This poster on the Hamburg Rut Test was presented at the 95th Annual Transportation Research Board (TRB) Annual Meeting in January 2016.

1. THE HAMBURG RUTTING TEST– ALTERNATIVE DATA ANALYSIS METHODS AND HMA SCREENING CRITERIA
Jun ZHANG, Civil Engineering Department – The Texas A&M University System, TX, USA | j-zhang@tamu.edu
Xiaodi HU, Transportation Research Center, Wuhan Institute of Technology, Wuhan, China.| huxiaodi625@hotmail.com
Research Sponsored by: Research Conducted by:Abu NM FARUK, Texas A&M Transportation Institute (TTI), College Station, TX, USA | a-faruk@tti.tamu.edu
Introduction Alternative HWTT Parameters Summary and RecommendationsTest Results and Analysis
Item Parameter or Characteristic
Loading type Cyclic loading under a moving wheel
Test Specimen dimension 6” φ x 2.5” thick
Sample Sitting time prior to testing Not specified
Test temperature 50 ±1 ⁰C (122 ⁰F)
Loading rate 50 ±2 wheel passes/minute
Wheel Load 158 lb (72 kg)
Pass/fail mix screening Criteria < 12.5 mm rut depth after 20 000 cycles (15 00 for PG 70-XX
and 10 000 for PG 64-XX)
Test Duration < 7 hours
Field Performance CorrelationMix-Design CharacteristicsHWTT Setup and Test ProcedureAbstract
Sang Ick LEE & Lubinda F. WALUBITA, TTI & PVAMU – The Texas A&M University System, College Station, TX, USA | lfwalubita@tamu.edu
Background & Problem Statement
 The HWTT is routinely used for screening HMA mixes in the lab
with the standard pass-fail criteria of rut depth ≤ 12.5 mm after
20,000 load cycles.
 Several premature field rutting failures have occurred with HMA
mixes that had passed the HWTT screening criteria in the lab
Research Objectives
 To evaluate if the current Texas HWTT screening criteria is
simulative of the current Texas field conditions for HMA mix-design.
 To explore new HWTT data analysis methods and parameters to
supplement the traditional HWTT pass-fail screening criteria that
take the HMA rutting path-history into account.
 The Hamburg Wheel Tracking Test (HWTT) pass-fail screening
criteria was evaluated to investigate its suitability in simulating
current Texas field conditions.
 New data analysis methods were explored and new HWTT
parameters were developed to take into account the rutting
path-history of the HWTT samples.
 The developed HWTT parameters include rutting area,
normalized rutting area, and the shape factor.
 The developed HWTT rutting parameters were capable of
capturing the HMA rutting path-history and yielded promising
results in terms of predicting the early-life rutting performance
of the HMA mixes in the field.
 Current Texas HWTT protocol specifies rutting
performance of any HMA mix at the end of the test only,
without considering the rutting path-history.
 Three new HWTT data analysis parameters were
introduced, namely the rutting area (Δ), the normalized
rutting area (RutΔ), and the shape factor (SF), designed
to capture the HWTT rutting path-history.
 Based on the testing of commonly used Texas mixes, the
RutΔ and the SF parameters showed promising potential
to capture the HMA rutting response and path-history.
