dampness when it freezes can crack anything! as long as damp air or moisture can get into it and seep in.
go real far north, like halfway to the North Pole, and you see they only use concrete for the lower half of the structure. Utilities antennas, goverment piers and docks, everything even houses all have concrete bases, or full basements, and the concrete goes up a few feet above ground.
assuming the dock is built to last. governments always want to look like they are going to remain the authority, so they want to build to last. Also, in the long term they have much fewer problems with maintenance and responsibility concerns if it's made tough.
There are hundreds of kinds of concrete products. Some have a lot of air in them, some have none. Damp air will let H2o get in and crack-freeze in winter and spring.
A single long freeze is not a problem, so a long cold winter causes almost no damage. In the fall, as temperatures drop the moisture content in the air also lowers slowly, so there is less and less moisture in the ambient environment too, so the first big loong freeze causes no damage. The worst thing is if moisture is in the concrete in spring -- when daily cycles between thaw and freeze let water percolate (slide around) which lets it occupy (like "expanding") into the micro fissures, and then it applies brand new pressures overnight when it freezes. Repeat for 45 days and you have aged your concrete the equivalent of 100 winters. After ten springs (ten years) your concrete could have aged as if 1000 years old, or it could be fresh and new looking, and it all depends on whether you managed to keep it dry in February, March, April and May when the sun is strong during the day but the night time temperature is below freezing.
david