According to National Geographic Education, ice wedging is an example of mechanical weathering, not chemical. This type of weathering happens when rocks are broken down into smaller and smaller pieces by physical forces without changing their chemical composition. The weathering is caused by the endless freeze-thaw cycle of water.
Water can seep into small cracks and crevices found in rocks. When the temperature drops low enough, the water inside these cracks freezes and then expands. The ice formed between the cracks then acts as a wedge, slowly widening the cracks until the rock splits.
When water thaws, it then penetrates deeper into the rock’s cracks and crevices, where it can freeze again. As the freezing and thawing of water goes on and on through time, this process slowly creates larger cracks and holes in the rock. Eventually, there will be too many cracks and holes, and the rock will crumble.