Blacktop vs. Concrete

[codyg1985]

While concrete lasts longer (much, much longer) than asphalt, when it rains, the spray kicked up by the vehicles can just about blind a driver.  Over the past 4-6 years, Caltrans has used a new type of asphalt on some Bay Area freeways (most notably US 101 between San Jose and S.F. and I-880 from San Jose to Hayward) that contains ground up tires mixed in with the asphalt.  This surface provides a nice smooth, quiet ride and when it rains, there is very minimal spray because the rubberized asphalt allows the rain water to drain through the pavement.  IIRC, I-880 was repaved about 5 years ago and the rubberized asphalt is still in very good condition.

Obviously, this type of pavement works in California due to our mild climate but I suspect it's not really an option in harsher climates (freezing cold or blistering heat).

It's not necessarily the rubber in the asphalt that allows the rain water to drain through the pavement. With asphalt pavements, the top layer or "lift" is often designed as open graded layer ("open grade" being rock material containing very small fines or pebbles and bigger rocks or crushed aggregate pieces). The open grade material bonds together with asphalt binder, but since there's no small stone material in the mix, the result is a top layer (typically about 2" thick for major roads) that is porous. This allows rainwater to drain down slightly from the pavement surface and travel between asphalt lifts off to the side of the road or gutter due to the natural cross slope of the roadway.

From what I remember the rain performance of this top layer of "open-graded" AC is superor to any other type of pavement, and acoustically the openings in the fines also cause the roadway surface to be very quiet indeed. However I remember that after just a few years 3-5 or so, this roadway surface had deteriorated down ehough that the noise was much louder to the more exposed agregate and also the rain performance was also greatly diminished. In these cases water spray from tires can actually be worse than PCC pavement. Since Open-graded asphalt has such improved safety benefits initially it seems to make sense to use it where possible although it will need to be replaced every 5-6 years versus 10-12 years for regular AC-Overlays. It is too bad that this pavement will not work for mountainuous or snowy regions as the freezing and thawing and plowing would likely damage the roadway after one or two seasons.

Alabama and Florida uses the open graded friction course AC on most of it's interstates, but they have had mixed results with it in terms of how well it stands up to traffic. There was a stretch of I-65 north of Birmingham around Gardendale that had the open-graded asphalt, and it deteriorated rather quickly (I think two or three years after it was resurfaced), so ALDOT had it repaved with standard Superpave on the wearing surface.

[codyg1985]

Hey US-43/72, I know exactly what you mean by "trying to randomize the grooves". This problem happened on some bridge decks here in Illinois on I-270, I-55/70, and Route 255 (all within ten miles of one another).

The grooves on the bridge decks I mentioned are not uniformly spaced, but they form a pattern that goes, wide-narrow-wide-narrow-wide-narrow. The pattern breaks, but then repeats again, and so on. The spacing between every other groove is 3 inches, so the pitch of the sound is three octaves lower than the "whining" sound on a typical transverse-grooved pavement with 1 inch spacing. Likewise, the texture or timbre of the sound is very unusual, almost sounding like an alien.

Here are some links to videos that I uploaded of the weird-sounding bridge pavement. Tell me if they sound similar to the ones in Indiana:

video one (going 63 mph) http://www.youtube.com/watch?v=etktVDvKhbc&feature=relmfu

video two (going slow 45 mph) http://www.youtube.com/watch?v=CFFTIus8-NU&feature=channel_video_title

video three (going 63 mph) http://www.youtube.com/watch?v=FaGqm-QAiMA&feature=channel_video_title

video four (also going 63) http://www.youtube.com/watch?v=FvUF1Nma3Ec&feature=channel_video_title

Some of those bridge decks sound a lot like those in Tennessee, actually.  Nothing like Indiana.

That does indeed sound like Tennessee bridge decks (TN 385 in Memphis comes to mind for me).

