Post on 03-Feb-2022
POLISHED CONCRETE FLOORS
Contact:
Christopher Bennett
Architectural Specifications Consultant
Husqvarna Construction Products
17400 West 119th Street
Olathe, KS 66061 USA
phone: 206-375-3066
fax: 866-711-9650
christopher.bennett@husqvarna.com
hqv03a - An AIA Continuing Education Program
Credit for this course is 1 AIA HSW CE Hour
© Ron Blank & Associates, Inc. 2012
Please note: you will need to complete the conclusion
quiz online at ronblank.com to receive credit
An American Institute of Architects (AIA)
Continuing Education Program
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An American Institute of Architects (AIA)
Continuing Education Program
Please note: you will need to complete the conclusion quiz online at
ronblank.com to receive credit
Course Description
During this one hour online course we will review methods for
polishing concrete floors including wet and dry techniques and
discuss densifier, sealer and guard options. Through a review of
environmental and safety benefits, the design professional will
have a better understanding of how to incorporate polished
concrete flooring into their next project.
Learning Objectives
By completing this course, the design professional will be able to:
Describe the process of polishing concrete floors
Compare and contrast the different methods for polishing
concrete floors and list options for densifiers, sealers and
guards.
List several safety and environmental benefits of utilizing
polished concrete flooring.
Explain the life cycle cost benefits of polished concrete floors.
Introduction
Concrete is one of the most common and durable building elements in modern construction and design. It most commonly contains primarily aggregate, cement and water. It may also contain a mixture of additives such as sand, crushed limestone, granite, and even creative elements like crushed glass, marble chips and sea shells.
Waste byproducts that would otherwise end up in landfills, like fly-ash, silica fume and slag cement, can also be used as additives. At the end of its long life or service, concrete can itself be recycled.
Evolution of Polishing
Polishing concrete is an extension of stone and
terrazzo polishing that has been practiced for years.
Concrete was a natural step in the evolution of floor
polishing and stone work.
Polishing Concrete & Surface Preparation
When we talk about polishing concrete here, we are referring to the professional grinding of large concrete slabs. Smaller scale polishing, of concrete countertops and surface areas, employs many of the same techniques, but is usually not referred to as “professional grinding.”
What Makes a Polished Concrete Floor?
In polished concrete, a chemical densifier is applied to strengthen the top most layer of the slab. The exact densifying process varies from manufacturer to manufacturer; most apply the densifier in the grinding process between the transition from metal to resin bonds, but there are those that apply the densifier at the end of the grinding process as well. The concrete surface is then polished with progressively finer grinding tools.
The three basic varieties of floor finishes for polished
concrete include:
exposed aggregate
salt and pepper
cream
Each of these varieties
can have a matte finish
or “high shine” depending
if the use is commercial,
industrial or residential.
Polished Concrete Finishes
What Makes a Polished Concrete Floor?
Concrete is not considered “polished” until around a 400 grit diamond segment has been used to grind the surface, but floors can be finished up to a 3000 grit level which produces a “mirror like” glossy shine.
Experienced polishing contractors know when to switch between grits by observing the characteristics of the floor surface and the amount of material being removed by the grinding process.
Concrete floors can also be scored to have radial lines, grids, bands, borders, and many other designs in the final product.
Polishing Concrete: Wet or Dry
Polishing concrete can be done wet or dry. If done wet,
no vacuum is required, but concrete slurry is produced
and must be disposed of in a responsible manner as it is
deemed a hazardous material by the Occupational
Safety and Health Administration (OSHA).
Polishing Concrete: Wet or Dry
For convenience, most concrete grinding is done dry. However,
when polishing dry, one must employ a HEPA filter equipped
vacuum to capture the fine dust and silica that may be present
in the air due to the grinding process.
Silica is harmful to the lungs and may lead to Silicosis. A
reliable vacuum will ensure a safe working environment.
Retrofit Floors
1. Existing floor slab can be cut or sanded and the exposed natural aggregate will be “the look” of the concrete floor.
2. Prepare an old floor by pouring a topping slab with a minimum thickness of 50 mm. This is useful if the older floor is cracked, uneven or does not have the physical appearance desired by the designer.
Grinders
The professional machines that
prepare or polish concrete are
manufactured to handle high
stress loads and come in two
main types, gear-to-gear and
planetary. Planetary grinders
are further subdivided into
single and dual-drive
machines.
Grinders
Gear-to-gear machines came directly from the marble and
stone grinding technologies of the past and were the first
evolution in concrete preparation and polishing.
As the name implies, gear-to-gear grinding is done with the
gear mechanisms touching each other directly to turn the
grinding heads.
Grinders
Single drive planetary grinders are the next step in professional
grinders and employ a belt drive that turns a planetary disc
which then allows for the grinding plates to turn in an opposite
direction on the grinding surface. An onboard computer usually
regulates grinder performance.
