Home >Documents >Warm Mix Asphalt & Recycled Asphalt Pavements

Warm Mix Asphalt & Recycled Asphalt Pavements

Date post:20-Jan-2016
Category:
View:61 times
Download:5 times
Share this document with a friend
Description:
Warm Mix Asphalt & Recycled Asphalt Pavements. Cassandra Simpson | Greg Stephenson Robert Patience | Rick Hennig. Background to US Mixes. Virgin Source Aggregates “Combined” Grading (eg passing ½” retained ¼”) More Variability in US Virgin Mixes Fractionated RAP (Single Size) - PowerPoint PPT Presentation
Transcript:
Slide 1Warm Mix Asphalt
Background to US Mixes
More Variability in US Virgin Mixes
Fractionated RAP (Single Size)
More Important at High Percentages of RAP
Helps in Design of High RAP Mixes
Fractionating RAP and non-fractionated raw materials
AAPA 2010 Study Tour – WMA RAP
Background to US Mixes
Who owns the RAP
*
Integrates transportation functionality and ecological sustainability
Green Highways are:
www.greenhighways.org
Environmental issues are increasingly impacting on highway construction. The use of RAP and WMA are just some of the ways that these issues can be addressed.
Main driver for using RAP is economics & sustainability has become the new driver.
AAPA 2010 Study Tour – WMA RAP
Advantages of Recycling
Environmentally Responsible
Bitumen ~10 to 200 million years
Still high quality aggregate.
Advantages of Warm Mix Asphalt
Improved working conditions
Is Warm Mix the Future for Asphalt?
100% of production could be WMA in the future with up to 50% WMA within 5 years
AAPA 2010 Study Tour – WMA RAP
WMA + RAP - Benefits
Improves TSR values
www.aapa.asn.au
The main production benefit is the ability to run higher temperatures so that the exhaust gasses are at temperatures above their dew point (bag house).
Product benefits of WMA+RAP (which lead to improved performance) include:
Addressing the potential issue of the less aged WMA binder,
Increases the TSR of the resultant WMA+RAP blend
Ensures virgin aggregates are dry (due to super heating) prior to mixing with the virgin binder (and RAP)
Environmental benefits include:
Recycling reduces the dependence on natural resources (aggregates and crude oil)
Reduce “waste” to landfill
States That Have Tried WMA
& Higher RAP
RAP and WMA
Lower mixing temperature resulted in less oxidation & light oil remaining in virgin bitumen
Steam produced from drying RAP creates inert atmosphere
Recovered binder from WMA with 25% RAP has same rheological properties as recovered binder from HMA with virgin bitumen
Co-mixing (or interfacial mixing) of binders (virgin with RAP binder) is being investigated using an atomic force microscope. Additional work is also being undertaken to assess the resultant dynamic modulus of the WMA/RAP blend
Expanded RAP mixing study utilizing dynamic modulus E* evaluation criteria developed by Advanced Asphalt Technologies: Bonaquist & Christensen
E* from specified mixing and compaction temperatures compared to fully blended condition E* determined through the Hirsch model (assuming 100% blending of RAP and virgin binders)
AAPA 2010 Study Tour – WMA RAP
Specified Binder 58-28
25% RAP
DSR = Dynamic Shear Rheometer; G*/sin delta = Rutting Parameter of Superpave bitumen specification.
Original binder is PG58-28
Original binder (RTFOT Aged) is equivalent to the binder of hotmix after manufacture and placement
WMA (Post Plant) is the binder recovered from a WMA with 25% RAP
HMA (Post Plant) is the binder recovered from hotmix with 25% RAP
This basically indicates that the WMA (Post Plant) binder (containing 25% RAP) and the original binder (RTFOT Aged) are equivalent i.e. the addition of RAP stiffens the (WMA) binder to a level equivalent of the virgin binder in hotmix – addressing concerns that may exist with the tenderness of WMA.
AAPA 2010 Study Tour – WMA RAP
RAP and WMA
Will RAP and New Binders Mix at WMA Process Temperatures?
Co-mingled binder properties?
