PAVEMENT DISTRESSES Causes & Treatments 28-29/01/2015 PAVEMENT DISTRESSES Causes & Treatments Kyriacos Avlonitis/Civil Engineer-Nievelt Consultant B.Eng/Civil Engineering MScE /Road &Traffic Engineering Environmental Management NIEVELT ingenieur GmbH for Consulting and Supervising engineering in Roads & Housing Laboratory LTD

Part I: Pavement Maintenance and Preservation Chapter 1 Types of Maintenance Today's increasing budget constraints require that government perform more work with less money. Historically, the emphasis of local highway departments has been on building new roads, but the new focus is on maintaining and preserving existing pavement surfaces. This shift has resulted in three types of pavement maintenance operations:   Preventive Maintenance Corrective Maintenance Emergency Maintenance

Pavement Preservation Critical elements of a successful pavement preservation program are: 1. selecting the roadway 2. determining the cause of the problem 3. identifying and applying the correct treatment(s) 4. determining the correct time to do the needed work 5. observing performance The program can then be adjusted according to the results.   Preventive maintenance activities can include conventional treatments such as crack sealing, chip sealing, fog sealing, rut filling, and thin overlays. They can also include emerging technologies such as ultra-thin wearing courses, very thin overlays, and microsurfacing applications. Aside from crack treatments, all of these treatments leave the pavement with a new wearing surface. A fog seal provides a new wearing surface, although it generally has a lower friction number than the original surface.

Keys to a Successful Program Education: To implement a pavement preservation program effectively, elected officials, top management, and maintenance staff should be educated about pavement preventive maintenance, why it is needed, and why it should be a priority. This education should stress that it is more economical to preserve pavements in good condition than it is to replace them when they wear out. Highway agency professionals need to develop a better understanding of the benefits of a program and the differences among preventive, corrective, and emergency maintenance. The general public also should be educated about pavement preservation.

Comparison of traditional pavement rehabilitation and pavement preservation maintenance strategies

Philosophy: Developing a preventive maintenance program requires a shift in thinking, from rehabilitation and reconstruction to preservation. Timing: Treatments must be applied in time to preserve the structure of the pavement. Distressed pavements may not be suitable candidates for preventive maintenance. Funding: An effective preventive maintenance program requires adequate funding. Criteria need to be established for the selection of pavements that qualify for preventive maintenance, and this policy must be enforced.

Emergency Maintenance Corrective Maintenance Corrective maintenance differs from preventive maintenance primarily in cost and timing. While preventive maintenance is performed when the pavement is still in good condition, corrective maintenance is performed when the pavement is in need of repair, and is therefore more costly.   Emergency Maintenance This maintenance activity may be performed during an emergency situation, such as when a blowout or severe pothole must be repaired immediately, generally for safety reasons, or to allow for traffic to use the roadway. Emergency maintenance also describes those treatments that hold the surface together until a more extensive rehabilitation or reconstruction treatment can be accomplished.

Chapter 2 Treatment Selection   Pavement distresses contribute to pavement failure in different ways. The most common flexible pavement distresses are cracking, roughness, weathering, raveling, rutting, and bleeding. If the distresses identified in a pavement arc related to structural deficiencies, the pavement section is most likely not a candidate for preventive maintenance treatment, and should instead be scheduled for rehabilitation or reconstruction. Other distresses can be corrected with preventive, corrective, or emergency treatments. To be effective, an engineering approach should be taken to select and construct the treatment. It is critical that the proper maintenance treatment be done at the right time for the pavement to function as designed and for the maintenance program to be effective.

