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6 CHAPTER TWO DEVELOPMENT OF A RECYCLING PROJECT Although each of the in-place recycling processes differs The contractor members of ARRA were asked to answer in purpose, the development of a recycling project has a the same survey questions as the state agency materials number of common considerations. Figure 4 outlines the engineers. A comparison of the responses for the two pop- steps needed for project selection, material selections, mix ulations of respondents provides insight into topics where designs, assessment of structural capacity, and construction there is good agreement and those in need of further educa- sequences. The following sections are organized in order tion, research, and clarification (see Figure 5). of the steps outlined in this figure. Each section identifies specific points in the development processes where different considerations are needed to select the best in-place recy- cling process for a given project. FIGURE 5 Comparison of agency and contractor responses for measurements of pavement condition used for in-place recycling projects. Pavement Condition Functional condition of an existing pavement describes roadway features that meet the users' need for ride quality FIGURE 4 Steps in selecting, designing, constructing, and (smoothness), safety (polishing, bleeding/flushing, friction), specifying in-place recycling projects. and geometry (e.g., lane widths). Distress measurements that influence the ride quality and safety include potholes, bumps, depressions, shoving, and slipping. Structural PROJECT SELECTION CRITERIA condition is the ability of the roadway to carry the traffic loads. Structural issues can be identified with nondestruc- tive testing such as falling weight deflectometer (FWD) and by quantifying load- and support-related distresses such as longitudinal cracking in the wheel paths, edge cracking, and fatigue cracking. Assessing Existing Pavement Condition Project selection is the first step in development of a recycling The two most common methods of assessing the condition project and consists of an assessment of existing pavement of the pavement are distress surveys and smoothness. Most condition, traffic, geometric and environmental consider- states, independent of in-place recycling processes, use dis- ations, and identification of surface treatments needed for tress surveys as the primary source of information for ini- weather (e.g., snowplows, wet roads), restriction of water tially identifying potential preservation, maintenance, and penetration, traffic, and anticipated capacity improvements. rehabilitation activities (Table 5). A more limited number of

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7 states also include ride quality measurements before placing TABLE 6 a recycling project. Specific layer properties and confirma- GENERAL GUIDELINES USES FOR IN-PLACE RECYCLING tion of layer thicknesses and properties are discussed in the BASED ON PAVEMENT DISTRESSES PRESENT IN THE EXISTING PAVEMENT (based on ARRA 2001) sections on material selection and mix designs of this report. HIR Distress Surface CIR FDR Remixing Repaving TABLE 5 Recycling AGENCY RESPONSES FOR PRECONSTRUCTION FIELD Milling Depths TESTING FOR IN-PLACE RECYCLING PROJECTS 25 mm (1 in.) X -- -- -- -- Preconstruction Field Testing: Before construction, I typically use: 25 to 50 mm X X X X -- Preconstruction States (1 to 2 in.) Work HIR CIR FDR 25 to 75 mm -- X X X -- (1 to 3 in.) AZ, CA, CO, AR, AL, CA, CT, DE, ID, CO, CT, DE, 50 to 100 mm AR, AZ, CA, -- -- -- X X IA, KS, MD, GA, ID, IA, (2 to 4 in.) CO, FL, ID, IA, MN, MO, MT, MD, MN, MO, 100 to 150 mm Condition KS, KY, MD, -- -- -- -- X NE, NH, NV, MT, NE, NH, (4 to 6 in.) Distress Survey MO, MT, NC, NY, OR, RI, NV, OR, SC, NE, NY, TX, SD, UT, VA, SD, TX, UT, >150 mm (>6 in.) -- -- -- -- X VT, WA VT, WA, WI, VA, VT, WI, WV WY Distresses AZ, CA, CO, Alligator Cracking P F G G G AR, AZ, CA, AL, CA, CO, Ride Quality ID, MD, MN, Bleeding, Flushing F F F F G CO, FL, GA, ID, MD, MN, NH, (smoothness MT, NH, NV, KS, MD, MT, NV, UT, VA, Block Cracking F F G G G measurements) UT, VA, VT, VT, WA VT WA, WY Bumps F F F F G Edge Cracking P F F F G Both agencies and contractors rely on distress survey Friction information when considering projects for recycling. These P F G G G Improvement assessments are increasingly important for CIR and FDR Longitudinal Cracks F F G G G projects. Contractors are less likely to consider ride quality (non-wheel path) when evaluating preconstruction test results. Longitudinal F F G G G Cracks (wheel path) In summary, pavement condition, particularly distress Oxidation G G G G G surveys, is one of the