Download - TOP DOWN CRACKING IN FLEXIBLE PAVEMENTS
INTRODUCTION
Top-Down cracks in pavements initiate at the
pavement surface and propagate downward.
The studies in TDCs are not given enough importance
till late 1990’s.
For many years, researchers have made an effort to
identify the underlying principles that govern this type of
failure.
Top-Down cracking must be dealt with during the
design, construction, maintenance and re-surfacing.
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Top-Down cracking on I-37 south of San Antonio,TX.
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TYPES OF TOP-DOWN CRACKING
Bottom up fatigue (or alligator ) cracking.
Surface down fatigue or longitudinal cracking.
Fatigue in chemically stabilized layers.
Pavement deformation or rutting.
Thermal cracking.
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CAUSES OF TOP-DOWN CRACKING
Pavement tyre loading such as load magnitude and tyre type effects.
Pavement temperature and temperature gradients.
Bitumen binder and mix aging.
Pavement structure.
Mix composition, raw materials and issues that related to the construction such as segregation of mix.
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Segregation of
coarse
aggregate
around
cracking.
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CONTROL OF TOP-DOWN CRACKING
Improved heavy vehicle loading control and appropriate
mechanical, axle and tyre technology implementation.
Improved renewable, specialized bitumen surface courses
with good permanent deformation resistance and enhanced
tensile and shear stress endurance.
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MAINTENANCE OF PAVEMENT SUBJECTED
TO TOP-DOWN CRACKING
A water proof layer to protect the underlying pavement.
Increased skid resistance.
A fill for existing cracks.
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MAINTENANCE (continued…)
Crack seals
Fog seals
Slurry seals
Micro surfacing
Patches
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CONCLUSION
Top-down crack and segregation seem to have a direct
relation.
Climatic conditions, traffic, aging, structure and
construction qualities are the main causes pointed out for
the initiation and propagation of Top-down cracking
Top-down type cracking may be longitudinal,
transversal or even alligator cracking and may be
found either in or out of the wheel path.
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CONCLUSION (continued…)
More studies on accelerated loading tests may improve
understanding of the effect of construction quality
parameters on the development of TDC.
The studies related to the influence of bitumen aging and
fatigue on TDC is also limited in literature.
More studies on the modeling of the base and sub-
grade layers accounting for the Top-down is necessary.
No relation was found between crack location,
direction and depth.
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REFERENCES
Myers, L.A., “Mechanism of Wheel Path Cracking That Initiates
at the Surface of Asphalt Pavements”, Master’s Thesis, University
of Florida, Gainesville, 1997.
Myers, L.A., “Development and Propagation of Surface Initiated
Longitudinal Wheel Path Cracks in Flexible Highway Pavements”,
Ph.D. Dissertation, University of Florida, Gainesville, 2000.
Jacobs, M.M.J., “Crack Growth in Asphaltic Mixes”, Ph.D.
Dissertation, Delft, The Netherlands, Nelft University of
Technology, 1995.
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Matsuno. S, and Nishizawa, T. (1992). Mechanism of
Longitudinal Surface Cracking in Asphalt Pavement. Proceedings,
Volume 2, 7th International Conference on Asphalt Pavements, The
University of Nottingham, pp. 277-291.
Gerritsen, A.H.; Van Gurp, C.A.P.M.; Van den Heide, J.P.J.;
Molenar, A.A.A. and Pronk, A.C.(1987). Prediction and
Prevension of Surface Cracking in Asphalt Pavements.
Proceedings, 6th International Conference Structural Design of
Asphalt Pavement, The University of Michigan. Ann Arbor,
Michigan, July 1987, pp. 378-391.
REFERENCES ( continued…)