Pavement Patching Practices (2014)

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48 This chapter presents the various survey responses related to research needs, and then the overall findings of the syn- thesis are discussed and summarized. The findings are based on a review of the literature and surveys of state, local, and international roadway agencies. Well over 100 reports were reviewed for this synthesis. Survey responses were received from 49 of 51 state agencies—a response rate of 96.1%. In addition, 20 local U.S. agencies in eight states, five Canadian agencies, and 36 organizations in the United Kingdom and Ireland responded to similar surveys. IDENTIFIED RESEARCH CONDUCTED AND NEEDED There has been a considerable amount of research done on pavement patching since the days of the initial Strategic High- way Research Program (SHRP). Much of that work has built on the SHRP research, continuing to evaluate some of the materials and practices addressed in SHRP and using some of the same tests and protocols. Other research has imple- mented an expanded suite of tests for particular applications and new patching materials. Research has also addressed man- agement aspects of patching operations, particularly regard- ing the use of technology and computerized systems to track and analyze patching and other maintenance programs and their cost-effectiveness. Research is still needed in several areas, judging by the survey responses. Approximately 30% of the states respond- ing to the survey indicated they have sponsored or undertaken research. The primary areas of that research were in the perfor- mance of patching materials and cost-effectiveness, as shown in Figure 40. Figure 41 shows the number of states indicating a need for research concerning certain aspects of patching. Of the 20 U.S. local agencies responding, none have sponsored research into patching; however, one is planning to study warrants and triggers for patching, management of patching activities, and cost-effectiveness. The agencies did report research needs, as shown in Figure 42. One local agency expressed a need for research on tools and materials for tack- ing and patching. As with the states, the greatest needs are for new materials and comparisons of materials. The perceived research needs are similar for both local and state agencies. Few of the overseas agencies contacted have undertaken any research. Lack of adequate funding is the main reason. Of the seven respondents who reported being engaged in research, the performance of patching materials is the primary concern; cost-effectiveness is second. DISCUSSION AND CONCLUSIONS Based on the literature review and surveys, the following general conclusions can be drawn: • Patching pavements is one of the most widely prac- ticed pavement maintenance activities. Every U.S. state uses patching to restore the functionality of distressed pavements, with most ranking it as a major component of their maintenance program. The few states that do not view patching as a major activity are mostly in warmer climates; cold weather definitely accelerates the develop- ment of potholes, the primary reason for patching. The percentage of the maintenance program budget that is spent on patching also varies widely. Comparisons are difficult because of the great diversity in the way patching is managed, if and how patching activities are tracked, and how costs are accounted for in the management system. • Maintenance management programs are increasing in importance and complexity as states come to grips with rising costs, decreasing numbers of employees, and decreasing budgets. It is increasingly important to effi- ciently manage an activity as pervasive and expensive as pavement patching. • Engineering judgment is still the primary consider- ation when selecting the type of maintenance activity. Engineers or maintenance foremen typically determine when a manually placed patch is to be used instead of a machine-placed patch, or when patching is not the right approach and more involved repairs are necessary. • Guidelines are being used to supplement engineering judgment and improve consistency across an agency; however, those guidelines differ from agency to agency. The size of a distressed area that requires immediate action, for example, may vary. • The triggers that call for patching and the distresses addressed are also reasonably consistent. Potholes; deterioration around joints, cracks, or previous patches; rutting; joint failure; delaminations; and spalling are the most common distresses that require patching. • The need for patching is most commonly identified through visual identification, public complaints, emer- gency safety problems, and potholes. chapter six CONCLUSIONS

49 80% 95% 64% 5% 6% 0% 20% 40% 60% 80% 100% UK/Ireland US Local US State Survey response Yes No Planning to initiate 20% 0% 30% FIGURE 40 Comparison of U.S. state, local, and U.K. responses to “Have you undertaken research?” (Source: survey responses.) 0% 20% 40% 60% 80% 100% UK/Ireland US Local US State Survey response Performance of patching materials Cost effectiveness of patching Improving speed of patching repairs Management of patching activities Warrants/triggers for patching (planning) FIGURE 41 Areas of research undertaken (Source: survey responses.) 0% 20% 40% 60% 80% UK/Ireland US Local US State Survey response Comparison of different materials Development of new or innovative patching materials Development of new/improved patching procedures Comparison of different patching procedures Understanding performance of different patching materials Development of new/improved equipment Use of bonding agents Improved maintenance management Improved guidance, training and specifications Maintenance records keeping Trenchless technologies Improved FIGURE 42 Percentages of agencies expressing needs for research on various topics (Source: survey responses.)

