SSPC SP13: Surface Preparation of Concrete Methods and Testing

SSPC SP13, also designated NACE No. 6, is the joint industry standard that defines how concrete must be assessed, cleaned, profiled, and tested before a protective coating or lining goes on. Published through the Association for Materials Protection and Performance (AMPP), it sets the common vocabulary and pass/fail criteria that specifiers, applicators, and inspectors use on industrial concrete work.¹ Get the preparation wrong and the coating fails; the standard exists so that “properly prepared” means the same thing to everyone on the project.

What SSPC SP13 Covers

The standard applies to concrete in industrial and atmospheric service, not decorative residential finishes. Typical settings include wastewater treatment plants, chemical processing facilities, secondary containment areas, and industrial floors exposed to corrosive substances.²

When a project specification references SP13, both the contractor and the inspector know which tests apply and which results count as passing. Facilities often call for compliance to satisfy insurance requirements, federal workplace safety rules for floor traction, or containment integrity regulations.

What to Check Before Preparation Starts

Mechanical work cannot rescue a substrate that is too young, too wet, or weak below the surface. The pre-preparation checks catch those problems before anyone turns on a grinder.

Cure Time

Fresh concrete needs to reach adequate strength and shed enough moisture before it can hold a coating. Industry practice calls for a minimum 28-day cure, the standard age at which concrete reaches its design compressive strength. Coat sooner and trapped moisture tends to blister or delaminate the lining later.

Moisture Testing

Even concrete that has cured for months can retain enough moisture to destroy a coating system. The simplest screen is ASTM D4263, the plastic sheet test: a polyethylene sheet of roughly 18 by 18 inches is taped to the surface and left in place for at least 16 hours.³ Condensation on the underside or darkening of the concrete beneath means the surface is too wet to coat.⁴

That test is pass/fail. When a project needs actual numbers, contractors use the calcium chloride test (ASTM F1869), which measures moisture vapor emission over 60 to 72 hours, or an in-situ relative humidity probe method (ASTM F2170). The coating manufacturer specifies which test is required and what threshold the product can tolerate.

Laitance and Surface Soundness

Laitance is the thin, weak layer of cement fines and water that rises during finishing. SP13 describes it as a brittle film whose thickness depends on water content, admixtures, and how aggressively the slab was worked.⁵ A coating applied over laitance bonds to that weak layer rather than to sound concrete, and the whole system can peel under load.

Soundness testing finds areas where concrete has delaminated below the surface. Dragging a heavy steel chain across a floor produces a clear ring over solid concrete and a dull thud over hollow zones. Hammer tapping then marks the boundaries of weak spots so they can be repaired. These methods reliably detect delaminations within the top two to three inches of the slab.

Initial Surface Cleaning

Loose dirt, dust, and debris come off before mechanical or chemical preparation begins. ASTM D4258 lists basic methods including broom cleaning, vacuuming, air blasting, water washing, detergent scrubbing, and steam cleaning.⁶ None of these remove laitance or create a surface profile, so they are always preliminary rather than standalone preparation.⁵

Approved Preparation Methods

SP13 recognizes three categories: mechanical, chemical, and water-based. The method depends on the required concrete surface profile (CSP), the contaminants present, and site constraints. Contractors document the starting surface condition in a formal inspection report that justifies the method chosen.

Mechanical Preparation

Abrasive blasting drives media against the concrete to strip the weak surface layer and open a texture for bonding. The ICRI guideline defines 10 concrete surface profiles, from CSP 1 (near-smooth) to CSP 10 (very rough, with peak-to-valley amplitude exceeding a quarter inch).⁷ Thin-film coatings generally call for a low CSP; thick linings and polymer overlays need heavier profiles.

Where blasting is impractical because of dust, access, or safety constraints, power grinding, scarifying, and shot blasting work as alternatives. Walk-behind shot blasters are common on large floor areas because they produce consistent profiles with built-in dust collection. Scarifiers use rotating cutting wheels and are especially effective at removing thick existing coatings. Beyond removing contaminants, these methods open the concrete’s pores so the coating can anchor instead of sitting on top.⁵

Chemical Preparation

Acid etching uses a dilute acid solution to dissolve laitance and roughen horizontal concrete. The standard references ASTM D4260 for the procedure and requires complete removal of reaction products plus pH testing to confirm neutralization.⁵ Muriatic acid (hydrochloric) and phosphoric acid are both used, but the standard prohibits hydrochloric acid wherever it could corrode reinforcing steel or metal fibers embedded in the concrete.

Etching has real limits. It does not work on vertical surfaces, it cannot cut through curing compounds or sealers, and it requires handling, containment, and disposal procedures for hazardous materials. For those reasons, mechanical methods have largely overtaken acid etching on industrial projects.

Water Jetting

High-pressure water strips loose coatings and contaminants without the dust clouds that come with abrasive blasting. SSPC classifies water cleaning by pressure:

Low-pressure water cleaning: below 5,000 psi
High-pressure water cleaning: 5,000 to 10,000 psi
High-pressure water jetting: 10,000 to 25,000 psi
Ultra-high-pressure water jetting: above 25,000 psi

Removing loose coatings and surface contaminants generally requires high-pressure cleaning range or above. Operators balance pressure against the risk of damaging structural concrete or exposing rebar. Water jetting is especially useful in food processing, pharmaceutical, and confined-space environments where airborne abrasive dust is unacceptable.

