E.J. Breneman contributes to Asphalt Contractor:
Innovative Ideas within Proven Technologyby Mike Polak, E.J. Breneman
October 5, 2010 | Greg Udelhofen, Editor | Asphalt Contractor
E.J. Breneman L.P has been in the recycling industry since 1983. Breneman utilizes new and innovative processes in the business of maintenance and construction of highways. We believe in Pavement Preservation. The rage today is about Green Technologies, Green Initiatives, Greening our Environment, Reuse of Materials, Recycling our Resources, and so on. There are many types of pavement preservation available from Warm Mix Asphalt to Cold In-place Asphalt Recycling. All the major associations like the Asphalt Recycling & Reclaiming Association (ARRA), the National Asphalt Paving Association (NAPA), and the Portland Cement Association (PCA) are working to make the highway industry more responsible to the environment.
We are in a world that is changing and needs to continually change; change is a good thing for us all. In February 2002 the Federal Highway Administration wrote the Recycled Materials Policy. The policy itself is not a mandate and nor should it be. It should be pure common sense to recycle any material that we produce. We should never produce any material that cannot be recycled. The policy goes on to state that “Recycled materials should get first consideration in material selection.” Some of the best quality aggregates are already in-place in our roads and already paid for; and, in some cases these good quality materials are merely discarded as waste.
Cold In-Place Asphalt Recycling (CIR) addresses the top three to five inches of an old, aged, and oxidized asphalt pavement by milling, resizing, and mixing the RAP with different additives, hot and cold, then repaving the mix to the new desired depth and scope through a bituminous paver and compacting the mix.
Full Depth Reclamation (FDR) addresses a deeper depth of material, the soft and unstable sub-base as well as the asphalt pavement, normally between a depth of six and sixteen inches. In FDR a road reclaimer pulverizes the existing asphalt and a pre-determined depth of underlying materials. The pulverized material then has an additive added like Portland cement, quicklime, fly ash or foamed asphalt and emulsions. Excess material can be loaded and hauled away before the additive is placed. The pulverized material and additives are then mixed and graded to the correct cross slope required. In most cases a motor grader will move the materials leaving a windrow as it places material to the desired grades and slopes of the project. Once graded, the required compaction equipment will roll the materials to the desired density.
There are never two construction projects alike. All highway and local roadway construction projects have their own issues and problems. Full Depth Reclamation is not just a matter of pulverizing a material, adding an additive, re-grading and compacting. The right additive needs to be established, the correct depth needs to be addressed, and the right overlay for the future loadings has to be established.
Working within a residential development, any construction practice will be inconvenient to the residents. Residents need to leave their homes and commute to work, and children need to reach the school bus pick up point in safety. There may be on street parking issues in high residential areas, and the construction contractor and public works department has to take all this into account before construction begins.
In industrial parks the importing and exporting of materials and products on time and with little delay is essential in the competitive world we live in. The processes of Full Depth Reclamation (FDR) will always be an intimidating experience for the traveling public. It involves very large equipment that is tearing up the roadway, graders windrowing loose material, dry additives that sometimes become airborne, and large compactors vibrating the road base, plus other construction issues dealing with mixing the correct amount of water into the mix so that the hydrating of the Portland cement and or lime is complete. It is common to have to go over a project several times to completely hydrate the additive.
Some Departments of Transportation have experimented using the Cold In-Place Asphalt Recycling Train to recycle up to depths of eight inches of asphalt and sub-base materials using Portland cement. The Delaware Department of Transportation, Limerick Township, Pennsylvania, West Norriton Township, Pennsylvania and Plymouth Township, Pennsylvania have successfully used this method for limited depth Full Depth Reclamation projects.
Limerick Township used the process in an industrial park that had been scheduled for Cold In-Place Asphalt Recycling. The park was relatively new; it was curbed with a few sanitary sewer manholes and catch basins. The industrial park was growing in size, and the increased construction activity was causing premature failure. The industrial park had an asphalt depth of four inches on top of a thin aggregate base. There were signs of some isolated soft areas, and the municipality new some other areas may become evident after the CIR process had concluded. Unfortunately, shortly after starting the CIR process the pavement under compaction became wavy and distorted. It was determined that CIR could not correct the pavement problems and that FDR Portland cement was the alternative. To move all the CIR equipment out and haul the FDR equipment in was going to be a huge mobilization cost. After a few hours of thought it was decided by both the municipality and the contractor that they would try to Portland cement stabilize the base using the CIR equipment. The weight of the mill did not seem to disrupt the pavement during the earlier process (CIR); it seemed to happen only when under compaction with vibratory compactors and large pneumatic rollers. The CIR equipment train had no difficulty in cutting the eight inches or mixing the Portland cement into the milled material. The mixed Portland cement was totally hydrated, one reason for this is the material stays in the cutting head for a long period of time and is continuously rotated and mixed around the drum, unlike a reclaimer that mixes the material once and expels it into the cut. A truck mount cement spreader laid the Portland cement at 35 pounds per square yard. A mix design was not completed on this project because of the late time of year and the necessity to complete the project so an asphalt overlay could be applied while temperatures stayed reasonable. We recommend a mix design is formulated before any type of CIR or FDR project commences. The project in Limerick was successful, no failures have occurred and the park has grown over the past four years. The equivalent to 19mm Super Pave hot mix asphalt was applied on top of the FDR at a depth of 2.5 inches.
