- Good surface preparation is critical for durable repairs. When a repair mortar is placed on a dusty or dirty surface it will bond to the dust. This is not good! Make sure the surface is clean of all contaminants including oils, sealers, debris, laitance, etc. and has a rough profile.
- It is also very important that the surface is sound. A material placed on a weak or deteriorating surface will bond to the surface. However, there is a good chance that the surface will delaminate from itself. Always remove material until the surface is sound. Saturate with Conpro Start to strengthen surface. Conpro Start is not a substitute for poor surface preparation.
- Cracking can result because of inconsistent adhesion to the substrate due to unequal stress. A hollow sound in the repair area usually means there is delamination.
- To determine the cause of failure, look on the back of the repair material that has been removed or has fallen out. A dusty surface (dust/dirt that was not properly cleaned from the repair zone) or some of the substrate (parent material) indicates the cause of failure.
- The shape of repair is important. Repairs should always be square or rectangular and a minimum of 1/4 inch deep. Long, narrow repairs have a much greater tendency to crack than even sided (square) repairs.
- Mechanical bond of a fresh material to hardened concrete is dependent on the surface profile. A rough surface is best.
- ICRI Surface Preparation Guide 03732 is an excellent reference guide to proper surface preparation.