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The Concrete World – With new opportunities

by Darren
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Following the regrettable closure of the C&CI and the strong reaction from the construction industry in response to a potential loss of services, The Concrete Institute was formed.

The South African building and construction industry was surprised and more than a little shocked at the recent closure of the Cement & Concrete Institute which was precipitated by the withdrawal of funding and the resignation from the C&CI by PPC, following which the other funders, AfriSam, Lafarge and NPC-Cimpor, were compelled to resign as PPC’s withdrawal left a significant void in the structure and funding of the non-profit organisation.

 

As one of the major sources of technical information, education and training, and authoritative publications in the Southern Hemisphere, the C&CI was at the hub of the industry and a main player in the specification and use of cement and concrete.

However, following the regrettable closure of the C&CI and the subsequent strong reaction from both the construction industry and the academic fraternity in response to a potential loss of services, The Concrete Institute was formed. The initial funders are AfriSam, Lafarge and Sephaku. The Concrete Institute will continue to provide the services previously provided by the C&CI, under the management of former C&CI managing director, Bryan Perrie. (See separate article in this issue.)

Industrial Floors

Despite being one of the most traditional and basic types of warehouse flooring, concrete is still the best for industrial floors, particularly with the treatments currently available.

If maintained properly, it has a life expectancy which exceeds that of many other flooring materials and is also one of the most durable, with a proven record for strength in a huge range of industrial applications. Also, it is cost-effective and versatile in its use.

However, because it is porous, concrete is prone to staining and can also be susceptible to pitting. Therefore, it may be advisable under certain circumstances to have it covered with a protective paint or sealant which will protect it from oils and chemicals and reduce the damage from wear and tear. This not only reduces the deterioration of the floor but also reduces the need for and cost of repairs, although the maintenance of some paints and sealants can prove to be expensive.

An epoxy floor using the concrete as a substrate makes it suitable for a wide range of applications, particularly as it offers functionality and high performance for the industrial and commercial sectors.

Epoxy treatments for concrete

Apart from various hardeners and other additives that strengthen the concrete to make it even more suitable for heavy industrial applications, there are several other treatments such as epoxy and polyurethane coatings that increase the versatility of the floor.

Depending on the type of system used, epoxy flooring can provide chemical resistance, low light reflectivity, non-slip surfaces, high impact resistance and protection from chipping and cracking – making it ideally suitable for harsh environments and tough working conditions.

Alternatively, a semi-flexible epoxy coating can provide extremely high impact resistance and protection from chips and cracks. This is especially important for automotive loading bays and drum storage areas, as well as mechanical equipment rooms and similar applications.

Furthermore, these flooring materials are designed for harsh environments and tough conditions, offering maximum durability and performance, even in extremes of temperature (e.g. freezer rooms, cold storage lockers and food processing areas).

Decorative concrete

Decorative concrete has become a material of choice for commercial and residential applications because it not only provides one of the most permanent floor finishes, but its versatility can be expressed in stained, coloured, painted, polished, stamped and personalised floors which are now regularly seen in retail stores, restaurants, offices and homes everywhere.

Available in vibrant colours, patterns and textures, concrete floors can be seamless with no place for bacteria, dirt and grime to hide, and anti-bacterial and -microbial treatments can be provided to make them truly hygienic and pet-proof.

Staining concrete is one of the most popular applications for transforming concrete slabs, and homeowners, architects, interior designers and builders often favour stained concrete because of the unique effects that can be achieved by combining colours and application techniques on the concrete flooring.

Stamped concrete: Once purely used as a patio feature, stamped concrete can be a designer’s dream for interior floors. The process employed achieves a textured appearance by using an imprinting mat on the fresh concrete, which can resemble tiles, bricks or even wood grain, and stencils can be used to provide even more design variations.

Stamping is usually carried out with a combination of two colours – the first being the base colour, and the second being the release agent that prevents the imprinting mat from sticking to the base. Many different colours and patterns can be combined to provide endless design options.

Polished concrete

Professional polishing provides a spectacular finish to an otherwise mundane concrete feature, giving the illusion of a highly waxed surface, without the hard work or slipping hazard.

An experienced contractor with the right machinery can buff any suitable concrete surface into a high shine, which can be enhanced further, depending on the colour or the concrete that is used. (See separate article in this issue.)

Bringing you up to date

To find out what the latest developments are in this sector of the flooring industry, FLOORS in Africa contacted Anathi Zitumane of Lafarge, Nic de Carvalho of Concrete Laser Flooring; and Andreas Hasselmose of Superb Flooring Systems for the current information, as shown below.

What are the latest developments re concrete for floors?

Anathi Zitumane, Lafarge: Getting concrete to look visually appealing; this can be done by adding colour to the concrete, or mixing a variety of coloured aggregate. The biggest problems with floors are the joints, durability and maintenance issues. In our sales programme we have a polish for concrete that provides a smooth texture like polished marble, silky to the touch and elegant.

Nic de Carvalho, Concrete Laser Flooring: We are currently launching a new patented jointless concrete flooring system. It consists of a concrete composite concrete mix design with proprietary admixtures and high dosages of steel fibres. This system allows us to design thinner floors and in panel sizes up to 6 000m², thus accelerating construction programmes and reducing the carbon footprint.

(Bryan Perrie of The Concrete Institute comments: “Reducing the thickness will reduce the CO2 footprint, but adding high dosages of steel fibres, which have a significantly high CO2 footprint than concrete, may more than offset any reduction.”)

