Main image courtesy of Diamond Products

Polished concrete is a concrete substrate that has been ground down and is sealed creating a natural look. The concrete floor is chemically treated and ground down with diamond polishing segments to create a shiny surface.

Polished concrete benefits

After the concrete has been ground down to achieve the desired look, a penetrating sealer is applied to seal the pores of the substrate. Polished concrete has ongoing benefits such as not allowing mould to grow and an easy maintenance and a standard cleaning regime.

We asked the industry what the top 6 questions are that they get asked about polished concrete.

1. Can any floor be ground and polished to give a shine?

Brian Clark of Diamond Products says, “Almost any concrete floor can be ground and polished. The condition and strength of the concrete can influence the result.”

Mark Griesel from Sika advise that the minimum requirement is 25MPa compressive strength and should be specified for polished concrete floors. Attempting to polish low strength concrete floors and screeds are extremely problematic, one can grind theses floors to expose the aggregate with a chemical treatment to achieve similar aesthetic finish.

Louis Visser from MAPEI is of the opinion, that generally, only concrete can be ground down to achieve a polished concrete effect, but aggregate type and size, as well as concrete density, play a large role in project success and final finish. “There have been some attempts in the past to grind(?) screeds, but this has not been very successful. Some self-levelling screeds can be bulked with aggregates, applied, and then ground down to achieve a polished concrete/terrazzo type finish,” he adds.

Sharon Margon of TAL advises that concrete slabs and certain decorative overlayments/screeds can be polished or ground. “It is essential that the original concrete or decorative overlayment/screed is of sufficient strength and integrally sound. There are various stages of grinding during which the substrate is transformed from a rough, exposed aggregate finish to a smooth, glossy finish. Each stage of grinding, often referred to as ‘tooling’, has different grades of grinding and polishing cups.”

2. Do you use a sealer or epoxy to get the shine on the concrete?

Brian says for the best results you should achieve a mechanical shine/gloss on the concrete before applying either a protective sealer or epoxy.

For optimum results, the concrete must be mechanically polished prior to applying a protective sealer. The sealer/epoxy is to protect and act as a barrier to maintain the polish.

The lobby floor of the Liberty Offices in Braamfontein completed by VPC Superfloors

Mark says one can choose between two methods. “The first method is using different grinding pads starting with course to fine and use a lithium base surface densifier normally with 3 or 2 polishing stages left to complete the polishing process. Method two will have fewer grinding stages for instance using a 50, 100 and 200 grit polishing pad. One will then “chemically polish” the concrete surface using a lithium base gloss surface densifier sealer coat with a final polish with a fine twister pad if very high sheen is required.”

According to Louis, there are numerous products on the market to achieve a polished look with numerous application methods to achieve different results, but the product selection is determined based on the requirements of the specific space.

“The term “Polished concrete” is exactly what you get, concrete ground down in various phases to achieve a very smooth substrate, densified or sealed but with products that penetrate the substrate, and once dried/cured they are buffed or polished to achieve the shine.

Coatings can also be used to achieve a similar aesthetic look, but generally, the term polished concrete is then not referenced. These coatings vary from metallic wax sealers, water-based epoxies or Polyurethane based coatings.”

Geoff McLean from Mactool says, “Sealer burnished into the floor after necessary prep done with a 3000# diamond pad.”

According to Johnathan Parker from Technical Finishes, “True polished concrete is done by densifying the surface of the concrete which makes it harder and makes the polishing process easier. Once a satisfactory level of polishing is achieved the surface is protected with a clear sealer which is then burnished into the floor leaving a permanent finish which will need to be maintained from time to time.”

3. How often do you have to maintain or repolish the floor to keep the shine?

Brian believes that a bespoke maintenance programme is of paramount importance from the beginning.

Maintenance of a polished concrete floor depends largely on several factors, the amount of traffic over the floor and the level of gloss are the most important. If it’s a very high traffic floor in a busy retail space, maintenance may be required every 3-6 months. If it’s a very high gloss floor in upmarket residential space maintenance with a diamond pad may be required monthly.

Richard Hugh says, “Some floors shouldn’t need any periodic maintenance. The shine will last the entire lifetime of the floor depending on the way it is cleaned. By using certain pads and water during your cleaning routine you are re-polishing the floor removing micro-scratches from the surface.”

Sharon mentions to keep a gloss finish is largely dependent on the service conditions that the floor is exposed to. “Heavy and high traffic will lead to scratches on a polished concrete floor, dulling the shine. If there is a coating applied, this can wear away over time and show scratches and scuffs requiring reapplication of the floor coating.”

4. Can you design a special colour concrete mix to be ground and polished?

According to Louis, this has been done in the past successfully, but the concrete does become rather expensive due to pigment costs and colour contamination of the ready-mix suppliers’ trucks, which requires excessive cleaning.

