shall be tested in accordance with American Society for Testing Materisla Standard Method C 39-44. cylinders taken, Of the three one will be tested for strength at 7 days and one will be tested for strength at 28 days; the third will be tested for strength at an elapsed time interval to be determined by the Engineer. If six cylinders are taken, three shall be tested at 7-days and three at 28 days. Con- crete made with high-early-strength cement shall have a 7day compressive strength equal to the specified minimum 28day compressive strength for concrete of the type specified made with ordinary Portland cement. 5-08. STORAGE: Storage accommodations shall be subject to the approval of the Engineer, and shall be such as to permit easy access for inspection and definite identification of each shipment in accordance with the report of tests. a. Cement: Immediately upon receipt at the site of the work, cement shall be stored with adequate provision for the prevention of absorption of moisture. b. Aggregate: Aggregate shall be stored to avoid the inclusion of any foreign matter in the aggregate and resulting concrete. Storage piles shall be maintained in & manner that will afford good drainage, prevent segregation of particle size and preserve the aggregate gradation. Sufficient live storage shall be maintained at all times tc allow placement of concrete at the required rate and permit application of such procedures as identification and inspec. tion. 5-09. TYPES OF CONCRETE AND USAGE: &. Coral Aggregate Concrete: Coral aggregate: con- crete of the various types required shall be proportioned a mixed for the strength as called for on tne urawings or as prescribed by the Engineer. All conerete for structural use not called for on the drawings, in these specifications or prescribed by the Engineer shall be 2000 p.s.i. at 28 days. A minimum of 1500 p.s.i. concrete may be psed for non structural work. Coral aggregate concrete shall be: used for all general concrete work unless otherwise directed by the Engineer. b. Limonite Aggregate Concrete: Limonite aggregate concrete of the types required shall be proportioned and mixed for the necessary strength as called for on the drawings, in these specifications, or as prescribed by the En- gineer. Limonite aggregate concrete shall be used in the scientific structures stations as called for on the drawing 5-6