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Suggested Citation:"Chapter 1 - Airfield Guide for Engineers." National Academies of Sciences, Engineering, and Medicine. 2022. Airfield Pavement Markings: Effective Techniques for Removal and Temporary Applications. Washington, DC: The National Academies Press. doi: 10.17226/26797.
Suggested Citation:"Chapter 1 - Airfield Guide for Engineers." National Academies of Sciences, Engineering, and Medicine. 2022. Airfield Pavement Markings: Effective Techniques for Removal and Temporary Applications. Washington, DC: The National Academies Press. doi: 10.17226/26797.
Suggested Citation:"Chapter 1 - Airfield Guide for Engineers." National Academies of Sciences, Engineering, and Medicine. 2022. Airfield Pavement Markings: Effective Techniques for Removal and Temporary Applications. Washington, DC: The National Academies Press. doi: 10.17226/26797.
Suggested Citation:"Chapter 1 - Airfield Guide for Engineers." National Academies of Sciences, Engineering, and Medicine. 2022. Airfield Pavement Markings: Effective Techniques for Removal and Temporary Applications. Washington, DC: The National Academies Press. doi: 10.17226/26797.
Suggested Citation:"Chapter 1 - Airfield Guide for Engineers." National Academies of Sciences, Engineering, and Medicine. 2022. Airfield Pavement Markings: Effective Techniques for Removal and Temporary Applications. Washington, DC: The National Academies Press. doi: 10.17226/26797.
Suggested Citation:"Chapter 1 - Airfield Guide for Engineers." National Academies of Sciences, Engineering, and Medicine. 2022. Airfield Pavement Markings: Effective Techniques for Removal and Temporary Applications. Washington, DC: The National Academies Press. doi: 10.17226/26797.
Suggested Citation:"Chapter 1 - Airfield Guide for Engineers." National Academies of Sciences, Engineering, and Medicine. 2022. Airfield Pavement Markings: Effective Techniques for Removal and Temporary Applications. Washington, DC: The National Academies Press. doi: 10.17226/26797.
Suggested Citation:"Chapter 1 - Airfield Guide for Engineers." National Academies of Sciences, Engineering, and Medicine. 2022. Airfield Pavement Markings: Effective Techniques for Removal and Temporary Applications. Washington, DC: The National Academies Press. doi: 10.17226/26797.
Suggested Citation:"Chapter 1 - Airfield Guide for Engineers." National Academies of Sciences, Engineering, and Medicine. 2022. Airfield Pavement Markings: Effective Techniques for Removal and Temporary Applications. Washington, DC: The National Academies Press. doi: 10.17226/26797.
Suggested Citation:"Chapter 1 - Airfield Guide for Engineers." National Academies of Sciences, Engineering, and Medicine. 2022. Airfield Pavement Markings: Effective Techniques for Removal and Temporary Applications. Washington, DC: The National Academies Press. doi: 10.17226/26797.
Suggested Citation:"Chapter 1 - Airfield Guide for Engineers." National Academies of Sciences, Engineering, and Medicine. 2022. Airfield Pavement Markings: Effective Techniques for Removal and Temporary Applications. Washington, DC: The National Academies Press. doi: 10.17226/26797.
Suggested Citation:"Chapter 1 - Airfield Guide for Engineers." National Academies of Sciences, Engineering, and Medicine. 2022. Airfield Pavement Markings: Effective Techniques for Removal and Temporary Applications. Washington, DC: The National Academies Press. doi: 10.17226/26797.
Suggested Citation:"Chapter 1 - Airfield Guide for Engineers." National Academies of Sciences, Engineering, and Medicine. 2022. Airfield Pavement Markings: Effective Techniques for Removal and Temporary Applications. Washington, DC: The National Academies Press. doi: 10.17226/26797.
Suggested Citation:"Chapter 1 - Airfield Guide for Engineers." National Academies of Sciences, Engineering, and Medicine. 2022. Airfield Pavement Markings: Effective Techniques for Removal and Temporary Applications. Washington, DC: The National Academies Press. doi: 10.17226/26797.
