|[ Top ]||Hot Rolled Asphalt and Bituminous Macadam|
The Idiots' Guide to Highways
A BRIEF PHILOSOPHY OF BITUMINOUS MATERIAL PRODUCTION AND LAYING
The bitumen manufacturer / supplier
The producer / supplier of the bituminous mixture
The laying contractor
Personal Notes / Site Supervision
MANUFACTURER / SUPPLIER
The supplier of the bitumen is usually the company that actually produces the binder, usually sectors of the main oil companies, e.g. "BP" and "Shell".
But there are major players in the industry who appear to be just involved in the manufacturer and supply of bituminous binders of all types, e.g."Nynas" (but it is likely they will have a strong link with an oil company, possibly a government owned producer, you are never quite sure who owns who in this industry).
The Road Bitumen Association
The RBA is the trade association for the UK's six bitumen suppliers who between them produce nearly all of the country's bitumen,
85% of which is used in road maintenance and construction. (Source "Modern Asphalts").
Asphalt / bitumen macadam production was 37 million tonnes in 1995, declining to 26 million tonnes in 1998.
(Source "Guest Column" in "Network" magazine autumn 1998).
I have been unable to find any reliable, up to date, figures on bituminous mixture production, you would probably need to look somewhere in the appropriate section of the "business" press.
The RBA is now a joint partner with the Minerals Products Association in the organisation the Asphalt Industry Alliance (AIA), a body promoting and lobbying for the use of "Asphalt", i.e. bituminous mixtures in the construction and maintenance of UK highway networks.
I quite like the content of the recent AIA promotional video which does indicate the importance of a properly constructed and maintained highway network and the very important role that bituminous materials can play in this respect, even hot rolled asphalt and precoats.
However, do not forget this organisation is primarily a trade organisation which is also heavily into lobbying government, which is not always of full benefit to the real customer, i.e. the motorist or transport company.
Read the Winter 2009-10 Newsletter for further background to the changes in the nature of these trade organisations, especially the advice and guidance they once provided to Engineers and Engineering Technicians, with regards to the "public relations" stuff that we get now.
The bitumen manufacturer will produce the bitumen from what is left after distillation of the crude oil into the other "lighter" based components.
Many sources of crude oil are not suitable for the production of road pavement grade bitumen, a few produce excellent bitumen for road making purposes, (e.g. Venezuelan Crude), and some crude oils will produce acceptable bitumens after a bit of modification.
The bitumen manufacturer will produce a range of products suitable for the various functions where a bituminous binder will be needed.
The bitumen manufacturer may well modify some bitumens to give enhanced properties, but also to "add value" to his basic product.
A modified bitumen is only necessary, where it is necessary, a straight run bitumen of the correct grade will be suitable for nearly all local highway network applications.
The bitumen manufacturer will expect the producer of bituminous mixtures to buy bitumen from him suitable for the product that is being produced, i.e. the correct viscosity and / or modified properties.
The bitumen manufacturer will expect the bitumen materials producer to store, and use his bitumen in accordance with the recommendations / specifications attributed to that binder, e.g. maximum temperatures for storage, both before and after mixing, and very importantly the length of time in storage after mixing.
It also seems
reasonable to assume that the bitumen manufacturer will expect his
products to be incorporated in mix designs that are suitable for the sites
where they will be used, and that bituminous materials will be stored,
transported, laid and compacted correctly, and in appropriate weather
Poorly performing bituminous mixtures could give cause for the comment that the bitumen was of poor quality, which may or may not be a correct assumption.
THE PRODUCER /
SUPPLIER OF BITUMINOUS MIXTURES
The producer of bituminous mixtures is usually, but not always, quarry based, predominantly owned these days by a multinational company, e.g.'s "Lafarge" and "Minorco".
The industry is truly international and the influence of what may appear to be quite a large regional buying concern, may be quite small in the global sense that these companies operate, and the influence that they can exert, even on governments.
This may leave the regional purchaser poorly placed to negotiate with a few such large organisations.
The Mineral Products Association ( Replacing the Quarry Products Association (QPA))
The Mineral products Association has replaced the Quarry Products Association (QPA) which had replaced BACMI, the British Aggregate Construction Materials Industry, as the trade association that includes representation of producers of bituminous materials.
There are many members of this association, but it is likely that the larger companies will have the controlling influence, perhaps one more than others.
The MPA is now a joint partner with the Road Bitumen Association in the organisation the Asphalt Industry Alliance (AIA), a body prompting and lobbying for the use of "Asphalt", i.e. bituminous mixtures in the construction and maintenance of UK highway networks.
I quite like the content of the AIA promotional video which does indicate the importance of a properly constructed and maintained highway network and the very important role that bituminous materials can, and do, play in this respect.
However, do not forget this organisation is primarily a trade organisation which also heavily into lobbying government, which is not always of full benefit to the real customer.
Read the Winter 2009-10 Newsletter for further background to the changes in the nature of these trade organisations, especially the advice and guidance they once provided to Engineers and Engineering Technicians.
The producer of bituminous mixtures, in purchasing a specified bitumen binder will expect that binder to possess the properties he has specified.
The producer will expect the binder to be delivered at the time he has specified, not before, holding tanks may not be empty and cleaned, and not after, he may have run out of that particular binder and had to cease production causing "knock on" problems.
The producer will expect binders to be delivered at agreed temperatures that do not cause handling or storage problems.
