Ice roads would be one application. Once it freezes, usual ferry services can often no longer be upheld. Then, one has to wait until the ice is thick enough to drive a car over the ice. If there was an easily applicable material to drive on ice less than usual 15-20cm of ice, that would decrease that waiting time quite a bit (and make ice roads/bridges possible in locations that would previously be unsuitable). And since it is ice, you can grow it somewhere else and transport in place with a barge.

Another is underground tunnel building. In sandy places, there are cases where they freeze the ground when building a concrete structure. If that could be reinforced with stronger ice, it might make working easier.

Similar, you can use ice as an temporary scaffold when e.g building a spanning bridge in winter. Stronger ice => easier application of said scaffold.