Table 3. Elastic Moduli and Poisson's Ratio Data 

 [Test specimen size was 6x12 inches (152 x 305 mm)l 



Type of 

 Specimen 



Total Age 



Main Curing 

 Environment 



Type of 

 Cylinders 



No. of 

 Specimens 



Elastic 

 Modulus, 



E 

 (psi X 10^) 



Poisson's 

 Ratio, 



Fog-cured 



5.6 yr 



100% RH;73°F 



cast 



24 



5.33 



0.21 



Ocean-cured 



5.6 yr 

 (includes initial 28 days 

 in fog room and then 2 to 

 5 mo of on-land field cur- 

 ing 150 ft from shoreline) 



ocean depth, 

 2,400 to 3,200 

 ft;40°F 



core 



15 



3.77^ 



0.24 



On-Iand 



5.6 yr 

 (includes initial 28 days 

 in fog room) 



90 days 

 (includes initial 28 days 

 in fog room) 



150 ft from 

 shoreline 



400 ft from 

 shoreline in 

 a building 



core 

 cast 



16 



2 



4.21" 

 4.12 



0.22 



Elastic modulus determined from unadjusted core data. 



in implosion strength may have been 

 greater than the reported 5% due to not 

 defining as accurately the compressive 

 strength for the preloaded spheres as for 

 the other cases. The coated spheres from 

 the ocean had relatively dry concrete. To 

 obtain a compressive strength of dry 

 concrete, the on-land concrete blocks 

 were used. The evaporable moisture con- 

 tent of the on-land blocks was 2.7% by 

 weight, which was less than the 3.5% by 

 weight moisture content for the coated 

 sphere wall (Appendix B). Hence, the 

 compressive strength listed in Table ^ 

 for Spheres no. 11 and 13 may be a little 

 greater than the actual strength of the 

 concrete in the sphere wall. If this 

 potential error was corrected, the effect 

 would be to increase the Pim/f'c fatio for 

 the coated preloaded spheres. 



Table 5 shows that for non-pre- 

 loaded spheres the dry concrete 

 specimens had an implosion strength only 



slightly greater than that for the satura- 

 ted concrete specimens. However, for 

 the preloaded spheres, the dry concrete 

 specimens were at least 14% stronger 

 than the saturated concrete specimens. 

 This difference in strength will be 

 discussed in the next section. 



The implosion data are limited. 

 When the implosion strengths of dry and 

 saturated preloaded specimens (Pim/fc" 

 0.299) were averaged and compared to 

 those of the non-preloaded spheres 

 (Pim/fc = 0-30'f), it was found that the 

 overall effect of preloading the spheres 

 to a stress level of about 50% their 

 ultimate strength for 5.3 years was quite 

 small. 



Views of the imploded spheres are 

 shown in Figures 15 through 18. The 

 visual damage, in terms of fragmenta- 

 tion, is rather mild in comparison to non- 

 preloaded specimens and, in particular, 

 to specimens that have imploded in the 



16 