Interfacial Mixing Study
Atomic Force Microscope
Lab Mixing Studies
Dynamic Modulus Evaluation
Co-mixing (or interfacial mixing) of binders (virgin with RAP binder) is being investigated using an atomic force microscope. Additional work is also being undertaken to assess the resultant dynamic modulus of the WMA/RAP blend
Expanded RAP mixing study utilizing dynamic modulus E* evaluation criteria developed by Advanced Asphalt Technologies: Bonaquist & Christensen
E* from specified mixing and compaction temperatures compared to fully blended condition E* determined through the Hirsch model (assuming 100% blending of RAP and virgin binders)
AAPA 2010 Study Tour – WMA RAP
NCHRP 9-43 - Sasobit
Sterling, VA 20166
100000
0.00001
1.4979187362
31.4715937245
1000000
0.000001
1.3799389198
23.9849556526
Recoveredbinder
wr relative to TD
Count
wr at Tr
G*, Pa
Fitted Binder G* and Hirsch Model Estimates at SPT Temperatures and Freqauencies
1.97E+06
G*, Pa
Measured E*
Sample 1
Sample 2
G*, Pa
100062996.261358
96103494.1297825
93038748.6989695
76904351.8509593
45894102.4851302
46799888.1644654
41609618.407297
37525069.0612734
17369814.5127846
19280995.387901
15297486.3204266
15709939.1452385
5366533.44413295
6635898.40706188
4580508.55352839
5579479.97053302
1355423.07942858
1899818.92571095
1120871.34976263
1672789.64390694
283616.179755483
454702.901540304
227607.122172374
424332.954241672
50273.1712968219
92192.8397491941
39275.837833642
91905.9030101143
7754.8803298773
16141.2744278981
5921.2886945949
17244.381424263
1069.9494319744
2494.9209054701
801.7812180567
2853.4774692802
This workbook is used in conjunction with the Simple Performance Test System to develop dynamic
modulus master curves. It has the capability to solve a modified version of the 2002 Design Guide master
curve equation, Equation 1.
Max
The maximum limiting modulus is estimated from mixture volumetric properties using the Hirsch model
and a limiting binder modulus of 1 GPa (145,000 psi), Equations 2 and 3.
ú
ú
ú
ú
û
ù
ê
ê
ê
ê
ë
é
= limiting maximum mixture dynamic modulus
VMA = Voids in mineral aggregates, %
VFA = Voids filled with asphalt, %
(
)
= fitting parameters
This workbook is used in conjunction with the Simple Performance Test System to develop dynamicmodulus master curves. It has the capability to solve a modified version of the 2002 Design Guide master
curve equation, Equation 1.
Max = limiting maximum modulus
, , and c fitting parameters
The maximum limiting modulus is estimated from mixture volumetric properties using the Hirsch model
and a limiting binder modulus of 1 GPa (145,000 psi), Equations 2 and 3.
)(000,435000,200,4
100
1
1
000,10
000,435
100
1000,200,4|*|
max
VFA
VMA
VMA
P
VMAxVFA
VMA
PE
c
c
(2)
where
58.0
58.0
)(000,435
650
)(000,435
20
VMA
VFA
VMA
VFA
P
c
(3)
E*
max
= limiting maximum mixture dynamic modulus
VMA = Voids in mineral aggregates, %
VFA = Voids filled with asphalt, %
If viscosity-temperature data are not available for the binder used in the mixture, the workbook can be used
to solve a master curve equation using shift factors from the Arrhenius equation, Equation 4.
25.295
11
14714.19
)log(
1
*)log(
T
E
t
a
e
Max
E
(4)
Where:
1.
3.
A spreadsheet to perform the 2002 Design Guide fit (VTSFIT)
4.
A summary report spreadsheet of the 2002 Design Guide fit
(VTSMASTERREPORT)
5.
6.
(ARRHENIUSMASTERREPORT)
DATA Spreadsheet
All data needed to develop a master curve is input in the highlighted cells in the
DATA spreadsheet. This includes VMA and VFA for computing the limiting maximum
modulus, A and VTS parameters for the binder for use in the 2002 Design Guide shift
factors, the reference temperature, and the measured dynamic modulus data. If only two
specimens were tested, leave the data cells for Specimen 3 blank. Note: A and VTS
parameters are only needed for the 2002 Design Guide master curve (VTSFIT)
VTSFIT Spreadsheet
This spreadsheet is set up for using the solver function to fit the measured data to the
2002 Design Guide master curve, Equation 1. Use the solver function tool on the yellow
highlighted cell (Cell J25) to minimize the sum of the squared errors between the
measured and predicted values. Initial estimates for the optimization should be input in
Cells B4 to B7. Suggested initial estimates are given. After solver optimizes Cell J25,
the final values of the master curve parameters are given in Cells B4 to B7.