Conditions at Application Time

A perfectly prepared surface still produces a failed coating if conditions are wrong when the coating goes on. Most manufacturers call for a concrete surface temperature between roughly 50°F and 90°F, with the exact window depending on the product. Epoxies tend to perform best between 60°F and 85°F.

The variable that catches crews out is the dew point spread. If the concrete surface temperature sits too close to the dew point, invisible condensation forms on the substrate and ruins adhesion. The widely followed rule is that the surface temperature must be at least 5°F above the dew point before, during, and through the cure period. Contractors check surface temperature with an infrared thermometer and dew point with a sling psychrometer or electronic hygrometer, and document both readings before each application shift.

How the Prepared Surface Is Judged

Before any coating goes on, the prepared surface runs through a short list of tests. SP13 states acceptance criteria in a table, and failing any one of them sends the crew back to more preparation.

Surface Profile Verification

The prepared surface is compared to ICRI concrete surface profile chips, physical reference samples that represent CSP 1 through CSP 10.⁷ The inspector holds the comparator chip against the concrete and looks for a visual and tactile match. The target CSP comes from the coating manufacturer’s technical data sheet, not from the contractor’s judgment. Applying a heavy-build novolac lining over a CSP 2 surface, for example, invites peeling.

pH Testing

After acid etching, ASTM D4262 confirms the acid has been fully neutralized.⁸ A pH indicator solution is applied to the rinsed concrete. SP13’s acceptance criterion is specific: the pH reading after the final rinse cannot be more than 1.0 unit below or 2.0 units above the pH of the rinse water itself.⁵ Residual acid reacts with many coating chemistries and causes blistering, so this check matters more than it looks.

Pull-Off Adhesion Testing

For critical applications, ASTM D7234 measures actual bond strength between the coating and the concrete. A metal dolly is glued to the coated surface and pulled off with a calibrated device that records the force. Protective coatings on concrete typically achieve pull-off values between 200 and 600 psi. The best result is when the concrete itself fractures before the bond fails (a cohesive substrate failure), particularly when the pull-off force exceeds 250 psi. Minimum acceptable values come from the coating manufacturer and the project specification.

Dust and Cleanliness

A pressure-sensitive tape test checks for residual dust. Tape is pressed firmly against the concrete and then examined for fine particles. Any visible dust film sends the surface back for more cleaning. Dust creates a weak boundary layer that functions much like laitance: the coating ends up bonded to the dust, not to the concrete.

Safety Rules That Ride Along

Preparation generates respirable crystalline silica, one of the most regulated airborne hazards in construction. OSHA’s silica rule for construction (29 CFR 1926.1153) sets a permissible exposure limit of 50 micrograms per cubic meter and prescribes engineering controls for virtually every tool used on concrete.⁹

Table 1 of that regulation goes tool by tool. Handheld grinders must use a shroud connected to a dust collection system with a filter at least 99 percent efficient. Walk-behind floor grinders require either integrated water delivery or the manufacturer’s recommended dust collection system. Handheld power saws need a continuous water feed, and workers using them indoors must also wear respiratory protection. Abrasive blasting on silica-containing substrates must comply with OSHA’s ventilation standards in addition to any alternative exposure-control plan.⁹

Acid etching carries its own hazards. Hydrochloric and phosphoric acids cause burns on contact and release harmful fumes, especially in enclosed spaces. SP13 permits etching only where hazardous materials handling, containment, and disposal procedures are already in place. Work in tanks or secondary containment also triggers OSHA’s permit-required confined space rules.

Certification and Buying the Standard

AMPP offers the C7 Abrasive Blaster Certification for workers performing blast cleaning on industrial substrates, including concrete. Candidates must document at least 800 hours of abrasive blasting experience in an industrial or marine environment, verified in writing by their employer’s human resources department.¹⁰ The credential is valid for four years. No federal law requires it, but refinery and petrochemical specifications often do, and a crew that shows up without certified blasters can be sent home on day one.

The current edition, SSPC-SP 13/NACE No. 6 (2024), is available as a PDF through the ANSI webstore for $125.¹¹ The standard cross-references several ASTM test methods (D4258, D4260, D4262, D4263) that must be purchased separately. Budget for the full set when bidding, because inspectors will hold the crew to the procedures described in those companion documents.

1
ANSI Webstore. NACE No. 6/SSPC-SP 13 – Surface Preparation of Concrete
2
ANSI Webstore. NACE No. 6/SSPC-SP 13 – Surface Preparation of Concrete
3
Association for Materials Protection and Performance (AMPP). Concrete Moisture Testing and Mitigation
4
ASTM International. ASTM D4263-83(2018) – Standard Test Method for Indicating Moisture in Concrete by the Plastic Sheet Method
5
SSPC-SP 13/NACE No. 6. Joint Surface Preparation Standard SSPC-SP 13/NACE No. 6
6
ASTM International. ASTM D4258-05(2017) – Standard Practice for Surface Cleaning Concrete for Coating
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International Concrete Repair Institute. Concrete Surface Profiles – Concrete Repair Bulletin
8
ASTM International. ASTM D4262-05(2018) – Standard Test Method for pH of Chemically Cleaned or Etched Concrete Surfaces
9
eCFR. 29 CFR 1926.1153 – Respirable Crystalline Silica
10
Association for Materials Protection and Performance (AMPP). Abrasive Blaster Certification (C7)
11
ANSI Webstore. SSPC-SP 13/NACE No. 6-2024 – Surface Preparation of Concrete