It is the second one found in that area this month.
The 12-inch bomb shell was found this morning by workers, and was taken away by the disposal team.
The site was not evacuated, while a Royal Navy spokesman said the inert bomb was not a danger to anyone at the site.
The Second World War shell was found by workers in sand and gravel that had been dredged by the firm.
A spokesman for Cemex said the discovery of shells was commonplace at the site.
A smaller shell was discovered by workers on January 7 after it was dredged up by crews.
A spokesman for Cemex said: "Finding a device is a regular occurrence and colleagues are trained to deal with such situations in an efficient and professional way."
A spokesman for the Royal Navy said: "The shell was taken away by the team, they didn't have to carry out an explosions and it did not post any danger."