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At the recently concluded Advances in Cement-based Materials meeting organized by ACerS’ Cements Division and ACBM, Karen Scrivener of the Ecole Polytechnique Fédérale de Lausanne (Switzerland) was selected by the organizers to deliver the Della Roy Lecture. Scrivener is a highly respected expert in the field of cements and she was an appropriate pick, having followed in Della Roy’s footsteps as the editor of the Cement and Concrete Research journal.

Scrivener is also the founder of Nanocem, a Europe-based initiative working on collaborative approaches (not just among institutions, but also between institutions and industry) to cements questions. One of the aims of Nanocem is to spur a constant effort to reduce CO₂ emissions:

“Evolving CO₂ emission caps in Europe mean that cement manufacturers will have to find solutions, or pay more to produce cement, which will reduce their competitivity. Nanocem is sponsoring fundamental research that will support technological solutions, not only to help secure the long-term health of the European cement industry, but also to address global CO₂ reduction by ensuring that cement manufacturing is not just shifted to regions of the world that have less stringent emissions regulations.”

The title of Scrivener’s Della Roy Lecture was “Modeling Hydration Kinetics of Cementitious Systems,” which was quite a good discussion about the what has and what’s yet to be done in the world of modeling cement microstructures.

But, as a non-expert in cements, I found Scrivener’s opening remarks, which provided the context for her technical presentation, a balanced and compelling discussion about the importance of cements and concrete to, well … the world!

A few of her salient points:

• Concrete is most used material in the world. It is the only material that can satisfy the demand for low-cost decent housing and infrastructure. There is no way to satisfy the demand for low-cost housing and infrastructure without concrete.

• The demand for concrete is growing and will continue to soar, especially in the developing nations. The demand may double or triple by 2050.

• Although cement production is energy intensive, the energy and CO₂ emissions of concrete (per ton) is among the lowest of all building materials, even lower than wood.

• The CO₂ problem associated with cements (5-8% of CO₂ production world wide) is primarily because of the volume of demand.

• There has been talk of achieving 5-10% reduction in emissions per cubic meter of concrete through the use of substitutes for Portland cement. It may be more like 1-2% given the amounts and choices of supplements (see below), but even a 1% saving would be equal to removing all the CO₂ emissions associated with steel production. “So that shows how much impact we can have by research to increase the sustainability of cement,” she said.

• The available elements in the earth’s crust imposes a fundamental limit on the options for substitute cementitious materials. Eight elements—oxygen, silicon, aluminum, iron, calcium, sodium, potassium, magnesium—make up 98 percent of earths crust. So, forget about making cement out of any other elements.

• The way this has been pursued over the last 20-some years is first of all process optimization. Cement kiln and other production operations have gotten much better and state-of-the-art plants are achieving 80% of their theoretical efficiency.

• So, recently the goal has shifted more to reducing the “clinker factor,” i.e., instead of grinding clinker and gypsum, add more and more supplementary cementitious materials. SCMs my be byproducts or waste products from other industries, such as limestone, fly ash, blast furnace slag, silica flume, natural pozzolans, etc.

• This has been a good and successful strategy (over the last 20 years 25% of the previous amount of clinker in cements is now substituted by SCMs).

• But … and this is a big “but” … this is going to be a difficult strategy going forward because under the best of circumstances, the amount of SCM available will be dwarfed by amount of cement produced.

• For example, people talk about using fly ash as an SCM and it is probably the most widely available. But, there simply isn’t enough fly ash worldwide to replace cement in any big amount. The availability of SCMs in underdeveloped countries, where the demand is going to be coming from, is small because by definition they don’t have the scale of industries to provide large volumes of slag and fly ash byproducts.

• So where are SCMs going to come from? More limestone, probably, but more calcined clays and natural pozzolans. Cuba may be a good source of calcined clays.

• There is no one single answer. All sustainability possibilities must be pursued in parallel. Eventually we are going to see a very diverse range of cements, which are adapted to locally available materials. But diversity means performance questions will be more and more complicated.

• For researchers to support sustainability, they must provide end users of concrete information that will make them confident about the use of the SCMs. This means having relevant performance tests. In particular, researchers need to know how to start with the variables—the composition of the cements, the SCMs, mixing techniques, curing times, relative humidities, etc.— and from this predict performance.

• Short term performance can be relatively easy to predict in the laboratory, but long term performance—where we expect structures to last 40-50 years without hardly any maintenance—is much harder to measure in the lab.

• Therefore, researchers have to pursue mechanisms to predict microstructure via advanced modeling techniques to pull all of this complex information together and have it make sense.

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Tubohotel in village of Tepoztlan, Morelos, Mexico. Credit: Luis Gordoa/gordoafotografia; Tubohotel.

Via Gizmag, and originally from archdaily:

“The idea came when we built Cafe Five, where we saw the need to adapt an inexpensive room for users. In our search for solutions, we found Desparkhotel, the work of the architect Andreas Strauss in 2006, using recycled concrete pipes for hotel rooms. Our client decided to make a hotel with the same characteristics as the Desparkhotel on a ground that is located on the outskirts of Tepoztlan, with excellent panoramic views of the Sierra del Tepozteco. Located in a wooded setting of unusual features, the surrounding environment provides an unique natural environment and for our project.”

Rentals go for 500 pesos (about $43) per night.

Also, some great construction photos can be seen at T3Arc.

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Steel rebar embedded in concrete (left) and “nanorebar” made of carbon nanofibers. Credit: F. Sanchez, Vanderbilt University; ACerS Bulletin.

President Obama announced the launch of a Materials Genome Initiative during his speech at Carnegie Mellon University last week when he also announced the launch of the Advanced Manufacturing Partnership. (Read our report on the AMP announcement). The goal of the MGI, he said, is to “to help business develop, discover and deploy new materials twice as fast…”

Stating the obvious — This is great news for the materials science and engineering community.

