A Story

Highways Agency, DMRB - BBA-HAPAS

Road Surface Texture

A Dedication

Recycling

Motto of the Month

Surface Dressing
"I like surface dressing", a simple and reasoned statement uttered because of the benefits this process can bring to local highway networks, in a very cost effective process.
I have spent quite some time recently in updating and adding to, the existing pages relating to surface dressing on this website so I will not repeat this information here, other than to say the 6th. edition of Road Note 39 was published early in 2008.
Road Note 39, is not a specification, but it is an excellent, comprehensive guide, and is regarded as the "bible" of surface dressing. 
You should obtain your new copies as soon as possible and study the revisions and the new reference information, although it is unlikely that the 6th. edition will be the reference document for 2008, but will be included in contractual arrangements for 2009.


On a personal note, I would just like to say a "thank you" to my old colleagues for the standard of work regarding surface dressing in my local area. I can only say that what I have seen appears to be first class. It is necessary to say appears because you can never really judge a surface dressing until after the following winter, but everything does look very good at the moment, and their past achievements would suggest that it will remain so.

I am led to believe that an Authority that had been "persuaded" to refrain from the procedure of surface dressing for newer and more expensive options has returned to the fold, welcome back.
Their return prompted by the poor performance of the more expensive options that they had been encouraged to adopt.
I must say that this information has come to me through the "grapevine", but from usually reliable sources, however it would not be gentlemanly to name the particular authority and possibly cause embarrassment. 

 I will continue to urge all those involved in surface dressing to take proper care and diligence in the performance of this process, because there are still those who seek to take this major, effective, and cost effective, highways maintenance option from you. 
Surface dressing is still a big "market" that others view enviously.

And one very important last note, to pursue a successful policy of maintaining local highway networks with the process of surface dressing you MUST use bituminous mixtures for your surface course / running course that lend themselves to being successfully maintained by the surface dressing process.
Your friendly, knowledgeable and experienced Materials Engineer will be able to assist you.

A Story
Once upon a time there was farmer that had a faithful donkey. The donkey worked the farm for the owner, with the beast knowing the procedures he had to undertake for successful results, and he worked steadily and well. 
However the farmer was unhappy because of the amount of money it cost to feed the donkey, so he implemented a course of action, involving the employment of a new "modern" farm manager.
The new manager resolved a plan to feed the donkey just a little less each day until the farmer had a donkey that did not need feeding and therefore cost nothing. The plan progressed, and was successful to the point where it was costing almost nothing to feed the donkey, and then it died.
It was then necessary for the farmer to hire a new donkey from a farmer who had many asses.
The owner of the farm then had to pay a significant price for the hire of the new donkey and had to meet the cost of feeding the donkey at, what could be construed, a surprisingly high level of nutrition.
The farmer soon found that the new donkey was not familiar with all the work practices of the dead donkey and it would often run off to his owner to ask him what he should do, and the donkey's owner would suggest different, often more expensive, methods of working.
The moral to this story is that if you have a faithful donkey, who is able to perform the work that is needed to maintain your farm in good condition, you should feed him an adequate balanced diet, as this will be the most cost effective option, over time.

But this is just a story ?

Highways Agency - Design Manual for Roads and Bridges (DMRB) - BBA/HAPAS
It has come to my attention that there is now a very useful links page on the Highways Agency (HA) website www.standardsforhighways.co.uk.
I mention this because on this links page there is a link through to the BBA/HAPAS website, which in turn has received some significant recent updating.
It has finally become possible to download the various "Guidelines Documents" for the, 
HAPAS assessment and certification of various products and "systems" that may be used in highways maintenance and construction.
E.g. "Guidelines Document for the Assessment and Certification of Thin Surfacing Systems for Highways.
You are able to download a, May 2008, edition of this document.

Those of you who read my pages regularly will know that I have been waiting for this facility to be created for some time. 
It is possible, and I say possible, because I found this update via the Highways Agency link, that the HA have had some influence in bringing this situation to a conclusion.
Considering "Thin Surfacing Systems" have been available, and indeed prescribed on motorways and trunk roads, since 1997/98 it is not before time that these documents have become easily available.
It is sad to say that some of these surfaces have not lasted as long as it was claimed they would.
I would most strongly recommend that Engineers and Engineering Technicians involved in the surfacing of Motorways and Trunk Roads, download a copy of this document and study it thoroughly.
This advice also applies to Engineers and Engineering Technicians who are employed by Local Authorities, this is because of the marketing of proprietary "Negative Textured Surfacing" (NTS), which are also supplied under HAPAS certification.
Bear in mind that this document is for the assessment of a "system" not an individual product.
It follows that you will be able to compare the assessed items on the "system" certificate offered by your supplier with the possible relevant criteria items included in the Guidelines Document.

