The petrographic examination of concrete and concrete repairs - Concrete Repair - page 73

and the substrate - especially where the bond is already weak. In other
cases cracks may be traceable as originating within the concrete substrate
and continuing into the concrete repair. Figure 2.4 illustrates an example
of ongoing deterioration in the concrete substrate due to the reinforcement
corrosion affecting a concrete repair.
Failure to correctly diagnose or to take account of on-going deterioration
in the concrete substrate will in many cases greatly reduce the lifetime of a
concrete repair. The petrographic examination of core samples that include
concrete substrate as well as the repair can be used to detect features such as
cracking that originate within the concrete substrate and continue into the
concrete repair.
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