As the seasons change, asphalt expands and contracts. This movement causes cracks. If cracks are not sealed, they will allow water to flow through the asphalt to the base. The base will become saturated and will not be able to support the asphalt above. More cracks will form allowing more water to enter the base. Without maintenance, this cycle will destroy your asphalt. Crack seal seals cracks from water. Crack seal is made of rubberzed asphalt which expands and contracts with the crack. Crack sealing is one of the most important things you can do to extend the life of your asphalt.