1. Does the treatment enhance pavement performance? Determining a Treatment's Cost-Effectiveness The decision process should include the following three questions, asked and answered in the following order:  1. Does the treatment enhance pavement performance? 2. Is the treatment cost-beneficial? 3. What is the best treatment method to use? Selection Factors  By removing normal biopolitics, and other subjective factors, pavement management systems enable users to determine the most cost-effective treatment. The selection is generally based on factors including: • existing pavement type • availability of qualified staff and contractors • crack condition • availability of quality materials • type and extent of distress • time of year of placement • roadway use and level of traffic • facility downtime • climate and environmental factors • pavement noise • traffic loading • surface friction • cost of treatment • expected life

Types of Maintenance Treatments Crack repair: A localized treatment method used to prevent water and debris from entering a crack, which might include routing to clean the entire crack and to create a reservoir to hold the sealant. It is only effective for a few years and must be repeated. However, this treatment is very effective at prolonging the pavement life. Includes the following three crack repair methods: Clean and seal: Used on all types of cracks, it involves using a hot air lance or compressed air to blow out the debris in the crack, then filling with a sealant. Saw and seal: Involves using a pavement saw to create transverse joints at regular intervals along a newly placed pavement, then filling with a sealant. Rout and seal: Used on transverse and longitudinal cracks. Involves using a pavement saw or router to create a reservoir centered over existing cracks, then filling with a sealant.

Crack filling: Differs from crack sealing mainly in the preparation given to the crack prior to treatment and the type of sealant used. Crack filling is most often reserved for more worm pavements with wider, more random cracking. Full-depth crack repair: A localized treatment method to repair cracks that are too failed to benefit from sealing. Secondary cracking requires the reestablishment of the underlying base materials. Fog seal: An application of diluted emulsion (typically at a rate of 1:1) to enrich the pavement surface and delay raveling and oxidation. Considered a temporary treatment. Seal coat: Used to waterproof the surface, seal small cracks, reduce oxidation of the pavement surface, and improve friction.

Double chip seal: An application of two single seal coats Double chip seal: An application of two single seal coats. The second coat is placed immediately after the first. This treatment waterproofs the surface, seals small cracks, reduces oxidation of the pavement surface, and improves friction. Slurry seal: A mixture of fine aggregate, asphalt emulsion, water, and mineral filler, used when the primary problem is excessive oxidation and hardening of the existing surface. Slurry seals are used to retard surface raveling, seal minor cracks, and improve surface friction. Microsurfacing: Commonly referred to as a polymer-modified slurry seal; however, the major difference is that the curing process for microsurfacing is a chemically controlled process, versus the thermal process used by slurry seals and chip seals. Also may be used to fill ruts. Thin hot-mix overlays: includes dense, open, and gap-graded mixes that improve ride quality, reduce oxidation of the pavement surface, provide surface drainage and friction, and correct surface irregularities. Pothole patching: Includes using cold- and hot-asphalt mixture, spray injection methods, as well as slurry and microsurfacing materials, to repair distress and improve ride quality.

Part II: Recommended Treatment Practice  

Chapter 3 Crack Causes & Treatments Flexible Pavement Distresses Flexible pavement surface distresses include a wide variety of pavement defects that generally fall into the following categories:  I. Cracking A. Alligator B. Edge C. Longitudinal D. Random/Block E. Transverse II. Raveling/Weathering III. Distortion IV. Rutting V. Excess Asphalt

✔ Insufficient pavement structure ✔ Inadequate base support I. Cracking A. Alligator Cracking 1. Description Alligator cracking is a series of interconnected cracks in an asphalt layer forming a pattern, which resembles an alligator’s hide or chicken wire. The cracks indicate fatigue failure of the asphalt layer generally caused by repeated traffic loadings and this distress allows water to penetrate the surfacing materials and subgrade, which furthers the damage. Alligator cracking, also called fatigue cracking, usually first begins as a single longitudinal crack in the wheel path. 2. Possible Causes ✔ Insufficient pavement structure ✔ Inadequate base support ✔ Poor base drainage ✔ Aging and traffic loading  

Low - Longitudinal disconnected hairline cracks no greater than 3,17mm wide.

Moderate - Longitudinal cracks in wheel paths forming an alligator pattern. Cracks may be lightly spalled and about 3,17 to 6,35mm wide.

High - Pieces appear loose with severely spalled edges; cracks are 6,35mm or greater and pumped fines may appear on the surface

B. Edge Cracking 1. Description Edge cracking is similar to alligator cracking only located within 0,30 to 0,60 m of the edge of the pavement. Failure begins at the edge of the pavement and progresses toward the wheel path. Pavement edge distress can result in worsening of the wheel path condition and allow moisture into the subgrade soils and base materials. Edge cracking also includes the longitudinal cracking associated with concrete base course widening. 2. Possible Causes ✔ Traffic Loading ✔ Environmental ✔ Construction Related ✔ Low Shoulder ✔ High Shoulder Holding Water

Low - Hairline cracks just beginning to show; random with no pattern may be up to 3,17mm wide.