50 • Several states and ample research support the concept of “doing it right the first time.” Making the right repair, however, depends on having the right materials, labor, equipment, traffic control, conditions, and, perhaps most importantly, funding. Research and experience show that the cost-effectiveness and level of service is greatly improved by avoiding the replacement of failed patches. • The decision of whether to patch or do more extensive rehabilitation depends on a number of variables; there- fore, guidelines for these decisions are not consistent between agencies. This is inevitable as costs, material availability, traffic, staff, and other factors vary. • Knowledge of the causes of distress and failure mecha- nisms enables selection of the appropriate treatment; the right treatment will perform better and be more cost- effective. • When patching is called for, the materials used fall into one of several categories. Cold mix, whether generic or proprietary, is routinely used for temporary patching. Hot mix is still the preferred patching material for semi- permanent patches in asphalt pavements. A wide range of cementitious patching materials is used for permanent patches on concrete pavements, with hot or cold asphalt mix for temporary patches. • The cost of materials is relatively low compared with the other costs of patching, such as labor, equipment, and traffic control. This can help to justify the use of superior materials to avoid the need to replace failed patches. • The throw-and-go patching method is not cost-effective and generally performs poorly. • In most cases, when properly constructed, throw-and- roll patches can perform as well as sawed patches on asphalt pavements. • State workforces are primarily responsible for reactive patching and much of the planned patching as well. Con- tractors are more often used when specialized equipment or expertise is needed. • Maintenance contracts are growing in popularity, per- haps as a result of cutbacks in personnel. Some states are letting major maintenance contracts, particularly for interstates. • Smaller agencies that cannot keep equipment and staff employed are more likely to contract out patching. On the other hand, some smaller agencies that do have staff available find it more cost-effective to do their own patch- ing since they have the necessary staff on the payroll. • Traffic management measures are somewhat consistent across agency lines, driven in large part by require- ments outlined in the Manual on Uniform Traffic Control Devices (MUTCD). Agency guidelines also exist for the use of traffic control devices for moving or stationary operations on different types of roadways. Flaggers are commonly used for patching operations, as are cones and arrow boards. Signage and variable message boards are also used. Barriers and traffic signals are used much less frequently; typically only for major patching and slab replacement operations, often done under contract. Changes in Patching Practices since SHRP Research on patching conducted under the SHRP maintenance studies addressed materials and equipment for patching con- crete and asphalt pavements. This synthesis compared today’s practices to the SHRP recommendations. These comparisons lead to the following observations: • The published SHRP research helped to standardize some of the terminology used to describe different patch- ing techniques. The terms throw-and-go, throw-and-roll, semi-permanent, saw-and-patch, chip-and-patch, and others are widely recognized and understood today. • The detailed, step-by-step installation procedures for these types of patches, as codified under SHRP, have been widely adopted—almost verbatim in some cases. States such as Tennessee and Indiana use these terms and steps in their maintenance guides. • In many states, the saw-and-patch and semi-permanent patching techniques described in SHRP, calling for verti- cally cut faces, are widely prescribed even though several research studies have found that having a rough surface for the patch to adhere to (such as through the chip-and- patch or throw-and-roll techniques) may lead to better survivability of the patch. • Spray injection patching was a fairly new technology at the time of SHRP. The SHRP research demonstrated the good performance of such patching when done by a skilled operator. Since SHRP the use of spray patching has increased dramatically in many states. The perfor- mance of the patches has generally been good in some states but not in others. • The SHRP research also demonstrated good perfor- mance of proprietary patching materials in general. Use of these materials has increased in the years since, and new products are constantly being introduced to the market. Many states use proprietary materials routinely; others report having difficulties purchasing proprietary products. Approved lists of patching materials are used in some places to facilitate the purchase. • Some of the tests recommended for evaluating these materials, such as the workability box and rolling sieve, are rarely used. Other SHRP-recommended tests such as coating, stripping, and draindown are sometimes used for initial approval of a patching material, but are less commonly used for routine quality testing. • Partial-depth patching was shown through the SHRP research to be a feasible approach to patching concrete pavements. That is now a widely adopted practice across the country, although research is still being done to explore cost-effectiveness and evaluate patching materials and procedures for partial depth repairs. Since

