Update on the current APT Project in Texas

TxDOT Project 0-6682 05/01/2012 to 08/31/2015 Title Validation of the Maximum Allowable Amounts of Recycled Binder, RAP & RAS Using APT Objectives Validate the performance of mixes containing the maximum allowed percentage of RAP and/or RAS from Special Provisions 341—024 and 340—003. Project durations = 3 years.

Study objectives: The key issues to be evaluated in this project include: Validate TxDOT’s maximum allowable amount of RAP and RAS Validate that poor lab results on prepared RAP/RAS samples translate to poor field performance under load; Validate the overlay design tools developed by TTI to predict mix cracking and rutting of new overlays; Determine if the balanced mix design procedures can be used to design RAP/RAS mixes with performances comparable to virgin mixes.

TxDOT Specification 35 10 20 5 40 15 30 45 Mixture Description & Location Maximum Ratio of Recycled Binder1 to Total Binder (%) Maximum Allowable % (Percentage by Weight of Total Mixture) Unfractionated RAP2 Fractionated RAP3 RAS4 Surface Mixes5 35 10 20 5 Non-Surface Mixes6 < 8 in. From Final Riding Surface 40 15 30 Non-Surface Mixes6 > 8 in. From Final Riding Surface 45 1. Combined recycled binder from RAP and RAS; 2. Do not use in combination with RAS or fractionated RAP; 3. May not be used in addition to unfractionated RAP; however, up to 5% of fractionated RAP may be replaced with RAS; 4. May be used separately or as a replacement for no more than 5% of the allowable fractionated RAP;

N Layout of the Experimental Sections Section C Section F Section B TRAILER 10ft Saw cuts Section C Section F Reflection Cracking 4 x 8 = 32ft Section B Section E Rutting Section A Section L Fatigue Cracking Section D Section G Section H Section J 10ft Instrumentation Boxes Section I Section K 75ft 75ft NOTE: Not Drawn to scale

RAP&RAS = (15%RAP + 3%RAS)+WMA BMD = Balanced Mix Design HMA Mixes Test Section Reflection Cracking Fatigue Cracking Surface 2.0 in. Intermediate Base 8.0 in. 3 in. 8.0 inch Subbase A Type D Type C Cement (3.5%) Treated Base L Bridgeport Rock Cement (2.0%) Treated B High RAP E C RAP&RAS F D BMD G Rutting Experiment Type D – contains no RAP High RAP = (19% RAP) RAP&RAS = (15%RAP + 3%RAS)+WMA BMD = Balanced Mix Design Type B and C mixes may or may not contain RAP These mixes and designs are subject to modification based on PMC review 6.0 in. 7.0 in. H Type B I J K

HMA Mix Designs Mix % Rock RAP % RAS % TD % AC % PG LAS % BPD BPMS MCMS FS Type D Control D134 - TTI 61 - 30 9 96.5 4.8 64-22 1 High RAP D119 - TTI 46 29 6 19 RAP & RAS D196 -TTI +WMA 48 5.6 15 3 5.0 BMD D196 - TTI 97.5 5.5 64-28 Type C FT1C195 50 27.6 5 2.4 97.0 4.7 Type B FT1B115 38 32 4.1 BPD – Bridgeport D rock FS – Field Sand LAS – Liquid Anti-strip BPMS – Bridgeport Manufactured Sand TD – Target Density OT – Overlay tester MCMS – Mill Creek Manufactured Sand OAC – Optimum Asphalt Content HWRT – Hamburg Wheel Rut Tester

Construction of HMA Layers

Pave_IR

APT TESTING

APT Loading Target temperature: Loading Conditions: “Fatigue cracking” and “reflection cracking” = 20°C (68°F), “Rutting” sections = 40°C (104°F) Loading Conditions: Bi-directional trafficking for “fatigue cracking” and “rutting” pavements sections Uni-directional trafficking for “reflection cracking” pavement sections. Single axle load = 81.6 kN (18,000 lb) Tire inflation pressure = 690 kPa (100 psi) Lateral Wander: Max Lateral Position = 12 inch, SD = 8 inch Accelerated loading will be applied until: 19 mm (0.75 in.) Permanent Deformation at the pavement surface; 25% of each lane area is cracked (equivalent to 50% of the trafficked area cracked).

N APT TESTING DONE 125k passes 615k passes 145k passes 417k passes TRAILER 10ft Saw cuts Section C Section F 125k passes 615k passes Reflection Cracking 4 x 8 = 32ft Section B Section E Rutting Section A Section L 145k passes 417k passes Fatigue Cracking Section D Section G Section H Section J 10ft 700k passes 700k passes Instrumentation Boxes Section I Section K 75ft 75ft NOTE: Not Drawn to scale

Lateral Wander Pattern

Average Daily Temperature 0.5 inch below pavement surface

Pavement Response and Condition Monitoring

Response Monitoring At 0, 5,000, 25,000, 50,000 and 100,000 passes and then at every 100,000 passes of the PTM axle: Five transverse profiles spaced at 8.0 feet interval to compute the rut depth and permanent deformation Crack mapping. Transverse and longitudinal strains by two gages each. Load on each wheel L-FWD tests with 3 geophones Temperature by 8 thermocouples: Every 15 minutes, in two locations along each pair At the surface and at three depths within HMA layer(s).

Permanent Deformation – Rutting Sections

Reflection Cracking

Post-Mortem Trenches

Reflection Cracking Sections Fatigue Cracking Sections

Post-Mortem Coring

CONCLUSIONS The mixes tested so far have excellent rutting resistance The virgin mix and the BMD mix had the best reflection cracking resistance. The with RAP&RAS&WMA had the best fatigue cracking resistance. A 10% RAP addition seems to lead to 20% in performance reduction Both TxME and TxACOL had reasonable prediction for performance of these APT test sections. A new program named Tx-Recycol was developed to predict performance of asphalt mixes with RAP/RAS. Impact of RAP/RAS on pavement performance can be directly analyzed since RAP and RAS contents become direct inputs to Tx-Recycol.

OUR EXPERIENCE Temperature of HMA during APT testing is not easy to control Impossible to achieve more than 60% utilization of the machine because of the weather We need a better method for moisture measurements We need a guide for strain/stress measurements

THANK YOU !!