Batched concrete is typically the best choice when repairing deep spalls and in structural applications. Particularly in new construction, mix designs can be selected to ensure that the material properties will closely match the substrate.

Failures at the bond line between the repair material and parent concrete are a common problem due to stresses that develop as a result of loading, differential thermal expansion,

drying shrinkage

and contraction between the repair and parent material.

To that end, using repair material that has a comparable coefficient of thermal expansion and a comparable or lower modulus of elasticity is critical for the long-term success of a repair when significant stresses are likely to develop.

Typically, it is not feasible to determine the modulus of elasticity and coefficient of thermal expansion in a member that has already been cast. The best solution is to use the same mix design for the repair material as that used when the damaged member was originally cast, ensuring that the material properties will be similar.