Moderate - Cracks 3,17- to 6,35 mm located 0,30 to 0,60 m from the edge of the road may have an alligator pattern.

High - Cracks greater than 6,35mm may have loose or missing pieces or potholes or alligator cracking.

C. Longitudinal Cracking 1. Description Longitudinal cracking denotes cracks that run predominantly parallel to the centerline. These cracks may be in the wheel paths, between wheel paths and at lane joints such as centerline or shoulder/surface. 2. Possible Causes ✔ Traffic Loading (wheel path cracks) ✔ Environmental (frost action) ✔ Improper Construction Practices (joint cracks) ✔ Poor Drainage ✔ Reflection Cracks

Low - Hairline crack(s) running parallel to centerline.

Moderate - Cracks parallel to centerline are about 3,17mm wide

High - Single cracks are wider than 3,17mm

D. Random/Block Cracking 1 D. Random/Block Cracking 1. Description Random or block cracks divide the pavement into rough, approximately rectangular pieces and typically occurs at uniformly spaced intervals. 2. Possible Causes ✔ Environmental (thermal) ✔ Aging

Low - Hairline cracks, essentially transverse but may connect to Longitudinal spacing of 15 to 30 m.

Moderate - Cracks range from hairline to 3,17mm wide and may be slightly spalled.

High - Cracks greater than 3,17mm wide that are random or have a block pattern, similar to a turtle shell.

E. Transverse Cracking 1. Description Transverse cracks are those considered to extend three-fourths of the width of the pavement or more, generally perpendicular to centerline. 2. Possible Causes ✔ Environmental (thermal) ✔ Swelling or shrinkage of the subgrade ✔ Reflection cracks ✔ Settlement (trench, backfill)

Low - Hairline to 6,35mm wide cracks perpendicular to centerline with no distortion.

High - Cracks 12,7 to 50,8mm wide larger cracks often are spalled and/or have noticeable distortions near them. Cracks greater than 50,8mm wide and causing extremely rough ride are rated “X”

II. Raveling/Weathering A. Description Raveling is the progressive wearing away of the pavement from the surface downward caused by the loss of asphalt binder and the dislocating of aggregate particles. B. Possible Causes ✔ Poor mixture quality ✔ Asphalt hardening due to aging ✔ Insufficient asphalt content ✔ Improper construction methods

Low - Minimal loss of aggregate or binder.

Moderate - Some aggregate loss small areas may be stripped away.

High - Sections greater than one square foot may be pitted, stripped or eroded away

III. Distortion² A. Description Distortion is defined as that distress in the pavement caused by densification, consolidation, swelling, heave, creep or slipping of the surface or foundation. B. Possible Causes ✔ Inadequate support or overloading ✔ Thermal and moisture stresses(freeze-thaw) ✔ Loss of bonding between base layer and surface layer ✔ Static load (depressions) ✔ Soft AC (Asphalt Concrete) ² No longer rated separately by Pavement Management personnel.

Low - Slight waves, sags, humps, corrugations or wash boarding of the pavement.

Moderate - Similar to low except distortions can be felt while riding in a vehicle.

High - Shoving and major changes in pavement profile that require vehicles to slow from normal speeds.

IV. Rutting A. Description A rut is a surface depression in the wheel path after pavement layers or subgrade deform from traffic load applications. B. Possible Causes ✔ Poor mixture quality ✔ Insufficient support ✔ Improper construction procedures

Low - Depressions in the wheel path less than 3,17 mm.

Moderate - Wheel path depressions of 6,35 to 12,7 mm.

High - Wheel path depressions greater than 12,7 mm.

V. Excess Asphalt A. Description Excess asphalt, also called bleeding or flushing, is used to describe a free film of asphalt on the surface of the pavement that creates a smooth, shiny, greasy, and reflective surface. It is usually found in the wheel paths and becomes quite sticky when hot. B. Possible Causes ✔ Mixture problems (bad oil, stripping aggregate, low air voids, high AC content, etc.) ✔ Improper construction practices ✔ Paving over excess asphalt

Low - Intermittent films of bituminous material create a shining, reflective surface.

