Blacktop vs. Concrete

[Mergingtraffic]

Actually CT DOT just "diamond grinded" CT-25 in 2012, the first time concrete was touched since 1983.  Meanwhile, just to the north on I-84 around Exit 15 or so, the highway has been repaved with blacktop at least three times since 1988. 
Just think of all the money that would be saved if most roads were concrete, especially here in the northeast. 

[Road Hog]

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.

You can do the same in concrete. Just takes longer.

[kphoger]

I'm curious if there's a known issue with snow melting more slowly on cement/concrete than on asphalt.

We recently got ice, followed by light snow, followed by bitter cold.  I noticed that all the blacktop portions of the parking lot at work are almost entirely clear of snow, while all the concrete portions are almost entirely covered still.

[J N Winkler]

I'm curious if there's a known issue with snow melting more slowly on cement/concrete than on asphalt.

We recently got ice, followed by light snow, followed by bitter cold.  I noticed that all the blacktop portions of the parking lot at work are almost entirely clear of snow, while all the concrete portions are almost entirely covered still.

Asphalt and Portland cement concrete have similar heat retention characteristics and asphalt has a lower albedo.

https://www.frostburg.edu/fsu/assets/File/clife/mscenter/FinalPapers/2008/Heat.pdf

But shade matters.  Over here concrete that is in the sun is mostly clear while asphalt that is in the shade is still ice-covered and excellent for testing ABS (which, thankfully, still works well in my 24-year-old daily driver).

[US71]

You can do the same in concrete. Just takes longer.

There's a street near me that is being rebuilt in concrete (it was asphalt). The first two lanes were finished fairly quickly and opened to traffic. The other two lanes are being done piecemeal.

[kphoger]

I'm curious if there's a known issue with snow melting more slowly on cement/concrete than on asphalt.

We recently got ice, followed by light snow, followed by bitter cold.  I noticed that all the blacktop portions of the parking lot at work are almost entirely clear of snow, while all the concrete portions are almost entirely covered still.

Asphalt and Portland cement concrete have similar heat retention characteristics and asphalt has a lower albedo.

https://www.frostburg.edu/fsu/assets/File/clife/mscenter/FinalPapers/2008/Heat.pdf

But shade matters.  Over here concrete that is in the sun is mostly clear while asphalt that is in the shade is still ice-covered and excellent for testing ABS (which, thankfully, still works well in my 24-year-old daily driver).

Heat retention isn't the same thing as reflection, though.  I still wonder if darker asphalt absorbs more radiant energy and helps to melt the snow/ice on top better than the lighter PCC.

[J N Winkler]

I still wonder if darker asphalt absorbs more radiant energy and helps to melt the snow/ice on top better than the lighter PCC.

This is what albedo means.  But actually with PCC you get more variation in it.  When it is dry, it generally ranges in color from cream to light tan (medium-high albedo), but when it is wet, it is generally dark brown in color (low albedo, close to that of surface water).  Fresh snow, on the other hand, has one of the highest albedos there is (as high as 80%).

This is why blading off a thin layer of snow on concrete allows you to get back to bare pavement relatively quickly, even if initially all this does is expose an ice underlayer.  The concrete is dark brown below the ice and direct sunlight will clear the ice in short order even if temperatures are well below freezing.  This mechanism doesn't work, of course, if the area of cleared pavement is in perpetual shade (e.g., is on the north side of a building), because the incident light energy due to ambient light during the day is typically far less than that of direct sunlight.  (A photographer's light meter will give you an idea of the disparity.  It will show the incident light energy on a reference target--typically a gray card--as a recommended f-stop at a given ISO speed.  Typically ambient light in shade results in readings several f-stops below that of direct sunlight, each f-stop representing half as much incident light as the next higher f-stop.)

I suspect your employer still has snow on the concrete portions of his or her parking lot as a result of some combination of the following:  (1) not paying for a commercial snow removal service; (2) liability concerns about sending out an employee to hand-shovel while cars are maneuvering in and out of the lot; and (3) shade.

[AsphaltPlanet]

Heat retention isn't the same thing as reflection, though.  I still wonder if darker asphalt absorbs more radiant energy and helps to melt the snow/ice on top better than the lighter PCC.

I think when you start to evaluate conditions at such a micro-level other factors would come into play as well.  Things such as pavement texture (whether asphalt of concrete) could conceivably play a factor in how snow and ice accumulates and subsequently melts from the surface of the pavement structure.

[kphoger]

I suspect your employer still has snow on the concrete portions of his or her parking lot as a result of some combination of the following:  (1) not paying for a commercial snow removal service; (2) liability concerns about sending out an employee to hand-shovel while cars are maneuvering in and out of the lot; and (3) shade.

One of the VPs at my company has his own snow plow, so they certainly don't contract the job out to someone else.  But we didn't get enough snow to even plow it at all.  At any rate, I'm talking about large patches that were repaved from asphalt to PCC (due to rutting a couple of years ago) still having snow on them right up to the line, and then the asphalt being clear of snow right on the other side of the line.

