TECHBRIEF Pothole Repair FHWA Contact: Monte Symons, 202-493-3144 Introduction Pothole repair in asphalt concrete pavements is one of the most com- monly performed highway maintenance operations. To better under- stand the performance and cost-effectiveness of various cold-mix materials and procedures for repairing potholes in asphalt concrete- The FHWA Pavement Technology The FHWA Pavement Technology Program is a comprehensive and fo- surfaced pavements, the Strategic Highway Research Program (SHRP) Program is a comprehensive and cused set of coordinated activities. undertook the most extensive pavement maintenance experiment ever Thesefocused activities set of coordinated are grouped activi- under conducted—the SHRP H-106 project. The project was subsequently con- fiveties. major These areas—Asphalt; activities are grouped Portland tinued under the Long-Term Pavement Performance (LTPP) program. underCement; five Pavement major areas—Asphalt; Design and Man- Portlandagement: Cement;Advanced Pavement Research; De-and Long-Term Pavement Performance. Objective sign and Management; Advanced The goal of the program is the devel- Research; and Long-Term Pave- The primary objective of the pothole experiment was to determine opment, delivery, and utilization of a which combinations of materials and patching procedures provide the broadment Performance.spectrum of improved The goal tech- of most cost-effective repair of potholes in asphalt concrete-surfaced pave- nologiesthe program that willis the lead development, to better-per- delivery,forming and utilizationmore cost-effective of a broad ments. spectrumpavements. of The improved program technolo- is product and end-result oriented with the in- gies that will lead to better-per- Experiment Design tent of significantly advancing and forming and more cost-effective improving pavement technology and Beginning in March 1991 and ending in February 1992, more than 1,250 pavementpavements. performance. The program is prod- cold-mix pothole patches were placed at 8 test sites across the United uct and end-result oriented with States and Canada. The sites were located on the following roadways the intent of significantly advanc- and climatic regions: ing and improving pavement technology and pavement perfor- • I-70, Vandalia, Illinois Wet-freeze region mance. State Route 25, Vermont Route 2, Prescott, Ontario • I-15, Draper, Utah Dry-freeze region US-395, Alturas, California US-97, Medoc Point, Oregon • FM 1570, Greenville, Texas Wet-nonfreeze region • Route 518, Las Vegas, New Mexico Dry-nonfreeze region Research, Development, and The following patching techniques were used in combination with the TechnologyResearch, Development and various cold mixes: Turner-FairbankTechnology Highway ResearchTurner-Fairbank Center Highway Throw-and-Roll—Material is placed in a hole, which may be filled with 6300Research Georgetown Center Pike water and debris, and then compacted by four to eight passes the truck McLean,6300 Georgetown VA 22101-2296 Pike tires. McLean, VA 22101-2296 www.tfhrc.gov Edge Seal—This is the throw-and-roll procedure plus edge sealing, www.tfhrc.gov using asphalt tack and sand on the road surface. Semipermanent—Water and de- Evaluations types of data were collected dur- bris are removed from a hole, the The performance of the various ing the field performance evalua- sides are squared up, and cold- combinations of materials and pro- tions. The first type was survival patch material is placed in the hole cedures was observed over time to data. This consisted of the number and compacted by rollers or vibra- determine which were the most of experimental and control patch- tory compactors. cost-effective repair types. Moni- es still in service along the test site. Spray Injection—Water and de- toring of patch performance was The second type of data collected bris are blown out of a pothole, vir- done under SHRP until March 1993 gauged the distresses present in gin asphalt and aggregate are and was then continued under the the surviving patches. These dis- sprayed into the pothole, and a lay- LTPP program. The last evaluation tresses included bleeding, crack- er of aggregate is placed on top of was made in November 1995. ing, dishing, edge disintegration, missing patch, raveling, and shov- the patch. Evaluations were made at 1, 3, and ing. A summary of material and proce- 6 months after the installations dure combinations used at each were completed, and semiannual To identify correlations between test site is provided in Table 1. inspections were performed for the material properties and field perfor- remainder of the study. Two main mance, comparisons were made TABLE 1. Summary of Material/Procedure Combinations Test Site Material Procedure CA IL NM ON OR TX UT VT