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august 2019 csengineermag.com 57 The Jubilee Church. Photo: Elio Lombardo, Alamy Stock Photo The Pantheon. Photo: Elio Lombardo, Alamy Stock Photo Concrete is the most widely used building product in the world. It's mostly made locally with local materials. It's cost effective, available everywhere, strong and durable. Although conventional concrete can tackle most jobs, it is also the material of choice for the tallest buildings in the world and infrastructure designed to last centuries. Although concrete is not always synonymous with innovation, new products and manufacturing methods are enhancing concretes performance to tackle modern challenges. This article explores some of these latest innovations. Self-cleaning Concrete Imagine concrete that can clean itself and even the surrounding air of harmful pollutants. That's what concrete made with tita- nium dioxide (TiO 2 ) can do. The function of TiO 2 cement is to break down harmful pollutants in the air via a reaction catalyzed by light, or photocatalysis due to titanium dioxide which is added to the cement during its production. This capability of TiO 2 cements was inspired by the ability of certain microbes to break down harmful chemicals by modifying their oxidation state, also through photocatalysis. However, in photocatylitic cements the reaction is carried out by the titanium whereas microbes rely on natural enzymes. The cement breaks down organic as well as inorganic pollutants, and it is intended to be used for projects in urban centers where air pollution and poor air quality are most pronounced. An example of how TiO 2 cements break down pollutants can be seen in its conversion of nitrogen dioxide (NO 2 ), a harmful compound mostly produced by burning fuels in cars and trucks. Nitrogen dioxide is one of the compounds responsible for acid rain, smog, respiratory problems and staining of buildings and pavements. The reaction with sunlight produces hydroxyl radicals which react with NO 2 to produce NO 3 which is dissolved by water after reacting with the cement surface. Research data of TX Active®, a TiO 2 cement marketed by Lehigh Hanson (a division of HeidelbergCement Group) in the US, indicates that "up to 50% of these atmospheric pollutants could be reduced in some cities if only 15% of the buildings and roads were resurfaced with TX Active® cement." TX Active® was first used for the curved panels on the Jubilee church (also known as Dives in Misericordia Church) in Rome, which used the photocatalytic cement panels for its stylistic shells. Since then, Italcementi (a division of HeidelbergCement Group) has dedicated decades of research to photocatalytic cement products. This cement is promising in its potential to greatly improve urban life and the environment. gasses. Some enhancements actually scrub pollutants from the surface of concrete and from the surrounding atmosphere which is what makes the concrete on the Jubilee Church so innovative. The exterior curved surfaces are coated with titanium dioxide (TiO 2 ) cement which eats smog, helping to keep the surface clean.

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