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39 Unsuccessful experiences, Previous experience with a treatment, Competing industries, and ADT or number of trucks, Lack of specifications. Urban versus rural roadway, Availability of contractors/equipment/materials, and Conclusive research in the state. Cuelho et al. also noted the three least important decision factors: Weather, Availability of design standard/manual, and Availability of state equipment/workforce. These lists generally agree with most of the agency and contractor responses. The agency and contractor responses were used to rank and summarize the importance of various barriers to increased use of in-place recycling (Table 40). FIGURE 32 Ontario, Canada, experience with CIR and FDR performance as measured with IRI and PCI (based on Kazmierowski 2008). TABLE 40 BARRIERS TO INCREASED USE OF IN-PLACE RECYCLING Barriers to Increased Use Frequency of Benefit Lack of mix design Often** Unsuccessful experiences Frequently Lack of experienced contractors Often** Lack of agency experience Often** Lack of engineering design Often** Competing industries Often Lack of project selecting criteria Often** Lack of specifications Sometimes Sometimes = between 10% and 25% average of agency and contractor with experience. Often = between 25% and 50% average of agency and contractor with experience. Frequently = greater than 50% average of agency and contractor with FIGURE 33 Perceived barriers to increased usage of in-place experience. recycling by agencies and contractors. Percentages are based *Contractor response was significantly higher than agency with experience. **Agency response was significantly higher than contractor with experience. on the number of survey respondents. Barriers more frequently cited by agencies than contrac- tors are a lack of SUCCESSFUL EXPERIENCES Mix design methods, The lack of successful experiences is a significant barrier Experienced contractors, and to using in-place recycling processes. This section provides Agency experience. brief summaries of successful in-place recycling projects found in the literature. More detailed project descriptions The only barrier cited more often by contractors than can be found in the associated references and references for agencies is a lack of project selection criteria. the case studies listed in Appendix C. Successful agency experiences with various in-place recycling projects are pro- Barriers were identified by Cuelho et al. (2006), who vided for the following topics: noted the following top five preservation treatment selection decision factors that need to be overcome or considered as HIR cost benefits in Colorado, potential limitations: HIR surfacing in Wisconsin,

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40 CIR additives used to minimize presurfacing traffic the equipment. If there was insufficient base, an alternative damage in Kansas, recycling method was needed, such as FDR. It was impor- CIR with foamed asphalt in Canada, tant to make sure the excess aggregates were swept and the CIR use on steep grades in Nevada, public was kept informed. CIR surface treatment selection for traffic consider- ations in North Dakota, CIR Additives Used to Minimize Presurfacing Traffic CIR subgrade support in California, Damage in Kansas FDR using emulsion stabilization for rehabilitation and lane widening FDR in Georgia, Thomas et al. (2000) documented a Kansas CIR project FDR choice of additive in Mississippi, where the initial problem was rutting and raveling in the CIR FDR cement stabilization in Alabama, under traffic and before the placement of the surface course. FDR selection to meet environmental policy in Texas, The agency used a Class C fly ash additive to solve this prob- and lem. A subsequent problem resulting from the use of the fly FDR cost benefits in Georgia. ash was premature cracking. Alternative combinations of emulsion and additives were evaluated with test sections. Fly HIR Cost Benefits in Colorado ash (10% by weight of millings) was used in the first section, and the second test section used a combination of solventless Denver, Colorado, has 5 years of experience using HIR on asphalt emulsion formulated for recycling and lime slurry its 1,800 centerline miles of roadway network (Udelhofen (1.5% hydrated lime by weight of millings). The lime was 2006). Over the 5 years, Denver used HIR to preserve about used to improve early strength gain and moisture resistance. 