In 2008 the Delaware Department of Transportation in Sussex County had been Cold In-Place Asphalt Recycling several roadways under contract to George & Lynch Inc. of Dover, Delaware. During the construction of SR 20 near Dagsboro, Delaware the department had an adjacent roadway that was scheduled to be Full Depth Reclaimed under contract to E.J. Breneman. Since this FDR project was so far south, and also because the CIR equipment was basically on-site, and no mobilization would be required, the department undertook their own experiment using the CIR equipment to FDR Portland cement stabilize the roadway. The depth once again was eight inches using around 40 pounds of Portland cement.
Wilguse Cemetery Road runs between SR 20 and 54A. Wilgus Cemetery is a two lane rural roadway with residential and agricultural traffic, and is used as a shortcut between the two state roadways. The roadway has several layers of oil & chip on top of a small layer of hot mix asphalt. The sub-base was primary sand and gravel material. A tractor pulled a Stolfus Spreader that laid the Portland cement in front of the CIR train that was comprised of a water tanker that is pushed by the down-cutting milling machine, in this case a CAT 750C.
A down-cut machine is used to control the size of the particles that are being milled. The cutting mandrel down-cuts on top of the asphalt, and the milling machine chips at the surface with pressure being applied from above. The forward speed of the mill, along with the down-cutting action, produces a modified sizing of the materials. If an up-cut mill would be used, the up-cutting action would course over sizing of the material and a secondary crusher would be needed to control sizing. Because all the milled material, including the Portland cement, is mixed in an enclosed chamber, the mixing resembles that of a cement mixer. Hydration is complete with no dry cement being left behind. The water is metered into the head, and the continuous auger built into the cutting mandrill makes sure the mix is thoroughly mixed and hydrated. The material is then placed onto the first stage conveyor, transferred onto the second stage conveyor and placed directly into the Caterpillar 1050B bituminous paver. Once the material is in the hopper of the paver it is placed back onto the roadway through the paver screed. The paver screed can adjust the full depth reclaimed material to whatever the depth and scope of the new material profile will be. Wilgus Cemetery was overlaid using a 12.5mm Super Pave Asphalt at a depth of two inches.
In Plymouth Township, Pennsylvania during the 2010 construction season two roadways have been re-constructed using FDR Train method. Brook Road had severe distress; this two lane industrial roadway serviced several steel recycling centers as well as a major “Trash to Stream Plant.” During the FDR process the roadway also took traffic from an adjacent roadway that had been closed to traffic while a new bridge was being built. Brook Road had an estimated traffic count during construction of about 12,000 vehicles. Much of this traffic, around 60%, was truck traffic, steel carrying, tractor-trailers, and tri-axel refuse trucks. Brook Road also has a large shopping mall, and connects the very heavily used Ridge Pike and Philadelphia by-pass I-495 to the area around Plymouth and Conshohocken. Brook Road being only two lanes wide needed to be constructed quickly, cured as fast as possible, prime coated and opened to traffic that same day. With the in-line train part of the issue resolved, traffic could at least be kept moving, although only one lane at a time. While traffic was stopped in the traffic pattern, it very quickly became a half mile back-up.
The other major problem was turning tractor-trailers who needed to enter and exit from the recycling plants along the roadway. This meant turning onto the newly placed FDR base. Breneman crews in most cases kept the trucks from turning until at least the first compaction effort had been accomplished. The trucks need to use both lanes when exiting these plants. Driveways into and out of the plants are also very narrow.
The only other issue was a concrete culvert that had been built and was now discontinued. This obstacle was at the north end of the project and was at grade so it had to be milled down to the correct profile to allow for the new hot mix asphalt overlay. As you would expect commuters where not happy while the project was being constructed; but, had Brook Road been constructed using traditional FDR or traditional re-construction methods instead of a one day construction period, it might have taken several days to a week.