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1-1  Purpose of the Airfield Guide for Engineers This airfield guide provides information to help engineers and others who are tasked with removing airfield markings from a variety of pavements using a variety of methods while also mitigating the appearance of scarring and reducing pavement damage from marking removal. It includes best practices for efficient, safe, cost-effective, and environmentally acceptable tech- niques for marking removal and for temporary marking applications. The guide also includes a comparative matrix of removal techniques and associated challenges, along with innovative methods and materials that can improve results and reduce the confusion that can be caused by remaining marking material or by scarred pavement created by removal operations. This guide, along with the field inspection guide that follows it, were developed as a result of ACRP Project 09-19, âAirfield Pavement MarkingsâEffective Techniques for Removal and Temporary Applications.â Airfield Pavement Marking Removal Airfield markings bond to the microtexture of the pavement. When they are removed, portions of the microtexture are removed along with the paint. This often results in discoloration, scarring, and pavement damage. Discoloration is often associated with scarring and pavement damage but can also be caused by cleaning the pavement surface. Scarring refers to the removal of the pavement texture, with some exposed aggregate. Pavement damage refers to situations in which more than 25% of the nominal size aggregate is uniformly exposed; this could allow the aggregate to loosen. Different pavement types, pavement conditions, marking materials, and reasons for the removal should be considered during the specification development portion of project plan- ning, if marking removal will be part of the project. This guide describes the factors to consider when selecting the method(s) of removal and best practices for conducting the removal. The goal of these guidelines and best practices is to provide acceptable marking removal options that minimize pavement damage and the potential for confusion that marking removal might cause. Establishing a Removal Method Selecting a removal method that is compatible with all of the variables (such as coating type, coating thickness, degree of removal, and type and condition of pavement, among other considerations) requires data and analysis. The Figure 1-1 flowchart suggests a process for determining the method(s) of removal. C H A P T E R 1 Airfield Guide for Engineers
1-2 Airfield Pavement Markings: Effective Techniques for Removal and Temporary Applications Considerations Based on Marking Type and Thickness The main consideration for removing any type of marking is its thickness. Paint markings are applied in thin layers but are often reapplied numerous times. This creates a thicker marking that is more difficult to remove than a single paint layer (often used for temporary markings) would be. Epoxy is more difficult to remove than paint because of its initial thickness and durability. Methyl methacrylate (MMA) and thermoplastic are thick and durable materials and are thus more difficult to remove. Blasting techniques do not work as well on thicker markings. Grinding techniques are more effective for thicker markings as long as the marking is not below the pavement surface. In situations where there is a thick buildup of marking on a surface that is grooved or made up of porous asphalt, using a grinding technique followed by a blasting tech- nique will often yield the best results. Reasons for Removal When airfield markings need to be removed, the airport or its engineers will solicit contractors to submit bids on the work. The contractor will often determine the method(s) of removal, which will depend on several factors, including whether the material to be removed is on concrete or asphalt, if the concrete or asphalt is in good or fair condition, and whether the marking is thick or thin. Oftentimes the specifications merely dictate percentage(s) of material to remove and the time allotted for the task. To improve on this process, those soliciting bids on the work should include additional information in the specification for the factors outlined in Figure 1-1, including a recommended removal method. The type and thickness of the coating to be removed should be considered as the plans and specifications are developed. A marking may not need to be totally removed. A 100% removal is most likely to result in the highest degree of scarring and possible damage. Different reasons for removing a marking should dictate the degree of removal required. Table 1-1 suggests reasons for removal and the corresponding degrees of removal to be achieved. Each type of marking removal is further defined in the following list. 1. Obsolete markings are those no longer needed because the surface is to be expanded or reduced, the markings are to be moved to a new location, or the markings are no longer required. Any remnants of the old marking could result in confusion, so efforts should be made to remove 95% to 100% of the obsolete marking to reduce this possibility. 2. Changing marking patterns means that the markings are to be modified and new markings will be superimposed over the old ones. For example, the magnetic variance may have changed, Type of Coating Thickness of Coating Degree of Removal Type of Pavement Condition of Pavement Grooved or Ungrooved Method of Removal Figure 1-1. Considerations for determining removal method.
