Photoment®-FAQ

FAQ – Frequently asked questions

Which company is behind Photoment®?

Photoment® is an innovative product which has been developed in a partnership between STEAG Power Minerals and KRONOS International, Inc.

STEAG Power Minerals GmbH, a wholly-owned subsidiary of STEAG GmbH, jointly with its numerous affiliates and regional partners, has for many years been the competence leader in the field of recycling by-products from hard coal fired power plants in Europe.

Website STEAG Power Minerals GmbH

KRONOS International, Inc. is one of the world leaders in the production and marketing of titanium dioxide, a white pigment which is widely used in paints, plastics and other materials.

Website KRONOS International, Inc.

What factors influence the effectiveness of Photoment®?

Light is required for the photocatalytic reaction to occur. Accordingly, the light intensity and the proportion of ultraviolet light are factors that influence the effectiveness of Photoment®. However, Photoment® is also effective when exposed to artificial light and/or visible light.

How much Photoment® do I need to achieve a reduction in nitrogen oxides?

The more photocatalytically active surfaces there are, the more nitrogen oxide can be decomposed. Even small Photoment® surfaces contribute to reducing pollution. Influencing factors are the light intensity and the wind directions.

Is there any proof of the effectiveness of Photoment®?

Yes. Photoment® has been designed to improve the quality of air and life. The effectiveness of Photoment® was shown by studies conducted by Prof. Dr. Dietmar Stephan at the Technical University of Berlin and verified by Prof. Dr. Michael Bruse, Director for Development and Innovation at ENVI-met GmbH using a simulation model of a real inner city area. Laboratory tests and studies conducted at the Technical University of Berlin on more than 1,500 paving stones have shown that Photoment® is capable of causing a reduction by more than 30% in nitrogen oxides under laboratory conditions. The strength of the paving blocks can be increased by up to 30% with the use of Photoment®. Furthermore, the studies also showed that the Photoment® paving stones are resistant to freeze-thaw and deicing salt, and retain their color..

Decomposition of nitrogen oxides (Scientific tests and studies)

What happens to the nitrate?

The nitrate resulting from the photocatalytic reaction is washed off by the rain and eventually makes its way into the groundwater. The quantity is so small that it is neither detrimental to the environment nor harmful to health.

Does Photoment® also work if exposed to artificial lighting?

Yes, it is a special feature of Photoment® that the photocatalytic reaction also occurs if it is exposed to artificial light/visible light. This also makes Photoment® an interesting option for use inside buildings or in tunnels, for instance.

Is Photoment® consumed by the reaction?

No. The photocatalytic reaction can be repeated any number of times. Photoment® retains its effectiveness throughout the entire life of the concrete surface

Do Photoment® concrete paving stones require cleaning?

As a photoactive additive for concrete, when exposed to light, Photoment® has a self-cleaning effect. However, the reaction needs some time to produce visible results. As an example, you can find a photo documentation of the removal of used oil stains from concrete paving blocks here (Download). Owing to the photocatalytic reaction, the surface cleans itself and stays clean for longer. Surfaces with Photoment® thus require less cleaning effort.

Does the self-cleaning work immediately?

You cannot see the self-cleaning effect of Photoment® at first glance. Contrary to what many people think, the self-cleaning effect is not based on the so-called “lotus effect”. The photocatalytic reaction brought about by Photoment® rather causes a superhydrophilic surface to be formed on the paving stones. As a result, particles of dirt can be undermined and easily flushed off by water. The growth of organic substances such as algae, mosses, lichens or fungi is impeded. This means that Photoment® paving stones are self-cleaning, and biofouling on the surfaces is inhibited.

Do the paving stones have a lotus effect?

No. The lotus effect refers to very high water repellence (superhydrophobicity) of a surface which also prevents soiling of the surface.
Paving stones containing Photoment® are photoactive. The photocatalytic reaction causes a superhydrophilic surface to be formed on the paving stones; as a result, particles of dirt can be undermined and easily flushed off. The growth of organic substances such as algae, mosses, lichens or fungi is impeded. This means that Photoment® paving stones are self-cleaning, and biofouling on the surfaces is inhibited.

Can I visually see that a paving stone contains Photoment® and thus has self-cleaning properties?

You cannot visually see the difference between “normal” paving stones and Photoment® paving stones. Photoment® paving stones can be recognized by the following label in the information material of the paving stone manufacturer

Where can I buy Photoment® paving stones?

