Understanding Surface Preparation Standards for Concrete

Surface preparation is a crucial step toward a successful outcome when applying a coating system, cement-based self-leveling mortar, resinous slurry, or repair mortar to a concrete substrate. The problem occurs when the installer must interpret the written word describing the surface profile needed. This should never be left open to interpretation.

When working on a repair or coating project, there will be a Design/Structural Engineer, material manufacturer, and installer involved. The Engineers’ responsibility is to specify the system to be used. The specification includes the material type, approved material by name, performance criteria of the material, and the installation process including the required surface preparation.

The material manufacturers are responsible for providing material that follows the Engineers’ performance requirements. This will include recommended mixing procedures, method application, and surface preparation.

The Installer is responsible for installing the specified material according to the manufacturer’s recommendations, including providing the recommended method of surface preparation.

Through this entire process, the method of surface preparation can be somewhat ambiguous. If the manufacturer recommends to “roughen” the surface, what does that mean? The meaning of the word “roughen” to one person might mean something different to another. Eventually, the concrete repair industry came together to develop a surface preparation guide, visually showing what the various levels of surface preparation look and feel like.

There are two organizations that have developed surface preparation guidelines for all parties to follow. The Association for Materials Protection and Performance (AAMP) is based on working with a steel substrate. They focus on corrosion control and protective steel coatings. The International Concrete Repair Institute (ICRI) focusses on concrete substrates. Whether the surface is to be repaired or coated, ICRI can be consulted. Both organizations are well respected within their perspective fields.

Concrete Surface Preparation Standards

AMPP, the Association for Materials Protection and Performance, is a global community of professionals dedicated to materials protection through the advancement of corrosion control and protective coatings. AMPP provides surface preparation guidelines to prepare the surface removing corrosion when coating steel is involved.

ICRI is also a worldwide organization providing surface profile means and methods to produce a multitude of concrete roughness. The ICRI developed a guideline based on the Concrete Surface Profile (CSP). CSP is based on the aggressiveness of the concrete surface profile. The values range from 1-10 with 10 being the most aggressive.

Both organizations offer valuable guidance within their prospective areas. If concrete is to be repaired or coated, ICRI guidelines are to be followed.

Overview of ICRI Standards for Concrete Surface Preparation

ICRI Standards have been specifically developed to visually describe the roughness of a concrete substrate after it has been mechanically prepared. The standard or Concrete Surface Profile (CSP) is the surface profile (hills and valleys) of a specifically prepared substrate produced with a specific piece of equipment.

ICRI recommends all surfaces be mechanically prepared prior to the installation of all resinous and cement-based systems. These systems can be used to repair overhead, vertical, and flatwork concrete. The guide, developed in the early 1990s, shows the profile of 10 different scenarios. These scenarios are performed using different surface preparation machines.

Why is this important? During the development of a specification, the writer needs to have an understanding of the preparation needed to professionally install a system. When a manufacturer formulates a material, the proper surface preparation needs to be determined to obtain the best bond to the substrate. The installation contractor is ultimately responsible for the success of an installation. If there is a failure, the first thing that is looked at is the method of surface preparation. As you can see, surface preparation is a concern of all parties involved.

The CSP method shows exactly what the substrate needs to be prior to the application of material. CSP chips are exact rubber replicas of each level of prep. If the manufacture requires a CSP 4, they can include that in the Technical Data Bulletin. This will provide the specifier and contractor with the exact profile for the project. There will be no guessing at that point.

ICRI CSP Levels

Material manufacturers want their materials to be installed in the best conditions. Every install starts with the surface prep. The CSP method almost ensures the prep will be up to their standards.

Thin mil (up to 10 mils) coatings require an open, durable substrate. The profile needs to be no greater than a 30-grit sandpaper. The cured film needs to fill in the valleys producing a flat, surface film. This is considered CSP 1-2. CSP 3-5 is usually for a self-leveling resinous or cement-based mortar. This profile is rough with angular peaks to develop a strong bond. CSP 6-10 are suited for a conventual concrete overlay. This consistency of concrete requires an extremely rough surface to bond. Concrete is flowable, but not enough to work its way into the concrete pore structure. That is why the substrate needs to be very rough to obtain a bond.

The ICRI CSP method of explaining what level is needed is an extremely easy, simplistic system. When the CSP level is shown, everyone can feel and see the profile.

Choosing the Right Equipment

Surface preparation equipment is available in assorted sizes and aggressiveness. The weight and tooling type dictates what the profile will look like once completed. Scarifiers, shot blasters, and grinders are the most popular machines used when preparing an interior concrete substrate when applying a floor system.

Scarifiers are the most aggressive of the three. It has a horizontal drum fitted with an abrasive bit/tool that spins at a high-speed abrading the surface. Each available bit/tool is designed to provide a specific profile. An industrial vacuum is attached to capture concrete particles. The profile the scarifier provides is CSP 5-10. This is the typical profile needed for a conventional concrete overlay. Conventional concrete needs a very rough surface to obtain a bond. Due to the concrete’s consistency, it is difficult for it to work into the pore structure. The bond obtained will be purely mechanical, locking onto the rough surface.

A shot blaster uses steel shot (beads) in assorted sizes to prepare a surface. Within the machine is a blast wheel that throws the shot to the surface. During impact, concrete breaks away leaving it well-prepared. As the concrete it removed, the debris is captured with an attached industrial vacuum. The shot then bounces up into a shot hopper to be reused. The profile produced is CSP 1-3. The varying profiles depend on the travel speed of the machine and the steel shot size.

The grinder is the most versatile machine. It can not only prepare a surface it has the capability of removing paints and coatings. At times, there will be a previously applied system that needs to be removed before installing a new one. A grinder fitted with the proper tooling can remove thick or rubbery systems. The same grinder fitted with a fine-grit diamond tool can also prepare the surface for a 2-mil coating. Thin coatings need a durable, open surface that feels like 30-80 grit sandpaper. Being a thin coating, the surface profile cannot reflect through the cured film. The surface profile can be CSP 1-5 which will be acceptable for more systems.

Conclusion

When multiple parties engage in a flooring project, all parties must have a good understanding of what needs to be done for a successful project. ICRI was formed back in the late 1980s to develop a method to do just that. Developing Concrete Surface Profile (CSP) enabled specifiers, material manufacturers, and installers to have an understanding of all levels of surface preparation. It starts with a manufacturer requiring a certain CSP value and ends with the installer performing the work to obtain such value.

At Niagara Machine, we are an ICRI member with full access to their surface preparation documents. If you have questions concerning the ICRI CSP Chip method, contact one of our well-trained field representatives for help. They will guide you through the surface prep process and provide you with the proper method to obtain your goal.