[bing101]

I noticed in the Los Angeles area most freeways are paved in concrete because of durability and long term usage. But in parts of Northern California Asphalt is used like on I-80 in Solano county it used to be in concrete but was repaved in Asphalt due to budget constraints when the planning took place.

[Hurricane Rex]

Does anyone else find the sound of driving on concrete relaxing?

[Plutonic Panda]

Does anyone else find the sound of driving on concrete relaxing?

Yes. I also find concrete more visually pleasing than blacktop.

For some odd reason though, I do like blacktop in the deserts. It just goes with desert cities better.

[InterstateGuy]

Does anyone else find the sound of driving on concrete relaxing?

Are you referring to the sounds of grooved concrete on highways? If so then yes. I always thought those sounds to be pretty cool. There is a bridge in Pennsylvania on I-80 that had an extremely unusual grooving pattern. The bridge started out with a rather sci-fi sound produced by a randomized groove pattern. Half way over the bridge is grooved in the usual one inch even spacing producing that familiar howling sound you hear in states like NY and NJ, which is pretty uncommon for PA. unfortunately the bridge was paved over recently (even though ther were little to no signs of wear or tear of the concrete) so it doesnt make those awesome sounds anymore. Here is what it looked like...

https://www.google.com/maps/@41.0519072,-76.8540271,3a,15y,200.9h,60.28t/data=!3m6!1e1!3m4!1sl5p1V87OAR7-PMZo5_w6nw!2e0!7i13312!8i6656

Here is a video I took going over it.

https://www.youtube.com/watch?v=0jWCunZULEk

[US 89]

The grooves have to be crosswise for it to make the whining sound. I-15 in Salt Lake City has that sound as well. I especially like driving over places where the pavement switches to crosswise-grooved concrete.

Unfortunately, new concrete freeways around here all have lengthwise grooves, so no whining noises. There are a few newer bridges that might have it, but UDOT has started paving over a lot of concrete bridges with blacktop.

[US71]

Does anyone else find the sound of driving on concrete relaxing?

Groovy, man

[Conn. Roads]

New York seems to like to just put down a fresh coat of asphalt every few years. A prime example is the Northway. When I moved to the Clifton Park/ Saratoga area, they were replacing it. Just last summer they killed up the seams between lanes, and just replaced them with fresh material.

On the other hand, I used to travel I88 to Binghamton for work. It is mostly laid in concrete. This was only opened in the 1980s. There were a few sections which had asphalt, but the concrete portions seemed to heave. They seem to perpetually have a crew cutting out these sections, and repouring them. It must be a cash cow payoff to the construction company, since there always seems to be an area under repair.

[Rothman]

In NYSDOT Region 1, they have had leaders that were focused on the interstates over the years.  Such focuses can ebb and flow as officials change.

There was one thin overlay project on the Northway near Exit 1 a couple of years ago that raised eyebrows at NYSDOT and may have led to a reorganizing of Region 1's program in that regard.

(personal opinion emphasized)

[UCFKnights]

I believe I-4 reconstruction in Orlando is using concrete for the express lanes and asphalt for the general use lanes. I found that interesting and unusual. Is this done elsewhere (where its all being built at the same time)?

[signalman]

I believe I-4 reconstruction in Orlando is using concrete for the express lanes and asphalt for the general use lanes. I found that interesting and unusual. Is this done elsewhere (where its all being built at the same time)?

My guess would be that blacktop was used for the general purpose lanes in order to get them open to traffic quickly.  Express lanes can remain closed longer to allow the concrete to cure without as much disruption.

[1995hoo]

I believe I-4 reconstruction in Orlando is using concrete for the express lanes and asphalt for the general use lanes. I found that interesting and unusual. Is this done elsewhere (where its all being built at the same time)?

They didn't do that up here on the Beltway–it's all asphalt. Unfortunately, the express lanes have a lot more patches and other pavement issues in certain segments making for a bumpier ride (especially between Exits 54 and 52). The split pavement idea sounds interesting, but even if it had been considered here (which I doubt) I'm sure it would have been rejected. The existing road was asphalt and they basically widened it by two lanes on the outside and then put up pylons to separate the express lanes (which had previously been the two left lanes)–so, essentially, even though it was a massive rebuild they weren't building "new" road for the express lanes.

[Beltway]

They didn't do that up here on the Beltway–it's all asphalt. Unfortunately, the express lanes have a lot more patches and other pavement issues in certain segments making for a bumpier ride (especially between Exits 54 and 52). The split pavement idea sounds interesting, but even if it had been considered here (which I doubt) I'm sure it would have been rejected. The existing road was asphalt and they basically widened it by two lanes on the outside and then put up pylons to separate the express lanes (which had previously been the two left lanes)–so, essentially, even though it was a massive rebuild they weren't building "new" road for the express lanes.

The I-495 Capital Beltway HOT lanes?  The pre-existing pavement is a composite design, asphalt overlaid over original concrete pavement, dating to the 8-lane widening project 1974-78.