tester", a sand patch kit, and a coring machine are all highly portable bits of equipment. It is unlikely to happen as "people" may become embarrassed by the subsequent information.
And an interesting aside, but not unrelated as regards actual, real, road surface information, whatever happened to "Triton" and the tyre noise data related to differing road surfaces that this piece of equipment was able to record? I have not heard much about it recently, well, nothing actually, and my browsing leads me to believe that there are "government" funded studies using "Triton" that are still unpublished.
IAN 166/12 - Important Addition -
The Interim Advice Note, IAN 166/12 Highways Agency Road Death Investigation (RDI) Guidance was published in June 2012 and is able to be downloaded from the Highways Agency website
In my opinion it is important that you obtain this document and study it carefully.
Yes, it is a Highways Agency document and as such is primarily for accidents on motorways and trunk roads, but it is likely to cause precedence for accidents on local highway networks.
Although not a technical document as regards actual skid resistance of a road, it may well have significance as to proportioning responsibility if a road surface is regarded as not having appropriate skid resistance for the prevailing site conditions, and is therefore deemed to have caused or contributed to the accident.
It is unlikely, but it may be that a single person of responsibility may be held accountable for the factor, i.e. the lack of appropriate skid resistance, that has caused the accident.
In my opinion it follows that
Highway Engineers that should keep themselves up to date with the
changes that are being considered to HD 28- Skid
Resistance with regard to the Polished Stone Value (PSV) of the
aggregate in surface course bituminous mixtures supplied to A Thin
Surface Course System, and the texture depth
requirements of the laid material.
Therefore I would like to bring to your attention the TRL publication/presentation, "Does (aggregate) size matter?" which was published/presented on the 17th. of July 2012.
This work was funded by the Highways Agency (HA), the Mineral Products Association (MPA) and the Road Bitumen Association (RBA).
(This study does not apply to Hot Rolled Asphalt and precoats, or Surface Dressing where deeper texture depths will still be required.)
I would like to think that this document will be available for download from an internet source quite quickly, this is to allow the correct amount of time for thorough peer revue before changes to HD 28 actually take place.
The nature of the study, and what I personally regard as a lack of full information on the material used in the exercise caused me some concern.
But I am retired, and will not have to make any decisions, or have them made for me, that may come under scrutiny as a result of IAN 166/12.
You may like to bring yourselves up to date with changes, reductions, that have already taken place with regard to bituminous mixtures supplied to a Thin Surface Course System by visiting this webpage.
Safer Roads 2008 Conference
Papers - added 27-07-2012
If you are a Highways Maintenance Engineer or Engineering Technician and you have a real interest in road surface skid resistance, and you should, may I suggest you visit the website.
www.saferroads.org.uk/2008papers.asp, and spend some serious time reading the various papers.
I have and I find some of them very interesting, with all offering some insight in to the subject of highway skid resistance from scientists and the various highway users.
I find this website a particularly useful "on line" resource.
I have not read all the papers yet, but I will recommend the presentation from Kent Police, as I still think they (the police) should play a larger role in examining the engineering charactersitics of a road surface after an accident.
These papers can be a source of information even for the professional (or retired professional).
I had realised that the Werner Schulze machine (from Germany) is being used for investigating and possibly changing skid resistance policy in the UK, so I was looking for information on the nature and use of this machine, and I was pleased to find papers/presentations providing this information.
However I was surprised to find that this equipment is operated with a contact pressure of 4 bar (58 psi), with the suggestion that this is the tyre pressure of a typical commercial vehicle.
So it depends what you regard as a typical commercial vehicle, a light commercial vehicle probably, but a heavy goods vehicle (HGV) certainly not. The tyre pressure of a "super single", the predominant tyre on HGV's in the UK is twice that, look it up on the "web", the information is there.
I admit I do not know if this large difference in the contact pressure in the laboratory test equipment compared to the contact pressure of a true HGV, has any bearing on the results, but it could.
But what I would suggest is that the results you find in the laboratory, and even the results you obtain from test vehicles on a highway, is not necessarily what you will find in reality with all vehicles, and the various tyres under various braking conditions. (And I continue to emphasise that it is wet skidding that needs to be primarily considered.)
The various testing regimes, whether in the laboratory or on the highway, are the best we have got at the moment and do provide a means of comparison of skid resistance that does allow monitoring to take place, so the annual skid resistance surveys are important and deliver useful information.