“Generally, designs are rather done with naturally coloured high-density concrete with selected coloured stone aggregates.”

Sharon confirms that decorative overlayments/screeds can be produced in a variety of colours.  These colourways can be further enhanced by the addition of various coloured aggregates in the mix.

At Technical Finishes there is a range of products that are formulated to be used as polishable overlay screed systems that are applied to existing concrete and can mimic the desired polished concrete look. For larger projects, the colour or design may be ordered on request from larger concrete (ready mix) plants.

Brian says that coloured concrete can be treated the same way as standard concrete with the same end results.

5. Is polished concrete more durable than coatings such as polyurethanes or epoxies?

“Yes, provided that the correct methodology was followed on installation and that the appropriate choice of sealer was selected. With polished concrete, the surface is extremely durable only susceptible to mechanical damage. Polished concrete is not suspectable to systems failures,” says Brian.

Mark feels that the floor finishes mentioned are different functional floors. “Floors finishes will be specified according to the customer’s needs i.e., aesthetics, heavy traffic, chemical resistance etc.  The maintenance cost of polished concrete floors over time is lower.”

Sharon explains, “Installed correctly, polished concrete tends to be very durable. The choice between polished concrete or a resin floor covering such as epoxy or polyurethane will be dependent on the operating conditions and service requirements. Consideration of these requirements will determine which option is fit for the purpose and therefore most durable for that application.”

6. Is polished concrete slippery when wet?

“Slip resistance depends largely on the level of polishing as well as what finishing and maintenance systems are used, says Johnathan. “Often “cheap” polished concrete consists of a grind and seal with epoxy clear which looks and feels like polished concrete but does not have the slip resistance you would expect.”

Stoneflow by TAL SA

Louis says that an array of different factors determine this. “Coatings will generally offer better cleanliness, chemical resistance, better impact resistance, superior thermal shock capabilities etc dependent on the specific application and requirement. In certain applications, a coating may be required to protect the concrete from degradation or attack.”

Brian says that polished concrete is not slippery when wet and has passed all the necessary slip coefficient tests in both America and Europe when using the approved sealers.  Richard says their floors surpasses the Dynamic Coefficient Friction Standard, which means it has more grip than self-levelling coatings and glazed tiles when wet.

What top trends do you see in polished concrete locally? Or overseas?

  • Brian Clark – Diamond Products: The greatest shift is to very large polished concrete commercial floors using faster and less expensive systems, offering the many advantages of polished concrete at a significantly more affordable cost.
  • Mark Griesel – SIKA: The trend these days is using the chemical polished method and where available the use of coloured aggregates with patterns. stained concrete and pigmented polished floors seems to be the latest market trends. A very good example is the new extension of the Durban Promenade from Moyo’s (formerly known) Pier to the Durban Harbour where a selection of pigmented concrete with patterns were used.
  • Louis Visser – MAPEI: There are no specific trends that really separate one floor from another, it is rather defined by personal choice and colour selection of the concrete/aggregate blend and if the final finish is gloss or matt.
  • Richard Hugh – Superb Flooring: In South Africa, I have seen a big change in the use of high standard polished concretes in large retail chains due to the performance of the floor. It is the most durable and aesthetically pleasing floor type but also has a very competitive installation cost with the lowest lifecycle cost of any other alternative.
  • Sharon Margon – TAL: Polished concrete with an exposed aggregate that resembles Terrazzo is extremely popular. This traditional floor covering has become a new ‘classic’ in design terms. It offers an extremely long-lasting floor if installed correctly, reducing downstream maintenance and refurbishment costs.
  • Johnathan Parker – Technical Finishes: More and more development in the construction industry with ever-increasing pricing on finishing systems for floors calls for polished concrete as it is purely the treatment and sealing of the existing concrete for a functional, dust free and aesthetically pleasing finish. “The top trends we see even in our own business are variety and choice over different looks and colours. What is popular in our business are the exposed aggregate Terrazzo finishes which we design with variable colours on aggregate as well as a choice of overall colour and finish.”

ED’s note: Polished concrete has become increasingly popular and has wonderful potential. However, as with any specialist flooring, quality products and equipment have to be used by a qualified contractor for the best result.

All the above companies offer free technical advice and assistance for your project – make use of this service.

Full acknowledgment and thanks go to Richard Hugh at www.superfloor.co.za; Geoff McLea at www.mactool.co.za; Brian Clark at www.diamondpc.co.za; Johnathan Parker and Yvette Watters at https://technicalfinishes.com; Geoffrey Green and Louis Visser at www.mapei.com/za/; Sharon Margon at www.tal.co.za and Romaine Cloete and Mark Griesel at www.sika.co.za for the information in this editorial.

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