most important factors in the selection Patches F G F G G of an in-place recycling method. Polishing P G G G G Milling Depths Potholes F G G G G Raveling G G G G G The existing pavement condition and the type, extent, and Rutting F G F G G severity of the distresses will indicate the depth of recycling Reflective F F G G G needed for preservation, maintenance, and rehabilitation, and Cracking hence help identify the most useful recycling process. ARRA Shrinkage -- -- -- -- -- (2001) provides recommendations for the various distresses Cracking that can be addressed with a particular recycling process, along Shoulder Dropoff P P P P P with the appropriate milling depths (Table 6). HIR projects are Shoving F G F G G recommended for milling only the top 1 to 2 in., CIR from 2 Slippage F F G G G to 4 in., and FDR for greater than 6 in. Table 6 includes typical distresses that can be addressed at each recycling depth. Transverse Cracks F F F G G Moisture Damage P F G G G The milling depths used by state agencies on HIR proj- Ride Quality F F F F G ects can go as deep as 4 in. when two passes are used (Table (distress related) 7). Seven states mill CIR projects from 1 to 6 in. As with Minor Profile F F F F G the other recycling processes, a limited number of agencies Corrections applied FDR outside the recommended depths. Written com- G = good process for addressing distress. F = fair process for addressing distress. ments indicated that a maximum depth for FDR may be use- P = not likely to fully address distress. ful, as some states reported difficulty in achieving adequate This table is included as a reference for general guidelines and should not be compaction in lifts thicker than 12 to 14 in. Four states use used exclusively to select a recycling process.

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8 FDR at shallower depths of 4 to 6 in., which is likely a func- tion of thin hot mix asphalt (HMA) layers common on low traffic volume roadways. Shallow depths of 2 to 4 in. reflect thin HMA layers or multiple surface treatments placed on the subgrade, which can be found on very low traffic volume roadways. TABLE 7 AGENCY RESPONSES FOR MILL DEPTHS USED ON RECYCLING PROJECTS Typical Milling Depth: Indicate the most common depth of milling for your recycling projects Agency Responses Mill Depths HIR CIR FDR FIGURE 6 Comparison of milling depths used by agencies and contractors for each in-place recycling process. AR, CA, CO, 25 to 50 mm FL, ID, IA, KS, KY, MD, NC -- (1 to 2 in.) MO, NC, NE, Traffic TX, WA AZ, CA, CT, Traffic levels can limit the use of some recycling processes. DE, ID, IL, IA, When asphalt emulsions are used in CIR and FDR projects, 50 to 100 mm KS, MN, MO, the emulsion needs time to break (set) and the water needs AZ, MD, MT MT, ND, NE, MN, NC (2 to 4 in.) NV, NY, OR, time to evaporate before placing the surface course. During SD, UT, VA, this curing time, the pavement needs to perform under traffic VT, WA, WY from 7 to 30 days. An appropriate selection of materials and 100 to 150 mm CO, DE, IL, additives can be used to minimize the time delay between -- MO, RI, VA, AL, DE, MO, VT recycling and placement of the surface course. Another con- (4 to 6 in.) WI sideration related to traffic level is the ability of the subgrade AL, CA, CO, GA, ID, IL, IA, MT, to support the weight of the presurface treatment traffic and >150 mm -- -- ND, NE, NV, NY, recycling equipment. (>6 in) OR, SC, TX, UT, VA, VT, WY All recycling processes have been used at traffic levels up to 30,000 annual average daily traffic (AADT; Table Contractors frequently use milling depths of 50 to 100 8); however, some states may limit the traffic for specific mm (2 to 4 in.; 4 in. requires two passes) for CIR processes, processes to less than 5,000 AADT. At over 30,000 AADT, with a significantly higher percentage of contractors than agencies consider using only HIR or FDR processes. agencies using milling depths outside of this range (Figure 6). There is good agreement between agencies and contrac- TABLE 8 tors on milling depths greater than 6 in. for FDR projects. A TRAFFIC LEVELS FOR IN-PLACE RECYCLING PROJECTS higher percentage of contractors use shallow (50 to 100 mm Question: I would consider recycling a roadway with annual average or 2 to 4 in.) milling depths for FDR projects than agencies. daily traffic (AADT) levels of up to: This may represent more nonstate work on low traffic vol- Type of In-Place Recycling Used ume roadways by contractors. AADT HIR CIR FDR A number of state agencies and contractors use the CA, DC, FL, CT, IA, KY, NC, ND, CT, IA, KY, MD, <5,000 NE, VT, WY NE, NY, VT, WY NC, NE, VT, WY ARRA-recommended range of recycling depths for each process; however, the actual depth of recycling can vary AZ, CA, CO, DE, ID, AK, CO, DE, MN, 5,000 to AR, AZ, IA, MD, MN, MO, NH, depending on project needs. Guidance on the maximum MO, ND, NH, 30,000 KY, MO, WA OR, RI, SD, UT, VA, OR, SC, SD, UT FDR recycling depth (i.e., lift thickness) is needed so that WA the desired layer density can be obtained. Agencies appear CO, ID, KS, CA, GA, ID, MT, to underuse FDR for thinner layers. >30,000 MD, MT, NC, -- NV, TX, VA, WI TX

