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12 summarized in Tables 2.11 and 2.12, respectively. These ranges Costs are based on information reported by various sources, repre- senting a variety of conditions, and using different perfor- Although treatment costs do not affect treatment performance, mance measures. As such, these reported ranges may be based certain cost considerations are inevitably a part of the treat- as much (or more) on perception instead of on well-designed, ment selection process. The cost of each treatment depends on quantitative, experimental analyses. features such as the size and location of the project, severity and Additional evaluation of treatment performance was per- quantity of distresses, and the quality of a treatment's con- formed in this study, taking into consideration factors such stituent materials. It also depends on the type and amount of as traffic volume, climatic/environmental conditions, and surface preparation work and the degree of traffic control existing pavement conditions. This evaluation, which is doc- required to accompany the treatment. umented in the project report, resulted in refinements to Allowing roads to deteriorate over time costs significantly some of the performance estimates listed above. The refined more than maintaining roads in good condition. The cost for estimates are presented later in this document as part of the reconstruction of a 25-year-old roadway can be more than treatment selection process. three times what it would have cost to "maintain" it using a Table 2.11. Expected Performance of Preservation Treatments Applied to HMA-Surfaced Pavements Expected Performance Treatment Pavement Life Treatment Life (yr) Extension (yr) Crack filling 24 NA Crack sealing 38 25 Slurry seal 35 45 Microsurfacing Single course 36 35 Double course 47 46 Chip seal Single course 37 56 Double course 510 810 Ultra-thin bonded wearing course 712 NA Thin HMA overlay Dense graded 512 NA Open graded (OGFC) 612 NA Gap graded (SMA) NAa NA Cold milling and thin HMA overlay 512 NA Ultra-thin HMA overlay 48 NA Hot in-place recycling Surface recycle and thin HMA overlay 610b NA Remixing and thin HMA overlay 715c NA Repaving 615 NA Cold in-place recycling and thin HMA overlay Between 68 and 715d NA Profile milling 25 NA Ultra-thin whitetopping NA NA Sources: Peshkin et al. 1999; Lamptey et al. 2005; Peshkin and Hoerner 2005; Dunn and Cross 2001; Newcomb 2009; Cuelho et al. 2006; Okpala et al. 1999; Caltrans 2008; NDOR 2002. Note: NA = Not available. a Current indications are that SMA overlays perform the same or slightly better than dense-graded overlays. b Range based on reported performance of surface recycle and subsequent surface treatment. c Range based on reported performance of remixing and subsequent HMA overlay of unspecified thickness. d Range based on reported performance of CIR and subsequent surface treatment (6 to 8 years) and CIR and subsequent HMA overlay of unspecified thickness (7 to 15 years).
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13 Table 2.12. Expected Performance of Preservation exclusive of traffic control costs and any associated surface Treatments Applied to PCC-Surfaced Pavements preparation costs. Expected Performance For HMA-surfaced roadways, the costs of crack sealing and Treatment Pavement Life filling are relatively low compared with other preservation Treatment Life (yr) Extension (yr) techniques; however, the other preservation treatments can effectively address a broad range of conditions, so a direct Concrete joint resealing 28 56 comparison of costs is not appropriate. Reported cost esti- Concrete crack sealing 47 NA mates for slurry seals are approximately $0.75 to $1.00/yd2, Diamond grinding 815 NA depending on the size of the project, materials used, and the rate of application. Costs for microsurfacing vary consider- Diamond grooving 1015 NA ably, but normally range between $1.50 and $3.00/yd2. While Partial-depth concrete patching 515 NA the cost of cold in-place recycling depends on numerous fac- Full-depth concrete patching 515 NA tors, including depth of milling and the properties of the Dowel bar retrofitting 1015 NA existing pavement, average costs are approximately $1.25 to Ultra-thin bonded wearing course 610 NA $3.00/yd2. The cost of recycling can be four to six times more Thin HMA overlay 610 NA than the cost of chip seals and can be higher than the cost of constructing a thin HMA overlay. Sources: Peshkin et al. 1999; Smith et al. 