Airfield Guide for Engineers 1-3  so the runway landing designation markings must be changed from â36â to â1.â In this instance, 100% of the marking â36â would be removed so as not to conflict with new â1â marking. 3. Seal coats or other surface treatments are noted in FAA Advisory Circular (AC) 150/5370-10, item P-101. Any rubber or marking on a surface that is to receive a seal coat or asphalt overlay should be removed. Seal coats and asphalt do not bond well to rubber or paint. Between 80% and 85% of the rubber or paint must be removed to provide a paved surface on which the seal coat or asphalt will bond. Application of a seal coat indicates a pavement condition that would likely not sustain a removal operation without damaging the surface. Reducing the percentage of removal to between 80% and 85% achieves the goal without damaging the surface. 4. Marking buildup is prevalent throughout airports resulting from the common practice of painting over a marking without cleaning it prior to the repainting. Forty mils, or approximately five coats of a standard waterborne paint, should be the maximum thickness of a marking on the pavement. Between 85% and 90% of the thickness or depth of the coating should be removed to reduce the likelihood of remaining foreign object debris (FOD) caused by the paint, such as chunks of paint or glass beads. 5. Changing paint colors on a marking requires 90% to 95% removal of the original paint, especially if the color to be removed contains glass beads. 6. Removal of a marking because the original coating is incompatible with the new type to be applied depends on the composition of the two types. Table 1-2 provides guidance on the compatibility of markings. Pavement Condition The condition of the pavement under the markings should be evaluated to determine what method of removal will do the least damage. Correlating the condition of the pavement under the markings with a pavement condition index (PCI) score or a subjective rating prior to the removal operation will provide some guidance on the ability of the pavement to sustain mechanical Types of Marking Removal Degree of Removal Obsolete markings and changing marking patterns 95%â100% Prior to seal coat application or other surface treatment 80%â85% Marking buildup/excessive layers 85%â90% Changing marking colors 90%â95% Incompatible materials 85%â100% (Manufacturer recommendations) Table 1-1. Types and degrees of marking removal. New Marking Material Waterborne Paint Solvent Paint Epoxy MMA Preformed Thermoplastic Ex is tin g (O ld ) M ar ki ng M at er ia l Waterborne Paint Y N N N N Solvent Paint Y Y N N N Epoxy Y Y Y N N MMA Y Y N Y N Preformed Thermoplastic Y Y N N N Notes: Y = Compatible materials, N = Incompatible materials Table 1-2. Material compatibility.
1-4 Airfield Pavement Markings: Effective Techniques for Removal and Temporary Applications method(s) of paint removal. Table 1-3 provides an example of subjective pavement ratings that can be used to assess the condition of the pavement under the markings that are to be removed. If markings have damaged the pavement under the paint, milling and overlaying those areas should be considered. Diamond grinding and regrooving are techniques that have also been used to remove thick, cracked markings and asphalt. Ultra-high pressure (UHP) water blasting at low pressures can subsequently be used to clean up all residue. Advantages and Disadvantages of Removal Methods Table 1-4 provides information on the advantages and disadvantages of different removal techniques. UHP water blasting and various forms of grinding (scarifying) are by far the most common types of marking removal. These methods can remove markings quickly and com- pletely, though any method can result in pavement damage if not done properly. Removal Methods by Pavement Type Concrete pavement, either grooved or ungrooved, is more durable than asphalt and more likely to be impervious to a UHP water-blasting operation. Asphalt will always be more sus- ceptible to scarring and possible damage during a removal operation. Table 1-5 presents the different methods of removal by pavement type and condition. Removal Method Selection Examples The factors shown in the flowchart in Figure 1-1 should be considered when selecting a removal method. Depending on the specifics of each relevant factor, the removal method and how to conduct it can be selected and written