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9 Significant differences between agencies and contractors The percentages were calculated using the number of were seen at traffic levels of less than 5,000 and greater than agencies or contractors indicating experience with a par- 30,000 AADT. Contractors are less likely than the agencies ticular recycling process. The category groupings were arbi- to consider HIR and CIR for the low traffic levels (Figure 7). trarily selected after reviewing general trends in responses. This may be related to the lack of adequate support for the recycling equipment on the thinner low-volume roadways. HIR, CIR, and FDR on roadways with AADT greater Contractors are more likely to consider any of the processes than 30,000 may be underused by agencies and overused on acceptable for the higher traffic levels. facilities with AADTs less than 5,000. Subgrade support for equipment needs to be considered. The reasons for the dif- ferences in acceptable traffic levels need to be explored. Roadway Geometry and Features Roadway geometry and features may also limit the use of in- place recycling processes. Different features will have vary- ing impacts depending on the recycling process. Geometry and features evaluated in this survey include Tight turns < 12 m (40 ft) or switchbacks, Mountainous terrains with grades exceeding 8%, Manholes or other castings in the pavement layer, Minor roadway-widening needs, Superelevation or cross-slope correction required (minor profile corrections), and FIGURE 7 Influence of traffic levels on the selection of in- Curbs and gutters. place recycling process. Features that limit state use of the HIR processes include The average of the percentage of positive responses from tight turns, steep grades, castings, and the need for lane wid- both the agencies and contractors was used to rank accept- ening. Agencies consider HIR projects needing minor pro- able geometric features of roadways for each of the in-place file (typically less than in. crossfall) corrections or with recycling processes (Table 9). Four categories of acceptabil- curbs and gutters acceptable features (Table 10). CIR use ity of each of the factors are defined: is limited by the presence of tight turns, steep grades, and castings. CIR is not limited by needs for roadway widen- ing, limited profile corrections, and the presence of curbs TABLE 9 and gutters. These features seem to have the least impact MAXIMUM TRAFFIC LEVELS CURRENTLY USED FOR on selecting FDR for projects. Tight turns, mountainous ter- IN-PLACE RECYCLING METHODS rains, and minor widening limit the state's use of HIR, CIR, AADT HIR CIR FDR and to some extent FDR. Minor profile correction limits the <5,000 F F G use of HIR but is considered acceptable for both CIR and 5,000 to 30,000 G G G FDR projects. Curbs and gutters can be addressed with any >30,000 G G G of the recycling processes. Contractors differ in choices of acceptable geometry and features in several cases (Figures P = Poor, lower than 10% average of agency and contractor. F = Fair, between 10% and 25% average of agency and contractor. 8 and 9). G = Good, between 25% and 50% average of agency and contractor. VG = Very good, greater than 50% average of agency and contractor. Steep grades and castings present less of a concern for contractors than for agencies when using HIR processes. VG = very good and represents that more than 50% of Contractors are less likely than agencies to consider tight agencies and contractors consider the factor acceptable. turns and steep grades as acceptable features for CIR proj- G = good and represents that between 25% and 50% of ects. The majority of contractors with experience placing agencies and contractors consider the factor acceptable. FDR projects feel comfortable using this process with any of F = fair and represents that between 10% and 25% of the features listed in this survey. There is better agreement agencies and contractors consider the factor acceptable. between contractors and agencies on the impact of the need P = poor and represents that less than 10% of agencies for lane widening, minor profile corrections, and curbs and and contractors consider the factor acceptable. gutters (Figure 9).

