Stachiw 



Table 3. Hydrostatic Pressure and Duration of Loading of Wet 

 and Dry Concrete Spheres in Static Fatigue Test; and 

 the Average Compressive Strength of the Correspond- 

 ing Dry Test Cylinders 



ll Stress calculated with Equation 1 (Figure 2), 

 l_l No implosion occurred during 3-day test. 



PERMEABILITY OF CONCRETE SPHERES TO SEAWATER - The rate of 

 seawater seepage into sphere at 750 psi has been measured to be 

 approximately 2.5 milliliters per hour, while for a sphere pres- 

 surized to 1,500 psi the rate was approximately 5 milliliters per 

 hour. When the leakage rate is divided by the surface area of 

 the sphere, it can be expressed as 6 x 10"-^ milliliters per hour 

 per square inch of area per inch of thickness at 1500 psi hydro- 

 static pressure. In both cases the salinity of water siphoned 

 from the interior of the sphere was about 20%, lower than the sal- 

 inity of the pressurization medium. 



From this rather sparse data, it would appear that permeability 

 of concrete to seawater under high hydrostatic pressure is quite 

 low, and that some chemical or physical phenomena, which occurs in 

 the concrete, results in a decrease in the salinity of the water 

 that passes through the concrete sphere wall. 



DEFORMATION OF CONCRETE SPHERES UNDER LONG-TERM LOADING - The 

 measured strains (Figures 12 and 13) showed that dry concrete on 

 the sphere's interior has a time-dependent strain rate, which is 

 very large immediately after load application, but which decrease?^ 

 with time. That the time-dependent strain is a function of both 



229 



