Introduction of methods of self healing for flexible pavements

1. SELF HEALING
TECHNOLOGY FOR
FLEXIBLE PAVEMENTS
CHINTADA SAILENDRA KUMAR
NIT Calicut
https://www.linkedin.com/in/sailendra
-kumar-chintada-681283127
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2. INTRODUCTION
 Road network plays an major economic and social role
 Operational health of road network signifies the nation’s
economy role
 Problems
Occurrence of cracks
Cause of CO2 emissions
Traffic disruption
Pavement deterioration
More operational and
More maintenance cost
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3. Benefits of SELF HEALING
TECHNOLOGY
 Improve traffic flow
 Reduce CO2 emissions
 Less Maintenance cost
 Less Operational cost
 Preserving natural resources
 Extend pavement life
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4. Self Healing Process
 It is ability to Restore its stiffness and strength by closing
micro cracks.
 It can be enhanced by adding a modifier
 It mainly consists of three steps
1. Wetting of the faces of two micro cracks
2. Diffusion of molecules from one face to the other.
3. Randomization of the diffused molecules
 These steps of process often termed as “Reversible
Hydrogen bonding”
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5. Self Healing Process
Time and Temperature dependent
It is a viscosity driven process
Schematic Representation of reversible
Hydrogen bonding
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6.  Necessary conditions for Self healing agents
1. Good compatibility with bitumen
2. High temperature stability
3. Ability to survive mixing and construction conditions
4. Healing temperatures between 30℃ and 40℃
5. Capable of continuous/multi-time healing
 Cracks do not heal below 20-30 mm inside
Self Healing Process
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7. Methods of Self-healing
 Self healing for pavements can be done in three methods:
1. Incorporation of nanoparticles
2. Induction heating
3. Rejuvenation
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8. Nanoparticles
 Nano clay
Have capacity to repair micro cracks in pavement
Principle:Nanoclay move towards the tip of crack by
surface energy and stops crack propagation and heal
damaged surface
used in pavement design to improve the ageing, rheological
and thermal properties of mix
Tabatabaee and shafie studied the effect of rest periods on
organo clay-modified mixes and concluded with 3% and 5%
Strain rates has increased fatigue.
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9. Nanoparticles
 Nano rubber
Have capacity to repair micro cracks in pavement
Rubber modifiers and polymers are used
Principle:Nano rubber move towards the tip of crack by surface
energy and stops crack propagation and heal damaged surface
can be used in pavement design to improve the and thermal
properties of mix
Conducted ductility self healing with two different types of
rubber (Nano A and Nano B) with percentages of (0-5%)
Performed on dog bone test ,cut at the centre and heal for 4h at
20-22℃ and self healing up to 70%
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10. Nanoparticles
 Nano rubber
Recovery can be in between 15-90%
Styrene-Butadiene-Rubber (SBR),Styrene-Isoprene-
Styrene are used.
Advantage:double role i.e.Durability & Self healing modifier
Disadvantage : of Polymer modifiers is their
thermodynamic incompatibility with the bitumen results in
variation of material density, polarity, molecular weight,
solubility between the polymer and the asphalt.
Bonding :Nano effect ,ionic and Reverse hydrogen
bonding.
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11. Induction Heating
 Conductive fibers and fillers can be added
 Principle: Three steps
1. Sending an alternating current through the coil
2. Generating electromagnetic field(emf) through the specimen
placed under the coil.
3. Generated emf Induces heat throughthe specimen by the
flow of Eddy currents
 Major healing mechanisms are capilary flow and diffusion of
bitumen at high temperatures.
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12.  Most progressive method of Self-healing reported till now
 transitioned from laboratory from site in a short time.
Induction Heating
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13.  Conductive fibres added to the mixture increases
Conductivity more than that of conductive fillers
 Liu studied the Induction Heating effect of steel wool and steel
fibres on asphalt pavements with equation
HI =C2/C1
where
HI =Healing Index (%)
C1 =No of loading cycles for the first time
C2 =No of loading cycles for the second time
Induction Heating
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14. Rejuvenation
 Rejuvenator-An engineered emulsion containing
maltenes and saturates.
 Asphalt binder - Asphaltenes + Maltenes
 Purpose: Rejuvenator is to reduce the stiffness
of oxidised asphalt binder and to flux the binder
 Self-assembled mono layer
When cracks within the surface of pavement
layer, a Rejuvenator can be applied to stop
the propagation of cracks
Life span of the pavement can be extended
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15.  Disadvantages:
1. applicable to the top few centimetres only
2. reduction in the surface friction of the road and it could be
harmful to the environment
Micro capsulation
Inclusion of Rejuvenator into mix via microcapsules
Principle :
 Micro cracks inside the pavement, microcapsules in the
propagation path encounter them
Rejuvenation
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16. The fracture energy at the tip opens the microcapsules
and releases the healing agent and then mixes with
binder to seal the crack
 Generally rejuvenators in microcapsules are aromatic oils
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Rejuvenation

