1. Update on the current APT Project in Texas

2. TxDOT Project /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.

3. 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.

4. 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;

5. 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

6. 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

7. 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

8. Construction of HMA Layers

9. Pave_IR

10. APT TESTING

11. 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).

12. 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

13. Lateral Wander Pattern

14. Average Daily Temperature 0.5 inch below pavement surface

15. Pavement Response and Condition Monitoring

16. 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).

17. Permanent Deformation – Rutting Sections

20. Reflection Cracking

22. Post-Mortem Trenches

23. Reflection Cracking Sections
Fatigue Cracking Sections

24. Post-Mortem Coring

25. 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.

26. 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

27. THANK YOU !!