Tech Brief PAVEMENT PRESERVATION HOW: ARIZONA, TEXAS, UTAH, AND NEW MEXICO EDC-4 PEER-TO-PEER EXCHANGES PAVEMENT INTRODUCTION PRESERVATION HOW On May 2nd and 3rd, 2019, an FHWA-sponsored EDC- The fourth round of Every Day 4 “How” Pavement Preservation State Peer-to-Peer Counts (EDC-4) innovations promoted quality construction Exchange was conducted in Phoenix, Arizona. State and materials practices that department of transportation (DOT) participants included apply to both flexible and 28 DOT representatives from Arizona, 1 from Texas, 2 rigid pavements. For flexible pavements, these include using from Utah, and 1 from New Mexico. Additional participants included improved specifications for thin 4 FHWA representatives, 1 consultant, and representatives from 5 county asphalt surfacings such as chip governments, 24 municipalities, and 9 tribal communities. Larry Galehouse seals, scrub seals, slurry seals, with the National Center for Pavement Preservation and Larry Scofield with the micro surfacing, and ultrathin bonded wearing courses; following International Grooving & Grinding Association and American Concrete Pavement improved construction practices; Association facilitated the day-and-a-half-long meeting. Arizona was the host state and and using the right equipment provided meeting room facilities. Antonio Nieves of the FHWA introduced the meeting to place these treatments. Rigid pavement treatments include the background and kicked off the meeting. rapid retrofitting of dowel bars to The meeting format consisted of each of the states identifying their current procedures, reduce future faulting; the use of new, fast-setting partial- and full- issues, and successes for each of the topics discussed. Table 1 indicates the depth patching materials to create discussion topics. a long-lasting surface; advanced pavement removal techniques to Upon conclusion of the peer-to-peer exchange meeting, the participants had the accelerate patching construction opportunity to tour the Chandler, Arizona, manufacturing facility of Crafco, Inc., a times; and advancements in leading supplier of pavement preservation products. diamond grinding that contribute to smoother and quieter pavement Table 1. List of pavement preservation treatments discussed surfaces with enhanced friction. Asphalt pavement preservation treatments Concrete pavement preservation treatments BACKGROUND Chip seal Partial-depth repair Regional peer-to-peer exchanges between states were initiated Micro surfacing and slurry seal Precast slabs to exchange knowledge on Cold and hot in-place recycling Diamond grinding “How” to effectively implement Crack seal — pavement preservation. Adoption of a comprehensive pavement Ultrathin bonded wearing course — preservation program will ultimately Scrub seal — result in an improved pavement condition and safety rating for Cape seal — the overall network, reduced agency and user delay costs, and decreased environmental impact. In SUMMARY OF IMPORTANT ISSUES OR SUCCESSES order to achieve these objectives, Asphalt Concrete Pavement Preservation an understanding of the concepts, capabilities, and applications Chip sealing: Two states place chip seals on a six- to seven-year cycle. They relevant to constructing pavement principally use emulsion-based chip seals. One state, which is one of the preservation treatments with quality largest users of chip seal technology in the country, mainly uses hot-applied materials must be implemented binder with precoated chips and an annual chip seal program budget of $280 to via a technology program aimed $300 million. One state uses in-house personnel for chip seal placements, and at transportation agencies, each of that state’s districts has its own equipment and trained crews. Some of contractors, consultants, and these districts use 100% recycled asphalt pavement (RAP) chip seals. Federal Highway Administration (FHWA) staff. 2 Pavement Preservation How: Arizona, Texas, Utah, and New Mexico All four state agencies try to do roadway preparation Micro surfacing and slurry sealing: While two states work 6 to 12 months in advance if possible, particularly seldom use these treatments, two states use them crack sealing and patching. If the construction project frequently. Micro surfacing is the major preservation includes crack sealing, in some instances there may be a treatment used on Interstates in the two states where the contractual delay before chip sealing begins. treatment is used frequently. These states prefer micro surfacing over slurry seals. One of the advantages of A moratorium on chip seal placement was recently initiated micro surfacing is that it can be placed at night, whereas in one state. That state partnered with industry to develop a chip seal cannot. While specifications have typically new specifications that require test section construction focused on methods, one