New Technology – “Smog-Eating Cement”

This year’s Construction Specifications Institute convention had a number of interesting seminars for the “geeks-like-me crowd” usually found at CSI gatherings, but the presentation that grabbed my attention was “Smog Eating Cement.”  Besides sounding like a 1950’s horror movie, the seminar title promised some interesting information about new green technologies.  Promised, and as it turned out, delivered. 

As often is the case, the cutting-edge in product innovation seems to come from Europe, this time from ESSROC Italcementi Group, as represented by Dan Schaffer.  And the key to “Smog Eating Cement” is not an actor in a lizard suit but photocatalytic nanotechnology, a term with nothing at all to do with the scary movies of my childhood and everything to do with the future of our practice.  Schaffer discussed results showing a 40% to 60% reduction in certain air pollutants from early studies of mock-ups and real projects where photocatalytic cement was used in buildings, paving and infrastructure.


Photocatalysis is defined as a reaction that uses light to activate a substance (catalyst) to modify the rate of a chemical reaction without the substance itself being involved in the reaction. Nanotechnology has been incorporated in building materials for a few years now.  In the area of glazing alone, many of us are very familiar with self-cleaning glass and advanced coatings that block ultraviolet or infrared light.  In fact titanium dioxide (TiO₂), which is the catalyst in self-cleaning glass used to break down dirt or pollution that can then be washed off by rain water, is also the basis for photocatalytic cement.
One of the first uses of photocatalytic cement in a concrete structure was Dives in Misericordia Church in Rome, designed by Richard Meier and completed in 2003, which used TiO₂ throughout the mix.  Italcementi’s Dan Schaffer pointed out that this cast-in-place example is probably not practicable for most projects.  Since the TiO₂ catalyst works only in the presence of ultraviolet light (UV) and UV only penetrates a short distance into the concrete, the benefit of the TiO₂ rapidly diminishes further into the structure.  In fact a thin surface layer, probably no more than 30 mm thick, is all that is required.  Any more depth is wasted, especially at a cost of perhaps $1 per sf for each inch of thickness.

Schaffer suggested that cost effective applications for photocatalytic cement are precast concrete, tilt up slabs, and paver blocks.  In these applications, a thin layer of photocatalytic concrete is placed first then backed up by much less expensive regular concrete mix.  Because his company focuses mainly on concrete cements, Schaffer focused the seminar mainly on concrete, but he made the point that the photocatalytic technology could lend itself to any cementitious product.  After seminar discussion suggested other possible uses: stucco, mortar, concrete masonry units and tiles, cementitious paints, and cementitious siding and roofing.

So, is this new technology viable for our current projects?  Based on the seminar, I think it is something to consider.  Can we afford it?  The obvious right solution is reducing to elimination the harmful pollutants we humans put into the air in the first place, but until that happens, “smog eating cement” might just be a product we can’t afford NOT to consider.  Especially if you remember, like I do, how the results of our pollution led to those science fiction monsters in the first place.

[Originally published on the CannonDesign blog]