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10 TABLE 10 INFLUENCE OF ROADWAY GEOMETRIC AND FEATURES ON THE SELECTION OF IN-PLACE RECYCLING PROCESSES Question: I would consider recycling a roadway with: Type of In-Place Recycling Used ADT HIR CIR FDR Tight Turns (radius 12 m (<40 ft) or DC, KS, KY DE, KY, MT, NC, NV, SD, UT AK, DE, GA, ID, KY, MO, MT, NW, NH, switchbacks NV, SD, UT Mountainous Terrains with Grades KY, MT, VT DE, KY, MT, NV, UT, VT, WA AK, DE, ID, KY, MT, NC, NH, NV, UT Exceeding 8% Manholes or Other Castings Within CA, FL, IL, MO CA, CT, DE, IL, ND, NH, NV, WI AK, CA, CT, DE, ID, NC, NH, NV, SC, WI Pavement Layer CO, FL, ID CO, DE, ID, IL, IA, KS, MO, NV, SD, UT AK, AL, CA, CO, DE, ID, IL, IA, MO, Minor Roadway Widening Needs VT, WI, WY MT, NC, ND, NV, OR, SC, DS, UT, VA, VT, WI, WY AZ, CO, FL, IA, AZ, CO, DE, ID, IA, KS, KY, MO, MT, AK, AL, CA, CO, CT, DE, GA, ID, IA, Superelevation or Cross-slope KS, KY NE, NV, NY, RI, UT, VA, WA, WI KY, MO, MT, NC, ND, NE, NV, SC, SD, Correction Required UT, VA, VT, WI, WY AZ, CO, CT, FL, CO, CT, DE, ID, IL, IA, KS, KY, MS, AK, AL, CA, CO, CT, DE, ID, IL, KY, GA, ID, IL, KS, MO, MT, ND, NV, UT, VA, WA, WI, WY MO, NV, SC, SD, UT, VA, WI, WY Curb and Gutter KY, MD, MO, MT, NC, NE, VT, WA Note: Agencies could respond to all that apply. FIGURE 8 Influence of traffic levels on the selection of in- FIGURE 9 Influence of roadway geometry and features on place recycling process (widening, minor profile correction, the selection of in-place recycling process (tight turns, steep and curb and gutters). Percentages are based on the number grades, and castings). Percentages are based on the number of agencies and contractors with experience using the specific of agencies and contractors with experience using the specific recycling process. recycling process. A written response from one agency noted experi- Information found in the literature revealed mixed opin- ence with rutting problems when CIR was used on grades ions about acceptable and unacceptable roadway features. greater than 4%; however, the agency indicated that its In 2002, Lee et al. found the following not to be appropriate experience was from 11 years ago. A single contractor features for CIR recycling projects: noted that, depending on the extent of cross-slope correc- tion required, off-site material may be needed, which must Numerous manholes or drainage outlets, be considered in the contract documents. This contractor Excessively steep grades [5% and 706 m (2,316 ft)], noted that it considers mountainous terrains on an indi- Heavily shaded areas, which increase cure times, vidual project basis. HMA layers less than 50 mm (2 in.) thick, and Numerous branch roadway accesses (e.g., driveways). The agency and contractor responses were used to rank and summarize the responses for judging the ability of recy- Lane and Kazmierowski (2005a) noted that one of the cling processes to accommodate various geometry and road- advantages of CIR was the ability to use this process on proj- way features (Table 11). ects with numerous entrances, side roads, and intersections because CIR would not result in raising the grade.

