How do I repair aerated autoclaved concrete?
Instead of trying to fix the crack, first try figuring out what is causing the crack.  You can fix a crack many times, but if you are fighting against something like water pressure (or one of the many other causes of cracks in concrete), you will never win.   Once you find what is causing the crack, then look to mitigate the problem somehow (proper drainage in the case of water buildup), and then fixing it one final time will take care of the problem.