into project plans and specifications. Tables 1-6 through 1-11 provide several examples of different situations and factors to be considered along with the types and combinations of equipment needed to achieve the desired degree of removal for each. If markings are on grooved or ungrooved Portland cement concrete (PCC) or asphalt cement concrete (ACC) that is in good to excellent condition and are less than 40 mils thick, then UHP water blasting is recommended (see Table 1-6). The use of metal strips or rebar is suggested to prevent damage to joint material. If markings are on concrete and are greater than 40 mils thick, a combination of scarification above the surface to remove excess thickness, followed by UHP water blasting, can be used to achieve the desired degree of removal and to clean up residue (see Table 1-7). The use of metal strips or rebar can prevent damage to joint material. If markings are on ungrooved asphalt that is in fair condition and have a thickness greater than 40 mils, surface scarification followed by light water blasting using a UHP unit with an integrated vacuum to remove residue is recommended (see Table 1-8). If markings are on grooved asphalt that is in fair condition and have a thickness of less than 40 mils, scarify to remove markings above grade and use UHP water blasting to achieve the desired degree of removal and to clean up residue (see Table 1-9). Rating Description Excellent No cracking Good Some slight cracking along edges Fair Slight cracking in non-uniform pattern Poor Uniform cracking throughout marking Very poor Severe cracking; thick, separating pavement Table 1-3. Pavement condition rating under the marking.
Airfield Guide for Engineers 1-5  Removal Type Advantages Disadvantages Grinding ⢠Hand-operated or vehicle-mounted. ⢠High efficiency with vehicle-mounted units. ⢠Effective on aged asphalt. ⢠Removes surface markings well. ⢠Can capture dust and some debris. ⢠High availability of equipment. ⢠Horizontal-rotating grinding units may cause less noticeable damage than vertical drum units. ⢠Vertical drum units with polycrystalline diamond cutters result in a smooth finished texture. ⢠Can be used in combination with a blasting system to remove thick markings and markings on grooved surfaces. ⢠Does not remove markings below the surface without pavement damage. ⢠Not good for grooved surfaces. ⢠Can leave noticeable scars and can damage pavement if not set up properly. ⢠Requires debris cleanup (generally with UHP water blasting or flushing with pressurized water) prior to new marking applications. Diamond grinding ⢠Removes 100% of the marking with minimal scarring. ⢠Leaves indistinguishable color difference in surface. ⢠Surface must be thoroughly flushed to remove residue. ⢠Regrooving is necessary if used on grooved surface. ⢠Removes some of the pavement with the marking. ⢠Leaves pavement wet. Water blasting ⢠UHP units can operate at a range of pressures. ⢠Lower-pressure units are available. ⢠Full-size vehicle mount or mounted on smaller cart. ⢠Has debris and water collection system. ⢠Efficient removal, especially on Portland cement concrete (PCC). ⢠Can remove markings below the surface with limited scarring or damage if underlying pavement is in fair to excellent condition. ⢠Can be used for surface prep. ⢠Leaves pavement wet. ⢠Some particulates may remain on pavement and will need to be vacuumed or blown off. ⢠Can damage pavement, especially aged asphalt. Shot blasting ⢠Vehicle mounted. ⢠Can remove a wide area (6 in. to 6 ft) in a single pass, depending on equipment type. ⢠Has a debris collection system. ⢠Does not work well on grooved surfaces. ⢠Some shot may be lost and become FOD; lost shot may also discolor the pavement or markings as it rusts. Sandblasting ⢠Hand-operated precision. ⢠Effective on thin markings. ⢠Slowâonly useful in small areas. ⢠Can remove markings on any surface, including grooved surfaces. ⢠Can remove markings with limited surface scarring or damage. ⢠Requires protective gear for the operator. ⢠Significant cleanup required. ⢠Less effective on thick markings. Chemical ⢠Can remove thin markings on most surfaces with limited surface damage. ⢠Some chemical systems are environmentally safe. ⢠May not be environmentally friendly and could therefore require additional safety measures. ⢠Slow. ⢠May leave a residue that needs to be flushed clean. Table 1-4. Comparative matrix of removal techniques.
