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Causes
of Pavement Deterioration
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Leading
to Reflective Cracking |
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Excessive
wheel loading way beyond original design. |
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Ingress
of water, de-icing salts and debris at joints
and fault cracks. |
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Subsidence
of sub-grade/sub-base. |
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Warping
and over stressing of the rigid pavement. |
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Failure
in the rigid pavement due to the inability
of construction joints to accommodate thermal
expansion/construction movements. |
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Lack
of load transfer at dowel tie bars. |
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Rocking
road slabs and temporary reinstatements. |
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Failure
of joint sealant/cracks in sealant. |
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Corrosion
or spalling of concrete pavement. |
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Voiding
of sub-base/sub-grade. |
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Where
utility companies maintenance/upgrading
has caused weakness and failure. |
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Summary |
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Any
one or a combination of these factors
can cause reflective cracking in overlays.
Cracking and Seating can remedy all of
these failure mechanisms to ensure that
even a minimum overlay will not fail due
to reflective cracking. |
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Why
Cracking & Seating must be considered
as an option for remedial and maintenance |
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A
Dtp directive states that a bituminous
overlay in the region of 150mm/180mm is
usually adequate to prevent/control reflective
cracking as long as all
existing defects in the grid pavement
have been repaired before overlaying,
or failure or reflective cracking can
occur.
It is probably unlikely in most cases
to economically carry out these repairs,
and apply an overlay of this depth, even
an overlay, half the recommended thickness
may be not possible where existing levels,
thresholds or costs prohibit. Cracking
and Seating allows for the treatment
of all existing defects and the application
of an overlay to meet existing levels
or new design. |
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What
are the real maintenance options? |
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1. |
Overlay
with 150/180mm overlay. |
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2. |
Full
depth reconstruction of pavement with flexible
construction. |
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3. |
Do
nothing and overlay. |
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4. |
Crack
and Seat and resurface with a reduced depth
of overlay. |
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Obviously
it is not long term cost effective or
permanent to do nothing, as all mechanisms
that have caused the rigid pavement to
fail will continue to operate throughout
the concrete road base. Cracking and Seating
is easily the best option from the above
as it is cost effective, fast, reliable
and practical. |
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Consider
these four prime factors: |
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1. |
The
consequences of not carrying out repairs
to the pavement. |
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The
ability of just overlaying to control reflective
cracking. |
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3. |
Cost
effectiveness. |
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4. |
Long
term durability. |
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Footnote: |
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After
considering all these options, factors
and recommendations Cracking and Seating
is simply the most cost effective, lasting
and easiest method of maintenance to concrete
road based carriageways. |
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