Grinders
A dual-drive concrete polisher has two motors which allow the
grinders to turn in the same or opposite direction of the
planetary disc as well as set different speeds. This allows for
different levels of aggressiveness while grinding.
Diamond Tooling
All concrete grinders use an abrasive element in surface preparation or
concrete polishing. In surface preparation/polishing a diamond segment “tool”
is used. The segments can be metal, resin or ceramic. The two major
components of a diamond segment are the matrix and the diamond
crystals. The matrix is the material that holds the diamond particles in place
until they wear away, and the diamonds do the cutting or “grinding.” Metal
bonded diamond tools are generally used for more aggressive work while
resins and ceramic bonded diamond segments are used for the finer work of
polishing.
Diamond Tooling
When polishing with larger professional machines, higher quality
diamond segments tend to be favored because lower quality
diamond tools can glaze over or wear out very quickly.
Diamond Tooling
Be aware of your concrete slab’s pounds force per square inch (PSI) of the floor as well as the aggregate mix.
A scratch test can be taken to ensure that the concrete’s PSI is not abnormal.
Including your polishing professional in pre-construction meetings will help in avoiding problems and delays.
Densifiers, Sealers and Guards
Liquid silicates are used extensively in construction to accelerate
concrete setting and in the manufacture of refractory and
chemically-resistant bricks, mortars and gunning mixes. Silicates
act as a binder as well as a source of alkali and silica to
enhance heat resistant properties. In polished floors, liquid
silicates are used as penetrating concrete sealers known as
densifiers. The most common densifiers in use today are sodium,
lithium, and potassium silicate mixtures.
Densifiers, Sealers and Guards
Sodium silicate (Na2SiO3) is an inorganic chemical made by combining sand and sodium carbonate at high temperatures. It is sometimes referred to as water glass or liquid glass.
Potassium silicate (K2SiO3) is a water-soluble solution that first gained wide-spread use in Europe for manufacturing purposes, but became available in the United States during World War II. This molecular structure of Potassium silicate is smaller than that of Sodium silicate.
Lithium silicate (Li2SiO4) ranges from a clear to opalescent white color that absorbs carbon dioxide on exposure to air. It has the smallest molecular structure of the three silicates listed here. Flammable hydrogen gas may be produced if this silicate comes in contact with aluminum, zinc, lead or tin, but this is rare. It has increased in use as a concrete densifier in the last decade.
Applying Densifiers
A silicate is applied to the concrete surface to react with the Calcium Hydroxide (free calcium, Portlandite or free lime) that is formed during the production of concrete
The product of this reaction is calcium silicate – a crystalline/glassy structure.
The calcium silicate forms in the pores of the concrete near the surface and is the main contributor for increasing the surface hardness and abrasion resistance of the concrete.
As surface hardness is significantly increased, the requirement for surface coatings in many applications is eliminated.
Guards and Sealers
A penetrating guard/sealing product can also be applied as a final step to
significantly increase the concretes resistance to fats, oils, water and acids.
These coatings can also enrich the color of the polished concrete floor, its
reflectivity and overall beauty.
If applied properly, most guards and sealers will typically have to be
reapplied within 3-7 years, depending on floor traffic and use. All organic
sealers will have some measure of VOCs, so be sure to calculate that into
your “VOC budget”.
Introduction
Polished concrete is an extremely durable flooring option for industrial,
commercial, institutional and residential applications. It has the strength and
versatility of concrete plus the increased abrasive resistance of the top
polished layer. It is noncombustible, has the lowest levels of Volatile Organic
Compounds (VOCs) of any flooring option, and will not support the growth of
mold or dust mites. Polished
concrete is also a safe floor
to walk and work on as it has
more than sufficient slip-
resistance.
VOCs
The Environmental Protection Agency (EPA) describes volatile organic compounds as “gases emitted from certain solids or liquids… including a
variety of chemicals, some of which may have short and long term adverse health effects.” These include paints, lacquers, epoxy and
sealants. A concrete densifier like Potassium silicate is not organic and therefore is considered a zero-VOC product.
VOCs
Many Environmental building associations like the United States Green Building Council (USGBC) and the Energy and Environmental Building Alliance (EEBA) award points in their systems for reducing the amount of VOCs in your project in order to help provide a healthy location for people to live and work in. Lower VOC ratings mean increased safety and more points awarded for exceeding standards.
For more info visit: http://www.epa.gov/iaq/voc.html
Mold, Dust & Allergens
Carpets and other flooring types harbor dust mites and allergens which cannot be removed by vacuuming
Mold grows on any organic material and feeds on carpets, wood studs and joists.
Concrete floors do not allow space for allergens and dust mites - will not support the growth of toxic mold.
