08-08-2012, 04:19 PM
guide to concrete repair
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Causes of Damage to Concrete
The more common causes of damage to
Reclamation concrete are discussed in this
chapter. The discussion for each cause of
damage consists of (1) a description of the
cause and how it damages concrete and (2) a
discussion and/or listing of appropriate
methods/materials to repair that particular type
of concrete damage. The format for the text of
this chapter was chosen in recognition of the
importance of first determining the cause(s) of
damage to concrete before trying to select the
repair method. It is expected that the full
discussion of the selected repair method, as
found in chapter IV, will be consulted prior to
performance of the work.
Faulty Design.—
Design faults can create
many types of concrete damage. Discussion of
all the types of damage that can result from
faulty design is beyond the scope of this guide.
However, one type of design fault that is
somewhat common is positioning em-bedded
metal such as electrical conduits or outlet boxes
too near the exterior surfaces of concrete
structures. Cracks form in the concrete over
and around such metal features and allow
accelerated freeze-thaw deterioration to occur.
Bases of handrails or guardrails
Sulfate Deterioration.
Sodium,
magnesium, and calcium sulfates are salts
commonly found in the alkali soils and
groundwaters of the Western United States.
These sulfates react chemically with the
hydrated lime and hydrated aluminate in cement
paste and form calcium sulfate and calcium
sulfoaluminate. The volume of these reaction
byproducts is greater than the volume of the
cement paste from which they are formed,
causing disruption of the concrete from
expansion. Type V portland cement, which has
a low calcium aluminate content, is highly
resistant to sulfate reaction and attack and
should be specified when it is recognized that
concrete must be exposed to soil and
groundwater sulfates.
Standard Methods of Concrete Repair
Proven methods of repairing concrete are
described in this chapter. Sections 24 through
38 contain detailed discussions of each of the
proven repair methods. Construction
specifications for these methods/materials of
repair are contained in the latest revision of
Reclamation's Standard Specifications for the
Repair of Concrete, M-47, Appendix A. It is
essential that the provisions of these
specifications be closely followed during repair
of Reclamation concrete. It should be
recognized, however, that these "standard"
methods and specifications cannot apply to
unusual or nonstandard concrete repair
situations. Assistance with unusual or special
repair problems can readily be obtained by
contacting personnel of the Materials
Engineering and Research Laboratories,
Code D-8180.