Distresses in Bituminous Pavements

• Major distresses in bituminous pavements - fatigue cracking,

rutting, thermal cracking, bleeding and moisture susceptibility
Permanent Deformation in Bituminous Pavements
• Rutting - likely to be a failure that would occur in the early
stages of pavement’s life

• Fatigue & Thermal Cracking failures – old pavements that

I. Srinivasa Reddy become Brittle
Research Scholar • According to the National Cooperative Highway Research
Program (Witczak, 1998):
Department of Civil Engineering
Permanent deformation - selected as the most serious
Indian Institute of Technology problem in the United States
Kharagpur – 721302, India
Fatigue cracking-rated the second most serious problem
followed by thermal cracking

Permanent Deformation
• Rutting is the manifestation of permanent deformation

• It is called permanent deformation because it represents an

accumulation of small amounts of unrecoverable deformations
under the channelized repeated wheel loads

• Wheel path rutting is the most common form of permanent

deformation

Fatigue cracking • In recent years -- the amount and severity of rutting

– Increase in axle loads
– Traffic volumes
– Increased use of radial tires - exhibit higher inflation
pressures

• Tire pressure and axle load increases - near the pavement

surface is exposed to higher stresses than the levels assumed
Source: Witczak (1998) when structural designs are performed - IRC: 37 - 2001

Causes of Rutting

 Loading conditions – Magnitude of wheel load

Tire pressure
Traffic volume

 Environmental conditions – Temperature

Moisture

 Mix properties - Aggregate characteristics

(shape, texture and structure)
Binder type & content
Mix design

 Others - structural designs to carry loads

Figure: Typical Rutting Pattern on one of the National Highways
  Heavy axle loads
 Higher pavement temperatures

Figure: Effect of Wheel Loading Repetitions on Permanent

Source: www.malvern.com Deformation Profile (Eisenmann and Hilmer 1987)

Maximum and Minimum Pavement Temperatures in India

Table: SAW Distribution for 2 Axle Truck
Pavement Temperature (°C)
Single Axle Weight (t) Place Latitude
Minimum Maximum
Surat-Manor Road (NH-8) Delhi-Gurgaon Road Barwa Adda-Barakar
(NH-8) Road (NH-2)
Bangalore 12058'N 11.5 58.9
Description
Ahmedabad- Mumbai- Delhi- Gurgaon- Dhanbad- Kolkata- Thrivandrum 8028'N 18.7 56.7
Mumbai Ahmedabad Gurgaon Delhi Kolkata Dhanbad
Hyderabad 17027'N 9.3 64.4
Average (simple) 7.31 6.35 8.09 8.55 8.57 7.92
Chennai 13004'N 17.3 63.7
Average 7.80 6.86 9.10 9.57 9.68 8.77
(weighted) Mumbai 18054'N 15.4 59.7
Maximum 20.72 16.76 21.20 20.90 21.52 22.0 Bhopal 23017'N 4.8 66.0
Proportion(% of 37.37 25.98 44.33 44.32 42.37 35.68
total axles) of Ahamedabad 23004'N 6.4 67.2
SAW >8T
Amritsar 31055'N -0.5 66.5
Proportion(% of 22.36 8.39 34.58 40.11 38.61 32.74
total axles) of Delhi 28050'N 1.8 66.6
SAW >10T
Guwahati 26006'N 6.5 59.5
Source: Koul and Chakrabarti (1998) Shillong 25034'N 1.5 51.3

Rutting in Bituminous mixes Rutting in Bituminous mixes …..

