a 5-liter plastic bucket which also contained one intact cylinder prepared 
with two 6d nails in its interior. Ten weighed 6d nails were added to 
each bucket, and seawater was allowed to trickle into it so that it con- 
stantly overflowed. The seawater addition was from a sufficient height 
that splashing and consequent aeration of the bucket's contents occurred. 
The nails were periodically removed, ultrasonically cleaned, rinsed with 
demineralized water, dried, and weighed to determine weight loss. When 
the experiment was terminated, the intact specimens were crushed and the 
nails examined for the presence of corrosion products. 
In a parallel experiment, cylinders prepared with 6d nails both at 
the center and 1 cm from the wall were exposed to partial immersion. 
Here, each of the above cylinders was placed vertically in a 2-in.-deep 
pan through which seawater continually flowed. 
The test cylinders containing the nails were exposed in a partial 
immersion test for 446 days. Inspections were periodically made to 
determine whether possible oxidation of the steel caused cracking or 
spalling of the concrete. 
Biotoxicity Tests 
Two experiments were designed to determine the relative toxicity of 
certain of the toxicants employed as antifoulants. Fertilized eggs of 
the red abalone, Haliotis rufescens, were used as test organisms in the 
first experiment. Approximately 10,000 eggs were introduced into each 
of two 50-liter plastic containers, one containing a control concrete 
specimen, and the second a specimen prepared using TBTO-impregnated 
aggregate. The next day the development of the eggs in both containers 
had terminated at the multicellular level. These concrete specimens, as 
well as others, were then placed in flowing seawater and allowed to 
leach for 102 days. The experiment was then repeated using 1/-liter 
containers with ~5,000 fertilized eggs in each. 
A second experiment was designed to measure the relative concentra- 
tions of various toxicants required to kill larvae of H. rufescens. In 
this experiment, treated and control concrete cylinders were leached for 
12 days then placed in plastic pails containing 4.3 liters of seawater 
that was filtered to 1 micron and sterilized with ultraviolet radiation. 
The cylinders were immersed for 2, 20, and 200 minutes in such a way 
that no part of the cylinder contacted the container. The larvae were 
then introduced and the effect of the three concentrations of various 
toxicants was monitored by periodic microscopic observation of the 
larval development. 
FINDINGS 
Antifouling Properties 
Set no. 1, TBTO/Creosote Mixture. After 173 days of exposure, the 
concrete prepared with the TBTO/creosote-impregnated aggregate accumu- 
lated 44% as much biofouling as the untreated control. Table 3 presents 
these data and summarizes the final subjective evaluations made after 
163 days of exposure (10 days before removal of the cylinders). 
