Just as a thought I personally think if I were to consider a build such as one of these that I would first screen my aggerate to insure a more consistent size any larger rocks could be cracked or broken into smaller pieces this would reduce the possibility of having rocks in the mix with natural cracks hidden in them.
I know this is totally off base from what we are discussing but I have seen concrete structures crack in cold temperatures. The causes were determined the cracking was form moisture trapped in minute fissures of the larger rocks of the aggerate. Enough fissures with enough trapped moisture once fully cold soaked and boom the whole side of a concrete wall would look like mortar rounds went off in it