posted 5 hours ago
William, he used two gallons (7.6 l) of cement to make a block. My calculations in the previous post are for one block not for a bag of Portland.
I think the diiscussion revolves around foamy (insulating and cheaper) aircrete made by paddle mixing, but with a prospect of making it quickly in bulk in a mixer.
According to this recipe made IN THE MIXER a bag of portland cement will make only 0.87 m2 of 5 cm thick insulation, so it would be 9.3 sq ft of 2" thickness. Maybe other methods of foaming will produce much more, but not this one made in concrete mixer that basically converted 2 parts of cement to only ca 3 parts of mix.
Also, the test sample was made with a kitchen mixer (and used for measuring R value) and the block - in a concrete mixer, resulting in a very expensive (and different) product.
Mixing with a mortar paddle would result in much better foaming, the cost would drop significantly, but at the same time it would slow the production to build something bigger. I just liked the method of bulk mixing in an ubiquitous concrete mixer.
I would not recommend wasting insulating material in a regular CMU block cavities. Due to massive thermal bridging, the R value of a 8" block wall filled with PU foam increased from R2.0 to only 3.7. Block cavities were designed for reinforcing. Block wall needs continous rigid insulation on the outside or 2 wythe wall with insulation of choice in between.
I'm not against aerated concrete - just the opposite. I wish AAC blocks were available in every construction big box store as the cheapest quality building material available, allowing to (easily due to light weight) build bearing, insulating, breathing, fire/pest proof one wythe walls. CMUs are so 60s, when nobody cared about any insulation.
Rico, US and Canada are traditionally non masonry countries, so we have to resort to laborious DIY or use deeper pockets to purchase/import.