The Future of Building Materials

Stephen DeAngelis

July 20, 2010

In brief post about the amount of infrastructure that needs to be built over the next couple of decades [Chart of the day: Buddy, got $40T to spare?], my colleague, Tom Barnett, wrote:

“Of the $40T to be spent by 2030, $6.5 in North America, $9.2T in Europe writ large, $7.5T in LATAM, $1.1T in Africa, $0.9T in Mideast, and $15.9T in Asia. Per the Core Gap map, light in the middle and thicker along the edges. Breaking it down by category, it’s $22.6T in water, $9T in electricity, $7.8T in road and raid, and $1.6T in air & sea. A lot will be internal improvements, but plenty will be external improvements, i.e., improving linkages between states and regions.”

Forty trillion dollars of infrastructure is a lot. If countries cannot find that amount of money, desperately needed infrastructure will remain unbuilt and the benefits that could have resulted from that infrastructure will remain unrealized. With austerity measures being implemented in many places, the likelihood grows each day that the money won’t be found (at least from government sources). One thing that could help get more infrastructure built is finding more affordable building materials that reduce initial and/or lifecycle costs of infrastructure. Researchers are constantly looking for breakthroughs in materials and often look to nature for new ideas (for more on this subject, see my posts entitled Turning to Nature to Save Energy and Learning from Nature. Researchers in England are now exploring how the basic materials found in seashells can be used to make life on land better for people [“Sea shells inspire better building materials,” by Ben Coxworth, Gizmag, 13 March 2010]. Coxworth reports:

“Seashells have done an exemplary job of protecting their inhabitants for around a hundred million years, so perhaps it isn’t surprising that scientists and chemists have now replicated their unique structure in a manmade material. Taking inspiration from shells, researchers from the University of Manchester and the University of Leeds have successfully reinforced calcium carbonate, or chalk, with polystyrene particles such as those used in disposable drinking cups. Their achievement could lead to stronger building and bone replacement materials, or other practical applications. By combining calcite crystals with polystyrene particles, the scientists created a ceramic polymer that is less brittle than chalk, and thus less prone to cracking. When the material did crack, they noticed that the polymer lengthened within the cracks, instead of simply snapping – this is a known mechanism for absorbing energy and enhancing durability. By selecting particles of different shapes, sizes and composition, the scientists said the properties of the material could be tweaked for different purposes.”

Although the polystyrene particles lengthen to fill in cracks, the new material isn’t self-healing. Other researchers are exploring a number of materials that do have self-healing qualities. One is a self-healing cement [“Student creates cost-effective self-healing concrete?” by Ben Coxworth, Gizmag, 27 May 2010]. Coxworth explains why his headline contains a question mark:

“Self-healing ‘smart building materials’ have the potential to reduce structure repair costs, lower cement-production carbon emissions and even save lives. One barrier that has kept these materials from being commercialized, however, is their potentially labor-intensive and thus expensive production process. Recently, an engineering student from the University of Rhode Island (URI) announced that she has developed a self-healing concrete that would be inexpensive to produce. Michelle Pelletier, collaborating with URI Chemical Engineering Professor Arijit Bose, created a concrete matrix that was embedded with a micro-encapsulated sodium silicate healing agent. When cracks formed in the concrete, the capsules ruptured and released the agent into the adjacent area. The sodium silicate reacted with the calcium hydroxide already present in the concrete, and formed a calcium-silica-hydrate gel that healed the cracks and blocked the concrete’s pores. The gel hardened in about one week. When Pelletier’s concrete was stress-tested to the point of almost breaking, it proceeded to recover 26% of its original strength. By contrast, conventional concrete only recovers 10%. Pelletier believes that she could boost the strength of her mix even higher, by increasing the quantity of the healing agent. Other researchers have tried using bacteria spores that secrete calcium carbonate, or glass capillaries filled with a healing agent. According to Pelletier, her mix would be more cost-effective because it would be simpler to produce, and function more efficiently. ‘Smart materials usually have an environmental trigger that causes the healing to occur,’ she said. ‘What’s special about our material is that it can have a localized and targeted release of the healing agent only in the areas that really need it.’ Pelletier is now researching how well the healing agent would work for minimizing the corrosion of steel rebar within concrete structures.”

