April 29 2019 0Comment

The 3-Stage Concrete Grinding, Honing and Polishing Process

Polished concrete has captured the imagination of architects, engineers, property owners, interior designers and general contractors for a little more than 10 years. The entire design process is a mix of technical know-how, industry experience and artistic expression that can make or break the result, depending on the skill level of the polisher and crew. A good polisher will not only complete the technical training for concrete polishing, he will educate the customer on the type of processing, the total time and the cost of completing the job successfully.

Three Stages, Multiple Steps

Polishing concrete is a progressive process that changes and refines an existing concrete surface to a desired finish. This process starts with grinding and moves to honing and polishing. Each stage requires a series of steps that use consecutively finer grit abrasives to work the concrete, enhancing its aesthetic beauty, while a densifier is applied and absorbed into the concrete, creating a chemical reaction that makes it more dense and hard.

Three Types of Densifiers

  • Sodium
  • Potassium
  • Lithium

Meanwhile, a polisher must take into account variables he can control – and variable he can’t, that can affect the success of the polishing process, especially with an existing concrete slab. If it’s known that the concrete is to be polished before it is poured, use a polishing-friendly mix design and floor flatness rating for a better end result.

Controllable Variables

  • Equipment
    • Weight, RPMs, Speed
    • Planetary movement – active or passive, direction
  • Abrasives
    • Configuration of the diamonds’ face/tread
    • Saturation of diamond grit
    • Hardness of diamond bonding
    • Time to switch abrasives
  • Densifiers
    • Type
    • Application time
  • Physical grinding, honing and polishing
    • How the concrete surface is cut
    • Clarity of the cut surface
    • Refinement of the concrete from one grit to the next

Uncontrollable Variables

  • Condition of concrete surface
    • PSI
      • Residential concrete is generally a low, 2,500 PSI, hand troweled concrete mix; does not polish as well
      • Commercial concrete is a higher 3,500 PSI, machine troweled concrete mix in the open areas; hand troweled in corners and tight areas; polishes better
    • Imperfections to remove
    • Surface flatness and levelness
    • Hand or mechanically troweled
    • Presence of coatings, glues or mastics
  • The concrete mix design
    • Types of admixtures, fibers and polymers used
    • Aggregate
    • Vibrated for air removal or not

It’s All About the Grit Sequence

Polishers are looking for a number of conditions during the grinding, honing and polishing process:

  • Clarity of reflection
  • Sheen
  • Shine
  • Depth
  • Uniformity and color of reflection

To grind, hone and polish a concrete surface to the maximum “clarity of reflection,” use a sequence of grit abrasives, moving on to the next finer grit only when the previous one has done its job. This will insure a clean, crisp look of the concrete surface at a 200-, 400- and 800-grit resin while achieving a maximum surface durability.

Different stages of processed concrete look different to the seasoned eye:

  • Grinding level – the degree to which the surface is cut
    • Cream
    • Salt & Pepper
    • Exposed Aggregate
  • The level of clarity of reflection of the cut surface
    • Honed surface stops at 200- or 400-grit resin
    • Semi-polished surface stops at 400- or 800-grit resin
    • Highly polished surface stops at 1,500- or 3,000-grit resin
  • Decorative enhancements
    • Coloring with integral, acid-stained and water- or solvent-based stains and dyes
    • Saw cut patterns
    • Engraving

All Stone Restoration can restore your concrete floor or add in a new, sparkling one. Whether you need help deciding on the finish or decorative style. We have over 47 years of hands-on experience in all phases of stone and concrete restoration. Contact us today to get your free on-site estimate.