Chapter 8: Micro-Surfacing

Checklists: Suggested Field Considerations for Micro-Surfacing

The following tables are guides to the important aspects of performing a micro-surfacing project. The tables list items that should be considered to promote a successful job. Thorough answers to these questions should be determined, as required, before, during, and after construction. The appropriate staff to do this will vary by job type and size. Some topics may need attention from several staff members. The field supervisor should understand its contents.

The tables are not intended to be a report but to draw attention to important aspects and components of the micro-surfacing project process. Some information may be product-specific and should be contained in the agency’s relevant standard specifications, special standard provisions, or special provisions.

Preliminary Responsibilities
Project Review	Is the project a good candidate for micro-surfacing? Should a micro-surfacing seal be used? What is the depth and extent of any rutting? How much and what type of cracking exists? Is crack sealing needed? How much bleeding or flushing exists? Is the pavement raveling? What is the traffic level? Is the base sound and well drained? Have the project bid/plan quantities been reviewed?
Document Review	Bid specifications. Mix design information. Special provisions. Construction manual. Traffic control plan (TCP). Material safety data sheet.
Materials Checks	Has a full mix design and compatibility test been completed? Is the binder from an approved source (if required)? Has the binder been sampled and submitted for testing? Does the aggregate meet all specifications? Is the aggregate clean and free of deleterious materials? Is the aggregate dry? Is the emulsion temperature within application temperature specifications?

Pre-Seal Inspection Responsibilities
Surface Preparation	Is the surface clean and dry? Have all pavement distresses been repaired? Has the existing surface been inspected for drainage problems?

Equipment Inspection Considerations
Broom	Are the bristles the proper length? Can the broom be adjusted vertically to avoid excess pressure?
Calibration of Equipment	Has each machine been calibrated with the project’s aggregate and emulsion? Who carried out calibration and what documentation has been provided?
Micro-surfacing Machine	Is the machine fully functional? Has the machine been calibrated for this project’s aggregate and certified. Is the spreader rubber clean and not worn? Is the texture rubber clean and set at the right angle? Are all paddles in the pug mill intact? Is the spreader box clean and is it a micro-surfacing type box?
Rollers (if used)	Do the roller tire pressures comply with the manufacturer’s specification? What type roller will be used on the project (pneumatic-tired roller recommended)? Do the roller tire size, rating, and pressures comply with manufacturer’s recommendations? Is the pressure in all tires the same? Do all tires have a smooth surface?
Stockpile	Is the stockpile site well drained and clean? Does the Contractor have all of the equipment required at the stockpile site (loaders, tankers, and so on)?
Equipment for continuous run operations	Is all equipment free of leaks? Are Flow boys or other nurse units clean and functional? Are there enough units to allow continuous running with minimal stops for cleaning box rubbers?

Site Considerations
Weather Requirements	Have air and surface temperatures been checked at the coolest location on the project? Do air and surface temperatures meet agency requirements? Are adverse weather conditions expected? (High temperatures, humidity, and wind will affect how long the emulsion takes to break.) Is application of the micro-surfacing postponed if rain is likely? Are freezing temperatures expected within 24 hours of the completion of any application runs?
Traffic Control	Do the signs and devices used match the traffic control plan? Does the work zone comply with the agency’s requirements? Are flaggers holding the traffic for reasonable periods of time? Are unsafe conditions, if any, promptly reported to a supervisor (contractor or agency)? Does the pilot car lead traffic slowly, 40 kph (24 mph) or less, over fresh micro-surfacing? Are signs removed or covered when they no longer apply?

Application Considerations

Determining Application Rates

Have agency guidelines and requirements been followed?
Have rut filling and leveling course application rates been calculated or estimated separately?
Has a full mix design been done?
Is more material applied to dried-out and porous surfaces?
Is more material applied on roads with low traffic volumes?
Is less material applied to smooth, non-porous, and asphalt-rich surfaces?
Has moisture content been adjusted when calculating the application rate?

Project Inspection Responsibilities
Micro-surfacing Application	Has a satisfactory test strip been done? Have field tests been carried out and are the results within specification? Are enough trucks on hand to provide a steady supply of material for the slurry machine? Does the application start and stop with neat, straight edges? Will an edge box be used? Is a rut box is used for ruts deeper than 12 mm (1/2”)? Is a leveling course used with a steel strike-off for ruts less than 12 mm (1/2”)? (Two courses are used where rut filling or leveling is employed.) Does the application start and stop on building paper or roofing felt? Are drag marks present due to oversize aggregate or dirty rubbers? Are rubbers cleaned regularly and at the end of each day? Does the machine follow a straight, even line with minimal passes to cover the pavement? Is the mix even and consistent? Are fines migrating to the surface? Is the application stopped as soon as any problems are detected? Does the application appear uniform? Does the surface have an even and uniform texture? Is the application rate checked based on amounts of aggregate and emulsion used? What is the time between spreading, foot traffic, and opening to vehicular traffic?
Rolling	Does rolling wait until the mat is stable? (Roller is 5-6 tonnes maximum (7).) Is the entire surface rolled only once? Do the rollers travel slowly, 8-9 kph (5 mph) maximum?
Truck Operation	Are trucks staggered across the fresh seal coat to avoid driving over the same area? Do trucks travel slowly on the fresh seal? Are stops and turns made gradually? Do truck operators avoid driving over the micro-surfacing? Do truck operators stagger their wheel paths when backing into the paving unit?
Longitudinal Joints	Is the meet line overlapped a maximum of 75 mm (3 in)? Do the spreader box runners avoid running on the fresh mat? Are the meet lines made at the center of the road, center of a lane, or edge of a lane, not in the wheel paths?
Transverse Joints	Do all applications begin and end on building paper? Is the mixture not too wet at start up? Is the building paper disposed of properly?
Brooming	Does brooming begin after the micro-surfacing can carry traffic? Does brooming dislodge the micro-surfacing? Is the surface raveling? (Follow-up brooming should be done if raveling is high or if traffic is high.)
Opening the Micro-surfacing to Traffic	Does the traffic travel slowly — 40 kph (24 mph) or less over the fresh micro-surfacing? Are reduced speed limit signs used when pilot cars are not used? After brooming, have pavement markings been placed before opening to traffic? Have all construction-related signs been removed when opening to normal traffic?
Clean Up	Has all loose aggregate from brooming been removed from the traveled way prior to opening to traffic? Have all binder spills been cleaned up?