CIM Industries Blog

Coatings fail to bond to concrete for two reasons:   

1. Lack of sufficient surface profile.
2. Moisture in the concrete

Today, most coating manufacturers require concrete substrates to be dry (<5% moisture content) with low vapor transmission (< 3-5lbs per 1000 sq. ft./24 hours) before applying most types of membranes. This applies to both new and existing concrete substrates, although each may have its own set of moisture-related problems. For example, a 90-year-old poured-in-place partially buried concrete tank may face an entirely different set of circumstances from a newly constructed concrete slab with a steel tank mounted on it. Ultimately, the concrete needs to be dry prior to coating.

The first thing that usually comes to mind when people think of profiling concrete to prepare for coating application is sandblasting. Unfortunately, this method may not always be practical. Sandblasting is loud and can create excessive dust so other alternatives are sometimes required.

When applying elastomeric coatings over concrete, abrading the surface is almost always required. This prerequisite to abrading the surface is twofold:

1) Remove the “laitance” or weak surface layer of the concrete.
2) Create an anchor profile for the coating to adhere.

The requirement which most coating manufacturers use to measure the roughness of the concrete surface is the Concrete Surface Profile or “CSP”. CSP was developed by the International Coating Repair Institute (ICRI) and is divided into 10 classifications often depicted by molded rubber comparison chips (CSP 1-10) as shown below.