Best Practices for Crack Treatments for Asphalt Pavements (2014)

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14 C H A P T E R 3 Summary of the Survey Results Scope of Work A survey of crack sealing and crack filling procedures was developed, distributed, and analyzed. The survey was sent to state department of transportation (DOT) maintenance engi- neers through the American Association of State Highway and Transportation Officials Subcommittee on Maintenance. In addition, the survey was distributed to the Transportation Association of Canada, the National Association of County Engineers, and the International Slurry Surfacing Association. One-hundred fifty-seven individual responses were received, representing 28 state DOTs, 106 counties, 3 cities, 2 Federal Highway Administration (FHWA) representatives, 1 Cana- dian province, 2 U.S. contractors, and 1 contractor from New Zealand. Eighty-two of the 157 respondents answered all of the 71 questions. A response was received from all but nine U.S. states. The questions in the survey were grouped into the following categories: • Respondent Information; • General Issues/Project Selection; • Contracting Procedures; • Materials; • Construction; • Quality Control; and • Performance. As would be expected, not all respondents answered every question. As a result, the number of responses varies by ques- tion and the percentages may not add up to 100%. General Issues/Project Selection A key issue raised in the survey is whether a distinction is made between crack sealing and crack filling. While the tech- nical literature is quite clear regarding the need for a distinction between crack sealing and crack filling, 62% of the survey responses indicated that no distinction is made. Whether the respondent was a state or county employee was not a clear predictor of the response. This survey response is an indica- tion that the state-of-the-art and the state-of-the-practice are not the same. In general, the comments were that crack sealing is used for “working” cracks that are moderate in size, in climates with sig- nificant temperature swings, and that have been routed. Crack filling is for all other applications, with a significant emphasis in warm-weather areas. Crack filling is also frequently done in preparation for a chip seal application. Approximately 80% of the survey respondents agreed that the following are the three key criteria for determining if a pavement is a good candidate for crack sealing and/or crack filling: • Type of crack • Percentage of cracked area on pavement • Crack width About half of the respondents also indicated that crack depth was an important criterion. “Don’t wait till it’s too late” was a well-advised comment. “Almost every road is a good candidate” illustrates the pervasiveness of the cracking issue in pavement management. How organizations specify crack sealing/filling can be summed up with one comment received: “Everyone has a dif- ferent specification, which is a problem.” The specifications identified by the respondents roughly fall into one of the following categories: • Well-defined, specific criteria (e.g., California, Michigan, Minnesota, Indiana, Texas, Montana, Wyoming, Nebraska) • Manufacturer’s recommendations • Anecdotal based on experience As with most products, the DOT specification is the most commonly referenced guideline for most cities and counties. State-of-the-Practice in Crack Treatments

15 The details of the specifications will be discussed in a later section. Almost 90% of the respondents indicated there are some conditions for which crack sealing or crack filling is not appropriate. • Situations where crack sealing is not appropriate: – Cracks are too wide, too deep, or too numerous; – “Non-working” cracks (filler is cheaper and quicker); – Pavement deterioration too severe (fatigue or alligator cracking); – If major surface rehabilitation/repair is scheduled within the next two years (e.g., overlay, in-place recy- cling, chip seal); and – If sealing would cover more than 25% of surface area (diminishes pavement skid safety). • Situations where crack filling is not appropriate: – “Working” cracks (1⁄8″ movement per year); – Pavement deterioration too severe (fatigue cracking); – If cold-in-place recycling (CIR) is scheduled in the near future; and – If reconstruction is scheduled within 2–3 years. Respondents were roughly evenly split (48% yes/52% no) when asked if a specific preventative maintenance cycle was a policy of their organization. Three to six years was a typical cycle time, with many expressing that funding was the key limiting factor for the cycle time. Treating the cracks before they get too large was a common factor. Crack treatments occurring one year after an overlay or 1–2 years before a chip seal was a common theme. Respondents were asked to estimate a typical life span for crack sealing and crack filling on both major and minor roads. Table 3-1 provides the estimated life spans for crack sealing and crack filling by percentage of respondents. The conclu- sion from this information is that the majority of respon- dents think crack sealing on both major and minor roads can perform for 5–10 years, but that crack filling will only last 1–4 years. Eighty-eight percent of respondents indicated that the crack sealing/filling requirements for major versus minor roads were the same. While there was agreement that cracks should be regularly treated, some respondents indicated that chip sealing for minor roads may be more cost-effective