Seal Coating What was the cause of the failure? Sponsored by: Minnesota LTAP Center Presented by: Michael Marti, P.E. SRF Consulting Group, Inc. Dan Wegman, P.E. SemMaterials

Minnesota has a Great Resource! Minnesota Seal Coat Handbook Updated in 2006 –FAQ –Trails –Specification guidelines Available from Mn/DOT Maplewood Lab Mn/DOT Research Services

What can make a chip seal fail? Rain or wet surface Cool Temperatures Dirty Rock Bad Emulsion Low Shot Rate Poor Workmanship High Traffic Count Not Enough Rolling 2 of the above = 50% chance of failure 3 of the above = 100% chance of failure

Weather, weather, weather! Most chip seal failures are a result of poor weather during construction

Condition of Aggregate Aggregate should not be too dusty or too wet or it won’t stick.

Shot Rate Depends Upon... Aggregate Size Aggregate Porosity Old Surface Condition –dry? –flushed? Traffic Weather!

Workmanship Equipment calibrated? Spray bar set right? Chips spread at the right amount & time? Rolling, Rolling, Rolling The whole crew on the same page

Nozzle Angle Setting = ° Spray bar Axis Proper nozzle angle setting

Single Double Triple Coverage Workmanship & Equipment: Spray bar height for the right coverage

Traffic control No traffic before rolling Lower traffic speed until seal is cured Pilot car - Keep wayward traffic under control!