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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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A Portland cement concrete research engineer at Iowa State University says poor decision making, not poor technology, doomed the Deepwater Horizon.

Bob Steffes, ISU’s Institute for Transportation, bases his conclusions on 17 years of overseas oil rig experience, including a blowout on an offshore well in the Middle East.

In a release from the university, Steffes asserts that a number of factors played a role in the disaster. He says that many of them relate to “loss circulation” – a common problem in this sort of drilling, in which drilling material (such as water and clay with dense additives such as barite or hematite) intended to be circulated back up the drill pipe instead filters out into the surrounding porous rock

“When I heard that loss circulation was a problem, I knew right away” what might have contributed to the blowout, Steffes says in the release.

Here are some of the factors Steffes believes played a role:

• The chemical wash operators decided to use to clear away the “filter cake” – the drilling mud that accumulates on the face of the drill hole through loss circulation – was not completely effective.
• Operators decided to use too few casing centralizers to keep the final casing in line. That may have resulted in the final cement seal being off-center, which can allow gases to escape.
• Operators used nitrified (or foamed) cement instead of a heavier, stronger version to seal the bottom of the well. Steffes says that the cement may have been lost in the same way as the drilling mud.
• Operators failed to perform a bond log, a process that uses sensors to determine if there is a uniform sheath of cement between the outside of the casing and the drilled hole. Gaps, if detected, are routinely filled – a “squeeze” operation, according to Steffes.
• Drilling mud was replaced by seawater. The net effect of this time-saving step reduced approximately 180,000 pounds of overhead load.
• The full-length casing that was used provided only a bottom hole cement seal. Using a liner would have provided a bottom hole cement seal plus a liner hanger seal.

Steffes notes that none of this would have mattered if the blowout preventer had not failed.

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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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