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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. 180^oC/150bar). The carbonates produced are heated at low temperatures (700^oC) 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:

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Geopolymer Ceramic mixing from Geopolymer Institute on Vimeo.

Geopolymer Ecological Cement mixing from Geopolymer Institute on Vimeo.

For more information on geopolymers, see this explanation from Trudy Kriven.

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In the revolutionary way that aerogel is starting to redefine insulation, geopolymer may be poised to redefine cement, concrete and a lot of other advanced composite materials. And, like aerogel, geopolymer hasn’t received the public attention it should.

In this video,  geopolymer expert Trudy Kriven, a professor of material science at the University of Illinois at Urbana-Champaign, explains how geopolymers are essentially inorganic polymers made from readily available aluminum- and silica-containing materials.

As Kriven explains, a motive for finding a replacement like geopolymer for traditional Portland cement is environmental: Portland cement production requires a tremendous amount of energy to heat and convert the raw materials (at 1450°C), and can generate nearly one ton of CO₂ for every ton of processed cement.

Geopolymer, on the other hand, doesn’t have to be fired. In addition, Kriven notes, geopolymer is twice as strong as cement in compression, three-times as strong in flexure and can set up in one day.

The reality is that given the need to reduce global CO₂ emissions and given the plans for large scale construction and transportation growth in countries such as China, alternatives to Portland cement are extremely important.

Besides using geopolymer to make concrete, this novel material can be used for fire and corrosion resistant coatings, water and air filtration, CO₂ sequestration materials, projectile armor, substrates for solar and fuel cells, and even a paint substitute.

Adding for clarification . . . Trudy’s comments at around the 3 minute mark can be misconstrued when she says the geopolymer “looks like a ceramic, feels like a ceramic, but wasn’t fired at high temperature.” She is referring to “traditional” ceramics that are fired in a kiln or sintered. However, geopolymer falls within the broad grouping of “ceramic materials.”

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Australia’s national science agency says it has developed a new, strong fire-blocking material. The Commonwealth Scientific and Industrial Research Organization calls the material HIPS (‘hybrid inorganic polymer system’).

According to the Melbourne-based CSIRO, construction materials given a coating of HIPS can withstand temperatures of over 1000°C.

CSIRO describes HIPS as a geopolymer: It contains an inorganic geopolymer resin and small amounts of polymer additives. “Geopolymers are an emerging class of ceramic-like inorganic polymers produced at room temperatures that have the potential to transform the building products industry,” says Damian Fullston, the project leader of the group developing HIPS, in a document on the CSIRO website.

Fullston goes on to note, “[Geopolymers] are not only fire-, blast- and acid-resistant, they are also strong, castable, sprayable and extrudable, making their potential uses almost limitless. The polymer additives in HIPS improve the flexibility and waterproofing properties, and provide stronger adhesion, which are important properties for a coating.”

CSIRO is now looking for partners in the manufacturing sector to develop and market HIPS applications. According to the agency, HIPS is would be ideal for fire-resistant coatings on wood, structural metal and brickwork. It can be applied by means of a brush or spray and cures at ambient temperatures.

The material also seems to be environmentally friendly. The agency says,”HIPS coatings are free of volatile organic compounds, do not burn or produce heat and do not release smoke or toxic chemicals at temperatures up to 1200°C.” Further, the feedstock can be derived from fly ash and blast furnace slag.

CSIRO has a podcast about HIPS.

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