Blocks made with Novacem cement. Credit: Novacem

A “green” material that has received growing press attention (at least online) in recent months is a product from Novacem that the company is billing as a “carbon negative cement.”

The most recent stimulus for these stories is that in February, a New York-based consultancy group called the Material ConneXion announced that they had given Novacem’s cement an award as Material of the Year for 2010.

It’s not clear how the award was determined. The consultancy’s website says, “The award recognizes materials juried into the company’s Materials Library in 2010 that demonstrate outstanding technological innovation and the potential to make a significant contribution to the advancement of design, industry, society and economy,” but its unclear if the winner was determined by a qualified jury or just the Material ConnXion staff. Regardless, the publicity triggered several glowing stories such as “Jetson Green“.

Novacem has also received recognition from Technology Review and the Wall Street Journal.

According to Novacem (London, UK), their MgO-based cement not only doesn’t emit carbon dioxide, but also absorbs it. Below is a partial description from the company’s website:

“Novacem has developed a new class of cement which will offer performance and cost parity with ordinary Portland cement, but with a carbon negative footprint. It is uniquely positioned to meet the challenge of reducing cement industry carbon emissions.

“Our cement is based on magnesium oxide (MgO) and hydrated magnesium carbonates. Our production process uses accelerated carbonation of magnesium silicates under elevated levels of temperature and pressure (i.e. 180oC/150bar). The carbonates produced are heated at low temperatures (700oC) to produce MgO, with the CO2 generated being recycled back in the process. The use of magnesium silicates eliminates the CO2 emissions from raw materials processing. In addition, the low temperatures required allow use of fuels with low energy content or carbon intensity (i.e. biomass), thus further reducing carbon emissions. Additionally, production of the carbonates absorbs CO2; they are produced by carbonating part of the manufactured MgO using atmospheric/industrial CO2. Overall, the production process to make 1 ton of Novacem cement absorbs up to 100 kg more CO2 than it emits, making it a carbon negative product.”

To avoid confusion, its worth noting that although it has some similarities, Novacem’s product is not to be mixed up with geopolymers, which is another family of cement alternatives.

According to members of the ACerS’ Cement Division, magnesium-based cements are far from new and have been around since at least 1867. They are sometimes known as “Sorel cements.”

While magnesium-based cements have a different chemistry than the magnesium silicate cements proposed by Novacem, some members of the division believe that they would likely be much more expensive than Portland-based cements.

One perplexing thing about this product is that there doesn’t appear to be any independent research on the properties of the Novacem cement, and that would be important to examine, for example, the durability and water-resistance of Novacem’s product compare with Portland-based cement. So, some caution must be exercised in regard to accepting their claims.

Certainly, there is an interest in “green” alternatives to Portland-type cements, the production of which requires major CO2 emissions and is very energy intensive. The mainstream cement industry, itself, has been taking steps to address some of these problems, but change has been slow.

One reason why engineers and contractors haven’t embraced alternatives, such as geopolymers and Novacem is that most building and construction codes are formula based rather than performance based. In other words, the codes tend to spell out in detail what mix of concrete can be used where, instead of establishing a set of characteristics (e.g., compressive strength). Unless these codes are modified — and there doesn’t appear to be any motion in that direction — general demand will be curtailed, and the small scale of specialty-type demand (e.g., emergency repairs of military airfields) will keep production costs high.

Nevertheless, Novacem appears to be optimistic about its cement. According to IBTimes website, “the cement will be released commercially starting 2014, but not by Novacem. Instead, they will sell the patent rights to producing companies, who will (hopefully) commercialize it at competitive prices.”

Here is an interview with Nikolaos Vlasopoulos, Novacem’s chief scientist and director: