Fri, Oct 3rd - 2:01PM
Concrete Crack Repair - Types and Methods
Polyurethane Foams for Low Pressure Injection Crack Repair
is the better choice: polyurethane or epoxy? Epoxy is the better choice
if structural strength is required to be maintained. If the crack is
only repaired to prevent water leakage then either product can
accomplish this task.
Cause of Cracks
of joints, to accommodate drying shrinkage and thermal movement during
the construction phase is one of the major causes of concrete cracks.
Settlement and overloading are also common causes of cracking.
Cracks usually appear within the first month after construction. These
cracks can leak as soon as they are formed or might expand and leak
later. Crack can grow and cause problems as they expand.
How Cracks Grow
which is the worst enemy of homes, enters the tiny cracks in the
concrete and in colder weather, freezes, enlarging the crack. Also,
movement of soils surrounding your home, through settling, can also
cause expansion of your cracks. In extreme cases, soils that are
unstable can overcome the inherent strength of concrete causing crack
caused by construction, heat, freezing and settlement can be corrected
by injection. Cracks caused by unstable soils must have soil problem
stabilized prior to attempting injection corrective methods.
Low Pressure Injection
method of injecting polymers into the concrete is adequate for repairs
of cracks not involving high volumes of water. High-pressure injection
is better suited for this type of application. Low pressure is defined
as injection pressures between 20 to 40 psi and can be used with either
ports or surface injection. Pressures as high as 250 psi may be used.
High Pressure Injection
to 10,000 psi utilizing injection packers usually placed in holes
drilled at 45 degrees to intersect the interior of the crack. This is
common method of repair using polyurethane foam. High cost of packers,
clean up of excess, potential stress damage and dangers of using high
pressure are overcome by using low-pressure injection methods.
use of surface ports (with one-way check valves) together with
low-pressure injection of a sealed crack eliminates these problems in
most situations. The injection of high-density foam is an effective
water proofing method.
best method for low-pressure crack repair is to slowly inject liquid
polymer into crack until crack is completely filled, filling of
adjacent surface port is visual confirmation. Using pressures above the
40-psi will allow polymer to rise and may indicate a false presence of
the polymer filling voids.
Methods of Surface Sealing and Placing of Surface Ports
are first cleaned with wire brush, and then surface ports are placed
along crack at intervals equal to the thickness of the wall. The
surface crack is then filled with epoxy paste which when sufficiently
hardened allows filling of surface ports to begin. Hydraulic cement is
used when cracks are actively “wet”. The ports must then be anchored to
prevent blowing off during injection.
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