than crack treatments. Ninety-three percent of respondents indicated that the same materials are used regardless of the road type. Organization budgets for crack sealing/filling were quite variable, ranging from $100,000 to $10,000,000. Eighty-six percent of the budgets reported were under $500,000. The number of miles of crack sealing/filling per year was also quite variable, ranging from 25 to 5,000. Seventy-seven per- cent of the respondents indicated less than 100 miles of crack sealing per year. Based on the survey responses, the installation of crack sealer and/or crack filler is done with in-house personnel about 60% of the time. The survey responses were frequently either 100% in-house or 0% in-house. The conclusion is that many agencies either do all of the installation or none of it. The materials and installation specifications were the same for both in-house and contract work for 84% of respondents. Eighty-two percent of respondents indicated that their expe- rience with in-house crack sealing/filling was good to excel- lent, with minor difficulties. The participants were asked to identify the primary and most common problems associated with in-house crack sealing/filling operations. Table 3-2 lists the primary problems and the most common problems in order of the importance given by the respondents. Years Major Roads Minor Roads Crack Sealing 1 – 4 46% 38% 5 – 10 54% 55% Crack Filling 1 – 4 56% 50% 5 – 10 36% 33% Table 3-1. Survey responses for typical life span for crack sealing and crack filling. Primary Problem Most Common Problem Application Equipment Application Equipment Overfilling Crack Overfilling Crack Routing Crack Routing Crack Drying Crack Temperature of Application Temperature of Application Underfilling Crack Underfilling Crack Drying Crack Handling Materials Handling Materials Table 3-2. Survey responses for crack treatment problems in work done by in-house personnel.

16 It is noteworthy that the first three issues in both lists in Table 3-2 are the same and in the same order. Sixty-seven per- cent of the respondents listed the first three as the primary problem, and 58% of the respondents listed the first three as the most common problem. Eighty-one percent of the respondents indicated that their experience with contract crack sealing/filling was good to excellent, with minor difficulties. The participants were asked to identify the primary and most common prob- lems associated with contract crack sealing/filling opera- tions. Table 3-3 lists the primary problems and the most common problems in order of the importance given by the respondents. It is noteworthy that the first five issues in both lists in Table 3-3 are the same and in the same order. Ninety percent of the respondents listed the first five as the primary problem and 92% of the respondents listed the first five as the most common problem. The most common comment regarding contract crack sealing/filling was the out-of-pocket expense to the owner. A higher level of inspection was also required for contract crack sealing/filling. In comparing the in-house versus contract sealing responses (Table 3-2 versus Table 3-3), some observations are noteworthy: • In-house sealing may not have good equipment available; • Improper crack filling, routing, and drying are consistent issues for both in-house and contract sealing; and • There appears to be a tendency for in-house sealing to overfill the crack and contract sealing operations to under- fill the crack. Overfilling/underfilling the crack is likely a reflection of a lack of training for both in-house and contract personnel. In-house personnel may believe that more is better. Contrac- tor personnel, particularly if the project is low bid, may be underfilling to save money. In either case, personnel need to understand the potential impact of their actions on the per- formance of the seal treatment. The survey queried the participants regarding the type of crack that is appropriate for both crack sealing and crack fill- ing. Table 3-4 presents the results of those questions. Respon- dents commented that the severity of the cracking and the timing of the crack treatment were key determinants. Some commented that all cracks are treated. These responses are in general agreement with the state-of-the-art recommendations. The survey asked participants to identify required climatic conditions for both crack sealing and crack filling. Table 3-5 Primary Problem Most Common Problem Underfilling Crack Underfilling Crack Routing Crack Routing Crack Drying Crack Drying Crack Overfilling Crack Overfilling Crack Temperature of Application Temperature of Application Application Equipment Handling Materials Handling Materials Application Equipment Table 3-3. Survey responses for crack treatment problems in work done by contract personnel. Type of Crack for Crack Sealing Type of Crack for Crack Filling Transverse Cracking Joint Cracking Reflective Cracking Edge Cracking Low Temperature Cracking Transverse Cracking Joint Cracking Reflective Cracking Edge Cracking Fatigue Cracking Fatigue Cracking Low Temperature Cracking Table 3-4. Types of cracks by treatment type—order of priority by respondents. Crack Sealing Crack Filling Minimum Air Temperature 89.4 60.6 Maximum Air Temperature 80.8 61.5 Minimum Pavement Temperature 88.1 64.4 Maximum Pavement Temperature 87.0 52.2 Recent Precipitation 89.2 64.6 Forecast Precipitation 87.8 65.9 Absence of Fog/Dew 87.5 77.1 Direct Sunlight 85.7 42.9 Table 3-5. Climatic conditions required, % response.

