The most effective encapsulation method involves placing a fiber-reinforced-polymer (FRP) jacket, or form, around a structural member, sealing the bottom, and then filling the annular cavity with a two-part epoxy grout, to which an aggregate (normally silica sand) has been added. 

This process has many advantages over other encapsulation methods:

• When installed properly, the FRP jacket, the epoxy grout, and the structural member bond, creating a monolithic structure.  Due to the low absorptive qualities of both the FRP jacket and the epoxy, seawater cannot contact the structural member.  Epoxy-filled FRP jacket encapsulation contrasts sharply with other methods, which frequently result in saltwater intrusion and thus the continued degradation of the structural member.
• The annular space between the structural member and jacket is minimal (often just 1/2 inch).  In contract, bags or jackets filled with cementitious grout can have an annulus of several inches.  The smaller annular space of epoxy-filled FRP jackets helps minimize the weight and wave loading on a structure.

Epoxy-filled FRP jackets have consistently performed better and lasted longer than all other encapsulation methods employed over the past century.  The first such FRP jacket installation, reported in 1971, is still in good condition.

See FRP vs. Steel Jackets.