Chipseal vs Hotmix

[Big Dave]

And seriously - The only issue with this is that so many people I know - and me for that matter - have dumped bikes because of accumulated piles of loose chip seal stones - or lost it on the flushed surface.

[Bass]

And seriously - The only issue with this is that so many people I know - and me for that matter - have dumped bikes because of accumulated piles of loose chip seal stones - or lost it on the flushed surface.

Ummm.......me included

[SPman]

The main reason Australian bikers wear less protective gear is because the roads are made from hotmix and are far less likely to 'betray' them.
Chip seal would just melt over there too.

Hotmix is SIGNIFICANTLY safer for motorcyclists. Provides better wet weather adhesion - because of the uniform surface and greater contact area - and has no likelihood of its surface wearing off and exposing slippery black death.

.

The predominant surface out of Perth is Chipseal - big hunks of sharpened granite that grind through leather like 5 grit sandpaper through pine! - (if you have the opportunity to test it...). Toodyay Rd has had some patches of hotmix put on it, and the official reaction was to lower the speed limit to 80kph (temporarily, of course...) until the "dangerous, slippery hotmix sections" have been expunged! (apparently, WA drivers fall off hotmix when it rains....)
The chipseal doesnt seem to melt like it does in NZ - its the traffic that seems to do it - pushing the chip into the seal and creating nice slippery grooves........

With good tyres, hotmix has better grip in the dry, and similar grip in the wet, but, chip seal is half the price.

[Big Dave]

My guess is the further up the fractional distillation tower they get the base material from - the higher the melting temperature.

Wasn't there something about making the roads from recycled engine oil in WA?

[Bass]

My guess is the further up the fractional distillation tower they get the base material from - the higher the melting temperature.

Wasn't there something about making the roads from recycled engine oil in WA?

It's the other way round mate. The heater in a distillation column is at the bottom and your lowest temp fraction comes off the top.
Normally the lighter fractions are the more valuable and the heavies are by-products. However, to get a really good bitumen may involve refining the lights out to a degree that is really high cost in energy terms.

Not sure about used engine oil.

I would have thought that it would have to be polymerised somehow to get enough heavies to make bitumen recovery worthwhile, but there could well be catalysts around that will handle that by now

[SPman]

Wasn't there something about making the roads from recycled engine oil in WA?

I thought they did - straight from the trucks to the road,,,,,,,,,

[The Stranger:Me]

the local roadies recently resealed a corner that was badly pot holed. its not much used by cars, but a LOT of stock feed trucks use that corner at all hours of the day. im picking about 20 trucks a day, maybe more? so 20 sets of tyres, all hitting the same line daily. that reseal lasted about 2 days, and now its twice as bad as before. im actually avoiding that road when im on the bike, its that badly damaged. and there seems to be no sign of proper repair. they used hotmix over chip seal, which may have had something to do with it, as they didnt remove the old road first.

20 trucks a day is a lot.
Sounds like the southern motorway, or perhaps Stanley st.


What's the problem?
The rougher the better, keeps you awake and on your toes. Means you have to work for your ride.

[Titanium]

Hot mix (asphaltic concrete) is 5 times more expensive than tar and chip seal. Is typicall more robust and when laid in a deep lift scenario is even better than concrete roads.

Also limitations around what raw material (asphaltic PAP 7mm percentage All Passings, as opposed to a TNZ40 Grade specification chip) there is to use in certain areas of new zealand and the location of ashphalt plants vs tar supplies.... greywackey vs basalt vs limestone all have different characteristics.

AC is also very quiet as a running surface and can be used where road noise is an issue (built up areas). Gives superior ride quality as well.

AC is typically more robust as a driving surface and can take a lot more punishment than a chipseal surface. AC takes a lot less R&M over full life but the upfront cost is nearly prohibitive at the moment. AC has probably a lower full lifecycle cost also can be recycled back into a roading surface where chip and tar can only be recycled back into a sub base using a hoe.

Surface resistance is not really taken into account when specifying which product to use.

Of course there are also differences in economies when preparing the subgarde for each of the products and also areas where one product may not be suitable to use.

The Americans use a lot of concrete in their roads, so does Australia.

[cooneyr]

Where to start with this lot. Firstly hotmix will be better in the dry due to the larger contact area similar to what a poster said about why racers use slicks. Thing of the other extreme - knobblies and what that does to traction on the same length of surfacing. The problems arise where there is a friction modifier in place i.e. water, especially whey the water cannot be dispersed quickly. I dont have figures but I suspect that it is much of a muchness when both are wet. If things freeze however chipseal wins hands down.

I would hope that greywacke is not used. It is known colloquially as Rotten Rock....

I'm not sure what part of the country you are from but crushed canterbury greywacke is the second best bar crushed volcanic rock chip in the country. You are right in that it will not stay as a solid mass but once it has erroded and worked its way down a river - the waimak say - only the hardest stone remains. The north island really struggles to get its hands on good chip due where as we souf islanders have an excess of it.

I can give you some details on this being a "roading person". ..... Still awake?? lol.

Well said. That is about as much detail as needed here.

No it innit. It's the whole point! Were it hotmix it (surface) would still be there and would offer significantly better safety & grip.