state attempted a warranty and approval prior to advancing the chip seal process. The specification, but warranties could not be successfully state now also requires training for both contractor and administered and were discontinued. All four states use agency personnel prior to construction. contractor-applied micro surfacing. Placement of micro One state does not raise the reduced construction speed surfacing over open-graded friction courses is not allowed limit until after the fog seal has been placed, which is in one state. Local agencies primarily tend to use slurry typically after seven days. seals instead of micro surfacing. They use Type III slurry on high-volume roads and Type II slurry on others. Latex- Some local agencies have rebranded chip seals as modified emulsions are preferred by some local agencies fractured aggregate surface treatments (FAST) and have for slurry. See Tables 3 and 4. developed one specification for high-volume roadways and another for low-volume roadways. For a summary of chip seal use, see Table 2. Table 2. Chip sealing Design Material type Construction procedures State Design Maximum Top Aggregate Stripe Pilot Aggregate Binder P200 Binder rate Rollers Sweeping Fog seal procedure ADT size rate pretreatment vehicle See table ⅜ 3 Special Broom and 0.01 yd3/ yd2 or 0.06 gal/yd2 or by Power and Arizona NA 40,000 in Section CRS-2 and NA pneumatic provision tack coat 0.06 Yes by mix design mix design hand broom 404-2.02.C ¼ in. rollers required gal/yd2 New NA NA NA HFE150P NA NA NA NA NA NA NA NA NA Mexico Rate sufficient Flush coat By unit weight; for 50% chip Minimum 3 See Table 0.11 ± 0.01 LMCRS-2 see Table 3 embedment articulating 7 days of Utah NA None 2 in Section ½ in. NA NA gal/yd2 7 NA and CRS-2P in Section before rolling and pneumatic curing 02785 days after 02785.3.5.F 70% embedment rollers chip seal after rolling Mostly hot Furnish Light applied, rotary, self- Texas NA Unknown ½ and ⅜ in. NA NA NA NA pneumatic- Item 315 NA NA CRS-2P for propelled tire rollers emulsions brooms Table 3. Micro surfacing Material type Construction procedures Design State Application Crack seal Tack in Sweeping Number of Calibration method Aggregate Binder Type Cement Test section rate in advance advance in advance courses verification 2, rut fill scratch Arizona NA NA NA NA NA NA NA NA NA NA NA course, then lane width New NA NA CSS-1HP NA NA NA NA NA NA NA NA NA Mexico AASHTO M Non-air See 208 grade entrained Minimum NA Gradation See Table Per mix CQS-1h Type I/ rate of 25 lb/ (cleaning Utah in Table 4 3 in Section NA Yes Yes, 500 ft long NA NA design (cationic) II portland yd2 (by dry with water in Section 02735.2.1.C emulsified cement, aggregate) allowed) 02735.2.2.B asphalt hydrated lime CSS-1P Hydraulic Submit sample of 3/8 in., see Residual cement or NA (remove CSS-1H or each aggregate, Method Tables 1 and asphalt hydrated lime raised SS-1H at min. 1 gal asphalt Texas NA NA NA NA NA spec 2 in Section 6%–9% at 0.5%–3% pavement 0.04–0.10 emulsion, min. 1 350.2.2 by dry unit by dry marking) gal/yd2 gal mineral filler, wieght aggregate and additives Pavement Preservation How: Arizona, Texas, Utah, and New Mexico 3 Table 4. Slurry sealing Material type Construction procedures Design State Application Crack seal Tack in Sweeping Test Number of Calibration method Aggregate Binder Type Cement rate in advance advance in advance section courses verification 2, rut fill Arizona NA NA NA NA NA NA NA NA NA NA scratch course, NA then lane width New Mexico NA NA NA NA NA NA NA NA NA NA NA NA See Gradation Cationic Use portland Asphalt 18–22 lb/ NA (cleaning Per mix in Table 1 emulsified cement, Utah slurry yd2 by dry with water NA NA NA NA NA design in Section asphalt grade hydrated lime, or seal coat aggregate allowed) 02789.2.4.A CQS-1h aluminum sulfate Texas NA NA NA NA NA NA NA NA NA NA NA NA Table 5. Cold in-place recycling CIR type Construction procedures Minimum State Foamed Plant type Final Cement Cure period Traffic Minimum Emulsion Moisture testing existing AC asphalt surface admixture before overlay restrictions thickness Central Roadway remaining Arizona Yes Yes Yes Yes NA Yes NA NA NA NA 2 in. New Polymerized high-float Existing pavement NA NA NA NA Yes 2 hours 2 hours 4 in. 1–2 in. Mexico emulsion HFE-150P or CSS-1 at 1 mi intervals Utah NA NA NA NA 1½ in. OL NA NA NA NA 3–4 in. 4–5 in. Texas NA NA NA NA NA NA NA NA NA NA NA Table 6. Hot in-place recycling Construction procedures State HIR type Plant type Minimum existing AC Minimum thickness remaining Central Roadway Arizona NA NA NA NA NA New Mexico Repaving and remixing NA Yes No minimum, but 2 in. maximum NA Utah NA NA NA NA NA Texas Surface recycling, remixing, repaving NA Yes 3 in. NA Cold in-place recycling (CIR): One state is currently the Hot in-place recycling (HIR): All four states have main user of this technology.