VTSMASTERREPORT Spreadsheet
This spreadsheet provides an output of the optimized master curve from the VTSFIT
spreadsheet. It includes the measured data, the optimized master curve parameters, and
plots of the dynamic modulus master curve, the shift factors, and the phase angle master
curve.
ARRHENIUSFIT Spreadsheet
This spreadsheet is set up for using the solver function to fit the measured data to a
master curve using Arrhenius temperature shift factors, Equation 4. Use the solver
function tool on the yellow highlighted cell (Cell I25) to minimize the sum of the squared
errors between the measured and predicted values. Initial estimates for the optimization
should be input in Cells B4 to B7. Suggested initial estimates are given. After solver
optimizes Cell I25, the final values of the master curve parameters are given in Cells B4
to B7.
ARRHENIUSMASTERREPORT Spreadsheet
This spreadsheet provides an output of the optimized master curve from the
ARRHENIUSFIT spreadsheet. It includes the measured data, the optimized master curve
parameters, and plots of the dynamic modulus master curve, the shift factors, and the
phase angle master curve.
1.
3.
A spreadsheet to perform the 2002 Design Guide fit (VTSFIT)
4.
A summary report spreadsheet of the 2002 Design Guide fit
(VTSMASTERREPORT)
5.
6.
(ARRHENIUSMASTERREPORT)
DATA Spreadsheet
All data needed to develop a master curve is input in the highlighted cells in the
DATA spreadsheet. This includes VMA and VFA for computing the limiting maximum
modulus, A and VTS parameters for the binder for use in the 2002 Design Guide shift
factors, the reference temperature, and the measured dynamic modulus data. If only two
specimens were tested, leave the data cells for Specimen 3 blank. Note: A and VTS
parameters are only needed for the 2002 Design Guide master curve (VTSFIT)
VTSFIT Spreadsheet
This spreadsheet is set up for using the solver function to fit the measured data to the
2002 Design Guide master curve, Equation 1. Use the solver function tool on the yellow
highlighted cell (Cell J25) to minimize the sum of the squared errors between the
measured and predicted values. Initial estimates for the optimization should be input in
Cells B4 to B7. Suggested initial estimates are given. After solver optimizes Cell J25,
the final values of the master curve parameters are given in Cells B4 to B7.
VTSMASTERREPORT Spreadsheet
This spreadsheet provides an output of the optimized master curve from the VTSFIT
spreadsheet. It includes the measured data, the optimized master curve parameters, and
plots of the dynamic modulus master curve, the shift factors, and the phase angle master
curve.
ARRHENIUSFIT Spreadsheet
This spreadsheet is set up for using the solver function to fit the measured data to a
master curve using Arrhenius temperature shift factors, Equation 4. Use the solver
function tool on the yellow highlighted cell (Cell I25) to minimize the sum of the squared
errors between the measured and predicted values. Initial estimates for the optimization
should be input in Cells B4 to B7. Suggested initial estimates are given. After solver
optimizes Cell I25, the final values of the master curve parameters are given in Cells B4
to B7.
ARRHENIUSMASTERREPORT Spreadsheet
This spreadsheet provides an output of the optimized master curve from the
ARRHENIUSFIT spreadsheet. It includes the measured data, the optimized master curve
parameters, and plots of the dynamic modulus master curve, the shift factors, and the
phase angle master curve.
2. A data entry spreadsheet (DATA)
3. A spreadsheet to perform the 2002 Design Guide fit (VTSFIT)
4. A summary report spreadsheet of the 2002 Design Guide fit (VTSMASTERREPORT)
5. A spreadsheet to perform the Arrhenius fit (ARRHENIUSFIT)
6. A summary report spreadsheet for the Arrhenius fit (ARRHENIUSMASTERREPORT)
DATA Spreadsheet
All data needed to develop a master curve is input in the highlighted cells in the DATA spreadsheet. This includes VMA and VFA for computing the limiting maximum modulus, A and VTS parameters for the binder for use in the 2002 Design Guide shift factors, the reference temperature, and the measured dynamic modulus data. If only two specimens were tested, leave the data cells for Specimen 3 blank. Note: A and VTS parameters are only needed for the 2002 Design Guide master curve (VTSFIT)
VTSFIT Spreadsheet
This spreadsheet is set up for using the solver function to fit the measured data to the 2002 Design Guide master curve, Equation 1. Use the solver function tool on the yellow highlighted cell (Cell J25) to minimize the sum of the squared errors between the measured and predicted values. Initial estimates for the optimization should be input in Cells B4 to B7. Suggested initial estimates are given. After solver optimizes Cell J25, the final values of the master curve parameters are given in Cells B4 to B7.