The discussion says that a chip seal is theoretically better in the wet. I don't agree, because the reality is it is inconsistent and more prone to failure.

As mentioned above getting hold of good chip and good pavement materials for that matter is hard in the norf island. As a result your roads tend to fall appart much quicker than those in the souf island. The higher traffic volumes don't help. Logic then says use a surfacing that will hold together better but if used correctly it actually acts as a structural member of the pavement as well. Overall hotmix will be a better product for most high traffic volume roads in the norf island, however the cost of hotmix is such that you just have to put up with crappy chipsealed roads in many locations.

I disagree here too, mate.
Data is data and all we are talking about is a coefficient of friction test. It doesn't even have to include a vehicle at all. A bit of rubber, a weight and a spring balance will give potentially useful results.

Called a British Pendulum. Lump of rubber on a pendulum of known weight and you measure how high the pendulum swings once skimming the surface. Good as a relative measure but pretty average as an absolute measure.

My guess is the further up the fractional distillation tower they get the base material from - the higher the melting temperature.

Wasn't there something about making the roads from recycled engine oil in WA?

There are predominantly two grades of bitument used in NZ and I'm buggered if I can remember what they are, 80/100 and 180/200 I think? The problem with these grades is that their softening temperature and freezing (such that they start loosing grip on the chip) are too close together. This becomes an issue in places like the McKenzie country where the surfacing temperatures can range from -10 to +50. To attempt to get around this polymers (sort of glue) are added however this normally is done to deal with the cold and it cannot help with the hot.

If the temp gets close to the softening point of the bitumen (of whatever grade) and then a heavy vehicle turns on it the heavy rolls the stones and brings the bitumen to the surface which leads to flushing. Bleading however is when the temps are so hot that the bitumen softens and the stones are punched down into the bitumen. The net result is the same - bitumen on top of the stones. This is not good for any vehicle the next time and every time after when it rains.

In short well maintained chipseal with good products is a very good solution for most of the roads in NZ. Poor products, poor maintenance poor pavement design or high traffic volumes really calls for hotmix.

Cheers R

[Ixion]

They are both crap. The only decent thing to make a road out of is concrete. There are miles and miles of concrete road, laid down in the 1930s, with cars still driving on them. Except the idiots have covered the concrete with a thin layer of asphalt stuff.

Take a gander when they are doing repairs to some of the older roads, Mt Wellington Highway, Ellerslie Highway, Onewa Road, lots of others. When they strip the top couple of inches off, underneath is the old concretae raod.

Concrete. That's what we want. Or gravel. Why do the roads have to be sealed at all?

[Big Dave]

They are both crap. The only decent thing to make a road out of is concrete. There are miles and miles of concrete road, laid down in the 1930s, with cars still driving on them. Except the idiots have covered the concrete with a thin layer of asphalt stuff.

Take a gander when they are doing repairs to some of the older roads, Mt Wellington Highway, Ellerslie Highway, Onewa Road, lots of others. When they strip the top couple of inches off, underneath is the old concretae raod.

Concrete. That's what we want. Or gravel. Why do the roads have to be sealed at all?

The raod in Lange wuth meny a winding tern.

[Ixion]

No, the other sort.

[SpeedMonger]

So do you have any information which could be used to compare the various types. Would be interested to know what sort of variation we see.

Yep, aggregates in NZ vary in PSV from low 40's up to mid 60's.

For example Blackhead Quarry in Dunedin is one of the lowest in the mid 40's, it is hard, fine grained and polishes easily. Canterbury Greywacke (more durable than Nth Island greywacke) is around 55, Auckland Basalt's are in the high 50's low 60's, Melter slag is also used from the steel mill up there it is in the mid 60's and the highest material used is Calcine Bauxite (imported) which is up in the 70's - this is generally only used on braking sections of road, there is some around Auckland - not sure of locations though. Quarries have to have their sealing chip tested every two years, most fall in the 50 - 55 range. Contractors are then supposed to apply chip of the approriate PSV for the section of road they are sealing, so they may need to haul high psv aggregate over large distances just to seal certain bends and use local materials for straight sections.

[SpeedMonger]

I disagree here too, mate.
Data is data and all we are talking about is a coefficient of friction test. It doesn't even have to include a vehicle at all. A bit of rubber, a weight and a spring balance will give potentially useful results.

yep you are right here, the basic machine used is a British Pendulum which has a rubber pad at an offset angle that is draged over the surface as the pendulum swings through it's arc. The distance it swings after passingover the pavement gives the psv reading. the more friction the less follow through there is. The rubber pad is a specific standard material but obviously cannot replicate all the different tyres/componds out there.

The one Transit refer to in the earlier post is the Scrim tester which is a large truck that drives along measuring as it goes. In NZ we have trailer mounted grip testers that use an offset wheel.


All three have differnet results as they are empirical test procedures but they correlate to one another. there is a test section of road here in Canty that all three were used on for comparison purposes.

Oops should have read last posts first, CooneyR is on the money

[Bass]

Yep, aggregates in NZ vary in PSV from low 40's up to mid 60's.

What does PSV stand for?

something something value presumably?