Rubblizing Concrete Pavement on an Urban Street
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The City of Kenosha, Wisconsin, like most other municipalities in Wisconsin, is limited in its efforts to rehabilitate city streets by traditional budgetary constraints. As a result, the engineering staff is constantly looking for ways to optimize use of public funds. Through research, the engineers concluded that edge milling, rubblizing and overlaying three failed city streets would yield the desired results.
The milling, rubblizing and Hot Mix Asphalt (HMA) paving on these streets was completed in September of 1998. The work progressed quickly and to the satisfaction of the city staff as well as the neighborhood residents.
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3 Inch Milled Butt Joint at Curb Flange After Rubblization
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To better assess the project progress and the process, the Administrator of Public Service, Fred Haerter, and the Director of Engineering, Mike Lemmens, were interviewed. The results of that interview follow:
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| Q. |
What was the pavement type and average daily traffic (ADT) on the three streets?
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| A. |
They were all 8 inch plain PC concrete, paved on subgrade, with curb and gutter. All have current ADT's of approximately 1,000 vehicles.
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| Q. |
What alternatives did you consider in making your final recommendation?
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| A. |
We looked at complete removal and replacement, milling and overlay, cracking and seating with overlay, rubblizing and overlay, keeping the grades and flow lines in the existing gutters intact and overlaying the existing gutters for all the alternatives.
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| Q. |
Where did you learn the process you finally selected?
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| A. |
Several professional journals carried articles on the process. We also interviewed contractors who specialize in both crack/seat and rubblizing, as well as HMA paving. Both had experience in the method that the city selected.
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| Q. |
Did you have concerns for underground utilities in the streets?
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| A. |
Yes, but there were not problems with any utility systems. We also were concerned about having thick enough HMA at the flange line of the curb and gutter. That is the area where the garbage trucks and snow plows travel. That is the reason we chose to mill a wedge of PCC pavement from the gutter to a point 6 feet into the driving lane. The wedge varied in depth from 3 inches at the flange to zero at the 6 foot point. The cross-section crowns were also improved on the three streets.
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| Q. |
Have you had any feedback from either the public or elected officials on either the work or the results?
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| A. |
The neighbors were surprised at the lack of noise and vibration they experienced with the rubblizing using the multi-head breaker. The paving went smoothly as well. General reaction was favorable. The projects look very nice in the field.
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| Q. |
What would you recommend to improve the process and the final results?
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| A. |
We probably would investigate subgrade conditions more thoroughly. These streets all have basement sump pumps discharging directly into the gutters. At some of these locations, the subgrade was saturated. We may have planned more undercutting before replacing curb and gutter sections in those locations. We also recommend a pavement design analysis to assure the HMA thickness will support anticipated traffic.
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| Q. |
Do you plan to use this technique on future city projects?
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| A. |
Yes. We think this procedure will help do more street rehabilitation with limited funds.
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WAPA thanks Jim Rosenmerkel, Payne and Dolan, Inc., Waukesha, WI for the information in this article.
Source: Wisconsin Asphalt Pavement Association, Inc. October, 1998
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