Road Construction/Rehabilitation

[shasan]

Hello,

I have a very basic question re: constructing a public roadway in Massachusetts. A road that's in pretty poor shape will be reconstructed and I need to know the standard process and specs to go about doing this. I am an environmental engineer, so this is a bit out of my field! Thanks for any help at all.

Sam Hasan

 

[Ron]

SHasan...that's a pretty tall order! Lots of variables that you haven't covered.

If you are looking at a simple reconstruct in place to same grades/lines/etc., then consider mix-in-place recycling. This process uses the existing pavement, pulverized, then injected with asphalt emulsion to create a new base material. New structural/wearing courses put over that.

Works well, is inexpensive and is much faster than full depth reconstruction.

 

[KirkW]

FHWA or the NHI has given some fairly good guidelines on how to determine what method of rehabilitation should be considered for the roadway being considered, the NHI course number is 13108. If you contact them, I am sure there will be a fee but the manual is called "Techniques for pavement Rehabilitation". It may be a good place to Start

 

[Laser28]

Why do people feel the need to get into something over their head. Please hire a pavement engineer for a few hundred $ and get the proper recommendations. Pavement rehabilitation may not be rocket science, or brain surgery, but why not use someone who is familiar with local techniques, abilities, costs, etc.

 

[BigH]

We are basically doing the same on my project - the specs called for CIPR (Cold In-Place Recycling) - and this forms the "base" on which profile correction asphalt is placed, then the pavement structure. The big problem here is that the suitability depends a lot on a number of factor one of which is the material under the CIPR layer. We've had the garbage pit full - just about anything.

Now the choice of rehab or reconstruct depends on a number of factors - one of which is the geometrics of the new road. If the horizontal alignment is straightened, you will have a lot of "new" sections or side-embankment sections of partial width. If you use CIPR in these cases, you may end up with longitudinal cracking from the "stable" existing and the less stable new (say with respect to foundation support and the little "adjustments" embankments make). If the vertical alignment is changed, then you may end up with a lot of profile correction asphalt - or varying thicknesses of granular on top of CIPR before the pavement. If the road width changes, then you have the problems associated with "new" partial embankments where the match line is down, perhaps, one of the wheel paths.

Given the above, my personal opinion is that CIPR is fine when the profiles don't change (horizontal or vertical) and when the underlying support to the CIPR layer is well established and known. I further believe that these should be for secondary and tertiary roads. For primary roads (interstates/national highways (thinking more of overseas ones)), I'd probably lean to reconstruction.

The above discussion is with caveats, of course. As Laser28 points out ( to him) get a pavement/highway specialist onto the project. It will be money well spent - compared to possible mistakes in the choices that lead to major problems during construction if design found inadequate.

 

[ACtrafficengr]

SHasan, check out the Bay States Roads program at

http://www.ecs.umass.edu/baystate_roads/index.htm

Unfortunately, you missed last month's workshop on recycling pavement. In the meantime, this might help:

http://www.ecs.umass.edu/baystate_roads/technotes/28_asphalt_paving.pdf

Everyone else, if you work for a public sector agency, check out

http://www.ltap2.org

to find the Local Technical Assistance Program in your state.

 

[MPENN]

Slow down. Why is the "poor shape" road being reconstructed? Has the pavement failed due to age and loading? Is there a failure of the base soils or from the impact of watertable or runoff? Is the "poor shape" the result of the current traveled way outlived it usefull life due to traffic volumes now being carried.

Reconstruction does not extend the life of a roadway, it provides a rebirth up to the current safety standards and current practice of design for a given traffic volume and load distribution.

We would hope that this reconstruction is based on recommendations resulting from a design study of the road.

 

[ACtrafficengr]

MPENN's right. Just like in environmental engineering, in road construction the first step is defining the problem.

PS: Remember the three basic rules of road design: Drainage, drainage and drainage.

(Get water off the road, get water out of the roadbed, and then get the water away from the road)