Most intermediate spalls, as defined in Section 1 of Chapter 2, are

repaired

using proprietary, bagged concrete repair materials.

Extending bagged cementitious repair material with coarse aggregate can significantly reduce the potential for shrinkage and cracking. When feasible, the Contractor should either use a pre-extended repair material or add coarse aggregate (typically pea gravel)

as allowed by the manufacturers

. Using extended material is often not practical when using trowel-applied materials in vertical and overhead applications.

It is a common misconception that higher compressive strength equals a better

repair

. In reality, excessively high compressive strength can lead to early failure as a result of excessive loads being transferred into the

repair

material. Engineers and Contractors should typically select materials that have only enough strength for the intended use. In most cases intermediate spall repairs will be non-structural in nature, and therefore compatible or lower compressive strengths are beneficial.

In general, slower strength development means better long term performance. Often, Contractors select rapid strength-gaining repair materials even when it is not necessary to do so. When it is practical, standard (non-rapid) strength-gaining materials should be selected.

Batched concrete should generally be used when

repairing

intermediate spalls in precast fabricator yards since it is readily available. Likewise, batched concrete should be used on construction sites when practical. Although bagged mixes can work well when applied correctly, batched concrete is typically a better alternative since the material properties will very closely match those of the parent concrete. Follow the provisions in Section 3 of Chapter 3 when using batched concrete to

repair

intermediate spalls.

Ensure maximum aggregate size is no larger than 1/3 of the clear space between reinforcement or the cover. For small repair area

, the largest of the coarse aggregate can be removed using a sieve to allow the material to flow adequately in the confined

repair

spaces.