It is also possible to download copies of the certificates for those proprietary products that have gained HAPAS approval from the websites of the various manufacturers, some of which have links on the BBA website.

I would hope that there are enough Engineers and Engineering Technicians remaining in the highways maintenance and construction industry who will now take advantage of the availability of these documents to increase their understanding of the BBA/HAPAS certification of "Thin Surfacing Systems", and make appropriate comment relating to any item that concerns them.

While you are on HA's DMRB "links page" you may like to appraise the many other links that direct you to other very useful websites of other organisations that provide, usually free, information relating to highways maintenance and construction procedures and processes.

Road Surface Texture - Interim Advice Note (IAN) 101/07
This is a complete revised 900 Series of the Specification, MCHW1 for Road Pavements -Bituminous Bound Materials.
It has been introduced to coincide with the publication of the new European Standards for bituminous mixtures BS EN 13108 family of standards for Bituminous Mixtures. from the 1st.of January 2008. 
The specification has also introduced a number of important changes other than those related to the specifying of bituminous mixtures to BS EN 13108

One of the most important of these changes, which in my opinion is not a "minor revision", is the reduction in initial texture depth of "thin surface course systems" (TSCS) on high speed roads, to not less than 1.3mm., and to not less than 1.2mm. on low speed roads and all roundabouts.
I urge you to obtain a copy of this IAN, it can be download from the HA website mentioned above, and study Clause 921-Surface Macrotexture of Bituminous Surface Courses.
In previous editions of the "900 Series" , e.g. November 2004, the figure quoted was the single figure of 1.5mm. for "high speed roads" but with no clear indication of what a high speed road was so the default was 1.5mm.
In the current IAN 101/07 there is a table containing the minimum texture depth requirements for defined surfacing materials and locations.
In my opinion this reduction in surface texture relating to thin surface course systems raises many questions as to how and why this reduction has been introduced.
Do not forget one of the basic reasons for having significant road surface texture is to promote removal of excess surface water from the road surface by the presence of "passageways" between the tyre and the road surface, not everybody is driving around on new tyres with deep texture depths.
The tyre cannot make contact with the actual road surface until the excess water is removed.
(The original, low void content stone mastic asphalt developed in Germany over 30 years ago, which had a relatively low texture depth was off set by a requirement for a high tyre tread depth on vehicle tyres. The policy in the UK, certainly during my period in the industry, is to have relatively high texture depths on high speed roads and permit reduced tyre tread depth requirements.
Both principles successfully allowing removal of excess water on road surfaces to achieve contact between the actual road surface and the tyre, with other engineering factors then coming in to action.
It is also stated in a number of reports that the roughness from deep texture dissipates energy contained in the forward movement of a skidding vehicle by the rapid manipulation (hysteresis) of the tyre tread and wall, producing heat, and hence reducing stopping distance.)

The questions and possible answers to this change in initial texture depth are so sensitive that even I will not enter into detailed discussion here, as anything I may say could be regarded as safety related and may put any organisation in a difficult situation if claims are made on a highway network manager as a result of an accident.
The fact that the HA have reduced the initial texture depth for TSCS has to be taken to mean that they regard these bituminous mixtures as safe at these initial texture depths. 
However in view of the continuing debate relating to safety issues of thin surface course systems this may not seem a very "politic" change in the specification. 
This specification change is likely to cause a number of Highways Engineers to ponder where this "advice" came from, and what its inclusion is meant to achieve, is it increased durability.   
It is not likely to increase safety even if it does not cause a decrease in road surface skid resistance.
Although the "900 Series" is specifically for motorways and trunk roads, the Specification for Highway Works is usually taken as the default document for local highway networks. 
It follows that Clause 921 is likely to be the default specification for initial texture depth for proprietary "Negative Textured Surfacing", that has been mentioned earlier on this page.
Highway engineers working for local authorities may like to take note of this situation and discuss it with their "management", because as I understand it a local authority is not bound to use the SHW as its default specification on all things, but usually does so because it is such an excellent document. On this occasion local engineers may like to give it some thought, remember this is an "Interim" Advice Note.
I am also puzzled that the initial texture depth requirements for hot rolled asphalt (HRA) and precoats, that you cannot use on motorways and trunk roads anyway, remains at 1.5mm.
In my opinion it would have been more logical to have reduced the initial texture depth requirement of a "positive" textured surfacing material than a "negative" textured bituminous mixture.
It follows that, in the future, you will not be able to make any like for like tyre noise generation comparisons between thin surface course systems and chipped hot rolled asphalt laid to the requirements of IAN 101/07, as it is generally recognised that texture depth plays an important role in tyre noise generation.

