August 22, 2000 response by Ben Brock, member of Board of NAPA (National Asphalt Pavement Association), to an inquiry by Elaine Sullivan, GVA Secretary, concerning noise abatement on Route 202, Section 300.
Elaine's e-mail request:
Ben,
Lynne gave me your e-mail address so I could pose my question to someone currently active in the asphalt industry.
The Great Valley Association (a Pennsylvania township group of which I am secretary) is interested in getting PennDot to use crumb rubber over the concrete highway they are building in our area to help diminish the noise level of the highway. The road will be concrete because we have so many sink holes here. What do you know about asphalt over concrete and any facts we could use in our presentation? Lynne did say it would be VERY expensive and that she did not know of any studies on the subject of material vs noise. She also said a smooth highway is a quieter highway. We do have funds for studies, info etc., if necessary. This highway goes through an area of $400,000 to $1.5M homes, and the owners are concerned about excess noise affecting their property values and their quality of life.
With best wishes, Elaine Core Sullivan
AUGUST 22, 2000 RESPONSE BY MR. BROCK
Elaine:
Asphalt (with or without crumb rubber) will give you and your association a few advantages in the long run. First, you will not have the expansion joints that concrete will have when finished. These joints are the "bump, de-bump, de-bump" you hear and feel when driving on a concrete road, and these are what will generate the most noise difference from asphalt over time. The concrete fans will tell you that they will grind these down before turning the road over to traffic, your answer should be that after one winter the expansion joint noise and rough ride will be clearly evident. (It will be for sure). There is not enough money in the PennDOT budget to grind the expansion joints every spring.
They will argue POT HOLES in asphalt. This has been asphalt's nemesis in the past, but with current technology in asphalt mix designs and placement on the road, this is no longer true. There are extremely successful asphalt interstates in the Boston area that are performing great.(They have tough winters there for sure.)
Second, the total life cycle cost of asphalt is considerably less than concrete. When the playing field is level, asphalt always will win out in this case. There are studies by the National Asphalt Pavement Association (NAPA) that will support this issue. Finally, asphalt is smoother than concrete. Period. There is no debate on this one from the concrete people. If you look into your state's specifications on road smoothness, concrete will not be required to meet the same smoothness required of asphalt because you can not get concrete placed on a road bed as smooth as asphalt. So the state is admitting in its specifications that asphalt is smoother! (You may need to really look into this in PennDOT's book, but I would not hesitate to lay a $100 bill on the table in a bet that if there is a smoothness specification in PennDOT's book that asphalt is held up to a tougher smoothness specification than concrete.)
The argument you can win is that a smooth road is a quiet road. Concrete will be rougher than asphalt, so it will be louder. To just lay asphalt (with or without crumb rubber) over a new concrete road would not work very well. The problem lies in the expansion joints under the asphalt in the concrete road. After the first winter these will break through the asphalt and produce a rough road again. (You have probably seen this and did not know that was the problem because often times old concrete is just overlayed with asphalt and within 6 months to a year it is rough again.) The best practice when overlaying concrete with asphalt is to use a machine called a rubblizer to break up the concrete, roll it flat and tight with a big roller, and pave over it with asphalt.The existing concrete road, if the base underneath it is good (as mentioned earlier) will make a great base for an asphalt overlay that will last a LONG time. Wisconsin and some of the snow belt states are doing this with high levels of success.
The problem is that if you have a new concrete road going down already you will not win the battle with PennDOT to put asphalt on top of it, and really should not fight it either for the reasons above. If the new road is already going down in concrete, the battle to fight is for the best smoothness you can get with concrete. Asphalt is typically asked to meet or beat 12" per mile on a profile-a-graph set on a two tenths blanking band (Highway talk).Concrete is typically asked to meet or beat 30" per mile on the same scale. Does that not blow your mind? Concrete can be twice as rough and get paid a bonus? To give you an idea of how good asphalt can get, we just had a customer in Louisiana hit 0" (ZERO) inches per mile - virtually NO BUMPS.
One more quick argument for smoothness and I will get off this stump. Arizona funded a study of smooth roads in relation to automobile maintenance. They found that the smoother the road, the less the maintenance per mile traveled per car. Another great fact. You may have more than you wanted here, but there is even more. NAPA is in Maryland and has all the information on asphalt versus concrete you could ever want. They would most likely give it to you for nothing. They have a toll free number of 888-468-6499. Ask to speak with Margaret Cervarich. She should know my name - I am on the Board of Directors - but you never know. Please let me know if you have any questions.
Ben Brock
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