1994-06-23_REPORT - M1977378 - Laserfiche WebLink

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B-L Brenneman Secondary Bulkhead Construction Certification Report Page 3 It was anticipated that water addition to the mix would decrease concrete strength therefore the original design was modified to account for a possible strength loss from 3000 psi to 2500 psi and the bulkhead was constructed accordingly. This modification was submitted to and approved by the Division and Board (TR-16) . The bulkhead form was filled over a time 10 1/2 hour time period on 4/28/94 - 4/29/94 . Initial start-up was extremely difficult with many line plugs . The entire line was dumped and upon restart approximately 2.8 yards were poured in the bulkhead when another line plug occurred causing a significant delay ( ie approximately 3 1/2 hours) . The concrete in the bulkhead was monitored and did not reach initial set conditions before the line was cleaned and recharged. Initial set time should be 5-6 hours due to the delay set additive used to delay set time and increase pumpability. This critical time limit was not reached. During the pour, 3 separate samples (4 test cylinders each) were taken. The approximate cumulative yardage points where sampling occurred was 1) 2 . 4 yards, 2) 5.8 yards and 3) 8 . 7 yards (end of pour) . The cylinders were cured at the bulkhead site until time for break tests. 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 average break strength at 28 days was 6836 psi with the lowest break being 6680 psi . The test reports are attached . Since all test cylinder breaks exceeded the 2500 psi design strength , no additional testing is planned. e) Low pressure grouting of the concrete-rock interface. Drilling and grouting of the B-L Brenneman Secondary bulkhead took place on May 5, 1994. A total of 7 holes were drilled into confirmed rock. The targeted contact intersection points were at the approximate center of the bulkhead at the left rib-sill intersection, left rib-midway between sill and back, left rib-back intersection, back center , right rib-back intersection, right rib-midway between sill and back and right rib-sill intersection. Grout take of this bulkhead was minimal with the only take being the left rib-back intersection and back center holes. Initial grouting pushed grout between these holes and out the front bulkhead-rock contact. These two holes were grouted, let set while the other holes were grouted and then regrouted to within the required pressure range (160 psi ) . All holes were pressured to 160-190 psi (within the 100-200 psi specification) .