Topics. Look Ma, No Mess. Demonstration. Demonstration. Demonstration. Pavement. Pavement Behavior. Pavement. New Approaches to Tack Application

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1 Topics Look Ma, Mess New Approaches to Tack Application TRB, January 14, 24 The need for a tack coat Strains, strength & pavement life Improved tack technologies Performance-related testing Measuring bond strength Materials & construction techniques Pavement Behavior Stress Distribution Transfer? Compression Demonstration Two pieces of plywood - Unloaded Tension Top of Pavement 4 5 / 16 in. Aggregate Base Soil Subgrade Demonstration Two pieces of plywood - Loaded Demonstration Two bonded pieces of plywood - Loaded Top of Pavement 3 12 / 16 in. 9 / 16 in. deflection With Nails Top of Pavement 3 15 / 16 in. 6 / 16 in. deflection 33% Less 24 Koch Materials Company. TRB 24 tack.ppt rev 1/11/4 1

2 BISAR What s the Impact of ing Strength? 4 in. Asphalt Concrete (2758 MPa) 4 in. Asphalt Concrete (3447 MPa) 6 in. Aggregate Base (27 MPa) Subgrade Soil (5 & 1 ksi) (34 & 68 MPa) 9, & 12, lbs (4 & 53 kn) Varying Degrees of Slip ( to 1) Between Layers More Deflection at Subgrade Deflection at top of Subgrade (mils) Increasing Deflection More Vertical Stress Vertical Stress at Top of Subgrade (psi) Increasing Subgrade Stress More Strain Increasing Strain at Subgrade 12 Vertical Microstrain at Top of Subgrade Lower Deformation Life Repetitions to Deformation Failure, NF Decreasing Deformation Life 3,, 2,5, 2,, 1,5, 1,, 5, Failure Criteria:.5 Rut More AC Tensile Strain at Bottom Increasing AC Tensile Strain Horizontal 15 Microstrain at bottom 1 of HMA Koch Materials Company. TRB 24 tack.ppt rev 1/11/4 2

3 More Stress mid AC Middle of AC - t in Compression! Horizontal 6 Stress - 4 Mid AC (PSI) More Tensile Strain mid AC Increasing Mid AC TENSILE Strain Horizontal 2 Microstrain 15 Mid AC Lower Fatigue Life Bottom of AC Cycles to Fatigue Failure, Nf 3,5, 3,, 2,5, 2,, 1,5, 1,, 5, Decreasing Fatigue Life Failure Criteria: > 2% Cracking Lower Fatigue Life Middle of AC Cycles to Fatigue Failure, Nf 3,5, 3,, 2,5, 2,, 1,5, 1,, 5, Decreasing Fatigue Life Failure Criteria > 2% Cracking Lower Fatigue Life All of AC Cycles to Fatigue Failure, Nf 3,5, 3,, 2,5, 2,, 1,5, 1,, 5, Decreasing Fatigue Life Top Lift Controls Failure Criteria > 2% Cracking Lower Fatigue Life Bottom 3,5, of AC 3,, 2,5, Cycles 2,, to 1,5, Fatigue 1,, 5, Failure, Nf Middle of AC 3,5, 3,, Cycles 2,5, to 2,, Fatigue 1,5, Failure, 1,, Nf 5, All of AC 3,5, 3,, 2,5, Cycles 2,, to Fatigue 1,5, Failure, 1,, Nf 5, Failure Criteria > 2% Cracking Decreasing Fatigue Life Top Lift Controls 24 Koch Materials Company. TRB 24 tack.ppt rev 1/11/4 3

4 Horizontal Loads & Slip? 1.5 Asphalt Concrete (31 MPa) 2 Asphalt Concrete (31 MPa) 8.5 Base (1 and 35 MPa) Subgrade Soil (83 MPa) Subgrade Soil (24.3 MPa) Interface Condition Full (Vertical only) Full (Vert & Horiz) Lost (Vert & Horiz) Full (Vertical only) Full (Vert & Horiz) Lost (Vert & Horiz) ABAQUS - Romanoschi & Metcalf (TRB 21) Type of Base Soil Cement Soil Cement Soil Cement Aggregate Aggregate Aggregate Fatigue Life (Reps) 766,, 355,, 28, 227, 135, 14,2 Subgrade Deformation Life (reps) 95,3, 9,3, 49,6, 33,1, 31,6, 17,6, What Affects Interface ing? Temperature rmal Stress Application Rate Type of Tack Material Moisture Aggregate interlock / milling Improved tack technologies Performance-related testing Measuring bond strength Uzan, et. al. Direct Testing 2.5 mm/min until failure Pen 6-7 Tack Coats increase interface strength Optimum App Rate : At 25 o C,.22 gal/sy Optimum App Rate : At 55 o C,.11 gal/sy Photo courtesy Florida DOT Uzan, Livneh, and Eshed, AAPT 1978 International Bitumen Emulsion Federation Worldwide Survey Results Design models: bond affects long-term structural behavior Most countries have liquid test specs Only a few bond-strength performance tests: Austria: shear resistance test Switzerland: SN tensile strength test United Kingdom draft: torsion test Swiss Standard SN : mode 15-mm core Thin surfacing pushed off substrate in shear mode Minimum shear force requirement : 15 kn between thin surfacing & binder course 12 kn between binder course & road base Chaignon, International Symposium on Asphalt Emulsion Technology, 1999 Chaignon & Roffe, CTAA, Koch Materials Company. TRB 24 tack.ppt rev 1/11/4 4