1-6 Airfield Pavement Markings: Effective Techniques for Removal and Temporary Applications Concrete Asphalt Poor Asphalt Seal Coat Equipment Type G U G U G U N/A Grinding N Y N Y N Y Y Shot blasting N Y N Y N C N Sandblasting Y Y Y Y Y Y Y Water blasting Y Y Y Y C C C Notes: G = Grooved pavement, U = Ungrooved pavement, Y = Acceptable for use, N = Not a preferred method, and C = Use in combination with grinding Factors Level Coating type Waterborne/solvent/epoxy Thickness 40 mils Degree of removal 80%â100% Pavement type PCC (either grooved or ungrooved) Pavement condition under marking Good to excellent Removal method Scarify/UHP Factors Level Coating type Any Thickness >40 mils Degree of removal 80%â100% Pavement type ACC ungrooved Pavement condition under marking Fair to good Removal method Scarify/UHP Factors Level Coating type Waterborne/solvent/epoxy Thickness
Airfield Guide for Engineers 1-7  If markings are on grooved asphalt that is in fair condition and have a thickness greater than 40 mils, surface scarification is recommended to remove excess thickness, followed by UHP water blasting to achieve the desired degree of removal and to clean up residue (see Table 1-10). The thicker the paint and the higher the degree of removal, the longer the removal effort will take, so more time should be allotted to the task as appropriate. If markings of any thickness are on grooved asphalt that is in poor condition, surface scari- fication and regrooving to remove paint in grooves, followed by UHP water blasting to remove residue, is recommended (see Table 1-11). Sandblasting is an option if the area is small. Visibility Concerns from Remaining Marking or Scarring Scarring is inevitable when removing paint from pavements, because the coating is bonded to the microtexture of the pavement. Minimizing scarring and preventing damage to the pave- ment is the goal of a high-quality marking removal. Removal of markings from concrete surfaces should only use UHP water blasting or scarifica- tion above the surface, followed by UHP water blasting to remove marking below the surface. Scarification of concrete surfaces to remove 100% of coatings is not recommended because it can result in permanent scoring of the pavement. Discoloration of the pavement where the removal occurred can be blended with the surrounding pavement by removing an area larger than the marking area in order to reduce confusion. This additional removal should be done lightly so that scarring does not occur. Scarring and damage to concrete pavements is difficult to repair and cannot be easily concealed below a seal coat. Removal of markings from asphalt surfaces will leave a scar that fades over time because of exposure to ultraviolet light. The use of seal coats to obscure scarring and residual paint is a typical practice. Removing an inadequate amount of an obsolete marking may result in a ghost marking. Ghost markings are the remnants of a previous marking that may be mistaken for a current Factors Level Coating type Any Thickness >40 mils Degree of removal 80%â100% Pavement type ACC grooved Pavement condition under marking Fair to good Removal method Scarify/UHP Factors Level Coating type Any Thickness >40 mils Degree of removal 80%â100% Pavement type ACC grooved Pavement condition under marking Poor to very poor Removal method Scarify/UHP; sandblasting (if area is small) Table 1-11. Thick marking on grooved ACC in poor to very poor condition. Table 1-10. Thick marking on grooved ACC in fair to good condition.
1-8 Airfield Pavement Markings: Effective Techniques for Removal and Temporary Applications marking (see Figure 1-2). The reason for the marking removal and its associated target removal percentage should be considered. Applying highly visible replacement markings or temporary markings can help alleviate confusion caused by ghost markings, scarring, or pavement damage. Ghost markings or markings that are inadequately removed can present a safety issue. The visibility of the removed markings and replacement markings should be evaluated in both daytime and nighttime conditions. In addition, the markings should be viewed at different times of the day, as the angle of the sun can affect visibility (see Figure 1-3), as well as during dry and wet weather conditions. Viewing the removed areas and replacement markings in these different conditions, from typical observer perspectives, is the best way to determine whether their removal will result in confusion. If it is determined that the removal may cause confusion, additional removal or corrective actions should be taken to improve the areas where the removal occurred. Figure 1-2. Ghost markings and scarring. Figure 1-3. Residual marking visibility difference depending on sun position.
