April 6th, 2011
HIGH FIBERPreserve Infrastructure, by Catherine Higgins.
Added fiber may help make asphalt pavement more durable.
UDOT roads are built to last. “UDOT typically designs our asphalt pavements for a 20 year design life, meaning they have the structural thickness to support 20 years worth of traffic,” says Gary Kuhl, UDOT’s Statewide Pavement Management Engineer. Once built, preservation keeps the road surface in good shape so pavement can reach or extend beyond that 20 year life.
UDOT is testing a new preservation treatment called flexible microsurfacing. Conventional microsurfacing is a thin asphalt “wearing course” that contains aggregate, emulsion and binder (usually cement) that is mixed on-site and applied to the road.
The new product has an additional ingredient – a strong, flexible type of fiber – that is intended to help the asphalt reduce cracking and resist damage from traffic and snow plows. Flexible microsurfacing uses a regular microsurfacing machine and a blower to add fibers to the conventional mix.
The two products were placed side by side on a busy arterial road in Davis County. After a two year evaluation, the flexible microsurfacing “shows little to no damage from snowplow activities and no raveling,” states a report on the test. Raveling happens when binder fails and rocks and asphalt chunks break loose. The conventional microsurfacing side shows reflective cracking (cracks from the bottom up) that stops where the flexible microsurfacing starts.
Scott Nussbaum, Materials Engineer for UDOT Region One, thinks “the initial performance is positive.” But its use is “still experimental” continues Nussbaum. UDOT will need to continue to study this product and develop specifications for its use.
UDOT engineers believe that the additive increases the toughness and durability over conventional microsurfacing to help reduce or delay cracking and resist raveling and snowplow damage. Kuhl is optimistic about the new product. “For a small extra cost we expect to get a stronger surface that will have less cracking. UDOT continues to test new ideas and will be monitoring how this one performs.”
For more information:
- Read a report on the test
- Read about how good roads cost less in UDOT’s Strategic Direction Performance Review and Measures
- More from Gary Kuhl: “UDOT found out a long time ago that ‘Good Roads Cost Less,’ so our approach has been to try and keep our pavements in good condition by strategically utilizing lower cost preservation treatments on a regular basis. Combined with a mix of rehabilitative overlays this has had the effect of extending the pavement life indefinitely. For the most part our reconstruction work is primarily due for widening and capacity needs, and rarely due to pavement failure needs.”