A few further points on this subject, 
(1) We are referring to initial texture depths, i.e. newly laid surfacing.
Surfacing materials supplied under the description of Thin Surfacing Systems are not all of the same nature/characteristics. 
The texture depth of low void content stone mastic asphalt type thin surfacing will increase with time as the "mastic" coating is worn off the larger aggregate particles, presented to the surface.
The texture depth of open textured, high void content surfacings, of a  porous asphalt type, will tend to lose texture as the voids fill up with detritus. 
And there are thin surfacing bituminous mixtures that can be regarded as a hybrid of both material types.

(2) Do not forget that we are talking texture depth measurement using "sand patch" measuring techniques, these figures must not be confused with the sensor measured texture depth (SMTD), they are different.
SMTD's are obtained from laser devices, e.g. SCANNER.
Talk to your Materials Engineer, to obtain clarification on this point, as I am beginning to cover too many related topics in this item, and will not try to explain the difference here. 

(3) We are talking initial texture depth, just one important aspect of the skid resistance of a bituminous mixture laid as a road surface, yes it will play a significant contribution in the early stages of newly laid road surface, and throughout its life, but you must also consider,

• Polished Stone Value (PSV) of the coarse aggregate
• In my opinion, PSV of the fine aggregate, e.g the fines in HRA has/had a requirement of a minimum of 45 PSV.
• Aggregate Abrasion Value (AAV)
• The actual design of the mixture, as there are a number of ways to design a bituminous mixture that will provide an initial texture depth of 1.2mm, or even 1.5mm. depth.
  The differing designs with similar initial texture depths may well have differing initial levels of skid resistance.
• The above can be dependent upon the grade/type of bitumen binder in the mixture, particularly the rate at which it will be abraded, by traffic, from the surface presenting coarse aggregate.

Texture depth of a road surface when it has reached its "natural" state can be quite different from the initial texture depth, often the critical factor being how long it takes to reach this "natural" optimum skid resistance condition.

My apologies, I have developed this item far further than I intended, but without being too specific.
I really do think that you need to discuss this matter with your Materials Engineer / Road Pavement Engineer / Consultant, as the topic is complex and, in my opinion, does need to be examined. 
I am beginning to form the opinion that major changes are taking place relating to highways maintenance, without full consultation of those actively engaged in the industry.

Recycling- In Particular the Recycling of Reclaimed Bituminous Mixtures & Materials 
Recycling, in whatever form is often considered, quite rightly, as a process for reducing damage to the environment by a reduction in waste disposal to landfill, or a reduction in the exploitation of finite resources from the environment, an example being quarrying in some areas of the countryside.

If these processes increase costs it is viewed as worthwhile to improve/maintain the environment.

However, I definitely believe the situation has now arrived where money can be effectively spent in recycling processes that reduce costs, especially with regard to the recycling/re-use of reclaimed bitumen based mixtures and products, as opposed to purchasing new materials.
 If you wish to call it asphalt recycling/remixing, so be it, I am uncomfortable with the use of the term "asphalt" to describe all bituminous mixtures
This belief in recycling has come about because of the rocketing price of virgin bituminous mixtures, whatever they are called, due to the significant rise in oil prices.
It is also due to the ingenuity, effort and money that independent "plant" designers and manufacturers have put into a range of machinery capable of safely and cost effectively recycling/remixing reclaimed bituminous materials.
If you wish to see true innovation in highways maintenance this is where to look for it, in my opinion re-branding is not innovation.
I am not going to say too much more in this newsletter, the information that you require to promote thought on these processes is already contained on this website, but I will classify the three main processes for recycling bituminous mixtures that a smaller authority/contractor can consider.