1.1 million square yards of HMA, saving the agency more than $5 million compared with conventional mill and fill. Equipment used on the project included one 3.6-m (12-ft) Most of the roadways were in residential streets with lim- milling machine, a trailer-mounted screening and crushing ited truck traffic. The projects typically used a 50-mm (2-in.) unit, and a mixing unit with belt scale and computer control. recycled leveling course and a 25-mm (1-in.) overlay with A conventional asphalt paver with pickup device was also 20% RAP in overlay HMA. A double screed allowed work used. Rollers consisted of a heavy 30-ton, seven-tire pneu- to be completed in one pass, and most projects were finished matic roller for breakdown and a double drum vibratory within 1 to 2 days of the start of construction. roller for intermediate and finish rolling (static). Benefits noted by the agency included cost savings, The results showed that transverse cracking was twice as shorter construction times than mill and fill, life extension frequent in the fly ash section as in the emulsionlime com- of the roadways, and an improved bond between leveling bination. No cracks were wider than 4.75 mm ( in.), with course and overlay. most cracks being about 1.6 mm (1/16 in.) wide. Longitudi- nal cracking was prevalent in the fly ash sections in one or HIR Surfacing in Wisconsin both wheel paths; if only one wheel path was cracking, then the cracking usually occurred in the outside wheel path. In VanTimmeren (2009) summarized a project in the city of some cases, the longitudinal cracks were side-by-side in the Mequon, Wisconsin, which needed to address more surface outside wheel path. There were few longitudinal cracks in distresses than could be handled using crack sealing. Streets the emulsionlime section. Rutting was either low or non- were evaluated to determine whether any drainage problems existent in either of the sections. Field results were substan- needed to be corrected before resurfacing. Culverts were tiated with a laboratory-loaded wheel rut tester and shear replaced as needed and the roadways were patched with modulus testing. The emulsionlime combination with the HMA as needed. One preheater and a preheater/scarifier CIR minimized cracking typically seen in CIR with fly ash. were used to loosen the top 50 mm (2 in.) of existing HMA, and a rejuvenator was added to soften the oxidized HMA. CIR with Foamed Asphalt in Canada Conventional equipment was used to place and roll the HMA, which was finished with a seal coat. Excess aggregate Lane and Kazmierowski (2005b) reported on the use of was swept off the surface treatment before opening to traffic. CIREAM. The emulsion sections needed a minimum curing time of 14 days, with fixed requirements for maximum mois- The benefits noted by the agency were that no shoulder- ture and minimum compaction. The foamed CIREAM sec- ing or driveway-matching work was needed and no waste tions needed a curing period of only 3 days, which was the material was produced in the process. Challenges noted by time needed to achieve compaction and TSR requirements. the agency included determining which streets were best The foamed asphalt binder curing time was less dependent suited for HIR. Coring was used to determine thickness on warm, dry weather conditions for placement to achieve and whether there was adequate base thickness to support the desired properties.

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41 The equipment consisted of a milling machine, a mobile CIR Surface Treatment Selection for Traffic screening and crushing deck, and a mix paver where emul- Considerations in North Dakota sion was added and the material was placed. Rollers were pneumatic tire rollers for breakdown and a steel drum for Kronick (2009) reported on construction considerations of finish rolling. For CIREAM, the mix paver was replaced CIR equipment weights resulting in punch-through problems with an onboard twin-shaft pugmill where the expanded for a 100-mm (4-in.) milling depth on a 140-mm (5.5-in.) foam was added and mixed. The mix was fed into a heavy- existing HMA layer. An alternative to the originally selected duty paver with dual tamping bards in the screed. CIR with double chip seal was to use CIR with overlay, but this was considered less desirable because of rapidly increas- Project requirements included compaction to 96% of the ing asphalt prices. A small portion of the project had higher target density established by laboratory testing, with no sin- traffic (1,800 AADT) compared with rest of the project (985 gle result