[MDOTFanFB]

Here in Michigan, there's a type of concrete called Continuous Reinforced Concrete where the concrete was heavily reinforced. Around here, it was used in the construction of almost all of I-275 and some of I-696 in the 1970's. By the 1990's, many cars got damaged by driving on those two freeway segments, portions looked like the freeway had been bombed and some even said those freeways were paved with gravel!!! (including the webmaster of the Michigan Highways site, see it here: http://www.kurumi.com/roads/3di/i275.html#275mi)   So around 1997, MDOT responded and totally rebuilt those freeways, the last of which was completed by late 1999. And MDOT no longer uses CRC!!

More information is at http://www.michiganhighways.org/listings/MichHwys250-696.html#I-275 and http://www.michiganhighways.org/listings/MichHwys250-696.html#I-696.

[Crazy Volvo Guy]

There was a stretch of I-65 north of Birmingham around Gardendale that had the open-graded asphalt, and it deteriorated rather quickly (I think two or three years after it was resurfaced), so ALDOT had it repaved with standard Superpave on the wearing surface.

Some of it is still there.  It's so deteriorated that it has actually completely eroded away above all the concrete joints below, allowing the slabs to free-float again.  It literally now feels like concrete with offset slabs.

I'm willing to bet the Michigan "CRC" was actually jointed-reinforced.  If it had transverse joints, it was jointed-reinforced.  CRC doesn't have transverse joints, hence its name, Continuous Reinforced Concrete.  I-459 in Alabama has CRC and most of Texas' concrete pavements are CRC.  Illinois uses it some as well.  I-74 in Peoria was recently redone in CRC.  In any event, early CRC didn't work well because of design issues with the steel reinforcing mesh.  Properly-designed CRC will certainly outlast plain-jointed pavements, which are only seeming to last 15-20 years, as opposed to some of the older jointed-reinforced pavements that lasted 30-40.

[kphoger]

Sorry, boys..... I'm an asphalt guy.  I don't like the low color contrast between pavement striping and surface material on PCC roadways, especially at night.  It drives me nuts to be stuck in head-to-head traffic on one side of a freeway while the other side lies completely ripped up; I'd rather have a quick resurfacing every 5-10 years than have a roadway totally undriveable for what seems like an eternity every 25.  In slick winter conditions, I actually prefer rough blacktop over anything really smooth, just for the added traction (shoot, if they could make a freeway out of gravel, I'd take that in some nasty weather conditions).  Pavement flaws in asphalt are usually small and avoidable (potting), whereas flaws in concrete threaten to send my car into orbit and are unavoidable.

Please don't throw things at me.  I know concrete lasts longer.  I've been on very smooth new concrete highways (some of which don't even produce a nasty whine).  I know, I know, I know.  But I still want to break out into song when I transition from a concrete portion onto a silky-smooth blacktop portion.

[J N Winkler]

Pavement flaws in asphalt are usually small and avoidable (potting) . . .

Not necessarily true--badly maintained asphalt tends to rut under heavy traffic, and these ruts are both hard to avoid and likely to cause hydroplaning in wet weather.  Badly maintained concrete leads to other problems like ride roughness going over spalled joints, but at least it does not rut.

[CL]

Pavement flaws in asphalt are usually small and avoidable (potting), whereas flaws in concrete threaten to send my car into orbit and are unavoidable.

Not at all. During winter in Salt Lake we have serious potholes forming on (older) asphalt surfaces, while our (old and new and anywhere in between) concrete roads do just fine.

[Beltway]

A couple of other things to consider:

There are often political factors involved. Do not underestimate the power of the asphalt (or PCC) lobby in a particular region. Not that engineering decisions would ever be made for political reasons...

There is also some volatility in the prices of raw materials. In particular, in periods of construction booms, PCC becomes more expensive because concrete is used for building footings, etc.

Trying using solely one type could easily overcome the industry capacity of a region, leading to much higher unit prices for that type.  That is why that usually you see considerable use of both types in a region.

