Light-Reactive Concrete Locks in Clean Air

Researchers at the Korea Institute of Civil Engineering and Building Technology (KICT) have developed a photocatalytic concrete that can remove fine particulate matter on roads. The technology holds promise for underground road tunnels, where poor air circulation prevents removal of fine particulate matter from automobile exhaust gases — which in turn contributes to poor air quality. The new photocatalytic construction material preemptively removes fine particulate matter precursors, making it a good candidate to address fine particulate matter pollution.

Photocatalysts, which are a semiconducting material, react with light to produce reactive oxygen species (ROS) with strong oxidizing power. Upon the reaction, the ROS converts the precursors of fine particulate matter — for example, nitrogen oxide and sulfur oxide — into harmless substances through a photocatalytic reaction. This effectively suppresses fine particulate matter generation.

In a trial application of the concrete, the researchers placed the photocatalytic material on the inner walls of the Banpo Underground Road Tunnel in Seoul, South Korea. The outcomes showed an approximate 18% reduction in nitrogen oxides (NO_x) concentration levels over a 24-hour period. An artificial light source was then installed on the wall of the underground road tunnel where the photocatalytic concrete was applied, allowing the photocatalytic function to work without natural light. The salts produced through the photocatalytic degradation of the exhaust gases were effectively washed away by rain, meaning that the function can last indefinitely without the need for maintenance.

An artificial light source has been installed, allowing the photocatalytic function to work even underground where natural light does not reach. Courtesy of Korea Institute of Civil Engineering and Building Technology.

Although photocatalysts perform well in removing toxic substances from the air, their high manufacturing costs have been a barrier to implementation in construction. To address this, the research team from KICT’s Green Construction by Photocatalyst (GCP) research group has been developing key technologies for cost-efficient mass production of photocatalysts from wastewater sludge since 2018. The group is supported by the Ministry of Land, Infrastructure, and Transport.

Mechanism of photocatalytic degradation of air pollutants on the surface of photocatalytic concrete. Courtesy of Korea Institute of Civil Engineering and Building Technology.

With the photocatalytic concrete developed and tested, the research group is now also working to establish various photocatalytic performance evaluation certification systems to facilitate commercialization. The group is conducting a comprehensive trial in collaboration with authorities in Gyeonggi-do Province to demonstrate the effectiveness of photocatalytic construction technologies.

According to Jong-Won Kwark, head researcher on the work, the group plans to build a system of cooperation with local governments and public corporations to expand trial demonstrations to other sites. The aim, Kwark said, is to achieve commercialization and distribution with practical effects.

The research was published in KSCE Journal of Civil and Environmental Engineering Research (www.doi.org/10.12652/Ksce.2022.42.2.0163).