Macadam Road 1

[skb505]

Has anyone in recent history been involved in constructing a true "macadam" or McAdam road? I have a private development project that the owner wants a true "macadam" road for two reasons:

1. The "rustic" look of the roadway.
2. He thinks he can have it built cheaper than typical asphalt pavement.

I can't argue the "rustic" look as it's an aesthetic issue, but from a serviceability and construction cost standpoint, I think he's missing the boat.

In our area, there's plenty of competitive contractors who can construct asphalt roads, i.e. good prices. For this type of work in this day and age, it's almost specialty work with specialty prices.

I also think that the roads will be destroyed by construction traffic by the time the 10th house is built. From the reading I've done, this system was adequate when folks were riding buggies, but now I don't think it's appropriate.

Any thoughts or suggestions, please?

 

[jheidt2543]

I'd suggest calling some of the local contractors for budget prices so you can compare the macadam and asphalt.

Remember, rustic once meant an outhouse out back. Not everything old is rustic. How are those home owners going to feel about the macadam being tracked into their houses on their kids shoes?

 

[ACtrafficengr]

True macadam was a form of stone and gravel road, which didn't last long after the invention f pneumatic tires. Steel tired horse-drawn wagons continually compacted the surface, while rubber tires picked up gravel and took it away.

This lead to tarmac (tar-macadam) roads, an ancestor of modern hot mix asphalt.

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"Come to think of it, there are already a million monkeys typing on a million typewriters, and the Usenet is NOTHING like Shakespeare.

- Blair Houghton

 

[HgTX]

I've heard people refer to asphalt as "the macadam". Are you sure he really wants true macadam?

Hg

Eng-Tips guidelines: faq731-376

 

[bltseattle]

I agree with jh. that tar being tracked could be a nasty issue with a tarmac road.

 

[BigH]

Are you talking surface dressed roads? This is where you spray down a bitumen product (MC3000 or A/C 85-100, etc), then place on a layer of single sized stone chips? This is a good system, I would think for a housing development - for his rustic look. Don't finish the road until the development is nearly done. But this forms the national highways in many countries - Laos, for example. It is used extensively in rurul Indiana roads and it is a good system. Many times it is also used to "renew" a cracked AC road that there is a desire to extend the life for another couple of years. - See Overseas Research Notes 3 and 31.

 

[Zambo]

He is not talking about tarmacadam (nowadays more often bitumen macadam)he is talking about either dry bound or wet bound macadam, i.e aggregate only without a cementitious of bitumenous binder.

By the way there is a differnece betwen USA and UK definitions of bitumen macadan and asphalt but it certainly isn't the same material. Different grading of the aggregates and different specs for the bitumen.

Zambo

 

[skb505]

Thanks for the input everyone. BigH, what you are describing sounds like what he's wanting, but there is no existing road to overlay. I'm just not sure how to actually make this system work for a new alignment. What are the Overseas Research notes you refer to?

 

[BigH]

skb505 - this is not just for overlaying. Countries all over the world use this as new road construction too. In Laos, we used 400mm subbase, 200 base (crushed) and then a double surface dressing. The ORN's (as they are called) are put out by TRRL of UK - I was able to download one of them once. I've copies, but no way to get them to you . . . Your university library should have them, they are a whole of a very good series - including building in mountainous terrain, slope stability in mountainous terrains, hydrology, etc.

 

[BigH]

Check out the following website - it is a most excellent site and should be visited regularly by all involved with road construction and maintenance. The extension is for surface dressed roads.

http://www.highwaysmaintenance.com/SDtext.htm

 

[ACtrafficengr]

Gravel roads need regular maintenance to remove ruts and washboarding, so, while the up-front cost will be lower, maintenance costs will be higher.

Different researchers have found different values for the traffic a gravel road can take before it's more cost effective to pave it, ranging from 4 to 150 vehicles per day.

You might want to look at this section of the Cornell Local Roads Program on gravel roads:

http://www.clrp.cornell.edu/techassistance/Gravel pdfs/Introduction.pdf

------------------------------------------
"Come to think of it, there are already a million monkeys typing on a million typewriters, and the Usenet is NOTHING like Shakespeare.

- Blair Houghton

 

[BigH]

A surface dressed road is not a gravel road. It is used for much more than 150 vehicles per day - many countries use it for more than 3000/day. Double surface dressing is for more trafficked roads; single for low volume low loaded roads. Triple surface dressing for intersections.

ACTrafficEngr is correct about gravel roads washboarding though. See the Plasticity Modulus about suitability of materials for gravel surfaced roads.

 

[ACtrafficengr]

I don't see how a surface-treated road would look more rustic than paved. To the uninformed eye, a chip seal looks a lot like asphalt.

Also, if the client wants to dedicate the road to the municipality after construction, check the munciipal road specifications. They'll very likely want more than gravel or surface treatment.



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"Come to think of it, there are already a million monkeys typing on a million typewriters, and the Usenet is NOTHING like Shakespeare.

- Blair Houghton

 

[Ron]

yes it can be done....commonly now called a "chip seal". Can be done in double or single application.

Have used it many time for several reasons....inexpensive surface treatment, and crack relieve layer.

 

[ACtrafficengr]

The Transportation Research Board just released a new publication on chip seals, aka surface dressing or surface treatment. See it here at

http://trb.org/publications/nchrp/nchrp_syn_342.pdf

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"Come to think of it, there are already a million monkeys typing on a million typewriters, and the Usenet is NOTHING like Shakespeare.

- Blair Houghton

 

[roncity]

remember that any "surface dressing " aggregrate must have adquate skid resisitance...both initially and long term ; both wet and dry.
Maybe your owner can provide specific examples of locally built rustic roads...see how they were built and how they are standing up.
the problem with experimenting with unusual non-standard pavements is that in any accident, you will have insurance companies saying your pavement was at fault...not their driver. So you may have to defend your pavement in court..

 

[BigH]

Besides the note of Roncity - you also, in any aggregate need to think of the stone polishing value. Usually it is a bit higher than for wearing course asphalt. Still the "chip seal" or "surface dressed" roads - the texture is much more apparent than for wearing course asphalt unless, of course, you've used too much bitumen and it bleeds up to the top - but this also occurs in asphalt.
- and thanks for the URL on the Surface dressing.