Since no one else has yet replied, I don't really know what aerated autoclaved concrete is, but one obvious answer is 'Don't aerate it!' Trapped air is one of the best insulators available, other than vacuum, so removing the air will significantly improve the thermal conductivity.
Dick
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Why would you want to improve thermal conductivity? One of its benefits is a high R-value for insulation (due in part to the many encapsulated air pockets).
Please expand on your question.
-John
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Not sure what your trying to do but I assume by auto clave you mean cement mixer. The industry has different additives for concrete for strengthening and coloring but not sure about changing thermal conductivity. If you want it to dry more quickly, there are accelerator additives that cause it to cure more rapidly, usually used in colder climates. There are also retarding agents to do the opposite, which are used in hotter climates to keep the concrete from setting up before it is in place. Las Vegas concrete companies use this extensively in their concrete mixer trucks in the summer. Strengthening is accomplished using nylon or fiberglass fibers, maybe other types also. Not sure what the coefficient of thermal conductivity is for concrete, but if you mixed strong fibers into the mix that have a higher coefficient of thermal conductivity than concrete, that would raise the coefficient of the mix somewhat, depending upon the relative ratio. I haven't seen it, but steel probably has a higher coefficient, so maybe steel fibers would do the trick. They use steel rebar in concrete, why not steel fibers? Just a guess. Post more info and I'll try again.