## Abstract

The concentration of health hazardous organic and inorganic substances are increasing in larger cities of the world. Two major reasons for this are the heavy traffic and the emissions that come from factories located near or in the cities. Emissions of inorganic pollutants such as nitrogen oxide and nitrogen dioxide (NO and NO ) can result in, given that the emission 2 rate is high, ground-level ozone formation. Ground-level ozone formation is a toxic gas that in low concentrations can cause lung damage. Ozone also plays a role in the formation of photochemical smog which can be described as a toxic, yellow and brown fog. Formation of photochemical smog has occurred in cities like Los Angeles and Mexico City, which has led to difficulties (mainly for the elderly) to be outdoors due to the health risks. A pollutant like NO can be reduced by using concrete provided with a certain type of titanium dioxide (TiO ) 2 a chemical substance with photocatalytic properties. Sunlight activates titanium dioxide, which acts as a catalyst, (and is not being consumed), while reacting with moisture and oxygen in the air as reactive oxygen radicals are being formed. Oxygen radicals further react with NO-molecules. Reduced NO leads to formation of new chemical compounds, for example certain types of salt minerals (nitrates) which are not considered dangerous for the environment. This project is a collaboration between Cementa AB, a company that produces and sells various cement materials, and the Division of Building Materials at Lund Institute of TiOmix - N Technology. The project aims at using titanium dioxide based additive materials, and - S (offered by Cementa AB) together with commonly used concrete additive materials, slag and fly ash, and then measuring the photo catalytic effect, estimated as the percentage of NO reduction in relation to an origin of NO content. A total of sixteen concrete specimen were measured. The concrete specimen have been casted with fast hardening Portland concrete and white Portland concrete in many combinations. Slag and fly ash have been of special interest to examine due to indications of the impact these materials have had on the photocatalytic effect. These materials are also being requested more by the concrete industry now than before. The photocatalytic effect was measured at Cementa Research in Slite, with one specimen at a time, in a test chamber made of stainless steel and with a lid of quartz glass together with a NO/NO (gas) analyzer. Although numerous parameters exist with an impact of the photo x catalytic effect, for example relative humidity, focus has been to measure NO reduction during defined conditions. The concrete specimen have only been exposed to UV-light with a constant UV-intensity as only nitrogen oxides and air have been added to the test chamber. The air content in an urban environment consists of varying amounts of other pollutants along with a significantly lower (varying) UV-intensity. The results from the measurements showed that concrete containing slag and fly ash have an equivalent NO-reduction to concrete without. To use a low amount of TiOmix-N has an equivalent NO-reduction compared to using a high amount of TiOmix-N. The photo catalytic effect was high for all of the specimen varying between 73-87 %with an exception for one specimen that did not contain any TiOmix. In this case the NO-reduction was negligible. Lastly, more measurements, based on or in real urban environments, should be included in further research dealing with the photo catalytic concrete of tomorrow, to better take into account variations in UV-intensity, relative humidity and wind conditions, to have mentioned a few factors that have an impact on the photo catalytic effect.