But to rely on them completely with no recourse to practical knowledge and experience is not wise in my opinion.
I see "super singles" everywhere on motorways, trunk roads, and main roads on local highway networks when I am driving, so in wet, and maybe even dry conditions, I want to feel that those hard tyres under high pressures have some significant texture to "bite" into if they have to stop quickly with 40+ tonnes of mass pushing them forwards, and possibly sideways.
In theory, from my viewing and listening of "Formula 1" events, the greater the down force the greater the friction, but it still all seems to get a bit "hairy" when it rains.
But please, do not believe me, do take a real interest in the subject of skid resistance yourselves, visit the Safer Roads website and take the time to read the various papers that have been archived there, you will come away a better informed engineer, technician, or even politician.
Scole Bypass - Road Pavement Temperature Monitoring
It has come to my attention that the road pavement temperature information on the A140 Scole Bypass has been updated on the Norfolk Partnership Laboratory website.
You will need to look at the bottom of the web page and look for and click the link "Pavement temperatures on the A140 Scole By-Pass" to be able to browse past and new information on the temperature data relating to depth in the pavement and the time of the year.
This information is extremely enlightening and is the sort of information Materials Engineers and Road Pavement Engineers should be aware of, and in fairness usually are, those that are left.
It is not just the information that is important, but the implications of the information, in the choice of bituminous surfacing materials, and the depth of these materials, especially when laid over a concrete base.
Whether this concrete base be a true CBM (cement bound material) as specified/described in the Specification for Highway Works, or an overlay to an existing "concrete road" where the pavement quality concrete is being left in place as the "base". This "base" having been "fractured" or left "entire". Both options, in my opinion, presenting problems if a sufficient thickness of overlay, of correctly designed "bitumen rich" bituminous mixtures, is not employed.
I am not going to say any more because Simon Shearwood of Norfolk is presenting a paper on this very topic at the SCI event, "Bitumen and the Dark Arts" mentioned above.
So, go to the event and present you questions to him, you may even get him to discuss the materials that were chosen in the design of the road pavement, but the information is available via their website link if you study it thoroughly.
I cannot conclude this item without saying it is good to see one of the remaining major Highways Materials Laboratories in the UK still involved in "real" highway engineering, take time to look at the entire website and see the facilities that it offers to to Norfolk Highways Department, in my opinion they are showing good judgement in retaining this facility.
But be aware the services that this laboratory provide are available to the rest of the UK.
It is my opinion that a Highways Department of any authority cannot function correctly without active access to such a facility, otherwise that authority will have little idea of what they are purchasing and how it is performing, before it fails that is.
I just hope my continued efforts to indicate the importance of Highways Materials Engineers and their supporting Materials Laboratories is not counter productive.
I sometimes get the distinct impression that the "industry" wants Highways Departments and their Engineers, those that are left, to know less and less about the materials that they are purchasing and using, rather than more, or perhaps even less than what they already know, all very sad.
Please do not believe the Public Relations people when they tell you how great the latest "wonder" material is, they really do not know what they are talking about. Put a good, independently minded, Materials Engineer in front of them to ask a few pertinent questions and their reaction is really quite entertaining, and I am not really a cruel person at heart, but I do hate being told "bull sh1t" and be expected to believe it, that is just insulting.
I am looking to wrap up this summer newsletter, but before I do I will just mention two forthcoming events that you may like to attend.
One event I feel is well worth attending because, in my opinion, you will hear some real and relevant information relating to the subject. The other, again in my opinion, is likely to be a gathering of the "suits", of the varying interested parties, where a lot of words will be exchanged but nothing much will be decided that will achieve the stated aims of the event.
I will be delighted to be proved wrong.
I will leave you to decided which events my comments are pertinent to.
Lightweight and Recyclable Aggregates
Presented by the Society of Chemical Industries (SCI) Construction Materials Group, and to be held at the SCI's headquarters in London on the 15th. of November, from 10:30 to 17:30.
Full details of the event can be found on the SCI website.
Synopsis of the meeting, and I acknowledge the copyright of SCI.
"Aggregates may be broadly classified as natural or artificial, both with respect to source and to method of preparation. The acceptance of an aggregate for use in concrete should be based upon specific information obtained from tests used to measure the aggregate’s quality, its service record, or both.
