Concrete do expand and contract due to changes in temperature and goes through a volume change.
IS Codes says any structure should not be made more than 45 meter in length, if it is to be built then expansion joints should be made, else it will break through all floors and show huge cracking everywhere.
During summer / hot weather, concrete and steel bar tries to expan and they need some space outside the structure areas between two continous structures made separate by providing expansion joint generall is of 50mm wide.
Same way during winter / cold weather, concrete and steel bars tries to contract (reduction in volume) and if there is no space left for counter acting on contraction force, concrete may face sever damages.
To allow / companset the effect of contraction, airated concrete is used.
So air bubbles inside in the concrete do really help it to protect its self from cold weather and expansion contraction cycles.