Increasing efficiency in the degradation of
airborne pollutants by photocatalytically modified concretes

Figure: Steag

Simplified representation of pollutant degradation on a photocatalyst after exposure to UV light. The activity of titanium dioxide is triggered by UV light; it acts as a catalyst for pollutant degradation by oxidation (red arrow) in the presence of oxygen and humidity (blue arrow) to create carbon dioxide, water, nitrates etc. (green arrow) as non-hazardous degradation products

Figure: Steag

Photoreactor with three inserted specimens to determine photocatalytic effectiveness

Figure: Steag

Flow chart of the measuring program

Figure: Steag

Abrasion resistance test according to DIN 52108 using the so-called Boehme disc; preparation of the specimens

Figure: Steag

Abrasion resistance test according to DIN 52108 using the so-called Boehme disc; test run

Figure: Steag

Compaction of Proctor specimens: reference with pure cement (grey), mixes with varying ratios of photocatalytically active Photoment

Figure: Steag

Compressive strengths of Proctor specimens: reference with pure cement (grey), mixes with varying ratios of photocatalytically active Photoment

Figure: Steag

Strength curves of standard prisms according to DIN EN 196, with pure cement or 80% of standard cement and 20% of Photoment. Blue: CEM I 52.5 R; red: CEM II/A-LL 42.5 R; black: CEM II/A-S 42.5 R. Samples with 20% of Photoment appear in a hatched pattern.

Figure: Steag

Nitrogen oxide degradation on reference specimens: The diagram shows the degradation curves of nitric oxide and the lighting sequence (on/off) over a period of six hours

Figure: Steag

Nitrogen oxide degradation on reference specimens with 55 kg/m³ of Photoment, all other constituents unchanged

Figure: Steag

Photocatalytic nitrogen oxide degradation in the photoreactor, percentage decrease of the initial concentration. Grey: reference (without Photoment); green: with 30 kg/m³ of Photoment; yellow: with 55 kg/m³ of Photoment; red: with 75 kg/m³ of Photoment

Figure: Steag

Detailed image of the concrete surface of the reference specimens containing a CEM II/A-S with a water ratio of 125 l/m³ ...

Figure: Steag

... and a water ratio of 145 l/m³

Figure: Steag

Freeze-thaw resistance of tested Proctor specimens: left, the reference with pure cement appearing in grey (not measured for all water/binder ratios), followed by mixes with varying ratios of photocatalytically active Photoment.

Figure: Steag

All results of the abrasion resistance tests were below 18,000 mm³/5,000 mm² of abraded material, and were thus categorized in Class 4 with the most demanding specifications

Figure: Steag

To reduce airborne pollutant concentrations, Steag Power Minerals and Kronos have developed a photocatalytic concrete additive to be used in the production of concrete pavers with air-cleaning properties.

1. Introduction

EU legislation increasingly defines limits for airborne pollutants as our awareness of the environment is growing, which directly influences our health and well-being [1]. Vehicle traffic is one of the major causes of frequently exceeding limits for particulate matter and nitrogen oxides (NOx) in heavy-traffic zones such as urban agglomerations. To reduce airborne pollutant concentrations, environmental zones have been implemented in some cities to restrict access to certain areas to low-emission vehicles. However, the base pollutant load from sources outside the environmental...