below 95%, and moisture contents of less than 2%, AADT); therefore, CIR plus a 37.5-mm (1.5-in.) overlay with no sublot exceeding 3%. was kept as an alternative if the CIR and chipped sections showed too much early rutting. This option was eventually Results showed that the CIREAM sections were ready to used in the higher traffic area. cap within 2 days of placement. FWD testing immediately after construction showed slightly higher deflections for Advantages associated with the CIR and double chip seal the CIR compared with the CIREAM sections, which was compared with the CIR with overlay for the county roads attributed to the CIR section not being fully cured. FWD were the elimination of edge dropoffs and minimal change in testing after 1 year showed that the deflections were similar roadway elevations. The edge dropoffs in the overlay sections for both CIR (emulsion) and CIREAM sections (Chan et al. are because the lifts are placed in progressively narrower lane 2009). The IRI was used to measure ride quality. IRI val- widths, resulting in a lip at the edge of the pavement that can ues were similar for both sections, but the CIR values were catch car tires and send a vehicle out of control. slightly lower than those for the CIREAM section. However, this section was micromilled before CIR for minor profile The CIR with double chip had an acceptable ride, but it corrections, which could have helped improve the ride in this was not as good as the overlay. Some reflective cracking in section. Both sections had little to no rutting after 1 year. a 1.5-mi section with overlay was seen, but it was much less Laboratory resilient modulus testing showed similar stiff- than was typically seen in other overlay projects. Microsur- ness for both mixes. facing was planned for a later date to address any rutting in the CIR with double chip section. Benefits of using CIREAM were an extension of the con- struction season and reduced curing time. Benefits noted by the agency were a substantial cost sav- ings. The cost of the CIR plus double chip was $80,000 per CIR Use on Steep Grades in Nevada mile (2007 prices), with the CIR plus overlay at $180,000 per mile. This was 56% less for CIR plus double chip. The costs VanTimmeren (2008) reported various strategy consider- did not include cost of traffic control, which was provided ations for maintaining the roadway at the Pequop Summit on by the county. I-80 in Elko County, Nevada. The desired life expectancy for the project was 20 years. After evaluations, an 89-mm (3.5- CIR Subgrade Support in California in.) CIR with a 100-mm (4-in.) overlay was selected because other traditional options would have cost about $8 million VanTimmeren (2009) reported the CIR experiences of the dollars more for the same life expectancy. city of Santa Anna in Orange County, California. The project was to maintain 50-year-old streets for which a soils report Challenges encountered, but overcome, included traf- showed the need for extensive full-depth base repairs. The fic control, length of time for lane closures (cure times), desire to implement more environmentally friendly technol- steep grades (up and down), and nonrecycling infrastruc- ogies and reduce the cost of rehabilitating the roadways led ture repair that needed to occur before paving. The pulling to consideration of CIR as the best choice. The planned work requirements uphill while milling to a depth of 89 mm (3.5 included header cuts at the gutters, 75 mm (3 in.) of CIR, in.) slowed the process. Traffic speeds increase on the down- with 25 mm (1 in.) of HMA. hill side of the interstate and can pose safety issues. Pipe work and other non-pavement-related work components in Construction started on the two streets in the worst con- the project area were completed before the recycling process. dition with respect to subgrade support for the heavy recy- The success of the project depended on constant communi- cling equipment. Repeated problems and lost time because cation for planning work activities. of punch-through problems were a significant concern. After

