Rigid pavement - noise reduction

[godier]

We have designed a concrete slab for a highway and have to find a way to reduce noise due to traffic. The construction is scheduled for the 2002 summer.

Are there any techniques available for that purpose? For instance, if we add a flexible pavement on the concrete slab, what would be the minimun thinkness to avoid peeling?

Thank you very much for any suggestion,

Yours Truly

 

[Ron]

One of the most significant noise producers on rigid pavement is the joints. Slight slab curl, coupled with regular joint patterns produces a rhythmic, but sometimes annoying sound. Tire sound is not significantly different between the asphalt and concrete.

A couple of things can be done to mitigate the noise issue. One is to use continuously reinforced concrete with minimal joints. Another is to space the joints at different intervals. The spacing variation doesn't have to be great, just patterned with short, long, short, long, long, short, etc.

One other method is to skew the joints so that two tires don't hit the joint at the same time. Be aware that this method will require closer attention to load transfer design.

Good luck.

 

[geb]

You did not mention if your design was for a major route or residential. I will assume major. There is a growing database if information indicating that tire noise is significantly reduced in Stone Matrix Asphalt (SMA) mixtures. These are very coarse mixtures and the current theory is that noise travels down into the "voids". This type of mix requires special care during design and placement, but the mix has a side benefit of significantly reducing water spray from tires. The thickness of the overlay would depend on your traffic loads, but full depth asphalt (next time) could be considered.

 

[jimbo]

1. The grooving with tines (or broom) has been used for tire grip improvement, but sometimes causes excessive noise. Michigan DOT has ground one area which I know due to resident complaints. [An Interstate with the average speed about 75 mph] Hot mix asphalt has not yet encountered such problems to my knowledge. [One of my previous employers loved to say "It may be white today but it will be black tomorrow".) %-)
2. The minimum thickness of asphaltic mat is usually 3x the maximum aggregate size, 1.5 inch minimum. Thinner mat thicknesses have been tried in MI over the last 50 years. None are in still place.

 

[swaalkes]

godier- The primary objectionable noise on new concrete pavements is due to the texture, and the primary way to lessen the noise is to use a longitudinal texture. Transverse textures (tining / grooving being the worst of these) produce the most noise. Longitudinal textures can be applied while the concrete is still fresh, which is the cheapest, these include longitudinal broom, astroturf drag, and longitudinal tining. After the concrete is hardened, or for mitigation purposes, the concrete can be diamond ground, which is what jimbo is referring to on I-275 in Detroit, Michigan. Diamond grinding is much cheaper and will last much longer than an asphalt overlay (cap) on the concrete pavement. For info on diamond grinding check out

http://www.igga.net,

the International Grooving & Grinding Association's website, or

http://www.pavement.com,

the American Concrete Pavement Association's website.