Micro Surfacing: Economical Roadway Maintenance

micro surfacing application

eFlex Demo in St. Petersburg, Florida

Hot Mix Asphalt is a crucial and important asset to any road network. It provides a durable, smooth surface with a rich, dark appearance commuters and agencies have come to appreciate and associate with a “good road.” It is, however, an expensive asset that can deplete road budgets in a less than efficient way when not maintained correctly.

Maintaining Hot Mix?

If you could afford to pave 10% of your network each year, you could apply and reapply hot mix and achieve great results. However, as few agencies have that luxury, consider the fact that with the same budget, you could achieve the same great results for a longer length of time, and as a bonus, cover more miles per year. That’s what pavement preservation is all about—long-term maintenance of a roadway network through regular treatments of the roads at different stages in their life cycles. You can actually improve the overall network’s health while staying within budget.

What Could You Do With $1 Million?

The City of St. Petersburg, just south of Tampa, FL, is no stranger to the concept of pavement preservation. Up until a few years ago, they allocated approximately $1 million of their annual $4.5 million road maintenance budget for micro surfacing treatment for their 2,000 lane mile network.

Micro surfacing is typically used as a preventive maintenance solution for roads in moderately good condition, in order to raise their Pavement Condition Index levels and keep them in good condition longer.

In the past, the poor performance of a specific micro surfacing system caused the city to reevaluate its use, spending the $1 million for hot mix asphalt overlays instead. While it’s an understandable response, hot mix overlays are between two to three times the cost of micro surfacing. In the case of St. Petersburg, by placing hot mix asphalt alone, they were limited to less than 99 lane miles of treatment per year. By reassigning $1 million to micro surfacing, that same $4.5 million budget could treat over 122 lane miles, an increase of almost 25%.

An Improved System Offers a New Opportunity

The city found themselves in need of a more cost-effective solution than the hot mix overlays and began looking into other treatments, even reconsidering micro surfacing. Ergon Asphalt & Emulsions, Inc., (Ergon A&E) took on the challenge of reviving the micro surfacing reputation in St. Petersburg with eFlex premium micro surfacing, a cost-effective pavement maintenance solution that provides increased durability and friction due to high levels of polymer modification.

The city agreed to a micro surfacing demo on four roads within their network. Two would be treated with eFlex while the other two would be treated with a standard micro surfacing system. Ergon A&E planned to prove eFlex as an improved and longer lasting solution.

17th Ave distress Ergon
17th Avenue prior to eFlex application.

One of the sections to receive eFlex treatment was 1,280 linear feet of 17th Avenue South, which was in moderately good shape, but displayed cracking, medium severity weathering and raveling. The other section was 1,490 linear feet of 11th Avenue South, which displayed cracking, high-severity weathering and raveling. This road runs adjacent to a high school and has a high traffic volume.

The roads to receive the standard micro surfacing treatment were 1,300 linear feet of 35th Street South and 1,040 linear feet of Queensboro Avenue. These roads also displayed cracking as well as weathering and raveling.

What’s the Catch?

It is recommended that cracks ¼” or larger be filled prior to micro surfacing for best results. While micro surfacing can make large cracks significantly smaller, the system can be too stiff and too thin to stop working cracks from returning. In addition to evaluating micro surfacing performance, St. Petersburg would also use this demo to test the effectiveness of their crack sealing program/methods, filling cracks along certain portions of 17th Avenue and Queensboro Avenue to be treated, and then comparing them to sections that were not crack filled. Crafco, Inc., was selected to supply the crack relief product.

Demo Time

A double lift of eFlex (30-34 pounds) was applied to 17th Avenue, with nearly 650 feet of the 1,280-foot demo section crack filled prior to application. A single lift of eFlex (20-24 pounds) was applied to the demo section on 11th Avenue, which did not receive a crack fill prior to application. Each treated section cured in less than an hour.

eFlex Micro Surfacing
17th Avenue after eFlex application.

Over on Queensboro Avenue, a double lift of standard micro surfacing was applied, with nearly 650 feet of the 1,040-foot demo section crack filled prior to application. On 35th Street, a single lift of standard micro surfacing was applied without prior crack filling.

The demo sections will be monitored for the duration of one year. Based on overall micro surfacing performance, the city may once again consider bidding for micro surfacing projects as part of their network maintenance program.

Ergon A&E representatives were on site throughout the demo project to offer assistance and ensure treatment was applied according to best practices. The city was pleased with the process, neatness of operation and the cure time of the eFlex application.

eFlex Micro Surfacing 11th Ave
11th Avenue after eFlex application.

A Proven Formula

Once you identify the variables in a proven equation, you’ll get the right answer every time. The adage “treat the right road with the right treatment at the right time” is a mainstay in the effective management of an agency’s network. There are many factors involved in proper road maintenance, but when applied correctly, the pavement preservation concept works and can stretch your budget miles down the road.