Things That Can Affect Your SmartStone

Natural phenomena that might affect the appearance of your SmartStone product

SmartStone is a beautiful product, made of natural aggregates. In many cases, SmartStone products simulate natural ones. 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.

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 time, but do not affect the overall structural integrity of concrete products. Concrete also absorbs 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 learn what these may be.

White Efflorescence shown on cobbles


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, rather than a deep-seated disease.

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 sub-grade (soil below the pavers). Over 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 ones.

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.

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 simply to leave it, as it will disappear with 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 recurrent and in other cases, it happens only once.

We conducted extensive research with the help of our sister company, Cretesol, to find a product which can clean traces of efflorescence; and we found the perfect solution. Guard Remover® Eco Efflorescence & Cement, imported from France and supplied by Cretesol, works rapidly to clean efflorescence off of pavers before applying concrete protectors or sealants. It does this in a minimally aggressive and non-corrosive manner.

Black Efflorescence:

Blackening or darkening of concrete products.

Black Efflorescence shown on concrete products

What is “black efflorescence”?

In some rare area-specific cases, certain pavers become black or darker. This may occur within a time-frame of two to 18 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 façades, for example).

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 present, the theory is that the blackening of concrete has something to do with the specific soil conditions in an area. Evidence of this is that neighbouring sites installed with concrete products will generally also show blackening.

Discoloration of pavers

Discolouration or “differential curing” in especially large products:

An obvious variation in the colour of individual pavers, with a distinct light or dark-hued “frame” and 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 aware 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 over time. Initially though, some might consider it unsightly.

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.

Evaporation then takes place, creating 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, particularly from the edges of the pavers. Cement, however, does not evaporate; it cures and leaves a stain. This stain often resembles a picture frame around the flagstone.

The grouting of SmartStone cobbles and flagstones should be done with SmartStone-approved grouting. We do not recommend using cement grouting, as cement staining is nearly impossible to prevent with this grouting method.  We recommend using a resin bound mortar, like Romex, which is supplied by our sister company, Cretesol. Unlike cement grouting, there is no chance of staining with this method if installed correctly. It is incredibly strong and long-lasting. Most importantly, Romex allows for a flexible joint between your pavers, unlike cement grouting – which eventually breaks and pops out.

Framing on pavers after installation

Small holes on paving after installation


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

For solutions on fixing the things which have a negative impact on your SmartStone, contact our sister company, Cretesol. Their products include specialist paving tools, sealants, protectors, grout, grout stabilisers, and cement & efflorescence removers.