As a side note, in a post entitled Go Green, Save Lives, I discuss some varieties of cement that possess characteristics that can help remove carbon dioxide from the atmosphere. Although self-healing materials may have higher initial costs, their lifecycle costs could be dramatically lower than traditional materials. The Economist reports that “researchers have devised an ingenious way for the damaged surfaces of metals to repair themselves when they come to harm” [“Metal, heal thyself,” 10 June 2010]. The article reports:

“Sadly for engineers, inanimate objects cannot yet repair themselves. But work by Claudia dos Santos at the Fraunhofer Institute for Manufacturing Engineering and Automation, and Christian Mayer at Duisburg-Essen University in Stuttgart, has brought the day when they will be able to do so a little nearer. They and their colleagues have invented a way for damaged metals to heal themselves.”

Repairing damaged “surfaces” can help maintain a structure in good repair and prevent further damage; but, repairing surfaces is a far cry from correcting deeper structural flaws. Nevertheless, it is a start and the article explains how it is done:

“The surfaces of many metal objects are coated with other metals for protection. Iron, for instance, is frequently galvanized with zinc. The basic idea of the new technology is to infiltrate this coating with tiny, fluid-filled capsules. When the metal coating is punctured or scratched, the capsules in the damaged area burst and ooze restorative liquids, in the form of compounds called trivalent chromates. These react with nearby metal atoms and form tough, protective films a few molecules thick to ameliorate the damage. The idea of doing this has been around for years, but it has proved difficult in practice because the capsules used were too big. Surface coatings tend to be about 20 microns (millionths of a meter) thick. The capsules were 10-15 microns across—large enough to disrupt the coatings, and thus do more harm than good. The trick worked out by Dr dos Santos and Dr Mayer is how to create capsules a few hundredths of this size. The capsules the researchers have come up with are made by mixing butylcyanoacrylate, a chemical found in superglue, with an oil carrying the healing compounds. This mixture is then mixed with dilute hydrochloric acid. The result is an emulsion of droplets between 100 and 300 nanometers (billionths of a meter) across. Each droplet has an oil core surrounded by a thin layer of butylcyanoacrylate. To make the droplets stable, phosphate is added to the emulsion. This triggers the polymerization of the butylcyanoacrylate into a tough plastic, which forms the outside of the capsule.”

The article notes that “the greatest challenge for the team … was not making the capsules in the first place, but stabilizing them during the plating process.” Having overcome that challenge, however, the team believes “that self-repairing metals should commonly be available in the years ahead.” Like self-healing cement, the initial cost of self-healing metals will be greater than traditional metals, but long-term maintenance costs of structures built with the material could be dramatically lower.

 

If you are looking for a material with lower initial costs, you might want to look in the nearest trash bin [“Medical waste no longer being wasted,” by Ben Coxworth, Gizmag, 1 May 2010]. Coxworth reports:

“Back in the 70’s, Mad Magazine ran a satirical article proposing crazy new methods of dealing with garbage. One of them involved taking the trash, compressing it into cubes, then building things out of those. Flash forward to 2010, and a Houston company is doing almost that very thing, and with medical waste, no less. Sharps Compliance takes items like needles, syringes and lancets, and presses them into a pelletized building material called PELLA-DRX. Sharps specializes in the disposal of injecting supplies from individuals and clinics. The waste is already being sent into them by the users, so no transportation is required solely for the production of PELLA-DRX. To make the product, the waste is first sent through an autoclave, which kills any pathogens. Next, it goes through a shredder, which reduces its volume by over 90%. Finally, it gets compressed into pellets, which bear no visual clues as to their origins. Sharps claims it utilizes 100% of the waste it receives, so absolutely none of it ends up in an incinerator or a landfill. PELLA-DRX is currently being used to make cement, although Sharps foresees it also finding its way into the production of lime and steel. Because it reportedly has a BTU content equal to coal, they also see it being used in the production of power – if they’re suggesting it be burned, however, you have to wonder about all that plastic going up in flames.”

