1994-03-21_REPORT - M1977378 - Laserfiche WebLink

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F-L Brenneman Secondary Bulkhead Construction Certification Report Page 3 The higher target strength was required because of a lack of field test data showing that the design mix could meet the required design compressive strength of 3000 psi . At the 0.45 w/c ratio, the mix is too dry to pump. For this reason and to provide additional time over the 1 1/2 - 3 hour initial set time of the concrete, two additives were used. These additives are a super-plasticizer to increase workability and a delay set to increase the allowable down time before a "cold-joint" condition could develop. The delay set retarded the initial set time of the concrete from approximately 1 1/2 - 3 hours to approximately 5 - 6 hours and increased the slump of the concrete mix which aided pumping. The concrete was mixed in 900 lb. (dry weight) batches, transferred to a concrete pump and pumped approximately 200 feet to the bulkhead form. Water was measured for each batch by use of a meter. There was some variance in consistency between batches either because of absorbed moisture from the air into the bagged mix or due to variance in cement content per batch. These were smoothed out by field adjustment and blending within the system. No major delays occurred during filling of the form which started at approximately 1 :30 p.m. January 27th and was completed approximately 2: 00 a.m. January 28th. During this period, 5 separate samples (4 test cylinders each) were taken. The samples were taken at the following yardage points 1) 2. 4 yards, 2) 7 . 4 yards, 3) 12. 1 yards, 4) 16 . 9 yards and 5) 19. 5 yards . Test cylinders from each sample set were broken at 7 days and 28 days with the remaining cylinders being saved for retest if required. The test reports are attached . The average break strength at 28 days was 7676 psi with the lowest break being 6830 psi . Since all test cylinder breaks exceeded the 3000 psi design strength, no additional testing is planned. The cylinders were cured at the bulkhead site until time for break tests. e) Low pressure grouting of the concrete-rock interface. The drilling and low pressure grouting of the F-L Brenneman Secondary Bulkhead took place during the period of 2/9/94 through 2/14/94. Grouting was considered complete when the bulkhead cement-rock contact would not take any grout at a pressure of 200 psi.