(3) A vacuvim of 25 inches of mercury was alternately applied and 

 released until all of the air in the porous aggregates was replaced 

 by the antifouling solution. The saturated aggregates were allowed 

 to stand immersed in the solution for another 6 hours. 



(4) The aggregates were suspended on a screen and drained for 

 several hours to remove excess chemical solution from their surfaces. 

 In most of the tests, additional solution was removed from the 

 surfaces of the aggregates by dipping them briefly in volatile 

 mineral spirits. The aggregates were then usually permitted to 

 stand, sometimes in an oven or in front of a fan, until the mineral 

 spirits had evaporated. 



(5) Finally, the impregnated aggregates were reweighed to determine 

 the uptake of chemical solution. 



Mixing the Antifouling Concrete 



Several preliminary tests were made to determine which ratios of 

 cement, water, and impregnated aggregates produced the strongest concrete 

 panels. On the basis of those tests, the following procedure was 

 adopted: a mixture was made from 0.45 part of water, one part of 

 Portland cement, and one part of impregnated shale aggregate, based on 

 the weight of the dry aggregate before it had been impregnated. 



Casting the Concrete Test Specimens 



The 1- by 6- by 12-inch test panels (Figure 1) were made by pouring 

 the concrete mix into a wooden mold lined with a thin polyethylene film. 

 The plastic lining eliminated the need to apply grease, oil, or other 

 mold-release agent to the interior surface of the wooden mold. A thin 

 coating of grease or oil on the surface of the test specimen might have 

 interfered with the exposure tests. The upper surfaces of the wet 

 concrete in the mold were leveled with a trowel, but the upper surfaces 

 of the finished specimens were not as smooth as the bottom surfaces 

 which were formed in contact with the smooth bottom of the mold. 



A few antifouling concrete panels with smooth tops and bottoms were 

 made in a special mold open only on one edge. The two broad faces of 

 the mold and all but the top edge of the mold were lined with a poly- 

 ethylene plastic film. The mold was suspended vertically, resting on 

 one edge. The concrete mix was then poured into the open edge. 



Two-inch concrete cubes (Figure 2) were made from the same concrete 

 mix from which the test panels were cast. The cubes were cast in a 

 three-compartment metal mold described in ASTM designation CI 09-63 

 [8]. 



For the shear test, 1- by 3- by 3-inch blocks (Figure 3) were cast 

 upon the surface of previously cured, untreated concrete panels. After 

 hardening, the 1 - by 3- by 3-inch blocks were sheared from the surfaces 

 of the untreated concrete panels. 