The president did not say much more about the MGI than the above quote, but the White House released a white paper the same day, “Materials Genome Initiative for Global Competitiveness (pdf),” written by an ad hoc committee of the National Science and Technology Council (a Cabinet-level cross-agency entity). In the press release announcing the MGI white paper, the White House says “current “time-to-market” from discovery to deployment for new classes of materials is far too slow, given the range of urgent problems that advanced materials can help us solve.”

The white paper presents a vision for “how the development of advanced materials can be accelerated through advances in computational techniques, more effective use of standards, and enhanced data management.” Envisioned is a comprehensive collaboration among stakeholders, from theorists to R&D labs to manufacturers that will encompass academia, small and large businesses, professional societies and government.

In broad strokes, the paper addresses key issues like materials deployment and acceleration of the materials continuum by developing a materials innovation infrastructure, achieving national goals with advanced materials and preparing the next-generation workforce. A six-point action plan outlines activities that will be coordinated by DOD, DOE, NSF and NIST. The president has written $100M into his FY12 budget to launch the MGI (but it is not clear whether this is included in the $500 million AMP funding request for FY12).

Computational tools are expected to be used extensively to get around the time-consuming and repetitive experimentation that is inevitable but necessary to the development and testing of new materials. The authors of the white paper observe that researchers need to have access to large data sets for accurate simulation and modeling, and that there is no standardized mechanism for sharing algorithms, models or data at present.

Getting good data to feed into models is easy to say, hard to do.

In the March 2011 issue of the Bulletin, the article “A perspective on materials databases,” addresses the issue of data, noting the importance of easy access to reliable materials property data, but large volumes of data are hidden in widely dispersed or unavailable databases. The provenance of available data is often unknown, so the quality of conclusions drawn from such data is also unknown. Old data with well-known provenance still can prove to be insufficiently well-known. The example of 96 percent alumina is given. The composition of the remaining 4 percent can matter enormously, but is not always known. Often processing and preparation information that can affect properties is missing.

The NSF is working to resolve this dilemma by requiring its investigators to include a plan for data sharing in their proposals. The article’s authors admit that the cost of developing and maintaining a comprehensive data system is a formidable obstacle, one which the MGI should help mitigate.

There are plenty of examples of computational tools being used already for materials engineering. In the May 2010 issue of the Bulletin, the article “Atomic-scale computational modeling of cement and concrete,” describes the application of ab-initio and molecular dynamics methods to the engineering of the concrete and cement, materials that nearly everyone worldwide knows. Nanoscale engineering of skyscrapers!

The Chicago-based company, QuesTek - with the tagline “Materials by Design” - is an alloy development company that uses computational methods to expedite alloy development including the commercially available Ferrium line of alloys, one which is under consideration for a use as a helicopter gear by Bell Helicopter. QuesTek’s computational know-how is based on the industry-funded research of its founder, Greg Olson, professor at Northwestern University.

Not surprisingly, QuesTek has come out in strong support of the MGI.

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Researchers at Missouri University of Science and Technology believe that increasing the amount of fly ash in concrete up to 70 percent can result in excellent concrete in terms of both strength and durability. And it could prevent millions of tons of the waste product from ending up in landfills.

“Traditional specifications limit the amount of fly ash to 35 or 40 percent cement replacement,” says Jeffery Volz, assistant professor of civil, architectural and environmental engineering at Missouri S&T in a university press release. “Recent studies have shown that higher cement replacement percentages - even up to 70 percent - can result in excellent concrete in terms of both strength and durability.”

Fly ash is commonly used as a concrete additive, but increasing the amount used will cut CO2 emissions, but it also brings its own set of challenges.

“Construction workers might refuse to work with it,” Volz says. “And there’s also the issue of at what point is it not a hazardous material when used for beneficial reuse. Is it once it is added to the ready mix truck, which means it is a hazardous waste in the silo at the ready mix plant? Or is it once the concrete hardens, which means it’s a hazardous waste up to that point?”

The EPA supports adding fly ash to concrete, however the agency is considering designating fly ash as a hazardous waste. And although it has been proven that adding fly ash to concrete renders is chemically altered and unable to leach toxic material, a hazardous waste label would make it more difficult to garner wide acceptance.

Volz is working with the Missouri Department of Transportation to develop guidelines for the proper application of high-volume fly ash concrete in infrastructure components.

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(Credit: Jonathan Pankau/Wikimedia Commons.)

Last week we had about a report from researchers at Georgia Tech who show how concrete rubble from the earthquake can be safely recycled into stronger concrete using local resources and manual production and mixing techniques.

As a follow-up to this, I want to highlight an NPR story first broadcast yesterday regarding the challenge of the dealing with the rubble and how Haitians are already using manual rubble-crushing equipment brought in from Swaziland and recycling it:

“The machine’s parts are carried up the labyrinth of tiny walkways. Then the machine is reassembled and the crushing begins. It’s hard work, says Amos Laguerre, who makes about $5 a day cranking.

It takes three men to get the job done; two crank the handles, while the third drops boulder-size debris between the metal crushers. Singing helps the men get through the mind-numbing labor.

The crumbled rubble is collected in buckets. Sand and gravel are separated into plastic bags. On a good day, the crew fills 125 bags, about 5 cubic meters.

No one says this is a solution to the city’s rubble problem, but it is making a difference in small neighborhoods like Delmas 62. The bags of recycled rubble are mixed with cement and poured to make the foundations of temporary wooden shelters CRS gives to residents.”

As Georgia Tech’s experts point out, however, unless some simple-to-implement standards for concrete composition are adopted, the new concrete will likely be far below minimum construction standards and prone to new earthquake damage.

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