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11 TABLE 11 Fewer states use HIR and CIR processes in cold, wet cli- INFLUENCE OF GEOMETRIC FEATURES ON PROJECT mates (Table 12). Agencies prefer to use HIR in hot climates, SELECTION either wet or dry. FDR use is somewhat independent of cli- Ranking of Acceptable Features for matic conditions. Recycling Projects Geometric Features HIR CIR FDR Several possible reasons were identified that limit HIR Tight Turns P F VG and CIR in wet weather conditions: Steep Grades G G VG Rainy weather interrupts construction work, which Castings G VG VG requires moving large, slow equipment units on and Widening F G VG off the project. Parking large equipment during con- Minor Profile Corrections G G VG struction is an issue because of the size and very slow Curbs and Gutters G G VG speed of the equipment. Damp or wet pavements slow the hot recycling con- P = Poor, lower than 10% average of agency and contractor with experience. F = Fair, between 10% and 25% average of agency and contractor with struction process. experience. Possible performance issues exist if rainy weather sets G = Good, between 25% and 50% average of agency and contractor with experience. in before work is complete. VG = Very good, greater than 50% average of agency and contractor with Wet, cool weather delays the use of emulsion-based experience. CIR and lengthens the curing time. Roadway geometry and features need to be considered Contractors are more likely than agencies to limit con- when selecting the most appropriate in-place recycling struction of HIR and CIR in cold, wet and to some extent hot, method(s) for a project. Further research is needed to iden- wet conditions (Figure 10). Contractors are more likely to tify the reasons for the differences between agency and con- consider HIR and CIR processes appropriate choices in dry, tractor responses. cold or dry, hot climates. A significantly higher percentage of contractors construct FDR projects in any of the climatic Climate regions. A number of specifications contain weather restrictions on The average agency and contractor responses are ranked when recycling projects can be constructed. The survey to indicate the potential impact of climate on selecting an explored preferences for recycling processes used in four appropriate recycling process (Table 13). It should be noted general climate regions: that a good choice of materials used with a given recycling process can overcome some climate limitations. The useful- Cold and wet, ness of a recycling process ultimately should be considered Cold and dry, on a project-by-project basis. Communication between the Hot and wet, and agency and the contractor is needed to select the best options Hot and dry. for a given climate. TABLE 12 AGENCY CLIMATE PREFERENCES FOR RECYCLING METHODS Question: Environmental Conditions: I would consider recycling on roadways in the following climate regions: Climate conditions Climate HIR CIR FDR Cold and Wet CA, GA, ID, IL, IA, KS, KY, CA, DE, ID, IL, KS, KY, MN, MO, MT, AK, CA, CO, DE, GA, ID, IL, KY, MN, MO, MO, NC, NY, TX, VT, WA NC, NH, NV, NY, RI, WI MT, ND, NH, NV, OR, SD, TX, WI, WY Hot and Wet AR, CA, CO, FL, GA, ID, IL, IA, CA, CO, DE, ID, IL, IA, KS, KY, MT, CO, DE, GA, ID, IL IA, KY, MD, MT, ND, KS, KY, MT, NC, NU, TX, VT, NC, NH, NB, NY, RI, VA, VT, WA NH, NV, OR, SC, SD, TX, VA, WY WA Cold and Dry AZ, CA, CO, GA, ID, IL, IA, KS, AS, CA, CO, DE, ID, IL, KS, MT, NH, CA, CO, DE, GA, ID, IL, IA, MK, MT, ND, NY, TX, VT, WA NV, NY, RI, SD, UT, VT, WA, WY NH, NV, OR, SD, TX, UT, VT, WY Hot and Dry AR, AZ, CA, CO, DC, FL, GA, AL, AR, AZ, CA, DE, FL, IL, IN, KS, AL, AR, AZ, CA, CL, DE, FL, IL, MO, ND, ID, IL, IA, KS, MS, MT, NE, MD, MO, NE, NJ, OR, SD, TX, UT, VA, NE, NJ, OR, RI, SD, TX, UT, NY, TX, VT, WA VT, WA, WI, WY VA, VT, WA, WI

