29 CHAPTER Ii, SECTION 1 Variations in the physical properties of coral rock, as noted above, required the preparation of 14 design mixes for concrete in Eniwetok Atoll and 27 design mixes in Bikini Atoll. Concrete cylinders were carefully packed in wet sawdust for a period of 48 hours, which allowed the required initial period after casting before they could be shipped to the Test Laboratory. [t was found that wax-paper cylinder molds could not be easily stripped from concrete cylinders and, therefore, the one-use sheet metal cylinder molds were used. The use of these sheet metal molds was justified by the amount of time saved and the uniformity achieved in the quality of concrete cylinders. A_ total of 1,450 cylinders was taken from approximately 28,500 cubic yards of concrete placed during 1 July 1955 to 1 July 1956, amounting to one control cylinder for every 20 cubic yards of con- crete placed. The average results obtained from these tests as shown below. Specified 28-Day Breaking Strength Average 28-Day Bikini Atoll Average 28-Day Eniwetok Atoll 2000 psi 2500 psi 3166 psi 3177 psi 2984 psi 2718 psi 3000 psi 4145 psi The average concrete mix as used at Job- site contained approximately the following: 1800 lbs. course aggregate 1200 lbs. fines 6 sacks of cement 42 gallons of water The above average mix was varied to conform to the characteristics of the aggregate used at the place and time of the concrete pour. The high values obtained in the average strengths were primarily due to the large amount of concrete poured in water because, as a safety factor, additional cement was added to mixes that were poured in water and the actual strengths of the concrete were therefore much higher than specified in such cases. The coral aggregate obtained at Bikini was characteristically more consistent; this was due to a denser coral thus resulting in a more uniform ratio between coarse and fine aggregate producing a concrete mix of higher strength. 3914 psi Included in a variety of other activities of the Test Section was the making of CBRtests, Bitumen content tests, moisture tests of various mixes, strain gage tests on tower cable, tension tests on marine rigging and paint durability tests. The Inspection Department was organized with individual site Inspectors assigned to each major site, working under a Chief Inspector at each Atoll. This department inspected all phases of construction work from the first clearing and grading stage until final completion and acceptance. Preliminary work consisted of studying plans, specifications, bills of material, and any special conditions. Materials were then checked for conformance with specifications. With the commencement of work, inspection was continuous. Excavations and foundations were checked for location, dimensions, and orientation; forms were checked for adequacy and alignment; re- inforcing rods were checked for size, bends, spacing, ties and rigidity of support; embedded fixtures were checked for location and size. Con- A total of 15 tests of cement (Ideal, Santa Clara, and Santa Cruz) were made for normal consistency and time of set. Normal consistencies were about 25 per cent and the time of set varied from one to four hours, which con- crete was inspected during placement to ensure that it was well-compacted and bonded, and various cements observed in the field. cal items followed. firmed the difference in set qualities of the of proper mix. Inspection after placement for the removal of forms and backfilling was likewise continuous. With the structure formed, inspection on electrical, sanitary, and mechani- Page 2-7