The multi-factor formula for life cycle costs of a pavement type, does not lead to a large difference.  It is close enough that each industry can claim that its type is a bit cheaper, by arguing over the exact value of each factor.  We're talking a total of about 5 to 10% at most.

The Hampton Roads area in Virginia mostly uses concrete pavement on Interstates, because the very high capacity of the concrete industry in that area, makes it more favorable on a cost basis.

[hbelkins]

Kentucky hadn't consistently used concrete for new highway construction in many many years until a few years ago. Just about every bit of new highway construction that I can think of used asphalt.

Now, many contracts for new construction include the line "pavement alternatives." This means they are considering both asphalt and concrete. I don't know what kind of formula is being used to compensate for concrete's initial higher cost, but they do have some sort of system developed to allow the Awards Committee to make a determination.

[Crazy Volvo Guy]

but at least it does not rut.

No, it does - you just have to give it a lot of time.  I've been on plenty of 30-40 year old concrete that was pretty well rutted.

[roadfro]

^ Concrete doesn't rut the same way asphalt does. With the concrete, is more of a gradual wearing of fines and aggregates from the surface due to wear from tires (and chains in winter snow areas; see I-80 near Donner Summit) and is only surface rutting. Asphalt gradually ruts such that the entire pavement section (the various lifts in the asphalt concrete as well as the base or subbase layers) deforms causing the rut.

[J N Winkler]

^ Concrete doesn't rut the same way asphalt does. With the concrete, is more of a gradual wearing of fines and aggregates from the surface due to wear from tires (and chains in winter snow areas; see I-80 near Donner Summit) and is only surface rutting. Asphalt gradually ruts such that the entire pavement section (the various lifts in the asphalt concrete as well as the base or subbase layers) deforms causing the rut.

I have personally never seen concrete that was rutted deeply enough to overcome crossfall and accumulate enough standing water to cause hydroplaning.  The very few times I have hydroplaned on concrete have always been as a result of design faults such as undrained creases on bridge decks.  On the other hand, hydroplaning is such a problem on asphalt that I always look for glossy reflections in wheel ruts when I am driving on asphalt in or immediately after a rainstorm, and slow down when I see them.

We could more or less completely eliminate the risk of hydroplaning on asphalt by tightening pavement maintenance schedules, building high-speed roads with uniform 2.5% crossfall, and using surface textures which resist deformation under load and promote quick drainage.  This is more or less what the British have done since the late 1950's--hydroplaning is almost unknown on British motorways despite well over 90% of motorway mileage being bituminous-surfaced.

[Beltway]

^ Concrete doesn't rut the same way asphalt does. With the concrete, is more of a gradual wearing of fines and aggregates from the surface due to wear from tires (and chains in winter snow areas; see I-80 near Donner Summit) and is only surface rutting. Asphalt gradually ruts such that the entire pavement section (the various lifts in the asphalt concrete as well as the base or subbase layers) deforms causing the rut.

I have personally never seen concrete that was rutted deeply enough to overcome crossfall and accumulate enough standing water to cause hydroplaning.

I have ... some Pennsylvania highways in the 1970s, such as US-202 west of Valley Forge, and the Schuylkill Expressway, and some others.

[kphoger]

In fact, when it rains on rutted asphalt, I typically ride either the center line or the shoulder line, depending on the road.  I also do this at railway crossings to avoid the worst bumps, whether the road is asphalt or hydraulic concrete.

Gee.....Our roads could be better if they were built the way they should be built and maintained the way they should be maintained.  If only it were free of cost! (-:

^ Concrete doesn't rut the same way asphalt does. With the concrete, is more of a gradual wearing of fines and aggregates from the surface due to wear from tires (and chains in winter snow areas; see I-80 near Donner Summit) and is only surface rutting. Asphalt gradually ruts such that the entire pavement section (the various lifts in the asphalt concrete as well as the base or subbase layers) deforms causing the rut.