17 presents the percentage of responses for each issue. From this information, it is apparent that respondents pay more atten- tion to climatic conditions for crack sealing than for crack filling. The range of temperatures given most commonly was 40–70°F. Generally, cooler temperatures are preferred so that the crack is wider. Participants in the survey were asked the typical crack sealing/filling season. The answers were given in months. A numerical value was assigned to each month (January = 1, February = 2, etc.), and an average value was calculated. This calculation established that the average season was from May to August. Clearly this will be variable for different regions of the country. The season for hot, southern climates is generally during the winter months. The survey queried the participants regarding criteria for the type of crack for both sealing and filling. Table 3-6 pre- sents the percentage of responses for both crack treatments and the numerical values reported for each type of treatment. The interpretation of Table 3-6 is that about 80% of the respondents indicated minimum crack width was a criterion for both crack sealing and crack filling (80.3% and 81.7%, respectively). The respondents reported a minimum crack width of 0.24″ for crack sealing and 0.42″ for crack filling. The data show that both minimum and maximum crack width are the two most important criteria. As expected, the crack dimension criteria for crack sealing are smaller than for crack filling. The time since the last treatment is seen to be a low priority criterion but, for the few responses, does indicate an average time between treatments of 4–5 years. Contracting Procedures The manner in which agencies purchase goods and services is important regardless of the type of product. This section of the survey questioned participants about the process through which crack sealing/filling materials and services are obtained. Seventy-eight percent of the respondents did not have a prequalified contractor list for their organization. Remem- ber that 60% of sealing is done with in-house personnel. The type of contract and percentage of use are shown in Table 3-7. (Note: Respondents could check multiple contract types, so the values do not add up to 100%.) Two interesting comments were generated relating to the contract type. One was that warranty projects generally have better performance. The second comment described a modi- fied unit price approach. The agency (in this case, a county in Texas) provided the contractor with material for the crack treatment, thereby removing the risk to the contractor on quantity of material. The contractor then bid the cost of a crew (including equipment) as defined in the contract. Participants in the survey were asked how crack sealing/ filling is measured. Fifty-three percent of respondents indi- cated the measurement was by weight of material applied, 46% by linear feet of cracking, and 33% by quantity of crack sealer applied. Respondents could check multiple measure- ment methods, so the values don’t add up to 100%. Some com- ments were made about using centerline miles of roadway as the measurement method. This would require an established percentage of cracking in order for the arrangement to be equitable to both the owner and the contractor. Seventy-six percent of the respondents indicated that a warranty was required for crack sealing/filling projects. The average length of warranty was 1.4 years. Materials Selection and approval of materials is an important effort for any pavement owner. Generally materials are specified using standard generic requirements. This section of the sur- vey focused on requirements for proper materials for crack sealing and crack filling. This survey did not address specific crack sealing/filling products by name in order to avoid any proprietary issues. Often agencies have an approved list of materials for the products used in highway construction. For crack sealing/ Percentage of Responses Crack Dimensions, inches Crack Sealing Crack Filling Crack Sealing Crack Filling Width, min 80.3 81.7 0.24 0.42 Width, max 71.1 71.7 1.01 1.66 Depth, min 51.3 58.3 0.72 1.00 Depth, max 51.3 60.0 3.00 4.14 Time since last treatment 39.5 38.3 4.5 (years) 4.75 (years) Table 3-6. Survey responses on crack dimensions for crack sealing and crack filling. Contract Type Percentage Use Unit Price – Low Bid 90.0 Lump Sum/Firm Fixed Price 20.0 Cost Plus 6.7 Indefinite Delivery/Indefinite Quantity 6.7 Warranty 11.7 Table 3-7. Types of contracts used by respondents.

