Applications, Design & Construction of Ultra-thin. thin Whitetopping. Dr. Julie M. Vandenbossche, P.E. - University of Pittsburgh-

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1 Applications, Design & Construction of Ultra-thin thin Whitetopping Dr. Julie M. Vandenbossche, P.E. - University of Pittsburgh- Department of Civil and Environmental Engineering

2 Whitetopping Conventional (no bond) Ultra-thin thin (bond is key!)

3 Thin Whitetopping (TWT) Definitions > 100 to 200 mm Bond is not required PCC Overlay Existing HMA Ultra-Thin Whitetopping (UTW) 50 to 100 mm Bond is required PCC Overlay Existing HMA

4 Thin Whitetopping (TWT) Definitions > 100 to 200 mm Bond is not required PCC Overlay Existing HMA Ultra-Thin Whitetopping (UTW) 50 to 100 mm Bond is required PCC Overlay Existing HMA

5 How does UTW work? NA NA NA Tension 0 Compression Tension 0 Compression Bonded Unbonded

6 How does UTW work? Long Short Joint Spacing

7 When to consider UTW HMA thickness > 75 mm No stripping/raveling No excessive bottom-up fatigue cracking HMA HMA UTW UTW

8 Keys to UTW Performance Adequate (HMA and soil) support layers PCC-HMA bond (essential) Slab size / joint spacing Concrete material selection Design Inputs Traffic, layer thickness, climate, etc.

9 UTW Use by State >60 Jerry Voight - ACPA

10 Ultra-Thin Whitetopping Since 1990, over 300 UTW projects have been constructed Total Projec Year Jerry Voight - ACPA

11 Ultra-Thin Whitetopping Since 1990 about 1 million SY placed It is not experimental anymore Total Square Yar Over 835,000 m 2 1,000, , , , , , , , , , Year Jerry Voight - ACPA

12 Appropriate applications

13 Applications for UTW Streets Intersections Bus pads GA airports Parking lots Jerry Voight - ACPA

14 Stopping Areas Jerry Voight - ACPA

15 Chicago Bus Stops Building more than 1000 concrete bus stops (approximately 30 x 3 m) Cobblestone/asphalt base costly to remove Thickness constrained from 90 to 140 mm Increase strength Use structural fibers Jerry Voight - ACPA

16 UTW Commercial Projects Randy Riley: ACPA - IL Chapter

17 Lancaster, PA Rt 30 & 896 R. Riley

18 Lancaster, PA Rt 30 & 896 R. Riley

19 Whitetopping - Advantages Structural Improved structural capacity Low maintenance Reacts structurally as if on strong base course Concrete slabs bridge problems asphalt cannot Randy Riley

20 Whitetopping - Advantages Construction Can place on pavement in poor condition. Little or no pre-overlay repair needed. Avoid reconstruction problems. Minimal rain delays. Maintain traffic on existing surface. Randy Riley

21 Whitetopping - Advantages Safer Visibility Decreased stopping distances Non-rutting Less work zone reconstruction less accidents Concrete Asphalt Randy Riley

22 Albedo & Heat Island Rio Verde, AZ After Riley

23 Typical Distresses BUMP AHEAD!!CAUTION!!

24 Typical Distresses Transverse Cracking Corner Breaks & Transverse Cracking Corner Breaks

25 (1.5 ft x 1.8 m Panels) Typical Distresses L L L= Slab Length L/3

26 Findings from instrumented UTW

27 Minnesota Test Sections 102 mm m x 1.2 m Panels (polypropylene fibers) 76 mm m x 1.2 m Panels (polypropylene fibers) 76 mm m x 1.8 m Panels (polyolefin fibers) 152 mm m x 1.8 m Panels (polypropylene fibers) 152 mm - 3 m x 3.7 m Panels (polypropylene fibers) 152 mm - 3 m x 3.7 m Panels (polypropylene fibers & dowels)

28 Thermocouples Sensor Installations Prior to Paving Moisture Sensors Static Strain Sensors

29 Performance after 4 years Interstate highway with 25,000 ADT, 12-13% 13% trucks

30 mm m x 1.2 m Panels Nov 98 Jan 99 April '99 May '99 July '99 Sept. '99 Nov '99 Feb '00 Mar '00 July '00 Dec '00 April '01 June 98 Oct 98 Number of Cracks Cumulative Panels Cracked, % Corner Breaks Transverse Cracks 83 % of the distress occurred in the driving lane.

