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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. 1/2” Rutting in One Year. Ref: Mn/ROAD.
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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 1/2” Rutting in One Year Ref: Mn/ROAD
Fatigue vs. Air Voids Ref: WesTrack
Retained Penetration vs Air Voids Ref: NCAT Text Book
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) • 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 www.hotmix.org
Temperature 80OF Surface & Air Temperature, 5 mph wind
Temperature 50OF Surface & Air Temperature, 5 mph wind
Temperature 30OF Surface, 40OF Air Temperature, 15 mph wind
Compaction Support Weak Support Leads to Poor Compaction! Weak!!!
Compaction Support Strong Support Helps Compaction! Strong!!!
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
1” minimum 12” Max Agg. Size Notched Wedge Joint
First Pass - Steel Wheel Rollers Inside of edge ~ 6” Second Pass - Steel Wheel Rollers Overhang edge 3-6” Joint Rolling - Unconfined Edge
Longitudinal Joint 3” - 6” off joint 3” - 6” on joint Hot Mat Cold Mat
1/2 - 3/4 “ overlap Longitudinal Joint
Longitudinal Joint Unrolled Rolled
Minimizing Joint Problems • Minimize Joints • Pave in Tandem! • May Require More Lane Closures • But, It Minimizes Return Trips!
5 6 Final Quiz Q - What is the maximum number of rollers needed on a paving project? A - Whatever it takes to get density. 1 3 4 2
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