18 filling, 64% of the respondents indicated that their organiza- tion had an approved list of materials. As is often the case, most local agencies reference the state DOT specifications. Material handling safety is an integral part of any construc- tion project. The survey results indicated that 64% of respon- dents required safety training for employees. Forty-one percent required annual safety training. Some respondents indicated that the contractor might require safety training even though the agency may not. Seventy-seven percent of the agencies responding required Personal Protective Equipment (PPE) for workers applying crack sealing/filling materials. Typical PPE required are: long pants (97%), gloves (89%), safety shoes (85%), face/eye pro- tection (78%), and long sleeves (68%). Appropriate safety vests are of course required on all construction projects and, in some cases, so are hardhats. Construction If the construction process is not completed correctly, the best design and materials will make no difference. This section of the survey focused on requirements for proper construction of the crack sealer/filler. Traffic control require- ments are not included in this discussion. The typical road preparation methods prior to crack sealing/ filling are to sweep the pavement (77% of responses) and to dry the pavement (63% of responses). Stated objectives are to ensure that the cracks are clean and dry using either air blowing or a hot air lance. Cleaning of the cracks prior to sealing/filling is a critical ele- ment in good performance of the crack treatment. Table 3-8 presents the cleaning methods used by respondents. Backer rod is seldom used for rout and seal applications— just 19% of respondents indicated use. The primary uses are for very large cracks and for concrete joint sealing. The issue of whether or not to rout cracks is a contentious matter. There were 52 responses to the survey question, with 50% reporting they never rout a crack, 35% reporting they rout in areas of high thermal movement, and 31% reporting they rout in areas of high-performance applications. Out of the 52 responses, 27% of the respondents indicated they rout all cracks prior to treatment. Fifty-six percent of the survey participants indicated that the surface of the sealer is squeegeed after application of the sealer/filler. Another 16% stated it was done sometimes. Five different crack seal configurations were presented to the survey participants, with a series of questions relating to the use of each configuration. The configurations identified were as follows: • Recessed Crack Treatment Configuration • Flush Fill Crack Treatment Configuration with Routed Crack • Flush Fill Crack Treatment Configuration with Non- Routed Crack • Overband Crack Treatment Configuration with Routed Crack • Overband Crack Treatment Configuration with Non- Routed Crack Graphics 3-1 to 3-3 illustrate these configurations. For each of the configurations, the survey participants were asked about the conditions for use, the typical dimensions, and the typical procedures. Table 3-9 provides a summary of the responses regarding crack configurations. As noted in Table 3-9, 35% of respon- dents always use the recessed crack configuration, but 65% of respondents never do. The recessed crack seal configura- tion was used prior to same-season overlay, for construction joints, for wider cracks where rout and seal is done, for ther- mal moving cracks, and for wide longitudinal crack filling. The average dimensions reported by respondents were a res- ervoir width of 0.83″, a reservoir depth of 0.82″, and a recess depth of 0.29″. Forty-eight percent of respondents always or most of the time use a flush fill crack seal configuration, while 21% never use this configuration. Average dimensions for the flush fill routed crack were 0.86″ × 0.84″ for reservoir width and depth, respectively. Cleaning Method Percentage of Respondents Compressed Air 89.5 Routing of Crack 42.1 Hot Air Lance 35.5 Sawing 7.9 Wire Brush 5.3 Pressurized Water 1.3 Sand Blasting 1.3 Table 3-8. Crack cleaning methods. Recess Depth Reservoir Width Reservoir Depth Graphic 3-1. Recessed crack treatment configuration.

