Processed Concrete Floors in Renovations

Durable | Sustainable | Beautiful

Architects have been enamored of concrete’s beauty for a very long time; the general public - not so much. Never mind that Pliny the Elder praised the virtues of Roman “Opus caementum” in monumental constructions of the 1st century CE, “It looks unfinished” was a typical lament of the consumer of the vernacular, particularly up until the turn of the 21st century. Then came finishing techniques, densifiers and sealers that made concrete counters, tabletops, and floors chic, if only because their finishes afforded them looks that were less like concrete and more like stone.

Today, contractors can transform a once-utilitarian factory floor into a dramatic walking surface for lobbies and lofts. With a substantial history of successful adaptive re-use projects, the architectural team at Trivers Associates specifies the latest in proven techniques and materials to leverage the value potential of century-old concrete slabs into distinctive designs.

“Concrete Polishing” is commonly used to refer to changing an existing concrete surface by means of a mechanical process involving cutting and/or refining the surface to a desired finish. However, the correct terminology is “Concrete Processing,” as not all processed concrete can be called “polished” (if, for example, only Grinding and Honing steps are undertaken).

There are three fundamental visual aspects of a processed concrete floor finish – surface cut (i.e. degree of aggregate exposure), reflection (degree of polish), and enhancements, if any (stains, dyes, saw-cut patterns).

Finishing levels - basic, medium and premium - drive the amount of work entailed, both in terms of aggregate exposure and reflection/sheen.

frosario
Basic-level grind-finish, Medium-level honed-finished, Premium-level polished 

AGGREGATE EXPOSURE CLASS 

Aggregate Exposure Class

AGGREGATE EXPOSURE EXAMPLES 

frosario Class A cream exposure
Class A- Cream Exposure

Class B- Fine Aggregate Exposure
Class B- Fine Aggregate (Salt & Pepper) Exposure

Class C - Medium Aggregate Exposure
Class C- Medium Aggregate Exposure

Class D Large Aggregate Exposure
Class D- Large Aggregate Exposure

GLOSS LEVELS

Gloss Levels

DENSIFIERS

Densifiers are water-based chemical solutions that first work by penetrating into the surface of the concrete and reacting with calcium hydroxide to produce calcium silicate hydrate (CSH). The CSH that is produced fills the open pores of the concrete, increasing its density. The three types of densifier most commonly used are- sodium, potassium, and lithium. Lithium-silicates penetrate without scrubbing or adding large amounts of water. This saves time, money and energy. They also penetrate completely, which eliminates flushing, waste containment, collection, and disposal—and their costs.

Variables within a concrete processing contractor’s control:

Equipment
    Weight, RPMs, speed at which machine moves over surface in a linear motion.
Abrasives
    Configuration of diamonds’ face/tread
    Saturation of diamond grit in the bonding
    Hardness of diamond bonding
    Point at which operators switch abrasives
Densifiers
    When applied
    What type
Physical grinding, honing, and polishing
    Degree to which the concrete surface is cut
    Level of clarity of the cut surface
    Refinement of the concrete from one grit to the next
    How well the floor is cleaned between each grit adhesive

Variables of Existing Conditions not within a processing concrete contractor’s control:

Concrete Surface
    PSI
    Imperfections that need to be removed
    Surface flatness and levelness
    Presence of coatings, glues or mastics
    Finish: hand-troweled or mechanically-troweled
Concrete Mix Design
    Aggregate

PROCESSED CONCRETE FLOOR FINISHING – THE SUSTAINABLE CHOICE
Going forward, exposing and processing existing concrete floor slabs will increasingly be among the most popular value-added choices available in adaptive re-use buildings. Trivers Associates stands committed to delivering current and reliable specifications and detailing of this environmentally responsible process.

Sources: 
An Introduction to Concrete Processing
A Quick Guide to Polishing Concrete Floors
Polished Concrete Information and Options
Levels of Concrete Polishing 
Technical Resources for the Concrete Industry
Concrete Polishing Association of America (CPAA)

Published by Frank Rosario, AIA, Project Manager