Airfield Guide for Engineers 1-9Â Â Airfield Marking Removal Best Practices 1. During the design phase of the project, analyze the condition of the markings to be removed and the condition of the pavement under the markings (compare to most recent PCI of the subject pavement). 2. Specify the type(s) of equipment to be used based on the analysis of the markings to be removed. Bidders on the removal project should submit a list of equipment to be used on the project that conforms to these specifications. 3. Removal test lines should be performed with each type of equipment and for all types and degrees of removal to be used on the project to demonstrate the capability of both the equip- ment and the operator. Pictures of acceptable results should be taken and used as examples of appropriate degrees of removal and acceptable levels of scarring. Different degrees of removal may be required on the same project, and different pavement surfaces may require different removal techniques. 4. The work should result in the removal of the desired level of marking with minimized damage to the pavement surface. Removal of markings in grooved surfaces requires use of a blasting technique or a grooving machine to minimize pavement damage. 5. On asphalt surfaces, determine if the need to remove a larger predetermined area of the marking is necessary to reduce confusion from the remaining scar or color changes. Experi- ence has demonstrated that adherence to the guidance found in FAA AC 150/5340-1Mâ Standards for Airport Markings pertaining to asphalt surfaces does not always achieve the desired result and may erode the surrounding pavement unnecessarily. A sealant should be applied to obscure objectionable scars. 6. Debris from removal operations should be continuously contained and disposed of in accordance with local and federal environmental regulations. 7. Conduct a pull test with duct tape or other adhesive material by pressing the tape onto the surface where the removal was done. Pull the tape up to see if any residual debris is stuck to the tape. If debris is present, further cleaning (sweeping or rinsing with pressurized water) is necessary. 8. If markings are to be applied in any area where removal operations were conducted, ensure that the surface is clean and free of all debris to ensure a good bond of the coatings to the pavement. 9. After any paint removal or curing compound removal operation, the pavement becomes porous. The application of a primer or half coat, similar to a temporary marking application, is advisable to seal the pavement in order to keep the permanent coating from soaking into the porous pavement. The permanent coating must be a specified thickness to retain the required level of glass beads, and if part of it soaks into the pavement, glass bead embedment and retention may be compromised. 10. Inspectors should refer to the Field Inspection Guide when inspecting pavement marking removal operations on airfield pavement markings. Airfield Temporary Pavement Markings The removal of permanent markings (if applicable), the application of temporary markings, and the removal of temporary markings should be considered when developing project plans and specifications that include temporary markings. The following sections present methods of applying and removing temporary markings with the intent to minimize scarring or damage to the pavement and to minimize visibility concerns. Where available, results of research on various materials and methods are provided.