Moderate - Large areas or continuous strips of bituminous films where little, if any, aggregate can be seen.

High - Excess bituminous material appears wet and actually liquefies during hot weather.

Pavement Treatments ¹ Based on recommendations of the eight District Maintenance Superintendents and Materials & Research Division. Treatments are listed based on the frequency with which they were selected. Only treatments shown are those which were selected by more than two of the group. Other possible treatments are listed on the pages showing the distresses. ² Effectiveness of treatments other than 13, 14 & 15 will be minimal and short-lived. Pavement Extension Program (PEP) projects are typically 50,8 mm thick and are considered the maximum thickness of this treatment. 1 Do Nothing 9 Cold-in-place Recycle 2 Crack Seal/Fill 10 Hot-in-place Recycle 3 Fog Seal 11 Thin Cold Mix Overlay 4 Scrub Seal (Broom Seal) 12 Thin Hot Mix Overlay3 5 Slurry Seal 13 Patching 6 Chip Seal/Armor Coat 14 Thick Overlay 7 Micro Surfacing 15 Total Reconstruction 8 Mill

Remaining adhered to the walls of the crack, Crack Sealing Crack sealing and filling prevent the intrusion of water and incompressible materials into cracks. The methods vary in the amount of crack preparation required and the types of sealant materials that are used. Crack sealing is the placement of materials into working cracks. Crack sealing requires crack preparation and often requires the use of specialized high quality materials placed either into or above working cracks to prevent the intrusion of water and incompressible materials. Crack sealing is generally considered to be a longer-term treatment than crack filling. Due to the moving nature of working cracks a suitable crack sealant must be capable of: Remaining adhered to the walls of the crack, Elongating to the maximum opening of the crack and recovering to the original dimensions without rupture, Expanding and contracting over a range of service temperatures without rupture or delimitation from the crack walls, and Resisting abrasion and damage caused by traffic.

Remaining attached to the walls of the crack, Crack Filling Crack filling is the placement of materials into nonworking or low movement cracks to reduce infiltration of water and incompressible materials into the crack. Filling typically involves less crack preparation than sealing and performance requirements may be lower for the filler materials. Filling is often considered a short-term treatment to help hold the pavement together between major maintenance operations or until a scheduled rehabilitation activity. Crack filling is for active or non-active cracks created by ageing of the binder. Such cracks are not completely inactive and require some flexible characteristics. A suitable filler material must be capable of: Remaining attached to the walls of the crack, Possessing some elasticity, and Resisting abrasion and damage caused by traffic.

Table 1: FHWA Criteria for Crack Sealing or Filling

Figure 9 Traffic Load Effects on Crack Growth (Roberts, 1996) Figure 8 Thermal Effects on Crack Growth (Roberts, 1996)

Treatment Failures Treatment failures can be attributed to improper treatment selection, improper material selection, poor workmanship, and improper application or lack of post-treatments. Common treatment failures include: Adhesion loss: The sealant does not adhere to the sides or bottom of the crack. Cohesion loss: The sealant fails in tension by tearing. Potholes: The crack is not completely sealed, allowing water into the pavement. Continued corrosion leads to pumping and pothole formation. Spalls: The edges of the crack break away as a result of poor routing or sawing. Pull-on: The sealant is pulled out of the crack by tire action. Treatment Effectiveness The first step in determining a treatment’s effectiveness is establishing how much of the treatment has failed in relation to the total length of treatment applied (% failure). Once the amount of treatment failure is determined, the treatment’s effectiveness can be calculated using the following expression (4). Effectiveness = 100 - % failure Where: % Failure = 100 X [Length of Failed Treatment / Total Length of Treatment]

By routinely monitoring treated areas, a graphical representation of a treatments’ effectiveness can be generated like the one shown in Figure 10. From this figure, the projected life of the treatment used on this cracked area can be projected as the time at which the effectiveness has dropped to 50% (as defined above). Graphs like these can be used to determine when additional treatments may become necessary. Figure 10 Treatment Effectiveness (FHWA, 1999)

Cost Effectiveness The cost effectiveness of a treatment can be determined readily once the treatment effectiveness has been determined. Cost effectiveness is the total cost of a treatment divided by its effectiveness. Cost effectiveness may be converted into an annual cost by dividing the cost effectiveness by the number of years required to reach 50% effectiveness.

