Micro Surfacing

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The inspector plays a vital role on every construction project ensuring that the completed operations comply with the owner’s plans and specifications. Recognizing that many agencies were inexperienced in doing micro surfacing projects, and hesitant to add the treatment to their pavement management systems because of their lack of familiarity, the International Slurry Surfacing Association (ISSA) worked with the National Center for Pavement Preservation (NCPP) to develop a comprehensive Inspector’s Manual for slurry systems including micro surfacing. The Inspector’s Manual can be obtained at www.slurry.org.

Inspection Guidelines

With micro surfacing, like most paving projects, the primary goal is to produce a strong, durable and aesthetically pleasing wearing surface for the traveling public. Some of the most important things inspectors can do to help achieve this goal are as follows:

Mix Design: Verify that a full mix design has been performed by a qualified lab, and that all test results meet or exceed the specified standards.

Quality Materials: Confirm that the aggregate, asphalt emulsion and other materials delivered to the job are in conformance with both the specifications and the materials used in the mix design. Best practices include sampling the delivered aggregate to confirm the gradation is within the stockpile tolerance limits noted in the ISSA Inspector's Manual and to at least periodically take a sample of the delivered emulsion for testing.

Equipment Calibration: To ensure proper proportioning of the mix in accordance with the Job Mix Formula, the paver must be calibrated for the emulsion, mineral filler, and the specific aggregate being used on the project. Comprehensive calibration information can be found in the Inspector’s Manual including sample calibration worksheets. Referencing the equipment manufacturer’s recommended calibration procedures will also simplify the calibration process rather than adapting to the universal procedure outlined in the Inspector’s Manual.

Surface Preparation: Walk or drive the entire pavement to be paved for the day to ensure the surface has been properly prepared.

Traffic Control: Verify the proper traffic control is in place to keep the traveling public safe and out of uncured micro surfacing.

Acceptable Weather: Measure the air and pavement temperature to determine if construction can start/continue.

Temperature, humidity and wind conditions all affect micro surfacing break and cure times, and an experienced contractor will take these variables into consideration when utilizing water and field additives during the course of construction.

Quality Equipment: Verify the paver is properly calibrated for the materials being used on the project, and the equipment is clean, well maintained, and free of any leaks. Ensure the spreader box and rubbers are kept clean to avoid drag marks in the mat.

Quality Workmanship: Ensure straight edge lines, quality joints (longitudinal and transverse), and no drag marks or blemishes in the mix. Verify the finished surface is uniform and consistent in terms of color and texture.

Application Rates: Periodic checks should be made to verify that the amount of material being placed is in accordance with the specifications and appropriate for the gradation of the aggregate being used. Spot checking the yield over a specific pavement area a few times each day using the calibrated counters on the paver is recommended. Other methods for tracking the amount of materials placed include keeping a list of the quantities of materials on each truck as they are placed, or tracking the quantities of all materials delivered to the project and deducting for waste.

Additional Resources

90-minute webinar on the Inspector’s Manual: highlighting key points of the Micro Surfacing Inspector’s Manual. (Provided by ISSA and the Asphalt Institute) 

Micro Surfacing Application Checklist: Provided by Federal Highway Administration (FHWA) and the Foundation for Pavement Preservation (FP2).