Expansion joints are cuts in concrete slabs, or the joints between walls and concrete slabs, that go completely through the slab to the base material. The purpose of an expansion joint is to allow the concrete slab to expand and contract with temperatures changes, without cracking the slab.
Sealing joints in your concrete structures is key to prolonging the life of a concrete structure. Expansion joints must be sealed with a flexible sealant to prevent water from penetrating the joint and deteriorating the sub-base.