05: Microsurfacing Application Checklist
This checklist is one of a series created to guide State and local highway maintenance and inspection staff in the use of innovative pavement preventive maintenance processes. The series is provided through the joint efforts of the Pavement Preservation Program of the Federal Highway Administration (FHWA) and the Foundation for Pavement Preservation (FP2).
FHWA uses its partnerships with FP2, the American Association of State Highway and Transportation Officials, and State and local transportation agencies to promote pavement preservation.
To obtain other checklists or to find out more about pavement preservation, contact your local FHWA division office or FP2 (at http://www.fp2.org/), and check into these Web pages:
- Is the project a good candidate for microsurfacing?
- How much rutting is present? What is the depth and extent?
- How much and what type of cracking exists?
- Is crack sealing needed?
- How much bleeding or flushing exists?
- Is pavement raveling?
- What is the traffic level?
- Is base sound and well drained?
- Review project for bid/plan quantities.
- Bid specifications
- Special provisions
- Mix design information
- Construction manual
- Traffic control plan
- Manufacturers' instructions
- Material safety data sheets
- A full mix design and compatibility test have been done.
- The asphalt emulsion is from an approved source (if required).
- The emulsion is sampled and submitted for testing.
- Aggregate meets all specifications.
- Aggregate is clean and free of deleterious materials.
- Aggregate is not wet.
- The emulsion temperature is within application temperature specification.
Pre-Seal Inspection Responsibilities
- The surface is clean and dry.
- All pavement distresses have been repaired.
- The existing surface has been inspected for drainage problems.
- The bristles are the proper length.
- The broom can be adjusted vertically to avoid excess pressure.
- The machine is fully functional.
- The machine has been calibrated and certified for the specific aggregate being used (T209).
- Spreader rubbers are clean and not worn.
- All paddles in the pugmill are intact.
- The spreader box is clean and is a microsurfacing type box.
Rollers (if used)
- Rollers should be unballasted, pneumatic-tired 5-8 tonnes dead weight.
- The roller tire size, rating, and pressures comply with manufacturer's recommendations.
- Tire pressure is the same on all tires.
- All tires have a smooth surface.
- Stockpile site is well drained and clean.
- Contractor has the full line of equipment (loaders, tankers, etc.).
Equipment for Continuous Run Operations
- All equipment is free of leaks.
- Flow boys or other nurse units are clean and functional.
- There are enough units to allow continuous running with minimal stops for cleaning box rubbers.
Calibration of Equipment
- Each machine has been calibrated with the aggregate and emulsion to be used.
- The name of the person who carried out calibration and documentation has been provided.
- Air and surface temperatures have been checked at the coolest location on the project.
- Air and surface temperatures meet agency requirements.
- High temperatures, humidity, and wind will affect how long the emulsion takes to break.
- Application of emulsion does not begin if rain is likely.
- Application does not begin if overnight temperatures could be freezing.
Determining Application Rates
- Agency guidelines and requirements are being followed.
- Required rates for rut filling and leveling have been calculated or estimated separately.
- A full mix design has been done.
- More material is applied to dried-out and porous surfaces.
- More material is applied on roads with low traffic volumes.
- Less material is applied to smooth, nonporous, and asphalt-rich surfaces.
- Bulking has been measured.
- Moisture content has been adjusted for in the application rate.
- The signs and devices used match the traffic control plan.
- The setup complies with the local agency or Federal Manual on Uniform Traffic Control Devices (MUTCD).
- Flaggers do not hold the traffic for extended periods of time
- The pilot car leads traffic slowly-40 kph (25 mph) or less-over fresh microsurfacing.
- Signs are removed or covered when they no long apply.
- Any unsafe conditions are reported to a supervisor (contractor or agency).
Project Inspection Responsibilities
- Has a test strip been done-is it satisfactory?
- Are field tests carried out-are they in specification?
- Enough trucks are on hand to keep a steady supply of material for the slurry machine.
- The application starts and stops with neat, straight edges. Will an edge box be used?
- A rut box is used for ruts deeper than 12 mm (1/2 in).