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12 Surface Treatment Selection Surface treatments for HIR and CIR projects are commonly selected on the basis of climate considerations (e.g., drainage of surface water, providing impermeable membranes, snow- plows), noise reduction, and friction improvement. In some cases, overlays are selected to improve the structural capacity of the roadway. Survey results show that a structural overlay is commonly used as the final wearing surface for all types of recycling projects (Table 14). If an overlay is not used, then a combination fog and chip seal is the next most popular sur- face. Several states reported using slurry seal or microsurface treatments, but none use a fog seal by itself, a microsurface, or an open-graded friction course (OGFC) for HIR projects. FIGURE 10 Influence of climate conditions on the selection of in-place recycling process. Percentages are based on the The written responses indicate that other surfacings have number of agencies and contractors with experience using the specific recycling process. been used, including a chip seal (without fog), rubberized OGFC, stone matrix asphalt, and unreinforced concrete overlay. An additional question was included in the surveys to TABLE 13 assess the impact of climate conditions on the selection of RANKING OF CLIMATES THAT CAN INFLUENCE THE the surface treatment. Only a few states indicated that cli- CHOICE OF IN-PLACE RECYCLING PROCESSES mate is a consideration. Agencies rely more on the use of Climate HIR CIR FDR traffic [AADT, equivalent single-axel loads (ESALs), per- Cold/Wet F G VG centage of trucks], functional classification of roadway, Hot/Wet G G VG existing distresses, expected performance of surface course Cold/Dry G VG VG mix, cost, and experience. Hot/Dry VG VG VG Surfaces placed by contractors for FDR projects are fre- P = Poor, lower than 10% agencies and contractor with experience. F = Fair, between 10% and 25% agencies and contractors with experience. quently a structural overlay, integral overlay, or a fogchip G = Good, between 25 and 50% agencies and contractors with experience. combination. However, contractors use a wider range of VG = Very good, greater than 50% agencies and contractors with experience. other surface treatments (Figure 11) for all types of recycling projects. A key criterion for two contractors was whether In summary, climate conditions need to be considered snowplows would be used on the surface mix. Contractors when selecting an in-place recycling process. Specific rea- consider traffic, structural designs, existing distresses, per- sons for contractors' and agencies' climate preferences need formance (raveling, texture, ride quality, rut resistance), to be defined in future research efforts. cost, and experience when selecting a surface treatment. TABLE 14 STATE RESPONSES FOR TYPE OF SURFACE TREATMENT USED Surface Treatment: Indicate the typical top layer used for recycling projects. Agency Responses Surface Treatments HIR CIR FDR Fog and Chip Seal ID, KS, MT, NE CA, ID, IL, IA, MO, MT, NV, WA CA, GA, IL, IA, MT, SC, TX Fog Seal -- -- CA Structural Overlay AR, AZ, CO, FL, ID, IL, IA, AZ, CA, CO, CT, DE, ID, IL, IA, KS, AZ, CA, CO, CT, DE, ID, IL, IA, MN, KS, MD, MO, NC, NE, NY MN, MO, NC, ND, NE, NH, NV, NY, MO, NC, ND, NE, NH, NV, NY, OR, OR, RI, SD, UT, VA, VT, WA, WI, WY SC, SD, TX, UT, VA, WI, WY Integral Overlay AZ, CO, IA, KY, MO, TX CA, SD, VA, WA SD, VA Microsurfacing -- CA, IL, UT CA, DE, IL, UT OGFC -- NV NV Non-Structural Overlay AZ, CA, IL, KS, KY, NY, AZ, CA, IL, NY, VA, VT, AK AK, CA, GA, IL TX Slurry Seal ND, NE IL, WI IL, MD