Synthetic aggregates may be either byproducts of an industrial process, in the case of blast-furnace slag, or products of processes developed to manufacture aggregates with special properties, as in the case of expanded clay or slate. Some lightweight aggregates such as pumice also occur naturally.
To understand the role played by aggregate in the performance of concrete, it is necessary to define specific aggregate properties and show their effect on concrete properties.
This meeting has been a rare opportunity to bring together experts from the manufacturers and providers of aggregates from waste, bi-product, and specifically manufactured processes. The speakers will cover the sourcing, manufacture, properties and end uses of a broad range of available aggregates including furnace bottom ashes, incinerator ashes, expanded clays, exfoliated slate, sintered fly ash, and glass plus there will be one presentation on the UK development of a structural lightweight glass product.
The meeting is a must for everyone who produces or is researching concrete and concrete products."
Improving Local Road and Highway Maintenance: The Implications of the Potholes Review
Presented by the Public Policy Exchange, it is to be held on Thursday the 27th. of September 2012, from 10:15am to 4:39pm at a venue to be announced in Central London.
Full details can be found on the Public Policy Exchange website.
I bring this event to you attention, well those of you who are responsible for the maintenance of local highway networks, because the title specifically states "Improving Local Road and Highway Maintenance", and yet the main speakers are from the Department for Transport and Atkins, probably the main consultant to the DfT and the Highways Agency.
Perhaps a few "local" engineers should attend this meeting, because I personally would like to see the DfT/Highways Agency making a better job of maintaining motorways and trunk roads before they start lecturing local Highway Engineers on how to maintain their roads and highways.
And, I would once again bring your attention to, "Standardised Specification and standard Details, Stage 2 Report, Progress Report on Local Authority Specification Variations", that I mentioned above.
If this specification for local highway work does come into being, it will be a lot more difficult to make "local decisions", that is if you are permitted to make any such decisions.
And the part of this document that would be of particular concern to me is the choice, or lack of choice, of bituminous mixtures for surface course.
I personally would not want to see the same situation as exists with the current Specification for Highway Works where the only permitted surface course materials, in England and Wales, are proprietary "Thin Surface Course Systems".
The same or very, very, similar proprietary bituminous mixtures are being marketed for local highway use, but in local applications they are known as "Negative Textured Systems", or more recently, "Low Texture Asphalt", or whatever else you want to call proprietary bituminous mixtures for surface course.
It follows that they will have, or should have had, a BBA/HAPAS trial, prior to approval of the "system". (Although one trial approval will apply to many different mixtures within the "system".)
These material will not be supplied to a defined specification as with British/ European Standard (BSEN) Bituminous Mixtures.
In my opinion if more engineering scrutiny had been applied to many of these proprietary bituminous mixtures before they were "approved", and during their laying, we would now have a lot less potholes.
I wonder of Boris will be attending this event, a bit "flamboyant" but he seems to get things done, is London "local" I am not sure.
Finally if you are a local highway engineer and you are attending this event, you may like to take a copy of my "Pothole Discussion Document" with you, but I would not flash it around, but it may give you a bit of backup if any of the speakers try being too "clever".
And just for clarification, I did not pinch the image on their promotional material, somebody "borrowed" the fuller image they use on their flyer from my website, a little acknowledgement would have been nice.
I wonder if they know the nature of the failure, and the material involved.
Possibly the image was chosen intentionally to prove a point, or was it a most appropriate Freudian slip, or just plain ignorance, perhaps somebody knows, I do not.
Donations - Not for me, for Rainbows via JustGiving
On creating the .pdf download for surface dressing, see above, I was talked into setting up a "JustGiving" page by a very nice lady at Rainbows who is obviously good at her job to talk me into doing just that.
This system suits me in that once set up I have no further involvement and therefore no further hassle, and it keeps costs down at Rainbows, but if you do not want to donate via the internet you can always pop a cheque in the post to Rainbows, details on their website.
What this means is that anybody accessing my website and who thinks that they have benefited from the information that they found and would like to show their appreciation by way of a donation just go to the "JustGiving" page I have set up and you will find the details on how to donate.
I am not saying anything else, I have honoured my commitment to Kate, but I did not promise her that anybody would actually donate.
Motto of the Month
"Treason doth never prosper, what's the reason? For if it prosper none dare call it treason."
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