 RutΔ and SF parameters are recommended to be
considered in the HWTT test procedure with the
following tentative HMA pass-fail screening criteria:
− Rut∆ ≤ 8.0, and
− SF ≤ 1.25
HWTT Parameter Description Comment
Maximum Rut
Depth, Rutmax
HWTT rutting after 20,000 load-passes or 12.5 mm
(whichever comes first)
Traditional HWTT output
Number of Passes
to Failure, Nd
Number of load passes to reach 12.5 mm of rutting or 20,000
(whichever is smaller)
Traditional HWTT output
Rutting Area, ∆A
Area under the Rut Depth vs Number of Wheel Passes Curve
Accounts for the rutting
path-history
Normalized Rutting
Area, Rut∆
Accounts for the total
rutting and the shape of
the rutting curve
Shape Factor, SF
SF >1 : Convex curve
SF <1 : Concave curve
( ) ( ) ( ) ( ) ( )1 2 12 2 ... 2
2
d
A o n n
N
f x f x f x f x f x
n
−∆= + + + + +  
' ' A
d d
Areaunder Rutting curve
Rut
N N
∆
∆
= =
' ' A
B
Areaunder Rutting curve
Rut
Areaunderalinearcurve
∆
∆
= =
∆
#
Mix
Type
District
Climatic
Zone
Hwy Asphalt Binder Aggregate AC
1 Type B Waco M IH 35 PG 64-22 Limestone + 30% RAP 4.6%
2 Type B FTW WC APT PG 64-22 Bridgeport Rock + 30% RAP 4.2%
3 Type C Laredo DW Loop 480 PG 64-22 Crushed Gravel + 20% RAP 5.0%
4 Type C Laredo DW US 83 PG 64-28 Limestone + 17% RAP 4.6%
5 Type C Bryan WW SH 21 PG 64-22 Limestone + 17% RAP 4.8%
6 Type D Houston WW FM 2100 PG 64-22 Limestone/Dolomite + RAP/RAS 5.3%
7 Type D Paris WC US 277 PG 64-22 Limestone/Dolomite + 17% RAP 5.4%
8 Type D Atlanta WC US 59 PG 64-22 Quartzite + 20% RAP 5.2%
9 Type D FTW WC APT PG 64-22 Bridgeport Rock 4.8%
10 Type F Paris WC US 271 PG 76-22 Sandstone 6.8%
11 CAM Paris WC SH 121 PG 64-22 Igneous/Limestone 7.0%
12 SMA Waco M IH 35 PG 76-22 Limestone/Dolomite 6.0%
13 Type C
Corpus
Christi
M US 181 PG 64-22 Limestone/Dolomite + 20% RAP 5.1%
14 Type F Atlanta WC US 82 PG 70-22S Sandstone 7.8%
15 Type C Tyler WC US 259 PG 70-22S Sandstone + 1% Lime 4.3%
FTW = Fort Worth; Hwy = Highway; AC = Asphalt Binder Content; RAP = Reclaimed Asphalt Material; RAS = Reclaimed Asphalt Shingles
HWTT Parameters Field Rutting (Inches)
Top HMA Layer
Rutting (Inches)
Hwy
Rutmax
(Inches)
Δ
(in-cycle)
RutΔ
(inches)
SF
7 months after
construction
August
2014
7 months after
construction
August
2014
US 59 0.170 1865 0.090 1.099 0.006 0.130 0.002 0.045
Loop
480
0.190 2700 0.130 1.433 0.063 0.063 0.009 0.009
SH 121 0.500 4928 0.320 1.316 0.026 0.063 0.012 0.036
SH 21 0.370 4050 0.200 1.096 0.030 0.060 0.002 0.011
IH 35 0.110 1708 0.090 1.496 0.020 0.040 0.001 0.007
TrB2016 #16-1876
0
1
2
3
4
5
6
0 5000 10000 15000 20000
RutDepth(mm)
Number of Passes
Area ∆A
0
1
2
3
4
5
6
0 5000 10000 15000 20000
RutDepth(mm)
Number of Passes
Area ∆B
0
2
4
6
8
10
12
0 5000 10000 15000 20000
HWTTRutDepth
HWTT Wheel Passes
Mix A (Convex)
Mix B
Mix C
(Linear)
Mix D
(Concave)
Degree of preference
to mitigate early rutting
10mm rutting after
20,000 Wheel Passes
0
0.1
0.2
0.3
0.4
0.5
0.6
0 5000 10000 15000 20000
HWTTRutting(in)
Number of Load Passes
HWTT Rut Measurement
US 59 Loop 480
SH 121 SH 21
IH 35
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0 10 20 30 40
Averagerutting(in)
Months after construction
Top Layer Rutting
US 59
Loop 480
SH 121
SH 21
IH 35
ShapeFactor(SF)