• The type of rutting most concern to bituminous mix • Rutting in bituminous pavements is the result of consolidation
designers – deformation in the bituminous layers (Plastic or densification of pavement layers and shear deformation or
flow or Instability rutting) lateral plastic flow of the bituminous mix (Sousa et al., 1991;
White et al., 2002)
• Rutting results from the bituminous mix without enough
shear strength to resist repeated heavy loads • AASHO Road Test, as well as at other full-scale test tracks -
shear deformation rather than densification is the primary
rutting mechanism in bituminous mixes
• A weak mix will accumulate small, but permanent
deformations with each vehicle pass, eventually forming a rut
characterized by a downward and lateral movement of the • The downward movement is mainly due to compaction while
mix the lateral movement occurs as a result of shear failure

• Rutting of a weak mix typically occurs during the summer

 Consolidation Shear Deformation General Description of Pavement Rutting over Time
Repeated Rutting Test Results

Initial Rut Ratio

The is a measure of the deformation characteristics of bituminous
mixes

This ratio gives an indication of the rutting that would take place
in the earlier stages of service life

Bituminous Mix Design Superpave Mix Design

• Bituminous layers for the major highways in India - consists • The Superpave mix design method
of dense bituminous macadam (DBM) as the binder course
and bituminous concrete (BC) as the wearing course
• Superpave volumetric design procedure has resulted in some
improvements over the Marshall method of mix design
• In India - bituminous mixes are designed to satisfy the
Marshall Mix Design criteria (MoSRT&H, 2001)
• It is still devoid of a general strength test that would determine
• Marshall method of mix design the mixture’s suitability for resistance to rutting and cracking
- Developed in 1940’s
- Still the most popular and common method for design of • The industry has expressed the need for a simple ‘pass–fail’
bituminous mixes in India type of test to complement the Superpave mix design method

• Widely felt that Marshall method is inadequate to address the • Wheel Tracking Devices (Loaded Wheel Testers)
current in-service performance problems as does not indicate
any performance parameters of the mix directly

Test Methods for Evaluating Rutting in Bituminous Mixes Test Methods for Evaluating Rutting in
 Number of procedures and equipment are being used to
Bituminous Mixes (Contd… )
evaluate the rutting potential of bituminous mixes
(Zhang et al. 2002):
Empirical Tests
Fundamental Tests: 1. Marshall Test
1. Uniaxial and triaxial tests: unconfined (uniaxial) and 2. Hveem Test
confined (triaxial) cylindrical specimens in creep,
repeated loading and strength tests 3. Corps of Engineering Gyratory Testing Machine
4. Lateral Pressure Indicator
2. Shear tests:
– Superpave Shear Tester - Shear Dynamic Modulus Simulative Tests
– Quasi-Direct Shear (Field Shear Test) 1. Full-scale/ Accelerated Pavement Tests
– Superpave Shear Tester - Repeated Shear at Constant 2. Laboratory Wheel-Tracking Tests
Height
– Direct Shear Test

3. Diametral tests: cylindrical specimens for creep or

repeated loading test, strength test
 Test Methods for Evaluating Rutting in
Bituminous Mixes (Contd…)

• Ideally, laboratory tests should simulate the field conditions

and correlate well with the observed field performance.
- However in practice this is not always the case

• Stress conditions in a pavement - difficult to replicate the

actual loading conditions of bituminous mix in the
laboratory using fundamental tests like static creep and
triaxial tests

• Specifically stress reversal on the aggregate structure as a

vehicle wheel passes over it are extremely complex and
cannot be precisely calculated nor replicated in a
laboratory test on a sample of bituminous mix

Response of a flexible pavement during trafficking by uniform

load P; successive wheel positions A and B depict cyclic loading
that results in Tensile and compressive strains in pavement

Test Methods for Evaluating Rutting in

Bituminous Mixes (Contd…)
• The equipment for fundamental tests - complex, expensive -
unsuitable for evaluating rutting

• Empirical tests such as Marshall Stability and flow - outgrown

their usefulness for assessing rut potential of bituminous mixes Use of Wheel Tracking Testers in
• Simulative tests like wheel tracking tests have been shown to
The Design of Bituminous Mixes
be able to adequately simulate the field traffic and loading
conditions

• Generally good relationships - between wheel tracking test

results and rutting performance measured in the field and data
collected during full-scale tests