31 mm m x 1.2 m Panels Oct 98 Nov 98 Jan 99 April '99 May '99 July '99 Sept. '99 Nov '99 Feb '00 Mar '00 July '00 Dec '00 April '01 June 98 Number of Cracks Cumulative Panels Cracked, % Corner Breaks Transverse Cracks 73 % of the distress occurred in the driving lane.

32 mm m x 1.8 m Panels Nov 98 Jan 99 April '99 May '99 July '99 Sept. '99 Nov '99 Feb '00 Mar '00 July '00 Dec '00 April '01 June 98 Oct 98 Number of Cracks Cummulative Panels Cracked, % Corner Breaks Transverse Cracks 75 % of the distress occurred in the driving lane.

33 Whitetopping Crack Summary Cell Panels Corner Cracked (%) Cracks Trans. Long. Cracks Cracks x1.2m x1.2m x1.2m * x1.2m *All transverse cracks in 78 mm 1.2 x 1.2m section are reflective cracks.

34 Longitudinal Joint Layout 3.6 m 3.6 m.6 x.6m Panels 2 x 2 2 Panels x 2 ft Panels 1 x 1 m Panels 33 x x 33 ft Panels Traffic Traffic

35 Longitudinal Joint Layout 3.6 m 3.6 m 1.2x1.2m Panels 4 x 4 Panels 1.5x1.8m Panels 5 x 6 Panels Traffic Traffic

36 U.S. -169, N. Mankato, MN (10/ 98)

37 Debonding Debonding at Interface Delamination Between Lifts Raveling U.S. 169, N. Mankato, MN 10/ 98

38 Debonding Debonding at Interface Delamination Between Lifts Raveling SP208 near Sao Paulo U.S. 169, N. Mankato, MN 10/ 98

39 Temperature effects

40 Temperature Characterization (Thermocouple Data) mm Overlay Frequency Gradient, o C / cm

41 Temperature Characterization (Thermocouple Data) Overlay Thickness Temperature Gradients, C/cm Max. Negative Max. Positive 95% of the Time 76 mm to mm to mm to The mean gradient is approximately C/cm for all three overlays.

42 Microstrain mm x 1.5 m x 1.8-m Panels FWD Testing at Lane/Shoulder Joint (July 1999) Estimated Traffic, ESALS Top Bottom

43 Microstrain mm x 1.5 m x 1.8-m Panels FWD Testing at Lane/Shoulder Joint (July 1999) Resilient Modulus of AC, MPa Top Bottom

44 Temperature and applied load Asphalt Temperature ( ο C) Microstrain Top Bottom Asphalt Resilient Modulus (MPa) 40 kn FWD load in wheelpath for 76 mm 1.52-m x 1.83-m panels

45 ISLAB 2000 FEM Principal Stresses Modeling Assumptions: 76-mm 1,2 x 1.2m Panels Fully bonded 0.80 o C/cm gradient 356 kn Tandem axle load HMA temp. greatly influences stress (strains) 2. Temperature gradients have little influence on stress (strains) 2.

