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American Tunnel Bulkhead No.3 <br />Construction Certification Report <br />Page 4 <br />Pumpine of concrete, lillina of forms and concrete compressive strength <br />The same concrete mix that proved successful for the American Tunnel Bulkhead No.l <br />was used for this bulkhead. <br />The concrete mix was as follows: <br />#/cu, vd. <br />Portland Type II 720 <br />Coarse Aggregate 1673 <br />Fine Aggregate 1004 <br />F-y Ash, Class F 115 <br />Water 324 <br />Delay Set <br />The concrete was batched from the Sandco batch plant in Durango and the Type V <br />cement was added at their portable plant located in Silverton. Delay set was added at the <br />site. The concrete pump was set up downstream ofthe bulkhead form and concrete was <br />pumped approximately 30' to fill the bulkhead form. The concrete was hauled to the <br />bulkhead from surface in 6 cubic yard Moran cars where it was remixed before discharge <br />into the concrete pump and pumped into the form. <br />The bulkhead was poured on November 12, 2002 with the first truck arriving around 9:00 <br />a. m. The bulkhead form was determined to be full at approximately 6:00 p.m. on <br />November 12th. <br />A set of concrete test cylinders was taken for every truck placed in the bulkhead form. <br />The test cylinders were cured on-site. Break tests were performed at 7 days and 28 days <br />to verify that the 3000 psi design strength was met or exceeded. The average 7 day <br />strength obtained from the break tests was 3596 psi and the average 28 day strength <br />obtained from the break tests was 6436 psi, well in excess of the required 3000 psi. All <br />28 day samples exceeded the 3000 psi compressive strength required by design, therefore <br />no additional testing was planned or done. The test reports are attached. <br />• <br />