Throw-and-Roll 44444444 UPM High-Performance Edge Seal 444 4444 Cold Mix Semipermanent 44444444 PennDOT 485 Throw-and-Roll 44444444 PennDOT 486 Throw-and-Roll 444 4444 Local Material Throw-and-Roll 44444444 HFMS-2 with Styrelf7 ® Throw-and-Roll 44444444 Perma-Patch Throw-and-Roll 44444444 QPR 2000 Throw-and-Roll 44444444 Spray Injection Spray Injection 4444 444 Edge Seal 4 QPR 2000 Semipermanent 44 Edge Seal 4 PennDOT 485 Semipermanent 44 Surface Seal 4 Local Material Heat and Tack 4 between laboratory test values and • Of the eightTable agencies 1. Summary that par-of Material/Proceduremix. In most cases, Combinations the poorer mean field performance values, ticipated in this experiment, performance associated with in- such as survival rating and aver- three have switched from the expensive cold mixes will result age distress ratings. inexpensive cold mixes they in greater overall costs for patch- previously used to one of the ing because of increased costs Key Findings materials provided through this for labor, equipment, traffic con- project. One agency also has trol, and user delay. • The throw-and-roll technique purchased a spray-injection de- • Consider safety and user delay proved as effective as the semi- vice to replace its conventional permanent procedure when the costs in calculating operation cold-mix patching procedures. two procedures were compared costs. When justifying the pur- directly, using similar materials. chase of a more expensive cold The semipermanent procedure Recommendations mix, consider the reduced user has higher labor and equipment • Use high-productivity operations delay costs that will result when costs and lower productivity. in adverse weather. When repatching is avoided. Also, con- Thus, the throw-and-roll proce- weather conditions include cold sider the improved safety condi- dure is more cost-effective in temperatures and precipitation, tions made possible by reduced most situations, if quality mate- the prime objective of a patching crew time working alongside. rials are used. operation should be to repair • Testing should be performed to potholes as quickly as possible. • Pothole patches are intended to ensure compatibility of aggre- The throw-and-roll and spray-in- be temporary repairs, but the gate and binder. Whenever pos- jection procedures produced success rate observed in this sible, the aggregate and binder high-quality repairs very quickly project indicated that materials to be used to produce a cold-mix in all cases. Quality materials are available that can remain in material should be tested on a should be used with the throw- service for several years. Over- small scale to determine if the and-roll procedure, and the all, 56 percent of all patches sur- two are compatible. This testing spray-injection device should be vived until the last round of per- is especially necessary when well maintained and operated by formance monitoring, with 31 new combinations are being an experienced technician. percent failures and 13 percent used and there is no record of lost, as a result of overlays. • To reduce repatching, use the the patching material’s past per- • The spray-injection repairs per- best materials available. The cost formance. formed as well as the compa- of patching the same potholes rable control patches at all sites. over and over because of poor- This effectiveness, however, de- quality patching material quickly pends on the expertise of the offsets any savings from the pur- operator. chase of a less expensive cold Researcher: This study was performed by ERES Consultants, Inc., 505 West University Avenue, Champaign, IL 61820- 3915. Contract No. DTFH-93-C-00051. Distribution: This TechBrief is being distributed according to a standard distribution. Availability: This TechBrief is based on Report No. FHWA-RD-98-073, Long-Term Monitoring of Pavement Mainte- nance Materials Test Sites. A limited number of copies are available from the R&T Report Center, HRD-11, FHWA, 9701 Philadelphia Court, Unit Q, Lanham, MD 20706, Telephone: (301) 577-0818, Fax: (301) 577-1421. Copies are also avail- able from the National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161. Key Words: Asphalt cold mix, asphalt pavement repairs, bituminous materials, patching, pavement maintenance, potholes, asphalt pavement, spray injection. Notice: This TechBrief is disseminated under the sponsorship of the Department of Transportation in the interest of information exchange. The TechBrief provides a synopsis of the study’s findings. It does not establish policies or regu- lations, nor does it imply FHWA endorsement of the products mentioned, the conclusions reached, or recommenda- tions made. The U.S. Government assumes no liability for the contents or their use. NOVEMBER 1999 FHWA-RD-99-202.