15 March 2001
SPALL REPAIR PROCEDURES
16.1. Description. The repair process begins after the final cleaning of the area. The area must
be dry and free of dust, oil, dirt, etc. A good repair begins with a clean surface. Since the volume
of most spall repairs is usually small, most mixing must be done in a small drum or mortar mixer.
Some repair materials come premixed and others allow the mix to be extended by adding
aggregate (maximum recommended size is 3/8 inch or 10 millimeters). The material must be
consolidated through tamping, supplemented, when possible, by vibration, and the surface
worked to match the surrounding finish as closely as possible.
16.2. Joint Filler. If the spalled area is adjacent to an expansion joint or a crack, a joint filler
must be employed to prevent the repair material from fouling the joint (Figure 16.1.) and to retain
the joint shape. If the spall is next to a crack, the crack must be treated as an expansion joint.
Spall repairs must not bridge cracks or expansion joints. The crack must be formed up just as an
expansion joint. The joint filler should be the same width as the existing joint or crack, long
enough to cover the spall area, and deep enough to cover the full depth of the spall.
16.3. Bonding Agents. Bonding agents are utilized
to improve the bond between the patch and
the patch repair materials. A light coating of bonding agent must be used when using PCC as the
repair material. If using a rapid-setting or polymer concrete, consult the manufacturer's
recommendations on the use of bonding agents. For PCC repairs, the bonding grout used is a
mixture of one part portland cement to one part sand with a water-to-cement ratio less than 0.45.
The bonding agent must be brushed into cracks and crevices to ensure good contact with the
repair surface (Figure 16.1.). Many repair materials are proprietary and may also require a
proprietary bonding agent. When employing these types of material in the repair, the