Repair Mortars

Product Guide

For more information, see the Product Selection Guide.

Suggestions for form repair mortars include, but are not limited to, the following:

Removal of unsound concrete and proper surface preparation are critical. It is generally more important to spend time on the surface preparation than on application of the actual repair material. The unsound concrete must be removed with a minimum amount of damage to the sound concrete below.
All unsound concrete must be removed by mechanical surface preparation methods. Check for delaminations in unsound concrete by tapping the surface with a hammer or dragging a chain across the surface. A hollow sound indicates a delamination in the concrete that must be removed.
If the concrete base for the repair material is sound and no concrete removal is necessary, then all dirt, oil, grease, curing compounds, coatings and any other surface contaminations must be removed.
Methods for cleaning include shotblasting, sandblasting, waterblasting [minimum of 1500 to 2000 psi (10.3 - 13.8 MPa) pressure], scarifying, and chemical cleaning. Grinding is not typically recommended because it may make the concrete smooth and polished, reducing the bond with the repair material.
All areas to be repaired should have a defined edge. This sawcut edge should be a maximum depth of ¾" (1.9 cm). The smooth edge created by the sawcut should then be roughened prior to application of the repair material to increase the bond strength at the edges.
Reinforcing steel should be thoroughly cleaned with sandblasting or very high pressure waterblasting if corrosion is present. Badly deteriorated rebars may need to be totally replaced.
The repair area should always be primed by using one of the following methods:
a) Preferred: Surface should be in a saturated surface dry (SSD) condition before brushing in a scrub coat of the repair material. The scrub coat must be thoroughly brushed into all exposed surfaces and repair material placed before the scrub coat dries.
b) All surfaces to be repaired should be in SSD condition, with no standing water on the surface.
c) Brush on one of Symons bonding agents, like Strong Bond. The repair material must be placed onto the bonding agent before it dries out or the bonding agent could act as a bondbreaker.
The repair material should be poured into the formed area or placed with a trowel to ensure good consolidation and initiate contact with the concrete base. The material should be firmly worked into the sides and bottom of the patch area, eliminating any air pockets and assuring maximum bond, and leveled to the surrounding concrete.
When placing repair materials in larger masses, typically 1½" to 2" (3.8 - 5.0 cm) or greater in thickness, aggregate extension is recommended. Aggregate extension will absorb the heat of fast-setting materials and reduce the possibility of cracks. Larger aggregates, like 3/8" (1.0 cm) pea gravel instead of sand also reduce the amount of water required for mixing the material. This reduction of water will reduce drying shrinkage of the repair material and increase the physical properties. For example, compressive strength and long-term durability of the repair material will increase.
It is good concrete practice to cure all cement-based repair materials. The application of a Symons curing compound is recommended.
For additional information on successful concrete repairs, consult ACI and ICRI standards and guidelines or call Symons Technical Service at 877-854-0643 (toll-free, US) or send a fax to 913-279-4806.

Liquid Systems

Available in solvent or water-based formulations.

Cement Systems

Enhance concrete performance or correct problems.

Epoxy Systems

Resin-based systems correct structural concrete problems and protect concrete surfaces.

Polyurea Systems

Polyurea-based systems to repair and protect concrete joints and nosings, even in low temperature conditions.

Polyureas