MATERIALS Crack Sealing and Crack Filling - Moisture entering the lower layers of the pavement structure will weaken the pavement structure and is the primary cause of pavement corrosion. An effective crack filling/sealing program will prolong pavement life by preventing moisture and incompressible material from filling the crack. The FAA AC 150/5380-6B considers crack sealing and filling as the same procedure. This AC provides four guide specifications for crack filling: • M-361, Hot–Applied Joint and Crack Sealants for Rigid (Portland Cement Concrete) and Flexible (Bituminous) Pavements. • M-462, Cold-Applied Joint and Sealants for Flexible (Bituminous) Pavements. • M-362, Silicone Joint and Crack Sealants for Rigid and Flexible (Bituminous) Pavements. • M-461, Hot-Applied Crack Sealants/Fillers with Fibers for Flexible (Hot-Mix Asphalt) Pavement Overlays.

In contrast, CALTRAN’s Maintenance Technical Advisory Guide (TAG) considers crack sealing and crack filling as two different maintenance methods. The two methods vary in the amount of crack preparation and type of sealant. Crack sealing is more expensive and lasts longer than crack filling. Table 2 summarizes the various crack sealants and fillers with approximate costs and service lives. Crack sealing is a localized treatment method that places specialized material in “working cracks” – primarily transverse cracks and longitudinal cracks that expand during the winter and contract during the summer. The key characteristics of the crack sealant material are: 1) adherence to the walls of the crack over a range of service temperatures and 2) ability to stretch during periods of crack contraction and recover to original condition without rupture. The cracks are either sawed or routed (which is not commonly done in California) to create a reservoir 0,15 to 0,22 mm wide and approximately 0,22 mm deep for the sealant. Crack filling is also a localized treatment method that places specialized material in “nonworking cracks” – primarily bock cracks and most longitudinal fissures. Crack filling involves less crack preparation and less expensive sealant material.

Table 2: Crack Sealer and Filler Specifications

MATERIAL PLACEMENT METHODS  STORAGE AND HANDLING OF MATERIAL Hot pour materials require very high temperatures, typically between 188 to 200°C (370 to 390°F) . These materials may degrade or cross link when exposed to excessive temperatures for long periods of time. For this reason, the manufacturer’s recommendations must be followed exactly. MATERIAL PLACEMENT METHODS Once a suitable seal or fill material has been selected, as set forth in Caltrans Standard Special Provisions SSP 37-400 , the appropriate placement method must be determined. Placement methods vary according to the nature of the distress. When selecting the placement method, one should consider the method’s applicability to: the type of distress, the dimensions of the crack channel the type of crack channel (cut or uncut), and the finish requirements.

Flush Fill Method In the flush fill method, fill material is forced into an existing uncut crack. Once filled, the crack is struck off flush with the pavement. Figure 11 illustrates the flush fill method. Overband Method In the overband method, fill material is forced into and placed over an uncut crack. If the fill material is squeegeed flat, it is referred to as a ‘Band-Aid if not it is referred to as capped. Overbanding and capping should not be done if silicone has been chosen as the fill material. This is due to silicone’s poor abrasion resistance. Figure 12 illustrates the overband method with both finishing options.

if material is left above the surface if material is left above the surface. Overbanding can create a rough ride and/or excess road noise and causes problems when placing subsequent overlays. Reservoir Method In the reservoir method, the crack is cut or routed to form a reservoir that is filled with a sealant. The sealant may be left flush or slightly below the surface of the reservoir. The depth and width of the reservoir varies according to job requirements. Saw depths will be greatest when working with very active cracks and cracks in PCC pavements. Crack cutting will often depend on the number of cracks and whether the cutter can follow the shape of the crack. Typical reservoir widths range from 12 to 25 mm (0.5 to 1.0 in), and even up to 38 mm (1.5 in) in very cold climates. Reservoir depth ranges from 12 to 25 mm (0.5 to 1.0 in). Reservoir use is appropriate for pavements in good condition, without extensive cracking amounts. Crack cutting units, when operated by trained, experienced personnel, can follow meandering random cracks. Figure 13 illustrates the reservoir method.

