Maybe we should start a thread somewhere about testing materials! The only thing I wonder about is the fact that concrete / cement can explode under extreme heat. I have had fun watching water sweat out of concrete with a oxy acer torch. I wonder how close in molecular composition the cement board is. Now if you want some real heat transfer blocking material try asbestos board! I have some extra asbestos siding I might put a oxy acet torch to trying the same thing you did! But I need a IR thermometer first. Now how many people do you know have that lying around
