Well if Syria needed ordinary cement to build a reactor vessel, I seriously doubt that North Korea would be the preferred vendor. Concrete is ubiquitous.
Concrete is used to shield reactor vessels primarily because it is dense. It stops energetic photons and particles emitted by radioactive substances.
Powdered cement, or finished concrete products such as K-rails, storm drain or utility vaults, or other configurations, make a good cargo for a ship containing radioactive materials, for the same reason.