What information do you have concerning the ability of certain marine borers to penetrate concrete? Is it true that these creatures secrete an acid which is capable of dissolving concrete?
One confirmed instance of such penetration that we are aware of occurred in Los Angeles harbor and involved cement-mortar jackets surrounding wooden piles. This is reported in the American Concrete Institute's Monograph No. 4 by Hubert Woods on "Durability of Concrete Construction." Subsequent investigation established that the cement-mortar shell was of poor quality, very friable, and contained only sand aggregate of which 93 percent could pass the No. 50 screen. A subsequent careful study of major U.S. harbors failed to disclose any evidence that marine borers can penetrate structural grade concrete. The same investigation also exploded the theory that marine borers are able to produce acids capable of dissolving rock or concrete. Their serrated shells, which are replaced as they wear smooth, simply function as rasps.