I have personally never seen concrete that was rutted deeply enough to overcome crossfall and accumulate enough standing water to cause hydroplaning.  The very few times I have hydroplaned on concrete have always been as a result of design faults such as undrained creases on bridge decks.  On the other hand, hydroplaning is such a problem on asphalt that I always look for glossy reflections in wheel ruts when I am driving on asphalt in or immediately after a rainstorm, and slow down when I see them.

We could more or less completely eliminate the risk of hydroplaning on asphalt by tightening pavement maintenance schedules, building high-speed roads with uniform 2.5% crossfall, and using surface textures which resist deformation under load and promote quick drainage.  This is more or less what the British have done since the late 1950's--hydroplaning is almost unknown on British motorways despite well over 90% of motorway mileage being bituminous-surfaced.

[hbelkins]

^ Concrete doesn't rut the same way asphalt does. With the concrete, is more of a gradual wearing of fines and aggregates from the surface due to wear from tires (and chains in winter snow areas; see I-80 near Donner Summit) and is only surface rutting. Asphalt gradually ruts such that the entire pavement section (the various lifts in the asphalt concrete as well as the base or subbase layers) deforms causing the rut.

I have personally never seen concrete that was rutted deeply enough to overcome crossfall and accumulate enough standing water to cause hydroplaning.

I have ... some Pennsylvania highways in the 1970s, such as US-202 west of Valley Forge, and the Schuylkill Expressway, and some others.

And the old section of I-64 in Fayette County, Ky., just east of I-75, especially the westbound lanes. This was finally rehabbed in the late 90s and widened in the early 2000s.

[pctech]

Here in Louisiana I think that a good asphalt construction is a better plan in the southern part of the state. We have subsidence type soils there, as the roadway sinks concrete tends to buckle, crack and have sections sink in. Asphalt would flex with the settling better and it can be cold planed and repaved. Repairing concrete is much more expensive. What LA  DOTD generally does is put a "wad of asphalt" patch for a repair.

Some of their newer concrete roads that are on good clay foundations are crumbling apart. (must have used that hardware store "easy mix" stuff )

[codyg1985]

Some of their newer concrete roads that are on good clay foundations are crumbling apart. (must have used that hardware store "easy mix" stuff )

Depending on the type of clay you wouldn't want to be building on that either.

[cpzilliacus]

Sorry, boys..... I'm an asphalt guy.  I don't like the low color contrast between pavement striping and surface material on PCC roadways, especially at night.  It drives me nuts to be stuck in head-to-head traffic on one side of a freeway while the other side lies completely ripped up; I'd rather have a quick resurfacing every 5-10 years than have a roadway totally undriveable for what seems like an eternity every 25.  In slick winter conditions, I actually prefer rough blacktop over anything really smooth, just for the added traction (shoot, if they could make a freeway out of gravel, I'd take that in some nasty weather conditions).  Pavement flaws in asphalt are usually small and avoidable (potting), whereas flaws in concrete threaten to send my car into orbit and are unavoidable.

Please don't throw things at me.  I know concrete lasts longer.  I've been on very smooth new concrete highways (some of which don't even produce a nasty whine).  I know, I know, I know.  But I still want to break out into song when I transition from a concrete portion onto a silky-smooth blacktop portion.

This 2000 article from TOLLROADSnews should warm the hearts of asphalt pavement fans:

PAVEMENT:New Jersey Turnpike asphalt nears 50 & strong

John Kunna, chief engineer at the New Jersey Turnpike says his predecessors did a superb job designing and constructing the turnpike's pavement. And he says the Turnpike has generally done a good job since then of maintaining it. Full depth asphalt, most of it, was laid in 1950 and 1951, so it is approaching its half centenary. And it's going strong. Kunna says there is no foreseeable need to rebuild the pavement totally, as has happened with many other portland cement concrete and asphalt pavements well before this.

