Sunday, December 30, 2012

Building Materials Roundup


Concrete is a neat material. It’s strong, can be molded, and even colored. Now scientists have made concrete that heals itself using bacteria:
Bacterial spores and the nutrients they will need to feed on are added as granules into the concrete mix. But water is the missing ingredient required for the microbes to grow.

Concrete is the world's most popular building material, but cracking is a problem So the spores remain dormant until rainwater works its way into the cracks and activates them. The harmless bacteria - belonging to the Bacillus genus - then feed on the nutrients to produce limestone.The bacterial food incorporated into the healing agent is calcium lactate - a component of milk. The microbes used in the granules are able to tolerate the highly alkaline environment of the concrete.

"In the lab we have been able to show healing of cracks with a width of 0.5mm - two to three times higher than the norms state," Dr Jonkers explained.
Key test for re-healable concrete (BBC).

And previously technicians created self-cleaning concrete that can clear the air:
The idea of adding titanium dioxide to concrete is not a new concept. In 2007, Italian company Italcementi developed a cement that was also laced with titanium dioxide, and could neutralize certain harmful pollutants. It's called TX Active, and when exposed to sunlight or ultraviolet light, the titanium dioxide transforms any nitrogen oxides or sulfur oxides into harmless nitrates or sulfates which can be washed away by rainwater, much like the titanium dioxide mix that EUT researchers are testing in the Netherlands right now.
Fly ash from coal-burning power plants has been known to strengthen concrete for some time and is frequently used as an additive, diverting it from landfills. They are also experimenting with techniques to inject carbon into concrete to make the process carbon-neutral (5 percent of CO2 emissions come from concrete production):
[Atlas Block takes] CO2 supplied from local industrial sources and injects it directly into concrete masonry units (CMUs) during production using a specially designed mold. Atlas Block is using the CarbonCure system primarily to reduce the carbon footprint of its products, but injecting CO2 into CMUs during manufacture also improves their strength, reduces the amount of portland cement required, and speeds curing. Atlas Block also offers products with post-consumer recycled glass. Atlas Block / CarbonCure is the first product brought to market that sequesters CO2 without requiring a dramatic change in current manufacturing processes.
Building Green's Top Ten Green Products of the Year Are Not Sexy But They Will Make A Difference (Treehugger)

Insulated cement looks like a promising solution for building insulation:
When it comes right down to it, most insulation is simply some form of entrapped air, whether in foam or in fiberglass or in cellulose. The greenest one is going to have the fewest chemicals that can outgas, the lowest impact during manufacture, good stability so that it doesn't settle and good fire resistance. I was really surprised to find that it might also be made from cement.
Cement is not one of TreeHugger's favourite materials, given that a ton of CO2 is emitted for every ton of cement produced. But materials made with it have some great attributes, including longevity and fire resistance. If you mix it with air and foam it up with special equipment, you get AirKrete, a foam-in-place insulation that looks like shaving cream and has an R value of 3.9 per inch, which is pretty good.
AirKrete: Green Insulation From Cement (Treehugger)

A lot of “natural” materials can make insulation, such as the cork boards mentioned in the previous article, the trick is making sure they don’t rot and decay and become mold farms in the presence of moisture, which is why the manufacture and chemicals used are often so toxic. It’s a paradox of green building: the insulation and waterproofing that makes such buildings possible is also toxic to manufacture. But the highest insulator is actually a vacuum. Early Warning points out, “Vacuum-insulated panels have five times the R-value per inch of conventional insulation, but are currently too expensive and hard-to-apply to see widespread use.  Inventors and entrepreneurs needed over there please!” I’ve only seen vacuum panel insulation used in very few instances on existing structures where weight is critical and conventional  insulation cannot be added for some reason. Vacuum panels are clipped on the outside. Maybe we should push this along.

Vacuum Insulated Panel (Wikipedia)
Vacuum Insulated Panel (VIP) (Toolbase)

Taking this to its logical extreme, imagine an entire house as a vacuum bottle. They did – back in 1932! Try not to snicker at the warnings of the coming Ice Age, though.

Vacuum Bottle Houses From 1932 (Treehugger)

And you can make bricks anf tiles out of just about anything nowadays: Paper Waste Can Be Made Into Eco-Friendly Bricks (Treehugger). Time for a return of Brick Expressionism? How about Timbrel Vaulting?

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