Chapter 5: Chip Seals

2.0 Project Selection

The general selection of preventive maintenance treatments was covered in Chapter 1.  Selecting a candidate pavement for a chip seal project is based on structural soundness and the types of distress present. The ability of a treatment to address the current condition of a project is paramount in selecting an appropriate treatment.  The main criteria addressed by the varying chip seal types are:

Table 2 lists appropriate binder/chip seal combinations for addressing various distress mechanisms. Generally, chip seals are not used on roads with AADT > 40,000.

The main advantages of chip seals include:

• Improved Skid Resistance: The irregular surface of chip seals improves the skid resistance of the existing road surface.
  
• Cost Effective Treatments: Chip seals are typically cost effective when properly placed on the right type of pavement.
  
• Good Durability: Chip seals wear well and can have long service lives.
  
• Ease of Construction: Chip seals are typically constructed rapidly and cause less traffic disruption than other treatments that take longer.

Table 2: Binder/Chip Seal Combinations for Addressing Specific Distress Mechanisms

Binder/Seal Combination	Distress Mechanism
	Raveling	Aged Pavements	Bleeding/Flushing	Load Associated Cracks	Water Proofing	Climate Associated Cracks	Heavy Traffic Volumes	Stone Retention	Improve Skid Resistance
PME/ Emulsion Single Course	Yes	Yes	No	No	Yes	No	Yes	Yes	Yes
PME/Emulsion Double Course	Yes	Yes	No	No	Yes	No	Yes	Yes	Yes
PME/Emulsion Sand	Yes	Yes	No	No	Yes	No	No (light)	Yes	No
PBA/ PG Binders Single Course	Yes	Yes	No	No	Yes	No	Yes	Yes	Yes
PBA/PG Binders Double Course	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
PBA/Sand	Yes	Yes	No	No	Yes	No	No	Yes	No
AR/CMCRA SAM	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Yes
Rejuvenating Emulsion	Yes	Yes	No	No	Yes	No	Yes	Yes	Yes

The main disadvantages of chip seals are:

• Cure Time: PME Depending on the climate, PME chip seals need several hours before they can tolerate unrestricted traffic.
  
• Loose Chips: Chip seals must be swept to remove excess stone to prevent broken windshields, vehicle damage, and hazards to motorcycles.
  
• Noise Considerations: Chip seals may increase noise where tires come in contact with the chip seal. The noise is audible by motorists and occupants of adjacent buildings.
  
• Weather Considerations: Chip seals using emulsions must be constructed during the daytime in warm, dry weather. Hot applied (non-emulsion) chip seals may be applied in cooler conditions and at night.
  
• Performance: Chip seals create a rough surface and are generally not used for parking lots. Chip seals do not always improve ride quality.

Other limitations of chip seals include:

• PME Emulsion Seals: These are not normally suitable for high volume intersections or high stress areas.
  
• PBA PG Emulsion Seals: These cure quickly because they are not emulsions, but are not suitable for very high stress areas due to their low initial shear strength.