51 SHRP, the depth considered for a partial-depth patch has been increased, in some cases from one-third to one-half the depth of the pavement. • The automated patching machine developed under SHRP was never fully adopted as designed. The con- cept of using spray injection patching to reduce labor requirements, however, has been adopted in many agencies. Comparison of State Practices with Local Agency and International Experience A survey of highway agencies in cities and counties across the United States found that those agencies face many of the same pressures as the states and have adopted many of the same techniques and practices. • Local agencies often face even tighter budgets, must make do with smaller workforces, and may be dealing with thinner roads, poorer drainage, and other factors leading to significant pavement distress. Perhaps it is not surprising then that local agencies tend to place great importance on their patching programs. Many of them are quite forward-thinking in terms of manage- ment and oversight of their patching practices. • In terms of materials, equipment, and traffic control, the local and state agencies are in reasonably close align- ment. Many local agencies use the state’s guidelines and specifications. Local agencies tend to have fewer lane-miles of concrete pavement, so patching concrete is done less frequently. • Maintenance by contract is also less common at local agencies. In many, there is a maintenance work force on the payroll; therefore, there is a need to keep them occu- pied, so they may as well be placing patches. Also, the typically smaller budgets of most local agencies may make patching by contract less feasible. In other cases, local agencies prefer maintenance contracts because they cannot afford to maintain staff and equipment. Despite differences in how agencies are structured and ter- minology used, overall, the practices in the United Kingdom and Ireland are quite similar to those in the U.S. states and local agencies. Similarities and differences can be outlined as follows: • One difference between the United States and the United Kingdom and Ireland is in the use of mainte- nance contractors. That practice is much more com- mon overseas, even for local agencies. Some overseas counties and municipalities find it more cost-effective to contract out maintenance than to invest in building their own workforce and procuring equipment for their small networks. • The patching materials used are similar, as are the dis- tresses and triggers. Spray patchers are also commonly used overseas, especially in larger jurisdictions and by contractors. • Similarly, no major differences were observed between the Canadian and U.S. survey responses; however, the number of Canadian agencies responding was quite small and may not have been comprehensive and representative. GAPS IN THE KNOWLEDGE AND FUTURE RESEARCH NEEDS Among the previously identified research needs expressed through the survey, subsequent communications as a part of this synthesis revealed the following gaps in the state of knowledge and needs for improvement. Participants in this synthesis reported needing: • Ways to speed up patching operations, which could include more automated patching and more private sec- tor developments. • Hands-on training for employees. • Equipment for using recycled asphalt pavement to patch. • Evaluating patching as a pavement preservation technique. • Safer traffic control measures for short duration patching. • The true costs of patching, including all associated costs, such as labor, equipment, and traffic control. • Improved methods for tracking patch locations and the materials and techniques used to aid in evaluat- ing performance and cost-effectiveness of patching options. • Investigation into the reasons why spray patching is so successful in some states and not in others. Similar research needs were suggested by state, local, and international agencies. In addition, all the agencies were asked where they would invest more money if the funding were available. The responses are summarized in Figure 43. Procuring better materials was a high priority for all types of respondents; however, U.S. local agencies reported even higher needs for more and better patching equipment. Increased staffing was also a high priority. Research and “other” were less highly rated. More than 30% of all respondents would increase funding for all of the previous items. SUMMARY As one of the most common and expensive maintenance tech- niques practiced by highway agencies, improvements in man- aging patching activities, techniques, and materials could have

52 a major impact on budgets and pavement performance. This synthesis summarizes the state of the practice and updates the information available on patching practices to help agen- cies make informed decisions. The overall findings suggest that there are striking similar- ities and, similarly, striking differences in how agencies man- age their programs. There is apparently more consistency in the materials used, partly because of what is available in the market, but also because some materials work better in some situations than others. No major differences were observed between practices in the United States, Canada, the United Kingdom, and Ireland. Lastly, while there have been improvements since the SHRP research on pothole patching and spall repair, there are still significant research needs across agencies, suggest- ing that a coordinated research effort would be beneficial. FIGURE 43 Resource needs identified (Source: survey responses.) 0% 20% 40% 60% 80% 100% UK/Ireland US Local US State Survey response Materials Equipment Staffing Research Other All of the above