Combination Method: Sand Fill with Recessed Finish Combination Method: Reservoir with Band-Aid This combination method involves the formation of a ‘Band-Aid’ over the top of a cut reservoir. Figure 14 illustrates the combination method. Like the overband method, the combination method should not be used with materials that are prone to pickup due to traffic or materials with poor wearing characteristics . The combination method can be used on heavily trafficked roads, but care must be taken to squeegee excess material off the surface. Combination Method: Sand Fill with Recessed Finish Thermal cracking can develop over time and penetrate the full depth of asphalt pavement in a roadway. As thermal cracks progress down through the asphalt layers, they typically continue to widen and it is not unusual for such cracks to be 12 to 25 mm (0.5 to 1 in) or wider and exceed 102 mm (4 in) in depth. If these types of cracks are sealed or filled full depth, the large volumes of filler or sealer tend to soften and migrate under loads in hot weather, and begin to pull out under traffic. If an overlay is applied, the heat of the new mat will draw the filler and sealer materials up through the overlay. In areas with heavy sealer or filler applications, fat spots, flushing, and shoving in the overlay can occur. These symptoms can only be remedied by changes in construction procedures or the removal and replacement of the affected materials.

Sealant application should not exceed 25 mm (1 in) in depth Sealant application should not exceed 25 mm (1 in) in depth. For full depth wide cracks, backer rod can be used to limit sealant depth. Another method that can be used is to partially fill the crack with sand. Blow out any debris with air, fill the crack with clean sand to a point approximately 19 to 25 mm (0.75 to 1 in) below the adjacent pavement surface, and tamp lightly as needed with a steel rod or piece of rebar to reduce any large voids in the sand. Then apply the crack sealer over the top of the sand and along the crack faces, the surface of the sealant should be cupped slightly below the adjacent pavement surface. This recessed finish allows some movement of the crack and sealer material without creating an undesirable hump on the surface. This fills and seals the deep wide crack while limiting the impact on subsequent paving operations. Figure 15 illustrates this combination method.

Backer Rod (PCC Pavements) Joint sealing applications for PCC (Portland Cement Concrete) pavements may require the incorporation of a backer rod or bond breaker. The backer rod, typically polyethylene foam, is placed within a crack or joint to prevent the sealant from sticking to the reservoir bottom and to restrict the sealant depth to the upper portion of the joint. A backer rod is also incorporated in very large cracks or joints and when silicone is being used. Currently, Caltrans does not use self-leveling silicones. A backer rod is only used if it is cost effective and the cracks are relatively straight like those occurring in PCC joints. Figure 16 shows three typical backer rod configurations.

2.4 SELECTING THE APPROPRIATE PLACEMENT METHOD The appropriate placement method should be based on the governing considerations of the project. Governing project considerations include: Type and extent of the sealing or filling operation, Traffic conditions, Crack characteristics, Material requirements, Desired performance (expectations), Aesthetics, and Cost.

* Ride Quality is an important consideration Table 3 outlines method placement issues in relation to governing project Table 3: Placement Method Considerations * Ride Quality is an important consideration

EQUIPMENT REQUIREMENTS CONSTRUCTION SAFETY AND CONTROL The Resident Engineer (RE) can examine and approve the contractor’s traffic control plan prepared. The signs and devices used must match the traffic control plan. The work zone must conform to Caltrans practice and requirements set forth in the Caltrans Safety Manual and the Caltrans Code of Safe Operating Practices. All workers must have all required safety equipment and clothing. Signage shall be removed when it no longer applies. EQUIPMENT REQUIREMENTS Equipment requirements vary according to the treatment method chosen. Equipment may be required for: • Routing or Sawing • Crack Cleaning and Drying, • Backer Rod Placement (PCC Pavements), • Application of Sealer or Filler, • Finishing Method, and • Trafficking and Subsequent Treatments. .