2008; Peshkin et al. 2007; Caltrans 2008; NDOR 2002. For PCC-surfaced roadways, the cost for full-depth repairs Note: NA = Not available. on jointed pavements varies significantly. Typical costs in the year 2000 ranged from $75 to $150/yd2. Diamond grinding costs were, on average, between $1.75 and $5.50/yd2. Costs sequence of preservation treatments over the same 25 years. fluctuate depending on many factors, including the existing Hence, cost is a critical component in the selection of appro- pavement's aggregate quality and PCC mix properties, average priate treatments at any traffic level. depth of removal, and smoothness requirements. SHAs have Tables 2.13 and 2.14 list the typical unit-cost ranges and found that the cost of diamond grinding is generally lower than corresponding relative costs of preservation treatments the cost of an HMA overlay, and such cost-effectiveness makes applied to HMA- and PCC-surfaced roadways, respectively. diamond grinding an appealing alternative for many concrete The costs represent the in-place costs of the treatments, rehabilitation projects. Table 2.13. Estimated Treatment Costs for Preservation Treatments on HMA-Surfaced Pavements Treatment Relative Cost ($ to $$$$) Estimated Unit Cost Crack filling $ $0.10 to $1.20/ft Crack sealing $ $0.75 to $1.50/ft Slurry seal $$ $0.75 to $1.00/yd2 Microsurfacing (single-course) $$ $1.50 to $3.00/yd2 Chip seal (single-course) $$ (conventional) $1.50 to $2.00/yd2 (conventional) $$$ (polymer modified) $2.00 to $4.00/yd2 (polymer modified) Ultra-thin bonded wearing course $$$ $4.00 to $6.00/yd2 Thin HMA overlay (dense graded) $$$ $3.00 to $6.00/yd2 Cold milling and thin HMA overlay $$$ $5.00 to $10.00/yd2 Ultra-thin HMA overlay $$ $2.00 to $3.00/yd2 Hot in-place recycling (excluding thin HMA overlay for surface recycle and remixing types) $$/$$$ $2.00 to $7.00/yd2 Cold in-place recycling (excluding thin HMA overlay) $$ $1.25 to $3.00/yd2 Profile milling $ $0.35 to $0.75/yd2 Ultra-thin whitetopping $$$$ $15.00 to $25.00/yd2 Note: $ = low cost; $$ = moderate cost; $$$ = high cost; $$$$ = very high cost.
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14 Table 2.14. Estimated Treatment Costs Although these estimated costs depend on the condition for Preservation Treatments on of a particular roadway, as well as local contracting and con- PCC-Surfaced Pavements struction costs and materials and techniques used, the direct Relative Cost cost of the treatment is often the easiest to determine. Gen- Treatment ($ to $$$$) Estimated Unit Cost erally, this is available as historical cost data or estimated based on previous bids. In considering pavement condition, Joint resealing $ $1.00 to $2.50/ft a pavement with more cracks will take more money per mile Crack sealing $ $0.75 to $2.00/ft to seal or patch, and rougher pavements may take a higher Diamond grinding $$ $1.75 to $5.50/yd2 quantity of emulsion for a chip seal. However, treatments Diamond grooving $$ $1.25 to $3.00/yd2 such as milling and overlay or recycling are relatively inde- pendent of existing pavement condition, provided that the Partial-depth patching $$/$$$ $75 to $150/yd2 (patched area) pavement is in sufficiently good shape to be a candidate for (equivalent $2.25 to the treatment. $4.50/yd2, based on The cost of eventual rehabilitation should account for how 3% surface area patched) often the preservation process will be repeated and what needs to be performed. For example, a chip seal at the end of Full-depth patching $$/$$$ $75 to $150/yd2 (patched area) its life span can generally be covered with another chip seal. (equivalent $2.25 to However, if the project was an overlay in an urban area with $4.50/yd2, based on curb and gutter, milling might be necessary to maintain pro- 3% surface area patched) file before another overlay can be added. Although less than a quarter of the survey respondents Dowel bar retrofitting $$$ $25 to $35/bar (equiva- lent $3.75 to reported that they account for user costs when selecting a $5.25/yd2, based on preservation treatment for high-traffic-volume roadways, 6 bars per 12-ft these costs can represent a significant portion of the total crack/joint and cost and should be taken into account. Detailed guidance crack/joint retrofits every 30 ft) in computing certain forms of these costs is provided in Chapter 3. Ultra-thin bonded $$$ $4.00 to $6.00/yd2 wearing course Thin HMA overlay $$$ $3.00 to $6.00/yd2 Note: $ = low cost; $$ = moderate cost; $$$ = high cost; $$$$ = very high cost.