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42 extensive discussion between the city and contractor, the tion, which showed that 33% RAP and 66% gravel aggregate agency decided that CIR, although a good option, was not base were needed to achieve the FDR gradation. applicable in all cases. The city and contractor developed a plan for evaluating the soil-support characteristics for each Preconstruction testing showed that the original gravel street by coring, then using DCP testing to determine the aggregate base had a modulus of about 62 MPa (9,000 psi), structural capacity of the subgrade and base. More than 90% which was increased to about 1,241 MPa (180,000 psi) after of the remaining streets were considered acceptable for CIR FDR using emulsion stabilization. DCP data were used to work. For roads with low support values, an FDR process determine the consistency of the base, sub-base, and sub- was used to provide a cement-stabilized 200-mm (8-in.) base grade quality. In one area with 50 mm (2 in.) of sub-base silty with an HMA overlay. clay soil, an additional 50 mm (2 in.) of aggregate was added before the emulsion. The average modulus value calculated Benefits of this approach included a cost savings of 40% from the DCP data showed an increase of 177% when com- over conventional reconstruction, and that no waste materi- paring preconstruction to postconstruction properties (11 als were generated. months). The short-term DCP results are shown in Table 41. FDR with Emulsion Stabilization for Rehabilitation and Both mix designs were ultimately compared at an opti- Lane Widening in Georgia mum 4.5% of emulsion by weight. The criteria and results for these designs are shown in Table 42. In 2006, the Virlyn B. Smith Road in Fairburn, Georgia, needed significant repair and widening. Rather than install TABLE 41 full-depth asphalt concrete patches for about 40% of the SUPPORT DETERMINED FROM DCP FIELD TESTING FOR roadway, the agency chose to use FDR with EE for stabiliza- GEORGIA FDR PROJECT (Besseche et al. 2009) tion. The FDR project was approximately a mile of a 7-m DCP Results from Field Testing (23-ft) wide, two-lane roadway that needed to be widened Day of Testing Pulverizing to 8.2 m (27 ft) and the base support improved (Besseche R-Value kPa (psi) Depth, mm (in.) et al. 2009). About 0.6 m (2 ft) on either side of roadway Pre-construction 116 400 (58) 280 (11.0) was trenched, followed by pulverizing 240 mm (9.5 in.) of the existing HMA and base, which was spread over the new Immediately after 48 207 (30) 305 (12.0) emulsion added lane width. An extra 37.5 mm (1.5 in.) of prepulverized base End of 7 days of curing 71 400 (58) 261 (10.3) was added to trenches using a motor grader. A second round of pulverization was made to a depth of 200 mm (8 in.), and emulsion was added as a base stabilizer for the new 27-ft- During construction, the moisture content was taken wide roadway. Two passes of the pulverizer were needed to every 305 m (1,000 ft) to determine whether conditions to complete the second round of pulverization. A motor grader replicate mix designs could be met. Pre-emulsion moisture was used to smooth the surface to grade, and additional roll- content was 1.7% immediately before the overlay, which ing was completed with a pneumatic tire roller followed by increased to 3.2% to 3.5% after emulsion was mixed into the a steel wheel roller. The FDR surface was covered with 37.5 pulverized materials. Before placement of the overlay, the mm (2.5 in.) of HMA 7 days later. moisture content was reduced to 1.7%. The two methods of mix design evaluated for the project Density was monitored every 500 ft per lane using modi- were standard Marshall stability and the SemMaterials mod- fied Proctor, nuclear gauge, and sand cone. The modified ulus. Cores were taken for determining the extracted grada- TABLE 42 SUMMARY OF MODULUS AND MARSHALL MIX DESIGN CRITERIA AND RESULTS FOR ENGINEERED EMULSION FDR (based on Besseche et al. 2009) Modulus Design, 4.5% emulsion content Marshall Design, 4.5% emulsion content Test Criteria Results Test Criteria Results Indirect Tensile Strength, psi (ASTM D Coating Test, Modified, % Retained 35 min 36 80 min 90 4867) (LADOTD TR 317-87) Indirect Tensile Strength Ratio, psi (ASTM Initial Marshall Stability (ASTM 20 min 26 1,500 min 3,493 D4867) D1559), lb Cured Marshall Stability (ASTM Resilient Modulus, ksi (ASTM D4123) 120 min 144 2,000 min 5,820 D1559), lb Short-term Strength Test, Modified Cohe- Conditioned Marshall Stability after 150 min 187 1,000 min 4,590 sion (ASTM D1560) Soaking (ASTM D1599), lb

