Positive Experience with Rubblization of Rigid Pavement
by: Alan Rommel, Wisconsin DOT South - Project Team 3 Leader
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This past year, we in the Waukesha district of the Wisconsin DOT had a real positive experience with rubblization of a severely distressed concrete pavement on the USH 12 project. The project turned out to be successful in terms of cost to deliver, time to design and construct and overall quality of the constructed project. We were also able to minimize delays to the heavy amount of tourist traffic that uses this route. The key to the success of the project was a design team effort by DOT that included input from contractors, maintenance personnel, and other DOT offices.
The project had its beginning in 1997 when our staff managed the rehabilitation of a small section of one of the worst pieces of USH 12 that consisted of a half mile of crack and seat with HMA overlay. The biggest concern with the project was knowing where to stop. The county had been doing concrete joint repairs for the last several years and seemed to be fighting a losing battle. Both longitudinal and transverse joints showed severe deterioration all the way from the Illinois State Line to Lake Geneva, an 8.6 mile stretch of 4 lane divided highway. Along with the breakup of the joints there was a "shattering" of the surface that was taking place indicating that much of the reinforcing mesh in the concrete was too near the surface of the pavement. This shattering was not only causing problems but was creating safety concerns as chunks of concrete were becoming dislodged from the pavement.
The cross section of the existing road consisted of 9 inches of mesh reinforced concrete pavement with 60 foot joint spacing over the top of 6 inches of crushed stone aggregate over a 6 inch granular subbase course. The pavement, constructed in 1965, had an average daily traffic (ADT) in 1997 of 6800 vehicles. Due to the low traffic volume and competition with other projects for funding, this project was planned and stopped on several occasions. Maintenance had been increasing over the last several years and consisted primarily of concrete joint repair.
We went into this project planning to do crack and seating and to overlay the deteriorated pavement. As cracking and seating on the subsequent resurfacing project proceeded, we discovered some problems. The combination of temperatures associated with paving and some hot weather reacted with the pavement and caused some of the joints to tent up shortly after laying the first layer of HMA. At that time we discussed this with our contractor, B.R. Amon, and decided to do some asphalt base patching to remedy the situation. That worked, and we were able to finish out this job with no more problems. However, after some discussion among some of our DOT staff, we concluded that the mesh in the pavement was contributing to pavement stress and we needed to somehow eliminate this residual stress. If we could only come up with a method of totally disintegrating the pavement-----RUBBLIZING!!!!
We had heard about rubblizing, but we were not entirely convinced it was the solution. We needed to find out more about this technique and whether it was a suitable application. At this point we, hit the Internet, talked with several contractors, the Wisconsin Asphalt Pavement Association and other DOT offices. We were very fortunate to find a lot of good information and folks willing to meet and discuss what they knew about rubblizing. The more we looked, the more optimistic we became. We talked with George Meyer from DOT, District 1, Madison and he explained their experiences and what he thought were some keys to making it work, especially the importance of having a good subgrade.
About this time, we put the job on the fast track. It was November, 1997 and we found there was an opening in our construction funding program for May of 1998. If we could get this 8.6 mile stretch of road designed by March of 1998, 4 months, we could take care of our pavement problems on USH 12. Next the design team was formed consisting of Bob Wazniak, Project Manager, and Terry Sossaman, Design Leader, who would also lead the construction of the project.
The design team went to work immediately, and the first order of business was to put together a constructable plan that would minimize delay to the traveling public. At this point we obtained help from Gerald Waelti, WAPA, who facilitated putting together meetings where we could discuss issues like traffic control, production rates, and the constructability of preliminary plan concepts. We received input from Payne and Dolan, B.R. Amon & Sons and Antigo Construction who offered their opinions on key concepts of milling and rubblizing that we had no experience in.
When it was all complete, we put together a plan involving underdrain, rubblization and an asphalt overlay that would address the pavement concerns on the US 12 roadway. The project was let on time and at a cost of $7.5 million. During construction, the road was open to 4 lanes on weekends minimizing delays to tourist traffic. The prime contractor, B.R. Amon & Sons, started construction in July of 1998 and the entire 8.6 mile roadway was open on surface in September of 1998, three months later. Antigo Construction performed the rubblizing with a multi head breaker and put in extra efforts to keep the job on schedule. Profilograph specs were used on this job and a ride quality index of 2" per mile was obtained by Amon. To date there has been no reflective cracking and the new 5.5" surface is performing well.
Source: Wisconsin Asphalt Pavement Association, Inc. March, 1999
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