Bitumen Road Emulsions

CSS - Soils and Materials Design and Specification Group (SMDSG) - Minutes

Motto of the Month

Deep Road Planings Contaminated with Hazardous Substances
I have chosen the title carefully, although what we are mainly concerned with is tar bound mixtures of past years, or bituminous mixtures that have been cutback with tar derivatives, i.e. creosote.
If you have not been affected by this issue to date it is likely you will be before long, and if you are not prepared for it, it will be expensive.
To fully understand the situation is a steep and complicated learning curve. There is a great deal of information that can be downloaded from the web, from a number of sources, none of them agreeing in the detail, i.e. what levels of contaminants can be regarded as acceptable to not pose a future hazard when/if recycled.
If the decision is taken that any level of contamination by hazardous material is not acceptable, you either are not going to deep repair any roads, or most of that particular budget will be spent on disposing of hazardous material and very little will be spent on actual road maintenance.
I am not going to give you a list of documents to obtain but if you "Google" a few key words including "tar contaminated planings" or similar appropriate combinations you will be provided with many useful serious publications to study. 
But you very quickly need to understand your Poly(nucleic) Aromatic Hydrocarbons (PAH's), and you various benzine compounds, benzo (a) pyrine being regarded as the principle marker as to what is hazardous and what is not.
The top is now off Pandora's Box on the subject of tar / hazardous substances in deep road planing, and many other products and processes and forms of recycling. 
Even new bituminous production may come under the spotlight once routine testing for these substances takes place.
The good news, if there is any good news, is that testing for the 16 PAH's that determine whether the materials is to be regarded as containing tar is not expensive, but do be careful in determining that the sample you send for test is representative of the material you want testing.
It is necessary to be very careful in the nature of the planing process so that the lower, possible tar containing mixtures, are not mixed with the upper layers thus rendering the whole of the planings contaminated.
Until this whole situation has been resolved and guidance/specifications are published in the Specification for Highways Work and/or the Design Manual for Roads and Bridges, I suggest your contract documents, for any planing work, contain suitable clauses to place the responsibility for site investigation firmly with your surfacing contractor, with the cost of the investigation being included in the submitted price
I am led to believe, because of recent problems, this situation is being addressed by the CSS (County Surveyors Society) Materials Group as a matter of some urgency.
I hope this brief mention of the problems that can be encountered with deep planing and the possibility of disturbing lower layers containing bituminous binders now regarded as hazardous will assist any "wizard" Materials Engineer in promoting knowledge, discussion and research into the subject.
It is my opinion that there are pragmatic and safe procedures for providing a solution to the bulk of problems encountered with deep planing if the engineers rather than the accountants are allowed to prevail.
If engineering sense does not prevail I can foresee serious setbacks to the government's policy relating to encouraging recycling in road maintenance and construction.
Just one last important tip before I leave this subject, the way you use words in these situations is critical, it is not wise to call any planings that are produced "waste", they should be regarded as a "product" that will be reused/recycled in entirety or as part of a fresh product for inclusion in road maintenance/construction, until proved that option is not possible.

Bitumen Road Emulsions
There is now available from the British Standards Institute (BSI)  a draft copy of,
BS 434-2 : 2006 : Bitumen Road Emulsions : Part 2 : Code of practice for the use of cationic bitumen emulsions on roads and other paved areas
I find this an excellent document, full of information and guidance. 
It is only in draft form at this moment but buy a copy now, even though you will have to buy a further copy when it becomes a full standard.
I say this because often very useful drafts seem to take a long time before they become a full standard, sometimes with amendments that have removed, or added, items that I feel result in a lesser document than the original draft.
I repeat, the information and guidance contained in this document is extremely good and written in a way that most engineers and technicians should be able to understand.
(Some parts are so good I could have almost written them myself.)
If I have any reservations it is the fact that there are no "examples" of typical mix recipes/designs of materials such as slurry seal, and slurry macadam, these recipes/designs are present in tables in the current standard, so if you have a existing copy perhaps it would be wise to retain it as a reference document, but not for specifying.
Note the the new BS 434:Part 2 is now referred to as a "code of practice" and as such refers to the properties required in an  "end specification", which is good, but  a little more guidance on what a slurry seal, or a slurry macadam (micro asphalt) may consist of would not be out of place in my opinion.
I am going to list the principle changes listed in the foreword of the draft, no point in reinventing the wheel,
This new edition represents a full revision of the standard, and introduces the following principle changes:

• refers to BS EN 13808; *
• covers the use of polymer modified bitumen emulsions;
• includes guidance on the use of bitumen emulsions in the construction and maintenance of footways and cycleways;
• includes guidance on the use of bitumen emulsions as bond or tack coats;
• includes reference to permanent cold lay surfacing materials;
• includes a biography containing sources of further information on the various techniques included in this British Standard.

The above list covers the main changes, but the document contains far more information than is indicated above, such as surface dressing and "velocity patching", which I thought was a rather good generic name for "Jetpatcher" work, as I know of no other machine capable of this type of process.
I regard this standard, even in the current draft form, as a must have addition to the highways maintenance engineers library, but do not just put it on the shelf, read it.
And if you do not have a copy of the standard below perhaps you ought to purchase a copy of that as well. 
I do not get a commission from BSI, honest, I just like working to "standards" everybody should know where they are then, there are too many "people" trying to invent their own rules, and sometimes succeeding, but also spreading confusion in the industry.

* BS EN 13808 : 2005 : Bitumen and bituminous binders - Framework for specifying cationic bitumen emulsions
This document specifies the requirements for performance characteristics of cationic bitumen emulsion classes which are suitable for use in the construction and maintenance of roads, airfields and other paved areas.
This document applies to emulsions of pure bitumen, or of fluxed bitumen, or of cutback bitumen and to emulsions of polymer modified bitumen, or of polymer modified fluxed bitumen, or of polymer modified cut-back bitumen, which also includes latex modified bituminous emulsions.

CSS - Soils and Materials Design and Specification Group (SMDSG)
The minutes of the meeting of the above group held on the 7th. of June, at Sywell, Northamptonshire, have been posted on the CCS website, and can be downloaded for perusal, they were posted on the 19th. of October 2006.
I would suggest that everybody who has an interest in highways maintenance (and construction), especially those with a "local authority" interest should download these minutes and study them. 
In my opinion there are a great many interesting items in these minutes, and I feel that many of you should be concerned with comments included in the text.
I am not going to voice any of my concerns on individual topics, except to note that the CSS has appointed a "marketing consultant", (Item 06/03), I am not impressed, "what" or "who" are they going to "market", and who is going to benefit, apart from the "marketing consultant".
The County Surveyors Society was originally created to serve the interests of County (rural local authority) highway networks, and in my opinion this no longer appears to be the situation.
There are no County Surveyors remaining in place, anywhere, and this body now has representation from a number of very large commercial consultancy companies, and the Highways Agency, so the interest of Counties and rural local authorities, and indeed the maintenance of local highway networks, may not be represented as a priority, as was once the case.
Having said that all that, the  CSS is perhaps the only remaining body of some importance that local authority engineers can influence to ensure that appropriate working practices remain in place on their highway networks.
I am aware of a number of Engineers who work very hard to present the case of local authorities, and shall we say the more conservative, well tried, and cost effective methods of highways maintenance, than the "industry" would have us adopt. 
It would be good if these engineers could receive more active support, especially in ensuring the continued and prompt posting of the minutes of meetings, and in the provision of items for publication in the proposed newsletter.
I, personally, cannot see the provision of "long life pavements" being provided with the imposed  savings in highways maintenance and the introduction of commercial companies being responsible for these networks, and their tendency to employ more expensive proprietary products and processes. 
Apart from the very early years of my career in highways maintenance I have always been a "local" engineer and I take pride in that fact. 
The benefit you gain from having "locals" looking after local highway networks should not be under estimated, either with regard to the cost of the process, or of the provision of service to the community. 
Once you have "given" this workforce to a commercial company it appears to be only a matter of time before priorities change.   
If something is being performed inefficiently, ask why before outsourcing, I bet somebody can tell you the answer, if any body wants to listen.

Motto of the Month

"The weak have one weapon : the errors of those who think they are strong."