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43 Proctor was used as the reference density for developing FDR Cement Stabilization in Alabama nuclear density gauge correlations (Table 43). Prokopy (2003) reported the benefits of an FDR-stabilized Cores taken 1 year after construction showed that the base using cement for a 1.7-mi project. This project incor- resilient modulus of the FDR layer ranged from 214 ksi to porated 5% cement (440 tons) for stabilization, which pro- 474 ksi, with an average value of 349 ksi. The effective struc- duced a base with a minimum unconfined strength of 2,413 tural number was calculated as 3.36. This is equivalent to a kPa (350 psi). The base was topped with a double surface structural coefficient for the FDR layer of 0.24, compared treatment. This project was constructed with county forces, with the original coefficient of 0.07 for the gravel aggregate which used a nuclear density gauge to monitor compaction base (GAB). The structural coefficient from laboratory test during construction. A pulverizer was used to rip up the old results of the cores was calculated as 0.31, which gives a asphalt and base course. A motor grader was used to provide structural number of 3.91. the cross section and grade. A spreader truck was used to place the cement, which was mixed with water. Compaction Problems encountered during construction included a was accomplished with standard rollers. subgrade that was too soft in a few locations in the south- bound lane. There were also a few soft spots because of Benefits associated with using the cement-stabilized FDR excess moisture in the clayey sub-base, and the problem were a substantially reduced number of haul trucks, reduced areas were dug out. Good base material was placed to the fuel costs, no waste generation, and reduced project costs. side and the soft sub-base was removed [about 0.6 to 0.7 m This process allowed for recycling roadways with higher (2 to 2.2 ft) deep] and replaced with GAB. The GAB was traffic than previously considered and required significantly compacted, the good sub-base material returned, a 1.5% less material. emulsion was added, and the stabilized sub-base was the compacted. Problem areas were typically between 15 and FDR Selection to Meet Environmental Policy in Texas 30.5 m (50 and 100 ft) long and were too short to capture in preconstruction testing. PCA (2008) reported the construction of a cement-stabilized FDR where the main factor in the selection of the recycling FDR Choice of Additive in Mississippi process was defined by the waste management office in Dal- las, Texas. The project used FDR with cement stabilization, Prokopy (2003) reported details for an FDR project where an underseal, and a 50-mm (2-in.) HMA overlay. the selection of additives was based on the desired properties for the base. The original plan was to use foamed asphalt as Environmental benefits associated with this project the stabilizer, which worked well for the first 457 m (1,500 included reduced use of new materials, complete recycling ft). At that point, unexpected variances in soil and moisture of existing materials with no generated waste, and a quick needed further consideration. Hydrated lime was used for return of traffic to the roadway. next 305 m (1,000 ft) to help dry soil, but durability and den- sity requirements were still not met. Portland cement was FDR Cost Benefits in Georgia tried next and worked well. Portland cement (8,400 tons) was used for the remaining 30 mi of project. In 2005, Coweta County, Georgia, placed its first 1-mi FDR project to address reconstruction needs, as the county was Previous agency experience with cement-stabilized soil experiencing accelerated damage from heavy construction showed problems with high levels of cracking because of equipment moving in and out of the area (Nickelson 2010). the high percentage needed to meet the requirements. Dis- The initial county concerns were spread and cost of con- cussions with FHWA suggested that a low cement content struction. Increasing use of FDR over the past few years of about 3.5% worked well, and this content was used. The has demonstrated that FDR with cement provides a stabi- project was successful and other projects were being con- lized base with significantly improved pavement life. By sidered. Construction equipment was required to be moved 2008, 35 major county roadways in Coweta County were off roadway and parked remotely overnight. Extra care was completed, with another 10 mi of roadways planned for the needed to avoid damage to surrounding foliage and soils. next year. TABLE 43 CONSTRUCTION TESTING FOR GEORGIA FDR PROJECT (BESSECHE ET AL. 2008) Modified Proctor Nuclear Gauge, lb/ft3 Sand Density, lb/ft3 Lane Moisture, % Compaction, % Wet Dry Wet Dry Wet Dry North Bound 3.4 131.4 127.0 134.4 130.0 128.7 124.4 100 South Bound 3.7 132.2 127.5 136.0 131.3 133.8 129.1 101