• "Hot Mix" remixing on site, the principles are much the same, and there are a  rapidly developing range of sizes of plant appropriate to on site pothole repair to machines capable of producing sufficient tonnage for small schemes, e.g. footway reconstruction. ---> Click Here
• In-situ, no removal of material, hot mix recycling by the use of applying "infra red" heat to the failed areas to enable remixing, addition of some extra material, and possibly rejuvenators.
  A real advantage of this process is there are no joints to fail. ---> Click Here
• The recombining/bonding together of suitably granulated and graded bituminous mixture particles by using foamed bitumen in a cold/cool mixing process either in a fixed plant or in-situ. ---> Click Here

There are other options, carried out by larger contractors and suppliers, that will efficiently and successfully use very large tonnages of reclaimed bituminous materials, usually in the form of road planings fed into quarry based production plants, as a permitted proportion of the total mix.
The use of these materials being covered by the Specification for Highway Works, and the relevant British Standards. 
In my opinion it is unlikely that you will see any significant cost saving to the purchaser of recycling conducted by major companies.
But if you are an authority whose Highways Department is still the master of its own destiny I would recommend that you at least make yourself aware of the three "bulleted" items that should bring you a reduction in the cost of bituminous mixtures for a number of regularly performed small procedures and applications.
It is also important that you retain and look after reclaimed bituminous materials and planings, as they are now valuable, and have a habit of "going missing" if care is not taken in recording and storing amounts of materials. 
I personally think that any use of reasonable quantities of "clean" reclaimed bituminous materials not recycled into "fresh" bituminous mixtures is subtracting value, not adding it. 
But I must point out that all these processes require a significant level of skill and knowledge to gain maximum benefit from the particular procedure, and once again I am going to say a knowledgeable and experienced Materials Engineer will be a definite contribution to any team involved in recycling.
You really do need to know what you are recycling/remixing and how you can modify it, if need be, to produce a satisfactory mixture appropriate to the job in hand.
To me it is obvious that it really is possible to spend what budget you have far more cost effectively if you have people around you that actually know what they are doing. 
Unfortunately too many people who do know what they are doing are being lost to the industry by "efficiency" savings, but strangely, only to be replaced by people, not suitably qualified or trained, and often from a completely different background, and perspective for the future.

It may also be the time to consider the use of "rubber crumb" from recycled tyres, and available suitable recycled plastics, such as low and high density polyethylene, LDPE & HDPE, as part replacement for bitumen. 
This is if the cost of the recycled bitumen replacement is lower than the bitumen cost.
I know some universities have already done research in this area, and published results, perhaps it is time for a few more to do some work and make their findings more widely available.
I note from my internet meanderings that the use of "rubber crumb" in asphalt and other bituminous mixtures is high on the agenda of a forthcoming "China Asphalt Summit" in September.
In my opinion Western road engineers ignore the progress of Chinese engineers at their peril, they do not appear to be held back by established thinking, and procedures.
There are also articles on the "web" from India indicating that whole roads, all be it quite small schemes, have received surfacing using recycled plastic bags (LDPE) as the aggregate binder in the mixture.
There are obvious temperature issues to be considered in using recycled plastics as aggregate binder but I feel it would be unwise for the UK to fall behind in this technology.

A Dedication
I would like to dedicate this newsletter to Frank (MBE), in lieu of a retirement card, I already sent him one about 10 years ago when he retired the first time, and Frank is still not sixty five.
Frank, has been, and still is (your knowledge does not suddenly fall out of your head when you retire) one of the best Highway Maintenance Engineers I have ever worked for/with. 
His knowledge of total highways maintenance information is immense, I just know a bit about materials, you could almost say Frank knows the significant parts of "everything" relating to maintaining a highway network, especially a local authority highway network.
He received his MBE in recognition of his contribution to highways maintenance, amongst other good works.
However, and I am told that my "howevers" are becoming famous, Frank does have a fault.
If you are attending his leaving do you may like to ensure that you locate yourself near to the refreshment area and make sure that you go to the toilet before he starts his retirement "speech".
Frank is known to never use one word when twenty three will better describe a situation, this combined with his memory of an almost infinite number of highways maintenance anecdotes can mean that his oration will rival the efforts of any former Soviet politician.

Good luck Frank, it will be good for you to slow down. However, I cannot envisage a situation where you will not continue to contribute, in some manner, to highways maintenance knowledge in the industry, hopefully on the "client" side.
May your God always be with you.

Motto of the Month
"People of the same trade seldom meet together, even for merriment and diversion, but the conversation ends in a conspiracy against the public, or in some contrivance to raise prices."