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Microsurfacing, explained

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The Portland Bureau of Transportation (PBOT) uses microsurfacing as preventive maintenance on deteriorated roads that are not yet bad enough to warrant full reconstruction.
Microsurfacing diagram

Microsurfacing is a design mixture of polymer-modified emulsified asphalt, mineral aggregate, mineral filler, water, and other additives proportioned, mixed, and uniformly spread over a properly prepared surface.

The mixture is made by a specialized machine and placed on a continuous basis by mixing the materials simultaneously in a pug mill. Figure 1 shows the process in the microsurfacing machine, which results in a free-flowing composite material spread on the underlying pavement using a spreader box. The mixture’s consistency permits even spreading over the pavement, forming an adhesive bond to the pavement.

It is used as a pavement preservation and maintenance treatment to improve the functional characteristics of the pavement surface and extend its service life.  It can be used on pavements suffering from the following conditions:

N Michigan Resurfacing - microsurfacing in action
  • Loss of skid resistance
  • Oxidation
  • Raveling
  • Surface permeability
  • Rut damage

Advantages

  • Reduces life-cycle cost 25-45% compared to traditional resurfacing methods.
  • Reduces greenhouse gases by 44% and energy use by 54% or more compared to traditional resurfacing methods.
  • Reduces raw material by 35% or more compared to traditional resurfacing methods.
  • Return to traffic within one hour
  • Adds 6-8 years or more when applied for optimum preservation performance.
N Michigan Resurfacing - without and with
This photo shows a roadway divided by two counties. The one on the left went the Mill & Fill route while the one on the right chose to add a micro-surfacing treatment to the mix. The difference between the two surfaces four years later are dramatic!

Learn more about microsurfacing here.

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