5 Austrian Method: Tensile mode Metal plates bonded to each end of field core Core pulled apart in tensile mode Specifications : < 1.5 n/mm² for polymer modified bond coat < 1. n/mm² for non-polymer modified bond coat For each.1 N mm² below specifications severe fine imposed United Kingdom Draft Method: Torque mode Lab or field test method using 1-mm diameter core Metal plate bonded to thin surfacing measured in torque mode specification set - record value only Torque Tensile Chaignon & Roffe, CTAA, 21 Chaignon & Roffe, CTAA, 21 LTRC Method Simple Testing 5 lb/min until failure Residual:,.2,.5,.1, &.2 gal/sy CRS-2P, SS-1, CSS-1, SS-1h PG & PG 76-22M 25 & 55 o C Best : gal/sy t as strong as single lift! Mohammad, TRB 22 LTRC Method Sample Prep Mohammad, TRB 22 LTRC Method Test Procedure Stress (kpa) Stress vs Displacement Test Temperature 55 C NCAT Method Strength Testing Device Displacement (mm) Mohammad, TRB 22 Zhang; Courtesy of NCAT, 23 Equipment includes: Environmental Chamber & MTS 24 Koch Materials Company. TRB 24 tack.ppt rev 1/11/4 5

6 NCAT Method Loading Equipment Florida DOT Method Max Load Loading Rate: 2 /min Parameters: strength deformation Dissipated energy Zhang; Courtesy of NCAT Sholar, Page, Musselman, Upshaw & Moseley, TRB 24 Innovative Tack Technologies New Materials New Construction Methods New Materials Polymer modified emulsions CRS-2P, CSS-1P, SS-1P, etc. Rapid setting emulsions Materials developed for special processes Colas New Processes Colnet Process 1. Interface additive To adjust surface tension & improve adhesion 2. Emulsion 3. Breaking agent (Emulcol process) For instantaneous cure Vehicles will not disturb / track cured emulsion Colnet Distributor 24 Koch Materials Company. TRB 24 tack.ppt rev 1/11/4 6

7 New Processes Ultrathin bonded wearing course Emulsion application HMA application Tack: Polymer emulsion membrane Special machine applies both tack & PMAC Heavier membrane application; hot AC cures emulsion HMA applied without damaging membrane emulsion tracking Traffic in <15 minutes One-Pass Paver One-pass Paver The UTBWC Process 5/8 minimum Depth of Mix 3/8 minal Ag Size 3/16 Emulsion membrane depth The emulsion membrane wicks up around the HMA aggregates The emulsion cures, bonding the mix & pavement 9-12 mm coating on aggregates Existing Pavement UTBWC One-Pass Machine - New applications Florida DOT 23: 5 test sections on US 27 UTBWC (FDOT bonded asphalt concrete friction course, BACFC), FDOT FC-5 (open graded GTR crumb rubber mix), with & without special machine Preliminary results: one-pass machine placed materials look best UTBWC One-Pass Machine - New applications Arizona 23: UTBWC with asphalt-rubber binder in HMA Texas DOT 24: Thin ed Permeable Friction Course (TBPFC) over PCC Engineering News Record, 3/3/3 24 Koch Materials Company. TRB 24 tack.ppt rev 1/11/4 7

8 Lessons learned: ing between lifts essential for pavement design life Performance tests & specifications needed for bond strength Stronger binders (PMA) & faster breaking emulsions can help Improved construction equipment reduces tracking allows heavier application of modified emulsions Thank You. Questions?... Longer Lasting Roads 24 Koch Materials Company. TRB 24 tack.ppt rev 1/11/4 8