Andreas Hasselmose, Superb Flooring Systems: There are some new and interesting cement-based overlays developed lately that can be polished. These overlays can be as thin as 10-15mm and can be designed with the colour and aggregate you want to use. They give a very uniform look. This is beneficial when the customer wants something different from what existing concrete can offer.

What are the latest developments for polishing concrete?

Anathi Zitumane, Lafarge: The latest development is that it can now be used for outdoor applications.

Nic de Carvalho, Concrete Laser Flooring: The latest developments are the introduction of UV-stable dyes and integral colours that can be used to enhance polished concrete. This gives the designer of the floors options to be more creative and introduce various coloured patterns and designs onto the floor, preferably using dyes that are water-based and contain no volatile organic compounds (VOCs).

Andreas Hasselmose, Superb Flooring Systems: The technical benefits of a polished concrete floor are very advantageous for this market. The lifecycle cost is low and it’s easy to maintain, among other things. Polished concrete has also made headway where there is a need for floors that protect against electrostatic discharge. This is often a requirement for the electronics industry, and polished concrete is often a better and much more affordable solution than the traditional floors used.

What do you need from the concrete to produce a highly polished finish?

Anathi Zitumane, Lafarge: Using the correct mix which is at least 30MPa, and a higher stone content. Polishing has seven stages depending on the desired finish for internal applications; and up to four stages for outdoor applications.

Nic de Carvalho, Concrete Laser Flooring: Ideally we need dense concrete that is 30 to 35MPa in strength, and contains as little air as possible in the mix. The correct use and dosage of aggregates are critical to optimise the finish.

Andreas Hasselmose, Superb Flooring Systems: It needs to have reached strength of at least 25MPa to be polished.

How well does a polished concrete floor stand up to impact?

Anathi Zitumane, Lafarge: It provides a durable floor that is easy to clean (low maintenance).

Nic de Carvalho, Concrete Laser Flooring: Generally very well. The higher the strength of the concrete the better the floor will resist damage. The advantage polished concrete has over other flooring systems is that it is monolithic and the sealers that are used are penetrating and not topical, therefore you don’t run the risk of intercoat delamination between layers.

Andreas Hasselmose, Superb Flooring Systems: It stands up to impact better than the same floor would do if it was only rough concrete. You have ground it down to stone, flattened the floor and hardened it with a proprietary hardener in the process.

Independent tests show that this increases the wear resistance of the floor around 10 times and will improve its abrasion resistance. However, if you drop something heavy enough on the floor it will chip.

How simple is it to have a coloured and polished floor, and what limitations exist in this respect?

Anathi Zitumane, Lafarge: Coloured floors with a sealer also shine and you don’t see the colour of the aggregate. The sealer needs to be applied quite often as it is this that provides the shine. In polished concrete, the concrete itself shines and the aggregate is exposed.

Nic de Carvalho, Concrete Laser Flooring: There are two different ways to colour a floor: (1) We can dye the surface using dyes that penetrate the concrete, which allows for the floors to be designed with intricate patterns; (2) We use a proprietary system which integrally colours the entire depth of the slab. Both options have about 30 different colours in the range.

Andreas Hasselmose, Superb Flooring Systems: If it’s a new floor it’s very straightforward. You simply mix oxides in your concrete. Most readymix companies offer a range of colour and aggregate variations that you can choose from.

If it’s an existing floor you would have to use a dye. The limitation of this is that it might be difficult to get consistency in colour. Most of these are not UV-stable and is not recommended for outdoor use when used with a highly polished floor.

Some people criticise polished concrete because the corners of the rooms cannot be reached by the polishing machines. Is there any way of overcoming this problem?

Anathi Zitumane, Lafarge: Skirting will be used to cover the areas that are in corners. Hand tools are used closer to edges.

Nic de Carvalho, Concrete Laser Flooring: This criticism is absolutely correct, and we make our clients aware of this issue upfront. The reason is that on the edges we have to use hand tools, which do not remove or polish as well as the larger machines. We offer the client a 100mm stained border or place a thick skirting on the wall.

Andreas Hasselmose, Superb Flooring Systems: There are only very small areas in the corners that you cannot reach with a hand polisher and a disc of around 100mm in diameter. There is no machine that can reach all the way into the corner using the traditional diamond tools. If there is no skirting board covering these very small corner areas some contractors would use a corner grinder with sandpaper to smooth it down and then use a chemical to get a shine in that area. This would then match the rest of the floor much better.

What steps should be taken to obviate imperfections in the polished floor?

Anathi Zitumane, Lafarge: The correct mix and proper placing; Lafarge has trained contractors to place the concrete properly, and offer a service whereby one can appoint Lafarge to supply, place and finish the concrete to ensure the desired expectations of the client are met.

Nic de Carvalho, Concrete Laser Flooring: The most important step in producing a good, consistently polished floor is actually the correct and consistent placing of the concrete. Generally the finish of the floor is only as good as how well the concrete has been placed, so it is a good idea to use contractors who can place and polish the floor. This way the client will eliminate split responsibilities between the placing contractor and the grinding contractor.

Andreas Hasselmose, Superb Flooring Systems: For our customers it’s to follow our procedure for polished concrete, which is a tried and tested method. We do not jump stages (grit sizes) in the grinding process as this could lead to scratches and a lower shine on the floor. The first grinding step in the process is vital for the end result. This is where the floor is levelled and if this isn’t done correctly you will have imperfections in your floor.

The pouring of the concrete is vital for the best results with polished concrete. To use contractors with knowledge and experience about pouring the concrete with polishing in mind will help a lot.

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