Stachiw 



SHORT-TERM STRENGTH OF WET CONCRETE SPHERES - The average ulti- 

 mate compressive short-term strength of concrete spheres permeated 

 b^^ seawater has been found to be approximately 187o higher than the 

 compressive strength of identical dry concrete in 3 x 6-inch solid 

 test cylinders under uniaxial compression (Table 2), 



Table 2, implosion Pressure, Calculated Maximum Stress in 

 Wet Concrete Spheres and Average Compressive 

 Strength for the Dry Test Cylinders. 



Item 



Sphere 5 



Sphere 12 



Average 



Implosion pressure 



Compressive stress— 'on 

 the interior of the sphere 



Compressive stress-i-'on 

 the exterior of the sphere 



Average compressive 

 strength of 3 x 6-inch 

 dry test cylinders—' 



Wetting period at 1,500 

 psi hydrostatic pressure 



2,850 psi 

 12,950 psi 



11,550 psi 



10,500 psi 



4 days 



2,750 psi 

 12,500 psi 



11,100 psi 



11,060 psi 



13 days 



2,800 psi 



12,720 psi 



11,320 psi 



10,780 psi 



1/ Calculated stress with Equation 1 (Figure 2). 

 2l Under uniaxial compression. 



TIME DEPENDENT BUCKLING OF CONCRETE SPHERES - Long term pres- 

 surization of wet and dry concrete spheres has shown that wet con- 

 crete spheres are more susceptible to static fatigue than dry 

 concrete spheres loaded to the same fraction of their short-term 

 implosion pressure (Table 3). 



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