Shotcrete is a placement method for high-quality concrete. Here’s a link to an article of a rehabilitation of a concrete-supported lighthouse in the Saint Lawrence Seaway (Pointe de la Prairie Lighthouse) that provides a lot of detail on an installation similar to yours, including salt-water exposure in a tidal zone: (www.shotcrete.org/wp-content/uploads/2020/01/2014Sum_Sustainability.pdf). Plus, this project also has extreme freezing-and-thawing exposure.