J
@AbstraktLighting Hi: You can check some of my past posts but I think I can resume some here. First thing you need to do is go to your county or state or whoever owns jurisdiction regarding code in your area. Get the local codes in pdf or writing. In some states, they are adopting the 2016 international code. There are different codes, mechanical, electrical,hydraulic, sewage, etc. You can hire an engineer to design the whole concept for you, or if you want to save money but take longer, sit down with the codes and see the minumum requirements. To give you an example, some will require concrete blocks to have x amount of compressive and y amount of tensile strenght. It will have minimums for virtually everything. As long as your design comforms to the minimum, and have an engineer stamp of approval, you should have no trouble building it and passing your county inspection. Some counties only require an inspector of the county to check each stage of building, but an engineer stamp will make it far easier to approve, since many times the county inspectors are not engineers. If for example they require a minimum 2500 psi of compressive strenght on your design, and there is no parameters for your block, you can make several of the blocks, along with the mix proportions taken to an engineering firm, and they will make a compression test. From this test you will real numbers to comply with the code. This is not too expensive and when I did it they charged me around 75 dollars for each inspection, which included taking 4 to 5 cylinders of concrete to cure and test for a period of about 3 months.
Your local code will probably ask for higher tensile strengh, so you can fix this once you have your celular concrete dome built, to install iron rebar proportionate to the required streght(bar diameter and quantity), to either the inner or outter of your dome, and then spraying a layer of shotcreted magnesium oxyde cement over the rebar. This will give you the required tensile strenght, and most engineers can use a chart to give you an approximate of the tensile strenght of rebared concrete. This should put the design within the minimum requirements of your county. I still do not have a better recipe for light concrete, but a quick google search or youtube will give you many examples of people who have added the magnesium concrete or used other aggregates. Any aggregate will make celular concrete heavier, so keep this in mind. Before trying to experiment with any aggregate, you should try to first do a proper celular concrete block as explained by Domegaia. Only then would you be able to have a measured example from which to depart either heavier or lighter.
