MIT Study: Stiffer Roads = 3% better FE

[Duffman]

Originally Posted by 2000mc

quantified for big trucks by cummins a few years back

Relative Rolling Road Surface Resistance %
Concrete polished (best mpg) –12%
new baseline

Asphalt with finish coat 1%
medium coarse finish 4%
coarse aggregate 8%
Chip and Seal Blacktop (worst mpg) 33%

Road roughness can increase rolling resistance up to 20% due to energy dissipation in the tires and suspension (10% loss of mpg).


taken from p. 26 at http://cumminsengines.com/assets/pdf...whitepaper.pdf

Your post made me think of the Cat truck spec guide. Page 10 & 13 are relevant showing how to calculate rolling resistance.

http://www.google.com/url?sa=t&rct=j...52SwvXXGuFOQLw

[euromodder]

Originally Posted by rmay635703

To bad the concrete roads here in Wisconsin are replaced every year and are broken up wrecks in 6 months.

Are they made of concrete slabs, or continuous concrete without joints ?


The 20' concrete slabs we also have on some roads are worthless - even though it won't nearly get as cold as Wisconsin here.

[euromodder]

Originally Posted by jamesqf

It also depends a lot on how much wear the road has had. I haven't driven it recently, but there was a time when the stretch of I-80 between Donner Summit and (roughly) Auburn was so badly worn that I was worried about high-centering the Insight on the ruts worn into the concrete. It was also quite rough, with the concrete worn well down into a layer of about 2" or larger aggregate...

I'd put that down to bad concrete or bad workmanship in designing or building the road - and most importantly its foundations.

The concrete slabs tend to crack and rise or settle, but the continuously laid concrete has none of those issues.


We only have ruts in asphalt roads as asphalt is too maleable under heavy load - which increases rolling resistance.
During winter the top asphalt layer comes off as water gets into it, then freezes and cracks the asphalt into pieces.

[NeilBlanchard]

I've not heard of continuous concrete roads. How do they deal with the thermal expansion and contraction? Are there finger joints? What about road salt?

[jamesqf]

Originally Posted by euromodder

I'd put that down to bad concrete or bad workmanship in designing or building the road - and most importantly its foundations.

I'd put it down to heavy traffic combined with lack of maintenance by California. Also, this is a road going over a fairly high mountain range, which means that it gets frequent snowstorms (and ice, etc), so it is frequently sanded. Car & truck tires continually rub that grit against the road surface, so it's acting as a pretty good abrasive.

[Duffman]

Originally Posted by NeilBlanchard

I've not heard of continuous concrete roads. How do they deal with the thermal expansion and contraction? Are there finger joints? What about road salt?

Pretty sure some of our ring road is continues pour and we have one of the worst swings in temperature in the world. The road isnt that old yet but seems to be holding up well.

[rmay635703]

Originally Posted by euromodder

Are they made of concrete slabs, or continuous concrete without joints ?


The 20' concrete slabs we also have on some roads are worthless - even though it won't nearly get as cold as Wisconsin here.

They are slabs, I don't really understand why they bother laying them, sometimes the road they replaced was in better shape then they are.

[D.O.G.]

Maybe this is a factor in why I've had such good numbers over the last month or so, despite winter weather.

A few kilometres of the stretch of motorway included in my daily commute is being re-surfaced at night.
The fresh surface is so smooth, road noise suddenly dies when you reach it.

I wonder how long the improved figures will last?
I can already hear the difference in sections that are a few weeks old, compared to those only a few days old.

[euromodder]

Originally Posted by rmay635703

They are slabs, I don't really understand why they bother laying them

Yeah, the concrete slabs have all kinds of issues.
They're not very comfortable to drive on, as they tend to shift relative to the neighboring plates. Both warm and cold weather can push 'm up, because the slabs don't have the weight to resist that sort of push.

Originally Posted by jamesqf

I'd put it down to heavy traffic combined with lack of maintenance by California.

One of our motorways with continuous concrete, carries the road traffic between Antwerp harbour and Germany - that's a whole lot of trucks.
The asphalted stretches of this motorway have been resurfaced a number of times , the continuously poured concrete soldiers on.


While we don't sand our roads, we salt them, which isn't good for the roads either.

[Saskwatchian]

Not to detract from the talk about concrete slabs but I was thinking about the original topic of this thread when I drove back to work yesterday.

600km trip approximately 1/2 proper pavement and about 1/2 "thin membrane surface road" Both parts have very similar surfaces but I have always had better fuel economy in the south with the proper pavement and I decided to see what kind of difference there really was.

I used average FE from 30km sections along my drive that had no traffic. speeds were 90, 100, 110, 95, and 105km/h in that order for both road surfaces. Wind was very light a 5km/h from the west, travel was going north / north-east.



I was sort of surprised at how much of a difference there was, about 8%