According to Derek Taylor, owner of AAC distributor SafeCrete, the only manufacturer in North America right now is a German company whose block dimensions don't work for U.S. The barriers for builders don't stop with the mortar.We would like to add a few drawbacks that we've found: AAC requires a learning curve for builders, because the mortar application is more precise.(that was in 2006, and now there are almost none, since Xella has moved its Hebel operation to Mexico) this means higher costs, which is a huge barrier for adoption. There are few manufacturers in the U.S.In a report written for UC–Davis (PDF), Stefan Schnitzler finds few disadvantages to AAC. AAC also has excellent soundproofing properties.It's a better insulator, with a steady-state R-value just a hair above R-1 as opposed to something more like R-0.2 (neither of these factors in thermal mass, which we'll get to later).It's lighter, which cuts down on transportation costs and fuel use.Despite the energy-intensive autoclaving process, manufacturers say it takes about 50% less energy to make, because of the lower portland cement content by volume (we're haven't found anyone to challenge those claims, but are still looking for data).It uses less material-important for concrete, since portland cement is one of the most energy- and carbon-intensive building materials.It's still not wood, but in North America (unlike in Sweden at the time and in most of Europe now), wood is still plentiful and cheap.Ĭompared with conventional concrete, AAC still has advantages, though: The main advantage of AAC when it was first developed in Sweden in the early 20th century was simple: it wasn't wood. They are porous and light, like muffins, but not hollow. Like conventional concrete masonry units, AAC is sold in a variety of block shapes and sizes, but unlike conventional units, most don't have cores. SUPPORT INDEPENDENT SUSTAINABILITY REPORTINGīuildingGreen relies on our premium members, not on advertisers. The resulting blocks are so full of bubbles that a block of the same size has about one-fifth the material required by regular concrete. The concrete is poured into molds, left to rise, and then "baked" in an autoclave, which uses steam and pressure to complete the chemical reactions and speed up the curing process significantly-completing in hours rather than weeks. (Your muffins are full of carbon dioxide bubbles, but AAC is full of hydrogen bubbles.) AAC is similar to other concrete types, except that it contains no aggregate sand or fly ash is included, with aluminum powder added to react with one of these ingredients and "leaven" the concrete, creating tiny bubbles just like baking soda does when it reacts with the buttermilk in your muffin batter.
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