46 Lessons learned? Must obtain a good bond Initial condition of existing HMA HMA layer must have adequate structure Evaluate original structure (depth of HMA layers, condition of HMA ) Fibers help keep cracks tight Joint layout

47 Designing UTW

48 UTW Design Joint Spacing to 18 times pavement thickness 2. Keep longitudinal joints out of wheelpath

49 UTW Design Concrete mixture design.. Typical Higher Cement Content Fast track type construction Low Water / Cement Ratio Synthetic Fibers Durable, Quick Opening to Traffic

50 Macro vs Micro Fibers Macro-Fibers Diameters: 0.2 to 0.8 mm ( ) Materials: Steel, Synthetic Micro-Fibers Diameters: < 0.1 mm (< ) Materials: Polypropylene, Steel, Carbon,... Typically a 20% increase in the cost of the mix. Adapted from Jeff Roesler

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52 Sample mix designs UTW Design Polypropylene Polyolefin w/c Cement (kg/m 3 ) Fly Ash (kg/m 3 ) 0 0 FA (kg/m 3 ) CA (kg/m 3 ) Fibers (kg/m 3 ) 2 15

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54 Values chosen for design: Poor (E AC = 700 MPa) (E AC fatigue cracked, old Fair (E AC = 2,500 MPa) (E AC Good (E AC = 4,000 MPa) (E AC UTW Design HMA condition assessment.. rutting, no structural damage

55 UTW Design Equations Effective radius of relative stiffness l e = (1 I e )*k NA = ( E c t PCC 2 2 ) + E c t E b PCC t BIT t + E t b PCC BIT + t BIT ( Ect PCC ) t PCC 2 ( Ebt BIT ) I e = (Eh^3/ 12 )e = + Ect PCC ( NA ) + + Ebt BIT ( t PCC NA t BIT 2 ) 2

56 UTW Design Equations Determining total stress log( σ 18 ) = log( k ) log( L / l e ) log( l e ) Based on 2-D 2 D Finite element with 36% stress increase (partial bond) σ T = ( CTE* ΔT ) ( L / le ) σ Total =σ 18 + σ T Superposition assumes slab and HMA remain in contact

57 UTW Design Equations PCC strength characterization ASTM C Beams: 150x150x530mm Span: 450mm L/150 = 3 mm P1 L MOR = 2 bd P150 L f150 = 2 bd f150 R = 150 MOR *100

58 Stress Ratio UTW Design Equations R = f MOR *100 (ASTM C ) 07) R 150 values = 20% Stress Ratio (SR) = σ Total (1+R 150 )* MOR

59 Fatigue UTW Design Equations (1 R) * P R* = log N PCC = SR cr log( R*) total 0.217

60 UTW Design Procedure

61 UTW Design Traffic Category A Low truck volume Category B Medium truck volume Average Flexural Strength Third-point loading (ASTM C78) Composite k-value k of all layers below HMA

62 UTW Design Composite k-value k of all layers below HMA

63 Construction

64 UTW Construction Milling Use when rutting > 25mm Removes between 25 and 76mm Can shave off top of ruts Used with inlays Limited vertical clearances Single lane replacement Runway keelways Randy Riley

65 Bonded Concrete Overlays Grout or No Grout? 0 Lab Field - Smooth Field - Rough Damp w/grout Damp No Grout Dry w/grout Dry No Grout Ref. Resurfacing and Patching Concrete Pavement with Bonded Concrete, Highway Research Board, Volume 35, 1956 Randy Riley

66 600 Mill? Blast? Grout? 500 Shear Strength, Milled/Grout Milled/None ShotGlast/Grout ShotBlast/None Corner Centeredge Slab Center Average Ref. Unpublished Research, David Whitney, Department of Civil Engineering, University of Texas at Austin Randy Riley

67 Surface Preparation Clean surface Sweeper Compressed air Adapted from Randy Riley

68 Heat/Energy is Absorbed into Black Leveling Surface Heat/Energy is Reflected by Whitewashed Surface -10 C Jerry Voight - ACPA

69 Paving Mist surface Place concrete Paver Clarey screed

70 Loss % Varies by Depth Expected Loss Adjusted 25 cm = 75 cm 25 cm = 75 cm 25 cm = 75 cm 25 cm = 75 cm

71 UTW Jointing Apply curing compound Saw joints Seal joints (optional)

72 THANK YOU ANY QUESTIONS??