- A leveling course is used with a steel strike-off for ruts less than 12 mm (1/2 in).
- Two courses are used where rut filling or leveling is employed.
- The application starts and stops on building paper.
- No drag marks are present due to oversize aggregate or dirty rubbers.
- Rubbers are cleaned regularly and at the end of each day.
- The machine takes a straight even line with minimal numbers of passes to cover the pavement.
- Mix is even and consistent.
- Mix does not float fines.
- The application is stopped as soon as any problems are detected.
- The application appears uniform.
- The surface has an even and uniform texture.
- Check application rate based on amounts of aggregate and emulsion used.
- What are the times between spreading, foot traffic, and opening to traffic?
- Work time or mixture is adjusted to acceptable times for trafficking.
Rolling (if required)
- The rollers do not begin until the mat is stable.
- Rolling begins at one edge and moves to the other edge of the run, taking care to roll the joint. Overlap of runs is not a problem.
- The entire surface is rolled once.
- The rollers travel slowly-8-9 kph (5 mph) maximum.
- Trucks are staggered across the fresh seal coat to avoid driving over the same area.
- Trucks travel slowly on the fresh seal.
- Stops and turns are made gradually.
- Truck operators avoid driving over microsurfacing.
- Trucks stagger their wheel paths when backing into the continuous unit.
- The meet lines are not made in the wheel paths.
- The meet lines are made at the center of the road, center of a lane, or edge of a lane.
- The meet line is overlapped only 75 mm (3 in) maximum.
- The slurry unit spreader box runners do not run on fresh mat.
- All emulsion applications begin and end on building paper.
- Mixture is not overly wet at start-up.
- Building paper is disposed of properly.
- Brooming does not begin until sufficient bond has formed between the emulsion and the aggregate.
- Brooming begins after the microsurfacing is available for traffic.
- Brooming should not dislodge the microsurfacing.
- Followup brooming should be done if ravel is high or if traffic is high.
Opening the Microsurfacing to Traffic
- The traffic travels slowly-40 kph (25 mph) or less- over the fresh microsurfacing.
- Reduced speed limit signs are used when pilot cars are not used.
- After brooming, pavement markings are placed before opening pavement to normal traffic.
- All construction-related signs are removed when opening pavement to normal traffic.
- All loose aggregate from brooming is removed from travelway.
- Excess emulsion and spills are removed.
Common Problems and Solutions
- Drag marks:
- Clean rubbers, check aggregate grading.
- Flush surface:
- Reduce asphalt content of mix.
- Reduce water content and increase additive.
- Increase cement.
- Allow longer time before traffic.
- Reduce total fluids.
- Uneven surface-washboarding:
- Spreader box is incorrectly set up.
- Viscosity of the mix is too high.
- Add extra additive or water.
- Mix is breaking too fast.
- Ambient temperature is too high.
- Use water sprays on front of spreader.
- Poor joints:
- Too much water at start-up.
- Runners of spreader box running on fresh microsurfacing-use water spray.
- Excessive ravel:
- Mix is breaking and curing too slowly.
- Make mix faster; add cement.
- Control traffic.
- Wait until cured to trafficking level.
- Traffic or equipment speeds too high.
- Brooming or trafficking before the emulsion is properly set.
Information in this checklist is based on or refers to the following sources:
- "ABC of Slurry Surfacing." 2001. G. Holleran in Asphalt Contractor Magazine (July).
- Quality Control of Microsurfacing. 1992. Washington, DC: International Slurry Surfacing Association.
- Recommended Performance Guidelines for Microsurfacing. 2000. Washington, DC: International Slurry Surfacing Association.
For more information on pavement preservation, visit these Web sites:
For more information on the Pavement Preservation Checklist Series, contact:
Construction and System Preservation Team
Office of Asset Management
Federal Highway Administration, HIAM-20
U.S. Department of Transportation
1200 New Jersey Avenue SE, Room 3211
Washington, DC 20590
Publication No. FHWA-IF-03-002
Quality Assurance Statement
The Federal Highway Administration provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.
U.S. Department of Transportation
Federal Highway Administration