19 Forty-three percent of respondents always use an overband crack seal configuration (with an additional 8% using it most of the time), while 28% never use this configuration. Aver- age dimensions for the overband routed crack were 1.18″ × 0.94″ for reservoir width and depth, respectively. The average reported overband widths for routed and non-routed cracks were 2.49″ and 3.28″, respectively. Survey participants were asked about three different anti- tracking mechanisms: blotter sand, release agent, and plastic/ paper. All of these are used in different areas of the country to prevent tracking of newly placed crack sealer/filler by traffic. The predominant response is that blotting materials are not used—75% do not use blotter sand, 62% do not use release agent, and 70% do not use plastic or paper on the crack sealer/filler after application. General responses were that if tracking becomes a problem on a specific project, consider- ation would be given to one of these techniques as a solution. Two creative approaches are to (1) use dishwashing soap and (2) use toilet paper. Anti-tracking products are available from some manufacturers. The survey asked about possible changes in preparation, materials, configuration, or placement of crack sealant prior to an overlay or prior to placement of a surface treatment. The overwhelming response (92%) for the overlay scenario indicated the primary issue is the time between the crack seal- ing technique and the overlay construction. For crack sealing/ filling prior to a surface treatment, the response was just as strong, with 94% indicating that the time between activities is the principal issue. The preparation, materials, and configura- tion were considered incidental to the time between activities. Reservoir Width Reservoir Depth Routed Crack Non-Routed Crack Graphic 3-2. Flush fill crack treatment configuration, both routed (left) and non-routed (right). Overband Width Reservoir Depth Routed Non-Routed Overband Width Reservoir Width Graphic 3-3. Overband crack treatment configuration, both routed (left) and non-routed (right). Configuration Type Recessed (Graphic 3- 1) Flush Routed (Graphic 3-2[left]) Flush Non- Routed (Graphic 3- 2[right]) Overband Routed (Graphic 3- 3[left]) Overband Non- Routed (Graphic 3- 3[right]) Percent Usage* 35/65 48/21 48/21 43/28 43/28 Reservoir Width, in 0.83 0.86 --------------- 1.18 --------------- Reservoir Depth, in 0.82 0.84 --------------- 0.94 --------------- Recess Depth, in 0.29 -------------- --------------- --------------- ---------------- Overband Width, in --------------- -------------- --------------- 2.49 3.28 *Always Use/Never Use Table 3-9. Summary of crack configuration responses from survey.

20 For sealant placed prior to an asphalt overlay, 54% of the participants indicated that no changes were made to crack sealing/filling operations. The time to complete crack treat- ments prior to overlay varied from one to three years, with a one-year wait being a common response. If a same-season overlay is to be done, respondents believed that the configu- ration should be of the recessed type. For sealant placed prior to an asphalt surface treatment, 47% of the participants indicated that no changes were made to crack sealing/filling operations. The time to complete crack treatments prior to surface treatment is recommended to be one season before the surface treatment. If a same-season sur- face treatment is to be done, the crack treatment should be performed at least one month prior to the surface treatment— the longer time available, the better. Seventy-seven percent of respondents indicated that the crack sealing procedures do not vary depending on the type of surface treatment planned. Comments of note: • Do not rout cracks if microsurfacing is to be applied. • Create a test strip to validate compatibility of the crack seal with surface treatment, especially if any solvents are used. • Do not perform Hot-In-Place recycling over crack seal material—there is a fire danger. Quality Control For each element of the highway construction process, it is important to ensure the quality of the products and pro- cesses. It is generally understood in the highway construction industry that the contractor is responsible for Quality Control while the owner is responsible for Quality Assurance. These activities define the seller’s and buyer’s risk for the materials and processes used in highway construction. This section of the survey focused on requirements for Quality Control of the crack sealer/filler materials and application processes. Participants in the survey were asked if an inspector is on- site during the crack sealing/filling operation. The responses were 36% yes, 38.7% no, and 25.3% sometimes. The “some- times” generally depended on whether the work was being done by in-house staff or a contractor and on the availabil- ity of personnel for the inspection. While staffing is a chal- lenge for most agencies, the comment was made that there is generally better performance of the crack sealing/filling if an inspector is present during construction activities. From a performance perspective, the inspector primarily checks for application techniques and that the crack is clean and dry. Other issues