MODULE 3-2 Crack Sealing

Learning Objectives  Describe the primary sealant types  Describe the major factors that affect performance  Describe conditions best-suited for crack sealing  Describe procedures for crack sealing/resealing in HMA pavements  List safety considerations

Introduction  Crack sealing is applied to  Preserves the intended design life  Extend the service life of the existing HMA by reducing moisture infiltration  Prepare the existing pavement prior to construction of an HMA overlay

Do you seal or not, what is your practice?

Sealant Types  Thermoplastic sealant materials – common for HMA application  Thermosetting sealant materials – not commonly applied for HMA pavements  See Table 3-2.1

Thermoplastic Sealant Materials  Bitumen-based materials (e.g., ASTM D 3381, D 3405, D 1190, D 244)  Typically soften upon heating and harden upon cooling  Hot Applied  Cold Applied  Material cost: $0.10 – 2.00 per kg  Installed cost: $1.00/m

Thermosetting Sealant Materials  One or two-component materials  Set obtained by  Chemically cured  Solvent release  Material costs: $2.00 – 8.00 per kg  Installed costs: $2.00 – 5.00/m

Purpose and Application  Reduce moisture infiltration  Stripping, cupping, delamination  Reduce incompressibles filling cracks  Application - HMA pavement

Limitations and Effectiveness  Continuing debate regarding the cost effectiveness of crack sealing  SHRP experiments SPS-3 examined the effect of sealing activities on pavement performance  Crack sealing performed well except in dry regions of U.S.

Limitations and Effectiveness  General consensus among states that supports sealing cracks as a cost effective rehabilitation or maintenance treatment  66% of States seal cracks in HMA pavements

Is Crack Sealing Effective Here?  Do you seal by policy or by effectiveness?  What sealant is most effective for your climate, materials, and traffic?  How do you pick candidate projects?  Overlay  Preventive Maintenance  What effect on pavement life?

Design Considerations  Climate conditions  Highway classification  Traffic level and % trucks  Pavement condition and planned rehabilitation  Crack characteristics  Materials and placement configuration  Procedures, equipment, and safety

Would You Seal This?

Design Considerations  Two different procedures are now defined (SHRP-H-348)  Crack sealing: working cracks with movement ≥ 2.5 mm (0.1 in)  Crack filling: non-working cracks

Factors Affecting Performance  Candidate pavement  Sealant  Configuration  Preparation  Application  Quality control

Ideal Application Conditions  New or recently rehabilitated surface  Good base support  Little or no secondary cracking  Little or no raveling at crack face  Cool weather (fall or spring)  Proper preparation (clean and dry)

Placement Configurations Reservoir Material Crack Standard Reservoir And Flush Material Crack Simple Flush Fill

Placement Configurations Standard Reservoir And Recess Material Crack Recess Reservoir Material Crack Cap Capped

Placement Configurations Material Crack Deep Reservoir- and-Recess Reservoir Material Crack Band-Aid Shallow Recessed Band-Aid Backer Rod

Placement Configurations Material Crack Band-Aid Simple Band-Aid Reservoir Material Crack Band-Aid Standard Recessed Band-Aid

Cost Considerations  Amount of crack to be filled, sealed  Type of crack filler, sealer  Material costs: $0.10 to $8.00 per kg  Equipment and personnel required  Estimated performance of crack fill or seal  Method of payment – lf of cracks or pounds of sealant  Installed cost: $1.00 to $5.00+/m

Construction Sequence  Crack sealing  Crack filling

Crack Sealing  Crack refacing  Crack cleaning  Sealant installation

Vertical Spindle Router

Rotary Impact Router

Airblasting

Hot Compressed Air Lance

Excessive Hot Air Lance

Squeegeed Sealant

Finished Crack Seal

Crack Filling  Crack cleaning  Sealant Installation

Safety  Traffic  Hot Materials  Noise  Flying debris  Air quality  Pavement friction

Review  What are the primary sealant types?  What are the major factors that affect performance?  What are the conditions necessary for best performance of the pavement and crack sealant?  What are the major steps in the crack sealing/resealing for HMA pavements?  List three safety considerations in the crack sealing operation?

Key References  Hand, A. J., et. al “Cost-Effectiveness of Joint and Crack Sealing: Synthesis of Practice.” Journal of Transportation Engineering. November/December Volume 126, Number 6. American Society of Civil Engineers, Reston, VA.  Smith, K. L. and A. R. Romine LTPP Pavement Maintenance Materials: SHRP Crack Treatment Experiment, Final Report. FHWA-RD Federal Highway Administration, Washington, DC.

Key References  Smith, K. L., and A. R. Romine Materials and Procedures for Sealing and Filling Cracks in Asphalt-Surfaced Pavements – Manual of Practice. FHWA-RD Federal Highway Administration, Washington, DC.