The producer should be able to store bitumen in the manner recommended by the supplier and in accordance with various appropriate British Standards specifications.
The producer should incorporate the purchased binder into bituminous mixtures, regarding amount, type and mixing temperature, as specified in a British Standard specification or a Published Document, as set down in the design of a proprietary material, or as an agreed design/specification supplied by the Engineer.
The production plant will use a "recipe"/design to manufacture any bituminous mixture whether it is a British Standard "specified" mixture or a proprietary material, even if the material is to be assessed on a performance basis. There is no other way to produce large amounts of a uniform material other than to have a "recipe"/design in the control room of the mixing plant to know what to mix together to obtain the material you want.
The producer will have manufactured the material in accordance with the order placed at the plant by the laying contractor or engineer in charge of the work.
The producer cannot be held responsible if the material ordered is not suitable for the situation in which it is being used, he will produce and supply the material ordered.
If the laying contractor/engineer/"client" does not know what he wants that is not the problem of the producer.
the producer has promoted a proprietary material as being
suitable for particular site conditions and the passage
of time proves that the material is in fact not suitable
for the site then this is a different matter, and action
should be taken by the purchaser (contractor) against the producer.
This situation can be complicated if the "client" instructed the contractor to lay a particular material on the recommendation of the producers' "agent".
There is a basic two year guarantee for BBA/HAPAS approved proprietary Thin Surface Course System bituminous mixtures, this guarantee can be increased to five years with the inclusion in the contract of the appropriate clause from the Specification for Highway Works.
producer of bituminous materials is in the business of
"adding value" to his raw product, i.e. quarried
aggregate, by producing bituminous materials he
considerably increases the price at which he markets his
This process of course entails considerable investment in very expensive plant and machinery which has a high maintenance cost in the quarried stone environment.
However when you become aware of the very high tonnages the modern highly automated plants can produce the cost per tonne of material produced attributable to this investment is not high.
THE LAYING CONTRACTOR
Let me give a reasonable
"average" example, in a local authority situation, to support my
You have a "job" where 400 tonnes of a bituminous mixture is going to be laid on that day, and you will be paying on a "tonnage rate", i.e. the cost of the laying is included in the cost of the material, so material thickness may vary but you will only pay for the actual tonnage laid.
( As an aside this approach is a good method of ensuring the specified thickness of layer, as there is no incentive for the contractor to play the "permitted tolerance" card, which he is quite entitled to do when being paid on a square metre basis. )
Let us assume the cost of the material delivered to site is £75:00 per tonne, let us also assume the engineer was accurate with his estimate of the amount of material needed, so that is going to be £30,000:00 spent on bituminous material.
Let us now assume that you have a good man or woman on your own staff that is, amongst their other abilities, qualified and experienced in the supervision of all aspects of the laying of bituminous materials. This person, in my opinion has got to be worth £15:00 an hour, but the "administrative" side of your organisation will want to double this for "support" reasons.
So this person is costing you £30:00 an hour, and a "normal" laying period in a day will be 8 hours, so a cost of £240 pounds for the days laying.
Now if my maths are correct that is just 0.8% of the cost of the material and it being laid.
I regard this as a very small cost for the benefits that the presence of this person will bring to the work.
The clerk of works/engineering technician will also be there to supervise all other aspects of the work on site, such as tack coat/bond coat laying, quality of lifted ironwork, depth of any planing required, quality of road marking application, traffic control, possible safety issues, taking samples of supplied material, etc., etc., and also be able to give a quick, cost effective, response to any unforeseen situations that arise throughout the day as he will be representing the "client".
For those who think this supervisory presence on site is an unnecessary cost, and of no/little benefit I can only think that they have never spent much time on site, in the real world of highways maintenance.
Reducing staff numbers, and hence supervision, may be "saving" money on one side of the balance sheet, but believe me, or believe me not, it will be increasing the cost of maintaining your highway network over time.
In my opinion it is just as much the duty of the "client" to support
any contractor/supplier that provides a good service/product as to withhold/reduce payment,
or enforce remedial work, for a poor quality service/product.
Without this supervisory role of the "client" it is likely that there will be a downward spiral of quality in service provision and received product, as the provider of good service and product will perceive no benefit for his efforts from having provided the required quality.
I have found that most laying contractors have workmen that can achieve good quality work if they receive the support they deserve.
This can mean having enough men on site with the correct amount of fully working equipment.
I do not much like the saying "a bad workman blames his tools", perhaps he does, but you try laying a good hot rolled asphalt wearing course with precoats with a poorly maintained chipping spreader.
I have also found that most gangs take a great deal of pride in the quality of work they produce, and will refer to good lengths of surfacing that their gang produced many years after the laying, when you next meet up with them.
It was not uncommon ( and I can say this after 15 years of not being directly involved with the laying side of things ) to be tipped off by the gang foreman that a particular load of material was too hot, too cold, too "fatty", or whatever, to be laid successfully and could I put pressure on the supervisor for it to be sent back to the quarry, because he would not be able to refuse to lay it.
I have been sworn at and pressured (but never physically threatened) quite often in my on site dealings with laying gangs, it was part of the job, and most of it was "tongue in cheek" to find out just how much they could get away with, but I also learned a great deal by just watching and listening, and I know without a good laying gang everything that happens previous will be for nothing.
[ Top of Page ]