Natural phenomena that may affect the appearance of your SmartStone

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 becomes wet and then dries out in the sun. From these powerful and ever-present natural phenomena, certain visual effects may become evident in concrete products.

These are:

1. Efflorescence

Efflorescence is a natural phenomenon that occurs as a result of a complex chemical process and manifests as a white film on the surface of concrete, clay and natural stone products. It is caused by the formation of salt deposits on or near the surface of the product, or by the soil below the pavers. However, it is harmless and temporary. In time, efflorescence fades and, in most cases, disappears completely.

Detailed information on efflorescence is available on the Internet, or consult the Concrete Manufacturers Association brochure: Concrete BlockPaving:Efflorescence is only a temporaryproblem, available at www.cma.org.za.

Efflorescence and SmartStone. As efflorescence is a natural phenomenon, SmartStone cannot guarantee efflorescencefree products (pre- or post-installation). We believe the best cure for efflorescence is simply to leave it, as it will disappear in time. Many paving installations are not affected by efflorescence; some have efflorescence for a few weeks, while others may be affected for months. Sometimes efflorescence recurs and in other cases, it occurs only once.

2. Black efflorescence

Rarely, in some area-specific cases, pavers can become darker or even black. 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, often one will see normal pavers surrounded by a patch of dark pavers. Black efflorescence is usually a permanent condition and can happen to any concrete products, specifically on concrete bridges and building facades.

Black efflorescence and SmartStone. The blackening of SmartStone products 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. Currently, the theory is that the blackening of concrete may be affected by the specific soil conditions of an area. Proof of this is that neighbouring sites installed with concrete products generally also show blackening.

3. Discolouration or “differential curing ” , especially in larger products

An obvious variation in the colour of individual pavers (a lighter or darker border compared to the colour of the centre of the paver) may be present when unpacking your pavers. This condition is called “differential curing ” , which is temporary and is caused by a chemical process. The stains will become less noticeable and will usually disappear over a period of time.

4. Picture framing on concrete bedded flagstones

This phenomenon normally only becomes visible a few days after installation has been completed and some flagstones are more prone to it than others. The common denominator is usually that cement-contaminated water from the wet cement slurry grout is absorbed by the flagstones and transported through internal capillaries within the paver.

During the process of evaporation, a

“transport chain ” is created within the body of the paver, with cement-laden water being absorbed from the underside and joint faces of the paver. However, the cement residue does not evaporate; it cures and leaves a stain. This stain often looks like a picture frame around the flagstone.

SmartStone recommends that flagstones be moist when bedded and grouted in order to reduce the possibility of cementcontaminated water being absorbed by the flagstones.

5. Pinholes

In some instances, pinholes may be present on the surfaces of very large pavers, or they might appear a week or two after installation. Please ensure that your contractor does not install any flagstones with pinholes, as SmartStone will exchange products delivered with pinholes free of charge. However, if the pinholes appear after installation, DIY repair kits are available to fill them.