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SmartStone Complexities

Natural phenomena that might affect the appearance of your SmartStone product:

SmartStone is a beautiful product made of natural ingredients. In many cases SmartStone products simulate natural products . The advantages of SmartStone over natural stone is that SmartStone can create a wider variety of colours, manufacturing is cheaper and more accurate, and SmartStone can create a product which is closer to the market requirements than the natural product can be mined.

Supply is therefore far more reliable and environmentally friendly as natural stone quarries are destructive to the environment while ordinary aggregate quarries are a necessary evil required for all structural development. The quarried and other ingredients are mixed to form concrete. Concrete, like all other structural materials is subject to natural wear and tear from the forces of nature.

Rain and sun in particular attack the surface of concrete over a period of time but does not affect the overall structural integrity of concrete products. Concrete also absorbs water and releases water as it dries out in the Sun. From the above powerful and ever-present natural phenomenon, certain visual effects may become evident in concrete products. Please read further to discover what these may be.

Your SmartStone product may demonstrate the following:

1. Efflorescence

A white film on the surface of concrete, clay and natural stone products.

Efflorescence is caused by the formation of salt deposits, usually white, on or near the surface of concrete, clay and natural stone products. Apart from the discolouration, efflorescence is harmless. This is best described as being a temporary skin problem and not a deep-seated disease.

  • i) Efflorescence and SmartStone  In the greatest part of South Africa, efflorescence is most obvious in the rainy summer months, but may be observed throughout the year, especially in irrigated areas or after a sudden drop or rise in temperature. It can occur from within the concrete or from the subgrade (soil below the pavers). In time efflorescence becomes less extensive and in most cases disappears completely. Light coloured pavers might show the deposit to a lesser degree than darker coloured pavers.
  • ii) How it occurs Efflorescence is a natural phenomenon that occurs through a complex chemical or physical process or a combination of the two. Detailed information on efflorescence is available for research on the internet, or consult the Concrete Manufacturers Association brochure: “Concrete Block Paving, Efflorescence is only a temporary problem”  which is available on
  • iii) SmartStone’s take on efflorescence We are not bigger than nature. SmartStone can therefore not guarantee efflorescence-free products. (Pre- or post-installation.) We believe the best cure for efflorescence is to just leave it as it will disappear in time.
    Many paving installations have never been affected by efflorescence. Some have had efflorescence for a few weeks while others have been affected for months. Sometimes efflorescence is recurring and sometimes it happens only once.

2. Black efflorescence

Blackening or darkening of Concrete products

  • i) What is “Black efflorescence”  In some rare area-specific cases some pavers  become black or darker. This may occur within a time frame of two to eighteen months after installation. The blackening does not affect all the pavers on a site. In fact one will see a patch of dark pavers surrounded by normal ones. This is usually a permanent condition and may happen to any concrete products. (Pay attention to discolouration on concrete bridges and building facades for example.)
  • ii) Black efflorescence and SmartStone  The blackening of SmartStone or any other products manufactured with concrete is random and not yet well understood by the concrete industry. The blackening is beyond the control of manufacturers and does not affect the pavers’ structural performance. At this point in time the theory is that the blackening of concrete has something to do with the specific soil conditions of an area. Proof of this is that neighbouring sites installed with concrete products will generally also show blackening.

3. Discolouration or “Differential Curing” in especially larger products

An obvious variation in the colour of individual pavers, with a distinct light or dark hued “frame” with a light or dark hued “core” on the paver’s surface might develop or be present when unpacking your pavers. This condition is called “differential curing”. One should be conscious of the fact that the “curing” of concrete is not simply the evaporation of water. It is a chemical process that takes years. Therefore the “stains” will become less profound and almost invisible with time. Initially though some might consider it unsightly.

4. Picture framing on concrete bedded flagstones

This phenomenon normally only comes to light a few days after installation has been completed and some flagstones are more prone to it than others. The common denominator is that joints were filled using a wet cement slurry grout.

Basically what happens is that cement-contaminated water from the slurry grout is absorbed by the flagstones and carried through internal capillaries.

Then evaporation takes place. This evaporation creates a ‘transport chain’ within the body of the paver with cement-laden water being absorbed from the underside and joint faces of the pavers, and evaporation from the upper surface, and particularly from the edges of the pavers. Cement however, does not evaporate; it cures and leaves a stain. This stain often looks like a picture frame around the flagstone.
For this reason SmartStone recommends that flagstones should be moist when bedded and grouted in order to reduce the possibility of cement contaminated water being absorbed by flagstones.

5. Pinholes

In some instances pinholes will be present on the surface of especially large pavers or they could appear a week or two after installation. Make certain that your contractor does not install any flagstones with pinholes. SmartStone will exchange products delivered with pinholes, free of charge. If however the pinholes appear after installation, DIY repair kits are available to fill these little holes.

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