Got Density? Asphalt Pavement Assn. of Indiana Winter Conference December 2010
Why measure density? Surrogate for other properties –Strength –Durability –Permeability Easy and fast
Rutting vs. Air Voids Ref: WesTrack
Rutting vs. Air Voids Ref: Mn/ROAD 1/2” Rutting in One Year
Fatigue vs. Air Voids Ref: WesTrack
Permeability
Retained Penetration vs Air Voids Ref: NCAT Text Book
Pavement Life vs. Air Voids
Getting Density Lift Thickness Temperature Compaction Support Equipment
NCHRP Report 531 Relationships of HMA In-Place Air Voids, Lift Thickness, and Permeability (NCHRP 9- 27)Relationships of HMA In-Place Air Voids, Lift Thickness, and Permeability (NCHRP 9- 27) Recommended minimum lift thicknesses: –3 X NMAS for fine-graded mixes –4 X NMAS for coarse-graded mixes Thin lifts cool faster –less time available for compaction
MultiCool FREE Software for Computing Compaction Window –Base Temp –Weather Conditions –Lift Thickness –Mix Temp –Latitude Available at
MultiCool
Temperature 80 O F Surface & Air Temperature, 5 mph wind
50 O F Surface & Air Temperature, 5 mph wind Temperature
30 O F Surface, 40 O F Air Temperature, 15 mph wind Temperature
Compaction Support Weak!!! Weak Support Leads to Poor Compaction!
Compaction Support Strong!!! Strong Support Helps Compaction!
Balancing Production Balance of plant production, trucking, paver speed and rollers Slow and steady wins the race –Speeding up to get rid of trucks not recommended. Hurts ride Non-uniform compaction
Joint Density Controlling segregation important Proper joint construction important Sealers Echelon paving Joint density specification
Longitudinal Butt Joint
Notched Wedge Joint 12” 1” minimum Max Agg. Size
Notched Wedge Joint Attachment
Joint Rolling - Unconfined Edge First Pass - Steel Wheel Rollers Inside of edge ~ 6” Second Pass - Steel Wheel Rollers Overhang edge 3-6”
3” - 6” off joint 3” - 6” on joint Longitudinal Joint Hot Mat Cold Mat
Longitudinal Joint 1/2 - 3/4 “ overlap
Longitudinal Joint Unrolled Rolled
Minimizing Joint Problems Minimize Joints Pave in Tandem! May Require More Lane Closures But, It Minimizes Return Trips!
Final Quiz Q - What is the maximum number of rollers needed on a paving project? A - Whatever it takes to get density
The Future is Bright! Better Tools to Help Us! Oscillatory Compaction Intelligent Compaction –GPS Location –Mat Stiffness
Don’t Forget Quality Diamond Achievement Commendation Diamond Quality Commendation Diamond Paving Commendation