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Establish who approves the repair
Approve repair and joint-filler colors against a representative sample before applying them across the floor. Metzger/McGuire recommends that a project authority, rather than the installation contractor, select and sign off on the final color. The project specification determines the required approvals and how repair appearance is judged.
An approved repair does not have to disappear at every viewing distance. The Concrete Polishing Council (CPC) guide specification judges filled imperfections against the mockup from 20 feet away under the lighting expected after construction.
| Source | Approval requirement or recommendation |
|---|---|
| Metzger/McGuire color-matching advisory | Recommends final color selection and signoff by a project authority rather than the installation contractor. More than one color may appear to be a reasonable match. The advisory does not assign that role to a specific project party. |
| Albuquerque Public Schools (APS), Section 03 35 43 | The polishing contractor proposes crack and spall repair products, demonstrates them in a mockup, and obtains agreement from the Contractor, Architect and Owner before full application. |
| ACI SPEC-310.1-20, §§1.8.3.1 and 3.5.1.2 | Includes a simulated repair demonstrating acceptable procedures, color and texture. Production repairs use the products and equipment in the Contract Documents, follow manufacturer instructions and match the approved mockup. |
Our mockup planning and approval guide covers the sample’s construction and approval before production polishing. See the ACI 310.1-20 specification guide for incorporation into the Contract Documents and project-specific requirements.
Judge and match repair color
The CPC guide specification judges filled imperfections against the mockup at the specified viewing distance and under post-construction lighting. Matching repair color before the initial grind can produce a poor match after polishing. On an existing floor with no stain or dye and no access for a true mockup, a lightly ground, wetted area is only an approximation.
Judge visibility under the specified conditions
CPC guide specification §3.5 C requires patching compound and treatment to be worked until color differences between the concrete and filled imperfections are not reasonably noticeable, compared with the mockup, when viewed:
- From 20 feet away.
- Under the lighting conditions that will be present after construction.
Match color after the initial grind
Matching repair material to an existing surface before the initial grind can produce a poor match after polishing.
Where an existing floor will receive no stain or dye and there is no access for a true mockup, Metzger/McGuire recommends, at minimum:
1. Lightly grind a small surface area. 2. Wet the ground area. 3. Use it to approximate the concrete’s appearance after densification and polishing when selecting the repair or filler color.
The wetted area is an approximation, not a replacement for a full mockup where one is available.
Match color without promising an exact match
Unless otherwise specified, ACI §2.1.2 calls for polishable materials with these color requirements:
| Repair | ACI color requirement |
|---|---|
| Pinholes, surface pitting, aggregate popouts and scratches | Color coordinated to the specified floor color. |
| Cracks | Approximates the specified color. |
| Spalls | Approximates the specified color; add fine or coarse aggregate when required to approximate the slab finish appearance. |
For a non-resinous grouting system, ACI §3.4.2.1 requires mixing the approved repair material with grinding dust, the manufacturer’s tint or sand to match adjacent concrete surfaces.
Color is only one part of material selection. Our joint filler and crack repair material guide covers the separate material requirements.
Prevent staining from joint-filler overfill
Unless otherwise specified, ACI §2.1.6.1(c) requires a stain-prevention film or another prevention method if needed to prevent joint-filler overfill from staining or shadowing the slab surface.
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Frequently Asked Questions
Metzger/McGuire recommends selection and signoff by a project authority rather than the installation contractor. Contractual approval responsibilities come from the project documents. For example, the APS specification requires the Contractor, Architect and Owner to agree to demonstrated crack and spall repair products before full application.
No. The CPC guide specification requires color differences to be not reasonably noticeable against the mockup when viewed from 20 feet under the lighting expected after construction. It does not require invisibility at close range.
Metzger/McGuire recommends light grinding and wetting as a minimum fallback only where an existing floor will receive no stain or dye and no access is available for a true mockup. The wetted surface approximates the appearance after densification and polishing; it is not equivalent to a full mockup.
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