• Wheel tracking tests - easy to operate and conduct - ideally

suited for evaluating rutting potential on a routine basis (Zhang
et al., 2002; Kandhal and Cooley, 2003; Verhaeghe et al., 2007)

Hamburg Wheel Rut Tester

Hamburg Wheel Rut Tester
 French Rut Tester Asphalt Pavement Analyzer

Tentative Acceptance criteria after 8000 cycles

Criteria : 10 mm
(10 percent of the test slab
thickness after 30,000 cycles)

Wheel : Pneumatic (600kPa)

400 mm diameter,
90 mm wide

Load : 1124 lb (5000 N)

Specimen Size (mm) :

500 × 180 × 100

Temperature : Dry, 60ºC

PURWheel

Criteria : 12.7 mm
Indigenous Simulative Test Methods/
20,000 wheel passes Equipments Developed at IIT Kharagpur
or
until 20 mm of rutting
is developed

Accelerated Pavement Testing Facility (APTF) Accelerated Pavement Testing Facility (APTF)

• When the wheels moves in the forward direction, a protruding rod

• The Accelerated Pavement Testing Facility - dual wheel set attached to the rear guide wheel hits the sensor, which acts as an
which can be loaded up to 60 kN and is driven by a 20 kW, 440V off switch and cuts off the power supply and wheel comes to a
three-phase motor halt

• It can move to and fro on a linear track of 12 m long • It also has the option of being controlled manually

• The center-to-center spacing between the two wheels is 330 • After the desired number of wheel repetitions, rutting is measured
mm under each of the dual wheels with reference to a fixed datum

• The facility has a number of sensors, which control the • The average of the two readings is taken as the rutting of the
movement of the wheel in forward and reverse direction pavement

• The sensors act as an on and off switches • A straight edge is used for measuring the deformations at the
centers of each of the dual tires
 IIT KGP Rut Tester

It is a multi-functional wheel tracking device useful for

evaluating rutting and stripping of bituminous mixes

The wheel load is measured by load cell and can be

applied up to 500 kg

Capable of varying the temperature from ambient to 70ºC

Arrangement for inducing water for evaluating stripping

and moisture susceptibility of bituminous mixes

Facility to test beam or cylindrical samples (laboratory

prepared samples using Superpave gyratory and Marshall
compacted specimens as well as field cores)
Figure: Accelerated Pavement Testing Facility at IIT Kharagpur

IIT KGP Rut Tester (Contd…)

Dimensions of the slab samples are 300 mm long by

300/200 mm wide and 75 mm high

The conventional flexible pavement can be simulated

Facility to test the specimens in dry or wet conditions

Facility to test the specimens up to 20,000 wheel load

repetitions

Data acquisition using data acquisition software and

personal computer

Facility to operate both in manual and automated modes Figure: IIT KGP Rut Tester
Easy to operate and maintain

Rolling Wheel Control Panel

RUTTING TEST.mp4

Loaded wheel moving back and

forth over the Marshall Specimen

Data Acquisition Card Data Display in the Computer

 Conclusions Conclusions

• Wheel tracking testers, when properly correlated to a specific

• The bituminous mixes are time, temperature and stress site’s traffic and environmental conditions have the potential
dependent material to allow the user agency the option of a pass/fail or “go/no go”
criteria

• The adequate and accurate characterization of bituminous mix • The wheel tracking devices currently available are imported,
behavior is necessary in order to predict the pavement very expensive and difficult (costly) to maintain
performance realistically
• If equipment that can perform similar functions, can be
fabricated in India at a cost affordable by transportation
• Evaluation of bituminous mixes on the basis of their agencies and research organizations, it can provide needed
performance on in-service pavements will not only be impetus to the pavement researchers
expensive but also time consuming
• It is hoped that the indigenously developed equipments will
give a boost to the advancement of pavement research in India
• Therefore, it is necessary to use a method of accelerated and becomes very useful for the development of performance
evaluation of the mixes for assessing their performance based mix design methods

References References
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