For more information:
ASTM D 4300, Standard Test Methods for Ability of Adhesive Films to Support or Resist the Growth of Fungi
US MIL-STD-810E, Environmental Test Methods and Engineering Guidelines, Method 508.4 Fungus, 14JUL 1989
Slip Resistance
The American National Standards Institute (ANSI) describes slip resistance as “the relative force that resists the tendency of the shoe or foot to slide along the walkway surface.” Measuring the Coefficient of Friction (COF) produces a quantitative number which indicates the degree of slip resistance on a floor.
Measurement by the James machine, utilizing a leather sensor, is the most common method for assessing surfaces and products against the 0.5 standard for static coefficient of friction. However, there are other portable testers that may be used to measure static coefficient of friction including the Mark II Slip Tester, the NBS-Brungraber Tester and the Model 80 Tester.
Both ADA and ASTM hold the position that it is currently not possible to designate a single slip measurement device as the standard by which to compare. However, slip resistance measurements are useful when the methods are clearly defined and the results are properly reported.
Fall Factors
Environmental
Lighting
Surface contamination (dust, water or other materials)
Electrical cords (or other obstacles)
Internal or Pathological
Age
Stress
Health conditions
Use of medicinal or recreational drugs
Physical Characteristics
Uneven floor levels
Cracks in floor joints
ASTM & ADA
The American Society for Testing and Materials (ASTM) uses a scale of 0.0 to 1.0 to measure the slip resistance of a surface. A reading under 0.5 can be a slip hazard and anything over a score of 1.0 becomes a trip hazard. Both ASTM and the Americans with Disabilities Act (ADA) recommend a slip resistance of .50 for polished surfaces though a coefficient of .35 is considered normal for average walking.
OSHA recommends a 0.6 slip resistance measurement. A realistic expectation for polished concrete slip resistance should be around OSHA’s recommendations. This is a safe and acceptable level for any type of flooring.
To read more on slip resistance please refer to the following websites:
http://www.astm.org
http://www.osha.gov
http://www.safety-engineer.com/adasurfaces.htm
http://www.slipandfall.com/Other_Slip_and_Fall_Related.htm
The Cost of Concrete
Concrete floors range in price based on the size of the project
as well as the cost for materials and labor in your market.
Concrete floor prices compare favorably against ceramic tile,
quarry tile and wood flooring as well as similar floor like
terrazzo, marble and slate.
Life-cycle Costs
There are flooring options that will be initially
cheaper than polished concrete. However,
when you compare the life-cycle cost of a
concrete floor with other flooring materials,
polished concrete’s cost is substantially
lower. And unlike most other flooring types
(carpet, tile, epoxy coating, etc.) a concrete
floor will rarely, if ever, need to be replaced.
Life-cycle Costs
Maintenance Properly installed polished concrete floors will not need servicing for many years and will not suffer from effloresecence like unpolished concrete can. Effloresecence is the break down of your floor from the effects of hydrostatic pressure. Both effloresecence and normal everyday use will begin to tear down an unpolished floor. Polished concrete leaves you with a tight floor surface that repels water, oil and other contaminants.
Cleaning Instead of hiring a crew to come in and strip and polish a floor or shampoo a carpet, on-site maintenance staff can easily clean the concrete with soap and water. Business does not have to be interrupted to have a clean floor surface.
Energy Savings – Reduced Lighting
Polished concrete has highly reflective properties that can reduce the need for lighting fixtures though it is best to utilize diffuse lighting to reduce glare. With more ambient lighting comes a smaller carbon footprint and reduced energy bills.
Energy Savings
Thermal mass of concrete floors will
also reduce the heating and cooling
loads within a building. Concrete
floors will naturally collect, store and
distribute solar energy in the form of
heat in the winter and reject solar heat
in the summer through passive solar
design. However, when a radiant
heating system is added to a concrete
slab, the natural thermal properties of
the slab can optimize energy
performance and increase comfort.
Life-cycle Costs
The following chart illustrates comparative costs based on 10,000 square feet from a survey conducted by the National Terrazzo and Mosaic Association. The examination of flooring costs was done over a 20-year period. Your costs may vary based on square footage, preparation needs, coloring, etc.
Materials Comparison
Source: Polished Concrete versus
Other Flooring Materials
By Anne Balogh, The Concrete Network
Course Summary
Now the design professional will be able to:
Describe the process of polishing concrete floors
Compare and contrast the different methods for polishing
concrete floors and list options for densifiers, sealers and
guards.
List several safety and environmental benefits of utilizing
polished concrete flooring.
Explain the life cycle cost benefits of polished concrete floors.
POLISHED CONCRETE FLOORS
Contact:
Christopher Bennett
Architectural Specifications Consultant
Husqvarna Construction Products
17400 West 119th Street
Olathe, KS 66061 USA
phone: 206-375-3066
fax: 866-711-9650
christopher.bennett@husqvarna.com
hqv03a - An AIA Continuing Education Program
Credit for this course is 1 AIA HSW CE Hour
© Ron Blank & Associates, Inc. 2012
Please note: you will need to complete the conclusion
quiz online at ronblank.com to receive credit