CLIMATIC CONDITIONS Crack sealing treatments should be placed when the cracks are at their midpoint to maximum point of expansion. This is not always practical since cracks are at their maximum point of expansion during the coldest months. Most crack fillers and sealants have limitations to their ability to wet and form films at low temperatures. This is due to either a high viscosity or the fact that they are emulsified. Additionally, winter climates make working conditions difficult and in some regions impossible. Bearing these considerations in mind, the fall is typically the best time for application. At this time air temperature are typically between 7°C and 18°C. Under these conditions, cracks are usually at or near their mid-point of movement, which helps to ensure that the crack sealant or filler will not be extended or compressed too much when temperatures increase or decrease, respectively, following application of the sealant or filler. In addition, application during the fall (i.e., at moderate temperatures) ensures that temperatures have not dropped to a point where sealants will have difficulty wetting the crack walls or forming continuous films. In colder climate areas, spring and fall work conditions are required to allow workers to properly prepare the pavement surface and install products

PREPARATION Site preparation requirements vary according to the sealing or filling method and materials chosen for the project. The following paragraphs describe site preparation in further detail. Routing or Sawing When routing or sawing is incorporated, cracks need to be cleaned and dried prior to application of the filler or sealant. When pavements are cracked extensively, routing or sawing of cracks may not be appropriate. Crack cutting becomes especially important in climates where crack movement is very high. Crack cutting allows more filler to be used and provides better control of the crack channel shape. Secondary cracks along the primary crack are not usually routed. Routing is generally not used in HMA or PCC pavements . Crack cutting and routing equipment includes vertical spindle routers, rotary impact routers, and random crack saws. Damage to the pavement should be kept to a minimum by clean cutting. The use of carbide bits improves the quality of cutting and typically produces clean reservoir cuts.   Figure 17 illustrates a rotary impact router in use. Figure 17: Crack Routing Operation

Cleaning and Drying Debris left in a crack, resulting from sawing, routing, or pavement use will affect the adhesion of the sealant or filler. Debris also contaminates the sealing or filling material and reduces cohesion. Reduced adhesion or cohesion normally results in early failures. To avoid these contamination-related failures, sawed or routed cracks must be cleaned prior to being treated. Several cleaning methods can be used, including: • Air blasting, • Hot air blasting, • Sand blasting, and • Wire brushing.

FINISHING Finishing techniques will vary depending on the application and type of material chosen. Flush finishes and overbanding methods require the use of a squeegee. In some cases, a preformed plate on a hand lance assists in making the required flush result. Figure 21 shows three typical flat finishing techniques. As stated earlier, all sealant left on the surface shall be squeegeed to prevent a rough ride and is the only method recommended.

Blotter coats of clean sand are usually used with emulsion crack filling to prevent pick-up of an overband. A blotter coat is often used to prevent pick-up upon re-opening to traffic. To ensure a high quality blotter coat, only clean and dry sand should be used. Figure 22 illustrates the brooming of a blotter coat over a treated crack. This practice is not recommended by Caltrans as it leaves broom marks and voids in the sealant.

JOB REVIEW -QUALITY ISSUES Quality issues are typically related to the poor choice of sealing and filling methods and poor workmanship. Common examples of poor sealing and filling methods include excessive use of sealant and multiple uses of treatments over several years. One common example of poor workmanship includes over-filling without proper finishing. Figures 23 through 25 illustrate these commonly addressed quality issues. These practices directly impact traffic safety, smoothness and appearance for users.

TROUBLESHOOTING This section provides information to assist the maintenance personnel with troubleshooting problems with crack sealing and crack filling projects. TROUBLE SHOOTING GUIDE The troubleshooting guide presented in Table 4 associates common problems to their potential causes. For example, a sealant separating from the sides of a crack may be caused by application to a wet crack surface, dirty crack surface, poor material finishing technique, application of cold sealant, insufficient material, rain during the application, or application during cold weather.