Photoment® is an additive for concrete which can be added to almost all concrete paving stones, irrespective of the paving stone manufacturer. Please contact the paving stone manufacturer of your choice if you want to buy paving stones containing Photoment®. Please do not hesitate to contact us should you have difficulties finding a manufacturer, or if you have any questions concerning Photoment®. Contact

Can I apply Photoment® to my existing concrete pavement?

Photoment® is added during the paving stone manufacturing process to the so-called facing layer (i.e. to the 1 cm thick top layer) of the paving stones. Subsequent application to finished paving stones is not possible

Are Photoment® paving stones more expensive than normal paving stones?

Compared to normal paving stones, Photoment® paving stones deliver substantial added value: they clean themselves and decompose harmful nitrogen oxides. Accordingly, paving stones containing Photoment® cost slightly more than paving stones that are not photoactive. However, this extra cost is relatively low, so you can contribute to a healthier environment at affordable cost. Since Photoment® paving stones also require less cleaning effort, this is a worthwhile investment. The price of the paving stones is determined by the paving stone manufacturer.

Is there any scientific evidence of the effectiveness of Photoment®?

Yes. Photoment® has been designed to improve the quality of air and life, and its effectiveness has been confirmed by tests and studies conducted at the Technical University of Berlin and at the University of Mainz. Decomposition of nitrogen oxides (Scientific tests and studies)

Is Photoment® able to reduce nitrogen oxide pollution concentrations at particularly exposed nodal points of road traffic?

In an urban environment, under favorable conditions Photoment® can reduce as much as 12% of the local nitrogen oxide concentration directly at the exposed location, and thereby make an important contribution to keeping the nitrogen oxide concentration below the applicable EU limit of 40 micrograms/m³. Using Photoment® may thus help to avoid penalty payments imposed by the EU if the pollutant concentration exceeds this limit.

How much Photoment® do I need to achieve a reduction in nitrogen oxides?

The more photocatalytically active surfaces there are, the more nitrogen oxide can be decomposed. Even small Photoment® surfaces contribute to reducing pollution.
If you want to effectively reduce local nitrogen oxide concentrations, for instance at a particularly exposed road junction in the inner city area, the size of the Photoment® containing surface should be in a sound proportion to the road in question. As important influencing factors, the light intensity and the wind directions should also be considered.

How much do paving stones with Photoment® cost?

The costs of Photoment® are comparable to the costs of other concrete additives. As for all products delivering added value, the initial investment costs are higher than for products without added value.
The exact costs of the stones are determined by the concrete goods manufacturer.
Reasonable extra costs will pay off within a short period, because the surfaces stay cleaner; this will obviously save costs which would otherwise be incurred for cleaning. In addition, Photoment® decomposes harmful nitrogen oxides in urban areas and thereby makes an important contribution to reaching health and environment objectives

In what form is Photoment® delivered?

Photoment® is delivered in bags (20 kg) or on pallets (40x20kg). This makes handling and processing easy. Photoment® can be stored on pallets without any loss in photocatalytic activity; no additional silo is needed.

How is Photoment® used?

Photoment® is added to your standard facing concrete mixture. If you wish to use Photoment® for the production of photoactive paving stones, our experienced concrete technologists will be pleased to assist you in optimizing your concrete formulation for the use of Photoment®.

What are the benefits that Photoment® brings for the properties of the paving stone?

In tests on more than 1,500 Proctor samples, it was proven that…

  • Photoment® increases surface strength by as much as 30% (the proportion of cement could be reduced, which resulted in cost savings and avoided efflorescence).
  • Requirements regarding resistance to freeze-thaw and deicing salt are fully satisfied.
  • Photoment® can be used with any customary cement types and your standard mixture for the facing concrete can remain unchanged.

Can I use Photoment® with any cement?

Yes, it is one of the great advantages of Photoment® that it can be used with any cement. 

Does Photoment® also work with colored paving stones?

Yes. The effectiveness of Photoment® has also been scientifically proven for colored concrete paving stones. Please do not hesitate to contact us for advice on the ideal concrete formulation

Who can I contact if I want to produce concrete paving blocks containing Photoment®?

Contact

How much does Photoment® cost?

The costs of Photoment® are comparable to the costs of other concrete additives and depend on the exact formulation of your standard facing concrete mixture.