17. Rejuvenation
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18. Rejuvenation
 Synthesis of micro capsules by fabrication process
 Waste cooking oil can be encapsulated as a rejuvenator
 The size of the capsule can be controlled by regulating
the core/shell ratio
 Most successful capsules have been made of a
prepolymer of melamine-formaldehyde modified as
methanol
 This approach is most favourable method for self healing
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19. Rejuvenation
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20. Evaluation of self healing capability
 Self healing capability can be investigated by fatigue test
which is complex and time consuming process
 Displacement Controlled tensile loading but Later it is
modified as Direct Tension Test (DTT).
 Fracture-Healing-Refracture test used to evaluate self healing
capacity which is done by DTT.
 Experimentally done for two types of materials
1. A standard 70/100 penetration bitumen called PBmas
2. A styrene-butadien-styrene polymer modified bitumen called
SBSmas
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21. Evaluation of self healing capability
 Along with DTT specimen, two types of stress
concentrated specimens are developed
Double-edge notched shaped specimen(DN)
Double-edge parabolic shaped specimen (DP)
 These two are compared with a standard DTT
specimen
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22. Specimen Geometrics
Special geometrics (from to
bottom : DTT,DN,DP)
ABAQUS simulation of special
geometrics (from to bottom :
DTT,DN,DP)
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23.  Test Procedure
Preparation: Samples are prepared in preheated silicone
rubber mould and then de-moulded after cooling
Fracture : Samples are fractured with displacement
speed of 100 mm/min
Healing : The broken pieces are placed in silicone
mould at temperatures of 10℃,20℃ and 40℃ and observe
the healing temperatures for both PBmas and SBSmas
Microscopy is used to observe the morphological change
during healing
Evaluation of self healing capability
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Evaluation of self healing capability
• Re-fracture : Samples are Re-fractured with
displacement speed of 100 mm/min

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Self healing percentage, H =( Srefracture / Sfracture )x 100
Where
Srefracture – strength of the re-fractured sample
Sfracture – strength of the fractured sample
Evaluation of self healing capability

26. Conclusions
Test results of PBmas with
different geometrics at a
speed of 100 mm/min
Self healing results of the PBmas
and SBSmas at temperatures of
10℃,20℃ and 40℃
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27. Conclusions
Self healing master curves
of re-fracture strength at
20℃
Comparison of the crack closure
process and the strength recovery
process of both Pbmas and SBSmas
at 25℃
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28. Conclusions
Fluorescence microscopy of
c/s of the PBmas with different
healing times( 0,1,3,18hr)
Fluorescence microscopy of c/s of
the SBSmas with different healing
times ( 0,3,8 hr) 3/9/2020
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29. Conclusions
 The healing process includes two phases
Crack closure
Strength gain
 The negative effect of the polymer modification on the self
healing capability observed
 A strength recovery master curve at any temperature can be
obtained with time-temperature superposition principle
 Finally this test procedure is able to find the self healing
capability.
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30. Future Research towards SHT
 Development of damage sensing and repair triggering
elements
Elements incorporated should have ability to sense the
damaged part
 Development of multiple self-healing processes
 Development of self healing assessment processes
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31. THANK YOU
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