Appendix A 

 CONCRETE MATERIALS 



The mix design for the concrete is given in Table 

 A-1. Transit-mix trucks dehvered the concrete, and 

 final determination of water content was based on 

 workability. Table A-2 gives the properties of the 

 fresh concrete; average values were (1) water-to- 

 cement ratio of 0.40, (2) slump of 1-1/2 inches, (3) air 

 content of 2.4 percent by volume, and (4) unit 

 weight of 145.2 Ib/cu ft. 



Compressive strength of the concrete at age 28 

 days (Table A-2) averaged 7,660 psi for the fog- 

 room-cured specimens and 7,690 psi for the on-land 

 field-cured specimens (moist-cured in wet burlap and 

 wrapped in plastic for first 28 days). The compressive 

 strength of the concrete at ages varying from 45 to 

 174 days was obtained prior to emplacing the spheres 

 in the ocean (Table A-2). These strengths were used 

 to calculate the short-term implosion pressure of the 

 spheres (the compressive strength of the weaker 

 hemisphere was used) so that projected emplacement 

 depths could be calculated. For the uncoated spheres, 

 the control cyhnders were saturated with seawater 

 prior to testing. The method of saturation was to 

 place the specimens in a pressure vessel and apply 500 

 psi pressure for 7 days. The strength of saturated con- 

 crete has been found to be 10% lower than room-dry 

 concrete [8] . The coating was assumed to maintain 

 the concrete in a dry condition, so the control 

 cylinders were tested in a dry condition. 



Table A-3 is a copy of a typical mill test report 

 on the Portland cement used by the transit-mix 

 supplier. Southern Pacific Milling, during the 

 fabrication of the hemispheres. All of the cement 

 meets ASTM specification C-150-70, Type II, Low 

 Alkali, Portland Cement. 



X-ray diffraction patterns for three concrete 

 blocks, W-15, W-39, and W-41, were obtained 

 (Figures A-1 through A-3) for documentation of the 

 chemical composition of the concrete at the early 

 stages of the test program. At the end of the test 

 program, which could be many years away, samples 

 of concrete can be analyzed to determine whether or 

 not the concrete has been attacked by the sulphates 

 in seawater. Table A-4 gives the diffraction angle (26) 

 of the expected intensity peaks for concrete attacked 

 and unattacked by sulphates in seawater [12] . 



Table A-1. Concrete Mix Design 



Portland cement, Type II, low-alkali 



Santa Clara River aggregate 



Water-to-cement ratio = 0.41 



Sand-to-cement ratio = 1.85 



Coarse aggregate-to-cement ratio = 2.28 



Water-reducing admixture = 2 oz/slack of Plastiment 



Material 



Aggregate Gradation 



Sieve Size 

 Designation 



Percentage Retained 



Individual 



Cumulative 





3/8 inch 













no. 4 



2 



2 





no. 8 



11 



13 



Sand 



no. 16 

 no. 30 



17 

 28 



30 

 58 





no. 50 



28 



86 





no. 100 



11 



97 





pan 



3 



100 





3/4 inch 











Coarse aggregate 



3/8 inch 



70 



70 





no. 4 



30 



100 



19 



