Pykrete is made of water and sawdust frozen. Pykrete is far more durable and has a much higher melting point than ice. During WW II there was discussion of using this amazing material for ships. How about a temporary bridge instead? Your troops are on one side of a lake. The enemy is on the other side. Their camp is protected from all sides except their lake front. If the lake was frozen then you could cross the lake and attack the enemy. The lake is cold but not frozen but fortunately you happen to have a Pykrete Ice Bomb
The outer layer of the Pykrete Ice Bomb consists of sawdust encased in a dissolving bag. When the sawdust is dissolved into the water then a water activated trigger mechanism causes the bomb core to create an endothermic reaction and disperse the sawdust into the water at the same time creating a frozen Pykrete surface that your troops can walk across. This is basically an Ice-nine idea but using real life off the shelf technology.