VTSMASTERREPORT Spreadsheet
This spreadsheet provides an output of the optimized master curve from the VTSFIT spreadsheet. It includes the measured data, the optimized master curve parameters, and plots of the dynamic modulus master curve, the shift factors, and the phase angle master curve.
ARRHENIUSFIT Spreadsheet
This spreadsheet is set up for using the solver function to fit the measured data to a master curve using Arrhenius temperature shift factors, Equation 4. Use the solver function tool on the yellow highlighted cell (Cell I25) to minimize the sum of the squared errors between the measured and predicted values. Initial estimates for the optimization should be input in Cells B4 to B7. Suggested initial estimates are given. After solver optimizes Cell I25, the final values of the master curve parameters are given in Cells B4 to B7.
ARRHENIUSMASTERREPORT Spreadsheet
This spreadsheet provides an output of the optimized master curve from the ARRHENIUSFIT spreadsheet. It includes the measured data, the optimized master curve parameters, and plots of the dynamic modulus master curve, the shift factors, and the phase angle master curve.
MBD015A195B.doc
(
)
[
]
{
}
)
Max = limiting maximum modulus
(, (, ( and c fitting parameters
The maximum limiting modulus is estimated from mixture volumetric properties using the Hirsch model and a limiting binder modulus of 1 GPa (145,000 psi), Equations 2 and 3.
ú
ú
ú
ú
û
ù
ê
ê
ê
ê
ë
é
VMA = Voids in mineral aggregates, %
VFA = Voids filled with asphalt, %
(
)
WMA + RAP - US Practices
Texas DoT – 33%-50% of all WMA work contain RAP
North Carolina (Boggs) – only use WMA with RAP (15-20%)
South Carolina (Banks) – view RAP inclusion as insurance
California (Granite) – a means of achieving a similar binder to that of hotmix
Texas limits the amount of RAP in their specifications to 20% in wearing courses, 30% in the binder/intermediate courses and 40% in lower layers (greater than 100mm from the pavement surface). Also, if the RAP is not processed and fractionated, these maximum allowable limits are reduced by 10% i.e. 10%, 20% and 30% respectively.
North Carolina allows WMA only on secondary roads.
South Carolina limits the amount of RAP in their specifications to 10-20% in wearing courses, 10-25% in the binder/intermediate courses and 30% in base layers and is dependent on the mix type. Banks indicated that RAP eliminates stripping concerns and stiffens the binder to address tenderness/rutting concerns. RAP is also used to bump a PG grade rather than using an expensive intermediate grade (PG76 = PG70+RAP)
AAPA 2010 Study Tour – WMA RAP
Superpave Guidelines
use specified binder grade
use one full binder grade lower
Tier 3: Over 25% RAP (>35% for WMA)
use blending charts to determine required binder grade
Superpave guidelines exist for RAP% in hotmix but not currently for WMA. The values in red are currently being proposed by various industry personnel.
AAPA 2010 Study Tour – WMA RAP
Determining Blended Binder Grade
Production and Paving Notes
Make sure the burner is tuned for the temperature.
Keep bag-house temperature above condensation point - higher % RAP in WMA helped increase temperature of bag house.
Consider superheating aggregate ahead of RAP.
Follow normal placement practices.
Short Term Ageing of WMA Binders During Production (laboratory ageing protocols)*
Differences Between Field Produced WMA and HMA Volumetric Properties
Increased RAP Usage with WMA*
Shingle Use with WMA*
Rubber Use with WMA*
*
*
High RAP Mix Design
NCHRP 9-46 Mix Design and Evaluation Procedure for High Reclaimed Asphalt Pavement Content in Hot Mix Asphalt
Objective: Develop mix design method and specification for HMA containing up to 50% RAP.
AAPA 2010 Study Tour – WMA RAP
Questions?
10
100
1000
10000

Click here to load reader

Embed Size (px)
Recommended