1-10 Airfield Pavement Markings: Effective Techniques for Removal and Temporary Applications Temporary Marking Methods The application of temporary markings typically follows the removal or concealment of permanent markings. The removal of temporary markings needs to be considered; they are often applied using paint at lower application rates than those of permanent markings. In situations where the temporary markings will be removed and the previous marking pattern will be reapplied, the previous markings can be covered in black paint or concealed with a physical barrier. Half Rate of Typical Paint Temporary markings are customarily applied with waterborne paint at a 30% to 50% coverage rate, but removal of temporary markings still often results in scarring on asphalt pavements. When paint is applied at lower coverage rates, glass beads typically will not adhere. Temporary markings not in compliance with FAA AC 150/5340-1 will require a Notice to Air Mission regarding any nonstandard marking (e.g., temporary markings without beads). If nighttime visibility of the markings is critical, glass beads and a standard paint should be applied. Specially Formulated Temporary Paint Specially formulated temporary paint is a viable method of applying temporary markings and is easier to remove than standard paint. Two types of temporary marking paint were devel- oped and applied at 230 SF/gal (50% of the usual rate). ⢠The first temporary coating was similar to the original waterborne TT-P-1952B, an early federal specification developed when waterborne paint was introduced. When tested, removal of a marking that used this coating required three passes with a UHP water blaster at 14,000 psi and one pass at 22,000 psi. The removal required pressures and passes similar to those needed to remove standard TT-P-1952F Type II paint and was therefore not considered a successful option. Scarring of the asphalt was similar between this specially formulated temporary paint and the standard paint. ⢠The second temporary coating (removable paint) contained a weaker resin designed to release more easily. The paint was very viscous but sprayed well through an airless paint machine. The marking was removed with a single UHP water-blasting pass at 14,800 psi without scarring or disturbing the crack seal. The ease of removal was considered a success. Curing Compound Under Temporary Markings Application of temporary markings over curing compound has been successful on concrete. However, the markings may flake off prematurely depending on the age of the curing compound and the duration of the temporary markings. Curing compound can be applied to asphalt prior to the application of temporary markings in an effort to improve removability of the temporary markings and reduce potential damage to the pavement. This process is not as successful on asphalt as it is on new concrete because the curing compound has to be applied thickly, and the temporary markings often flake off as the curing compound sheds. Black Paint Under Temporary Markings Similar to the application of curing compound, black paint can be applied prior to the applica- tion of temporary markings. In a test of this method, black paint was applied to asphalt surfaces where temporary white markings were to be installed. Removal of the white paint resulted in removal of the black paint as well, and the resulting scarring was similar to that of applications that did not have the black paint applied. For these reasons, there did not appear to be a benefit to applying black paint under temporary markings.
Airfield Guide for Engineers 1-11  Covering Permanent Markings While Temporary Markings Are in Service Concealing preexisting permanent markings is an option in areas where the markings will be located in the same place after the temporary markings are removed. Blacking out existing markings using temporary black paint can conceal the permanent markings for a temporary application. This will prevent damage to the pavement that could result from removal of the permanent markings. The black markings can then be removed or striped over to expose the permanent markings. The underlying markings must be in good condition to sustain removal of black paint and retain marking integrity. If the underlying markings are greater than 40 mils thick, they should be partially removed to reduce paint thickness prior to applying the black paint. Care must also be taken to completely cover glass beads in the underlying marking to prevent confusion during dark hours. If the permanent markings that are to be temporarily removed are in areas closed to traffic, then they can be physically concealed. As part of this project, an area of markings on asphalt runway was covered with black tarps and black sandbags (see Figure 1-4). Covering the majority of the markings with tarps and sandbags for a short duration was successful, although the method required constant monitoring of the tarps and sandbags. When the work was over, the markings were exposed and there was no resulting damage to the pavement. Temporary Pavement Marking: Surface Preparation If temporary markings are needed on new concrete surfaces, the installation of those markings over a curing compound will facilitate their removal when they are no longer needed. Additional information on curing compound is provided in the Curing Compound Under Temporary Markings subsection. If temporary markings are to be applied in an area where old markings were removed, all residue remaining from the removal operation must be thoroughly removed. Cracks and crevices in the removal scar can hold debris and prevent any new permanent or temporary coating from adhering. Temporary Pavement Marking: Installation Criteria The installation of temporary markings should meet applicable installation requirements. Typical requirements include the following: ⢠Color must meet the requirements for the specific marking type and location. ⢠Coverage of the material should be uniform. ⢠Glass beads should not be applied to temporary markings. The coating of temporary markings is too thin to embed and hold glass beads because it is applied at a 30% to 50% coverage rate. Figure 1-4. Markings temporarily covered with black tarps and black sandbags.
