I consider yesterday’s blog post about making cast stone earthbags one of the most exciting developments in earthbag building. This newer, simpler geopolymer process sure seems like it will become popular. It sounds like a million dollar idea to me. I imagine millions of people would love to live in an all natural, affordable stone home that’s simple enough to build that anyone can do it. The building process is nearly identical to typical earthbag houses (which is rapidly gaining in popularity) except the fill material in the bags or tubes turns to actual stone. Yesterday I discussed how granite, basalt, sandstone or schist houses could be built. Bill McNulty, the inventor of the stone making process, has an additional patent that uses minerals from the calcium carbonate group, including aragonite, limestone, calcite, marble, dolomite, etc. to create an even wider range of stone homes. What’s not to like?!
Let’s briefly discuss some of the benefits.
– only two materials are required (stone dust and sodium carbonate) plus water
– materials are readily available at many quarries, sand and gravel yards, and cement batch plants as rock dust or crusher fines
– materials are low cost because they’re ‘reject fines’ (gravel is much more costly)
– bonding process begins immediately after adding water (no soaking materials in a pit and waiting two days for water to evaporate)
– good potential for thinner walls that use fewer materials and take up less space because cast stone is stronger than tamped earth
– easy to shape a keyway in the top of each course so earthbags lock together (increased perpendicular shear strength)
– barbed wire not required except in seismic areas, and for domes
– less tamping likely required
– good potential for natural fiber bags
– good potential for lower cost, lower strength bags since bag strength is less important
– bags can be tamped flat on the sides to greatly reduce plaster work
– bags can be cut away and recesses filled with the same material as the walls (geopolymer cement)
– walls can be sealed with wax to prevent build up of salt
– the process is going to be tested on powdered concrete rubble to provide housing in disaster areas such as Haiti (an earthbag team in Haiti has already been contacted)