West Norriton Township, Montgomery County Pennsylvania had two major industrial parks that had little maintenance over the past 25 years. The pavement was composed of two to three inches of very oxidized and very heavily cracked, alligator and potholed hot mix asphalt on top of a failed pozzolan base course. Pozzolan base course was an engineered mixture of aggregate, fly ash and lime, and if constructed with the proper moisture content, became a very stabile sub-base material. The industrial parks required in-line operations due to the amount of truck traffic, employees reporting for work shifts, and a very large child care facility. If windrowed material had been allowed there would have been major traffic issues due to personal vehicles not being able to traverse the windrowed material. The CIR equipment was ideal in this situation.
In recent years a new shopping mall and a series of strip-malls and hotels had sprung up around the industrial mall. A major retirement community had also been constructed in a neighboring township within a few thousand feet of the industrial mall. The intersection, which was also part of the project, included one entrance into the new mall. The intersection was also comprised of 14 lanes of traffic that had to be controlled through four different directions.
The industrial mall was curbed with no catch-basins, water was controlled by running its natural course, and wherever the undulating pavement allowed it to run. Storm water eventually ran to the lower end of the four major roadways that made up the industrial mall Boulevard of the Generals, and exited through curb cuts into natural swales. Breneman used a Wirtgen WR 2500S to excavate along all curb lines at a distance of four feet out from the curb face to gain valuable curb reveal. Sanitary sewer manholes where removed and steel plates placed over the holes before the in-place full depth reclamation could take place. As stated before, the problem with an eight inch cut around utilities is that the bituminous paver that is returning the mixed material to perfect lines and grades cannot pass over the high monuments. All utilities in West Norriton Township are required to be raised or lowered using brick and mortar or concrete risers. No steel riser rings are allowed in the municipality due to snow plows hitting the rims and damaging the plow or steel covers. The entire road system has a width of 32 feet; the crown is a central crown with no super-elevations on the curves.
One of the companies located within the industrial mall, an over-the-road carrier that used the industrial mall 24 hours a day, could not change their scheduled arrival and departure times to coincide with construction time. The Boulevard of the Generals has only one entrance and one exit, both being the same roadway, so keeping traffic moving became a problem. It was determined that the Boulevard of the Generals should be constructed at night while Foundry and Industrial Road had two exits and could be constructed during day light hours. The Cold In-Place Recycling Train using Portland cement to Full Depth Reclaim the roadways allows for only one lane to be disrupted during the operation. The dry Portland is placed in front of the operation and followed by the train shortly behind. Once milled and sized, the Portland cement and pavement are mixed with a predetermined amount of water that is controlled by an on-board computer. Once laid in-place a Geo-technical engineer checks for moisture and after compaction checks density. Samples are taken of the un-disturbed material before FDR, and after the process more samples of the mixed material are taken. The mixed samples are used to make plugs in the laboratory to verify that the mix and strengths of the materials is in-line with the project specifications.
The greatest advantage of using this method is the material is paver laid. There is no motor grader moving materials from side to side and coursing segregation of the mat in some cases. There are no low areas or high areas that are normally coursed by operator error. There are drawbacks to using this operation; the depth of cut due to the type of equipment is limited. Eight inches compacted is normally the thickness that the paver can accomplish. Greater depths and the paver has significant trouble handling the material, both in the hopper and through the screed. In metropolitan areas too many utilities are a disadvantage with the CIR equipment that normally only recycles three to four inches. Once it goes to eight inches, the paver has great difficulty traversing water and gas valves, as well as sanitary and storm sewers.
Once the Full Depth Reclamation is constructed, a prime coat is placed over the entire surface. This slows the cure down and also protects against air born dust that is a product common with the drying of cement treated bases in the FDR process. In West Norriton Township a three inch 19mm Super Pave Wearing Course was applied by Glasgow Incorporated. Full Depth Reclamation using Cold In-Place Asphalt equipment and technologies will address the entire pavement section. It will correct delinquent cross sections, increase the load-bearing strength of the base material, and utilize 100% of the existing materials at the required depth. Critical to the success of this process is the preliminary testing to establish design criteria for gradation, residual asphalt content and the use of additives. We recommend a Certified Geo-Technical Engineering Company that is independent from the construction company complete the mix design, do all on-site testing, and establish a final report for the municipality. In Pennsylvania, Liquid Fuels Funding is not available for this process. If a Municipality wishes to use this in-line system they must use General Funds or other means not associated with Penn-DOT funding. This reconstruction process requires a wearing surface that is a thickness determined by an analysis of traffic volumes and loading. Substantial savings are realized while meeting environmental goals.
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