A couple of years ago, a University of Utah professor applied for a patent for a process that turns trash into building material [“Invention: Recycled trash construction materials,” by Justin Mullins, New Scientist, 8 January 2009]. Mullins reports:

“Lawrence Reaveley, a civil engineer at the University of Utah in Salt Lake City, has come up with a scheme that could reuse some of this excess trash. His new patent application claims that a blend of waste plastic and cellulose from plant material can make a good building material, once appropriately sanitized. The mixture could either be held together using a bonding substance, or treated with heat and pressure to let the plastic already in the mix hold things together, the application says. Panels produced in this way could be used for sound or heat insulation, or they could be reinforced – for example with metal or fiberglass – to be used structurally for walls and other building features. The plastic/cellulose mix could even be burned for fuel, the patent application claims.”

Environmentalists continue to ask: “Who really needs a brand-spanking-new house framework constructed out of harvested lumber or chemically-saturated, spun fiberglass insulation when in many cases, eco-friendly options will work just as effectively with minimal or no negative impact on our planet?” [“Recy-Blocks: Eco-Building Material Made Out Of 100% Plastic Trash!” by Kieran K., GreenWala, 10 February 2010]. Kieran writes:

“Alternative building materials that make good use of recycled, reclaimed and sustainable (rather than virgin) resources are cropping up more frequently than ever before thanks to the innovative approach of forward-thinking product designers. … We’ve seen evidence of this before with the creation of cow-dung-composed EcoFaeBricks which are said to reduce 1,693 tons of carbon dioxide from the atmosphere on a yearly basis. Another eco-building product, UltraTouch Natural Cotton Fiber Insulation, converts recycled, shredded denim into batts that can be fitted between joists, studs and beams and generally releases no volatile organic compounds or air pollutants. One of the most outstanding innovations in recent years is Greensulate’s line of rigid panel home insulation composed entirely out of agricultural by-products and fungal mycelium. While all of the aforementioned are notable in their own right, they may have some serious competition now that Gert de Mulder’s ‘Recy-Blocks’ have burst onto the scene. The rectangular 100% plastic waste construction components are created by pressing reclaimed packaging material – which far too often ends up being a landfill casualty – into pillow shaped forms that achieve a solid state due to their exposure to high heat.”

Creating new materials and getting people to use them are two very different challenges. Colorado architect, Doug Eichelberger, is one designer who would like to see trash used as a building material [“Trash House,” by Glenn Meyers, Green Building Elements, 17 February 2009]. Meyers reports that Eichelberger would like to see trash bundled into bales for use in rebuilding third world communities devastated by natural disasters. Eichelberger admits, however, that such bales are not the strongest of materials and don’t offer a long-term solution for mitigating the effects of future disasters. A better alternative would be the kind of “ecological brick” that has been developed in Argentina [“Ecological Bricks,” by Keith R., The Temas Blog, 24 December 2006]. Keith writes:

“Bricks developed by Argentina’s Experimental Center for Economical Housing (Centro Experimental de la Vivienda Económica – CEVE). The Córdoba-based CEVE was created in 1967 as an R&D, technology transfer and training center in experimental, low-cost housing. CEVE is managed by the Association of Economical Housing (AVE) under contract with the National Council of Scientific and Technological Research (CONICET). In a project funded in part by Germany’s technical cooperation agency, GTZ, CEVE developed a brick made of used food (primarily candy) wrappers and plastic (primarily PET) soda and water bottles. Used beverage containers are provided by the city’s selective collection plant, collection points in schools and government agencies, plus rejects from the local bottling plant. The PE film is provided by the Converflex company (Arcor) in Córdoba province, which recycles PVC film but not other plastics. The plastics are ground up and then mixed with Portland cement and chemical additives to make the bricks and something CEVE calls ‘brick plates.’ … CEVE says that the resulting bricks are lighter (about 1.1 kg vs. an average 2 kg for a regular brick) and cheaper (by about half) than traditional bricks, but comparable in terms of durability, water and fire resistance, with good heat and sound insulation properties. In outdoor exposure tests undertaken by CEVE over the course of two years, the materials stood up well to both weather and ultraviolet radiation.”

With many of the developed world’s landfills reaching capacity, turning trash into bricks could offer a way to reduce building costs, create jobs, and help the planet along the way. I suspect that until the current recession can be seen fading in the rearview mirror people won’t be looking for new sources of building material. If and when infrastructure development heats up, the search for new for building materials will heat up as well.