Our polyurethane since it’s a synthetic material, will not change shape or breakdown like other materials such as sand or cement. However, the ground can and will move overtime depending on soil conditions. Also, water intrusion from poor drainage can erode the soil, which can cause re-settling.   Lastly, a long dry spell over the summer can cause the ground the shrink, which can impact your concrete. So typically if there is any re-settling it’s most likely due to soil conditions, poor drainage or extreme weather all of which would also affect new concrete. 

The key to preventing concrete from sinking is by filling voids and keeping water away. Open voids below your concrete should be stabilized with polyurethane foam. All open gaps such as cracks and expansion joints should be caulked to stop water from getting below the slab and eroding the base. Also, all water should be directed away from your concrete such as downspout. The sides of your concrete should also be properly graded so that the base cant wash away.