How Is Concrete Bonded?

Latex Agents

• Concrete bonding agents fall into two general types, latex emulsions and epoxies. Latex emulsions mix natural latex with various other natural and synthetic polymers to create a milky white, watery liquid that can be brushed or sprayed on. The liquid can also be mixed with sand and Portland cement and applied with a trowel. Most latex formulas cure within an hour after application and should be covered with new concrete during that time. Latex-based agents are a good general-purpose concrete adhesive but don’t perform well under extreme wet conditions with constant exposure to water.

Epoxy Agents

• Epoxy bonding agents combine epoxy resins, hardeners and modifiers to produce end products ranging from a filled paste for overhead applications to a thin, watery liquid for brushing or spraying. Epoxies are more versatile than latex agents because they can be formulated for specific applications such as extensive repairs to pavements or resurfacing walls and columns, for extreme environmental conditions or for specific cure times ranging from a few minutes to a few days.

Making Repairs

• When making a concrete repair, the area to be patched should be clean and sound. Clean off any oil, grease, soil, paint and broken concrete bits. If you're repairing a crack, use a hammer and cold chisel to enlarge the crack to at least 1 inch wide and undercut the sides of the crack to help the new concrete bond. Coat the crack with a concrete bonding agent and allow it to dry to the point of being tacky. Use a commercial concrete patch mix and force it into the crack with a trowel. Tamp the patch until it completely fills the entire area.

Finishing the Patch

• When the patch begins to set, smooth it down. Use a metal trowel for a smooth finish or a wooden board for a rough finish. Allow the patch to dry for about two hours, then cover the patched area with plastic or boards. Keep the patch covered for at least five days. Lift the patch cover each day and spray water on it so it cures correctly.