1-12 Airfield Pavement Markings: Effective Techniques for Removal and Temporary Applications ⢠If a temporary marking is required to be reflective, a full coverage rate using TT-B-1325D Type I glass beads should be used. ⢠If using removable paint, it should be applied under good weather conditions, prefer- ably during daytime hours. Because its formulation does not include the fast-drying solvents found in standard waterborne paint, removable paint requires at least one hour to dry at a temperature of 50°F or above with humidity below 85% and with a weather forecast of at least 12 hours with no rain. The coverage rate should be 230 SF/gal without glass beads. The paint equipment to be used should be clean in order to ensure that no other formulation is mixed with the temporary paint. Removal of Temporary Markings The process for removing temporary markings is similar to that used to remove permanent markings. Because temporary markings are almost always made up of thinly applied paint, they are usually easier to remove than thicker permanent markings. When removing temporary markings, the following items should be considered: ⢠To remove temporary markings made with standard waterborne material on concrete surfaces, UHP water blasting can be used; this technique produces minimal scarring. ⢠To remove temporary markings on an ungrooved surface, shot blasting or scarifiers can be used. ⢠To remove temporary markings made with standard waterborne material on asphalt surfaces, UHP water blasting at 22,000 psi at a rotation of 2,600 rpm on the bar and at a speed of 1 mph can be used. The tip array on the bar can range from 9 to 12 mm. A removal scar will likely be evident. ⢠To remove experimental paint Type 1, two passes with a UHP water blaster using between 14,000 and 16,000 psi have been successful; this is similar to the technique used to remove the TT-P-1952B formulation. Use of this technique leaves an evident removal scar. ⢠To remove paint designed with a weak resin, a single water-blasting pass using 14,800 psi has been shown to be successful; this technique leaves no scarring. The UHP water-blasting system used in the trial employed a 19-in. rotor bar with a tip array of eight 12 mm and ten 10 mm nozzles, with a maximum rotation speed on the bar. This left no scarring of the distressed pavement, and no crack seal was disturbed. The only evidence of the removal was a clean area where algae used to be, as can be seen in Figure 1-5. Such evidence could be removed by cleaning the algae in adjacent areas so that it would blend in with the area where markings were removed. ⢠To remove paint on pavement that is in good to excellent condition, scarifiers can be used on ungrooved pavement, and UHP water blasting can be used on grooved pavement. A darker surface can be expected where markings are removed using water blasting. Figure 1-5. Before and after the removal of experimental paint.
Airfield Guide for Engineers 1-13  Airfield Temporary Marking Best Practices Best practices for the application and removal of temporary pavement markings vary depending on the pavement surface and condition. A physical barrier to conceal markings that will go back into service after the temporary markings are removed should be considered on both PCC and ACC pavements. The following sections provide best practices for concrete and asphalt pavements. Best Practices on Concrete Pavements ⢠Apply temporary markings at a half (230 SF/gal) or full rate; include glass beads if reflective markings are required. ⢠If temporary markings will be in place for fewer than 30 days, apply the markings over curing compound or use removable paint. ⢠Use UHP water blasting on grooved or ungrooved surfaces, or shot blasting on ungrooved surfaces to remove temporary markings with the least amount of scarring. Best Practices on Asphalt Pavements ⢠If the pavement is in fair condition and grooved, use a temporary waterborne paint to avoid damage to the pavement that may result when the markings are removed. A seal coat should be included in the project to cover the area in the event that aggregate loosens. ⢠Apply removable paint under good weather conditions, preferably during daytime hours. The formulation of removable paint does not include the fast-drying solvents found in stan- dard waterborne paint. Removable paint requires at least one hour to dry at a temperature of at least 50°F or above with humidity below 85% and a weather forecast of at least 12 hours with no rain. Removal by water blasting at 14,800 psi should leave no scarring, even on poor pavement. Summary This airfield guide provides information to help engineers and others who are tasked with removing airfield markings from a variety of pavements using a variety of methods while also mitigating the appearance of scarring and reducing pavement damage. The guide includes best practices for efficient, safe, cost-effective, and environmentally acceptable techniques for marking removal and temporary marking applications. Following the best practices will help to ensure that marking removal plans, temporary marking specifications, and project plans will have the greatest chance of success. Well-developed project marking removal plans and specifications will help to minimize pavement damage, reduce confusion from marking removal areas, and improve subsequent marking application quality.
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