The NJ Tpk pavement structure is generally about a meter thick (40"). It started in 1950-51 with a 900mm (36") structure consisting of 450mm (18") of free draining sand with 150mm (6") of crushed stone, then 300mm (12") of asphalt. Most places have had a couple of 50mm to 60mm (2" to 2.5") overlays, giving it an asphalt depth of 400mm to 420mm (16" to 17") on top of a 600mm (24") sand and stone foundation.

[Crazy Volvo Guy]

Well, yeah, it was well engineered.  Not all states do that, sadly.

As for kphoger's comment, I'd probably like asphalt more if they could figure out a way to make it stay black.

[Mamba205]

While we're on the subject of noise, has anyone driven the newly rebuilt part of I-64 in St. Louis?  That's the quietest concrete I've ever driven on.  It makes almost no noise, period.

Yeah, it's a nice pavement. I believe they did longitudinal diamond grinding on the new I-64 in St. Louis. Diamond ground concrete is my favorite driving surface behind asphalt. I also like the longitudinally tined concrete in Michigan.

I know I brought this up two years ago, but because we're talking about quiet roads I wanted to talk about it again. If you cross the river from St. Louis into Illinois, your tires make a really weird sound on some of the bridges. This is because the drainage grooves were cut with spaces of 1-1/8 inch, 5/8 inch, 1 inch, 5/8 inch, 1-1/8 inch, 3/4 inch, 3/4 inch in 6 inch repetitions. This is an example of poorly "randomizing" the spaces between the grooves to reduce the generation of harmonics by preventing a narrow-band frequency in the audible spectrum from being produced.

[Road Hog]

I've noticed in some states, the DOT will go through and mill down old uneven concrete surfaces to make a smoother ride. When you go over a stretch of shifted segments and then hit a stretch of milled concrete, it makes a huge difference. Not as commonly done as I'd like, though.

[D-Dey65]

But I LOVE that sound!

Yes, I like it too. Of course if you think concrete is 100% perfect you'd be deceiving yourself. In Middle Island, New York, the concrete sections of Old NY 25 near Artist Lake buckled and they have metal driveway gates closing it off. I told somebody about it who lives in the area, and he didn't even know it used to be part of Route 25. He thought it was just a residential frontage road.

[vdeane]

That would be why concrete typically isn't used for two lane roads up here.  But a little wear gives it character.  I think some states re-mill these sections too often; if the damage isn't too bad, leave it be!  I've seen sections that look and feel new get re-milled, with the effect being that they look older and drive like asphalt.

[Mamba205]

I've noticed in some states, the DOT will go through and mill down old uneven concrete surfaces to make a smoother ride. When you go over a stretch of shifted segments and then hit a stretch of milled concrete, it makes a huge difference. Not as commonly done as I'd like, though.

That would be why concrete typically isn't used for two lane roads up here.  But a little wear gives it character.  I think some states re-mill these sections too often; if the damage isn't too bad, leave it be!  I've seen sections that look and feel new get re-milled, with the effect being that they look older and drive like asphalt.

IDOT has been milling and placing asphalt over the fairly new and already smooth concrete bridge approach pavements. There was faulting going on at the transition onto the approach slabs and that created a little "bump". What they should have done was diamond grind the pavement right at the joints, rather than resurfacing several hundred feet of good pavement. Not to mention the black asphalt made everything around it black and greasy looking.

[roadman]

Also, lets not forget considerations of traffic control when paving with concrete vs. asphalt.  Asphalt can be applied overnight, and the lanes opened up in time for the next day, while concrete often requires more extended lane closures.  Depending on the nature of the roadway, this could be done over a weekend, but some roads have enough weekend traffic and few alternate routes so this is just not possible. 

Not only that, but with asphalt, it's a very easy matter to resurface only part of the road and leave the remainder open to traffic.  This is common practice on MassDOT interstate resurfacing projects.  Most three and four lane interstates (one direction) in Massachusetts are resurfaced two lanes at a time (the three lane sections use the shoulder for travel when the left and center lanes are being repaved).

For obvious reasons, you would do this work late nights or weekends, but it's far less disruptive than completely shutting a highway down.