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.

polishing, grinders, tools and densifiers

CONCRETE

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”.

SAFETY AND ENVIRONMENTAL ASPECTS OF POLISHED CONCRETE

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

Costs of Concrete

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