included in the inspection are the material tem- perature, quantities, approvals, traffic control, and safety. Agency personnel perform 75% of the inspection activi- ties, with 11% done by a private consultant and 6% by the contractor. Seventy-one percent of respondents indicated that a final inspection is performed on the crack sealing/ filling operations. The final inspections are performed by agency personnel (39%), agency inspectors (32%), and road- way superintendents (29%). Sixty-seven percent of respon- dents indicated that no training and/or certification program exists for crack sealing/filling. Several participants mentioned on-the-job training as the key training approach. It is interesting to note that the 1967 NCHRP report on crack sealing recommended an education program to allevi- ate the problem of inadequate performance of sealing efforts (29). Not much has changed in that regard in an almost 50-year time span. In a 2008 document, Minnesota DOT further recommended training, stating that improvements in crack sealing installation procedures are needed (43). The results of this survey demonstrate that the recommendations are currently valid. Seventy-seven percent of participants indicated that no sampling and testing of the crack seal/fill material is done during the construction process. There is a wide range of sam- pling and testing approaches: some agencies pre-test material; some have approved supplier certifications; some sample from melters; some job sample and test later. Many commented that they only test when they think there is a problem. Ninety-four percent of respondents indicated that no field acceptance tests are performed. The foundation for most testing is the ASTM requirements. Eighty-four percent of participants indicated that no cali- bration or inspection of the application equipment is per- formed. Reference is made to state DOT specifications and daily “walk-arounds” but no specific calibration or inspec- tion program. Performance The most important part of any material application is the final performance of the product. This section of the survey focused on requirements for performance measurement of the crack sealer/filler materials and application processes. Seventy-four percent of the respondents indicated that no performance measurement for crack sealing/filling is con- ducted. Comments indicated that qualitative evaluations are conducted (e.g., visual examination), but there is no quanti- tative performance measurement (e.g., test results). Participants were asked to identify common distresses in crack sealing/filling and to indicate which was the most com- mon problem. Table 3-10 presents the results of these ques- tions. The responses clearly show that lack of bond is the largest source of failure for crack treatments, with cohesive failure being the second most common distress type. In addition to those distress types, respondents also identified oxidation of the crack sealer/filler and construction-related issues that impact performance of the crack sealer/filler.

21 Eighty-one percent of the participants indicated that deicer applications do not affect sealant performance. The only situ- ation in which deicer was noted to have an impact on sealant performance is if the sealant is applied shortly after a deicer application. Time between deicer and sealant applications appears to reduce any potential effect. Routing of the crack also removes some of the material that may be contaminated by deicer products. Ninety percent of the respondents indicated that they do not quantify the effect of sealant on pavement life. Research activities on this issue were discussed previously in this report. The final survey question asked the participants to rank factors in order of importance in minimizing defects in crack treatments. Table 3-11 presents the results. Clearly, cleaning the crack is considered to be the most important issue by all respondents. The second grouping of ranking values (4.21 and 4.68) includes the sealant used and precipitation at the time of installation, which were strongly considered to be of importance. The third grouping (3.33 to 3.75) includes con- struction procedures, temperature at installation, and crack routing. The participants did not consider the equipment used to be as important as the other factors. Distress Type Distress Observed, % Most Common Distress, % Lack of Bond 78.9 57.5 Cohesive Failure 48.1 20.0 Raveling of Crack 25.0 10.0 Spalling of Crack 17.3 12.5 Table 3-10. Distresses noted by survey participants. Conclusion The response to the survey was excellent. Participants were willing to share their experience with crack sealing/ filling through the extensive survey questions. The survey clearly indicates differences between the state-of-the-art and state-of-the-practice. These differences will be discussed in Chapter 4. Factors to Minimize Defects Average Ranking Value Order of Importance Proper Crack Cleaning 5.61 1 Sealant Used 4.68 2 Precipitation at Installation 4.21 3 Construction Procedures/Techniques 3.75 4 Temperature at Installation 3.71 5 Proper Crack Routing 3.33 6 Equipment Used for Installation 2.71 7 Table 3-11. Ranking of factors important to minimize defects in crack treatments.