Table 4: Trouble shooting Crack Sealing and Filling Projects

•Reduse the amount of sealant or filler being applied. In addition to the troubleshooting guide, Table 5 lists some commonly encountered problems and their recommended solutions. Table 5: Common Problems and Related Solutions Problem Solution TRACKING •Reduse the amount of sealant or filler being applied. •For hot applied materials, allow to cool ore use sand or other blotter.   •Allow sufficient time for emulsions to cure or use a sufficient amount of sand for a blotter coat. •Ensure the sealer/filler is appropriate for the climate in which it is being placed PICK OUT OF SEALER •Ensure crack are clean and dry •Increase temperature of application •Use the correct sealant for the climate •Allow longer cure time before trafficking BUMPS •Check squeegee and ensure it is leaving the correct flush finish •Have squeegee follow more closely to the application •Decrease the viscosity of the sealer •Change the rubber on the squeegee

Rigid Pavement

Rigid Pavement Typical Cross Section

Rigid Pavement Treatments Types of distresses in Rigid pavements include: A. Joint Distress B. Faulting C. Transverse Cracks D. Pattern Cracking E. Surface Distress F. Slab Cracking

Joint Distress Corrosion of the concrete within 2 feet on either side of a joint. Breaking or chipping of the pavement joints usually results in fragments with feathered edges.

Low - A few hairline cracks from the joint and/or discoloration at the joint.

Moderate - Frequent hairline to 3,17mm cracks radiating from the joint forming a web like pattern.

High - Cracks 3,17mm or larger forming multiple patterns and often having a white appearance.

Faulting Differential vertical displacement of a slab or other member adjacent to a joint or crack. Faulting may be either longitudinal or transverse and creates a “step” deformation of the pavement surface.

Low - Less than 3,17mm vertical displacement between adjacent panels.

Moderate - Displacement of 3,17 to 6,35mm between adjacent panels.

High - Displacement greater than 6,35mm between adjacent panels

Transverse Cracks Cracks that run perpendicular to centerline, resulting in a panel that is broken into two or more pieces.

Low - Hairline to 6,35mm wide cracks extending the full width of a panel.

High - Transverse cracks greater than 6,35mm wide extending the full width of panel.

Pattern Cracking Occasional to extensive interconnected cracks that may appear anywhere within a panel but do not extend throughout the entire depth of the slab.

Low - Negligible or occasional interconnecting 1,58 mm wide or less cracks.

Moderate - Interconnected cracks between 1,58 to 3,17 mm wide throughout the panel.

High - Occasional to extensive interconnecting cracks 3,17 mm wide or greater. Spacing between cracks is usually only a few inches

Surface Distress Scaling, spalling, chipping or disintegration of the concrete wearing surface that leads to roughness and poor durability.

Low

Moderate

High

Slab Cracking Unplanned longitudinal or diagonal structural crack(s) that extend through the depth of the slab

Low - Hairline, single structural cracks in a panel that may be longitudinal or diagonal in nature and extend from joint to joint.

Moderate - Two or three major structural cracks with no faulting or displacement.

High - Multiple structural cracks or cracks with evidence of faulting, displacement or spalls.

Rigid Pavement Distresses Table 1 : Rigid Pavement Maintenance Decision Matrix Rigid Pavement Distresses Low Moderate High Occasional Frequent Joint Distress 1,2 2,3 3,4 Faulting 1 6,4,1 6,4 Transverse Cracks NR* 2,8,4 Pattern Cracking 1,4 Surface Distress 3,8,4 Slab Cracking 2 2,4 2,7 2,7,4 3,9 * Not Rated ** Measured as square feet/panel Pavement Treatments 1.Do Nothing 2.Crack & Joint Seal/Fill 3.Partial/Full Depth Slab/Joint Repair 4.Thin Hot Mix Overlay ( 1 ½” ) 5.Mud jacking 6.Diamond Grinding 7.Cross Stitching 8.Slab Replacement 9.Thick Hot Mix Overlay

Low - Hairline to 6,35mm wide cracks extending the full width of a panel.

High - Transverse cracks greater than 6,35mm wide extending the full width of panel.

Table 2: Crack Sealer and Filler Specifications

Thin hot-mix overlays includes dense, open, and gap-graded mixes that improve ride quality, reduce oxidation of the pavement surface, provide surface drainage and friction, and correct surface irregularities.