Figure 63. --Subcontractor's grouting setup. The grout pump and two mixing tanks are mounted on an iron skid frame to facilitate moving. P113-129-234, August 10, 1959.

After samples of sand and aggregate were tested in the Denver laboratory, the sand was found to be beyond the acceptable range of specification requirement on the sodium sulphate test and the project was instructed to lower the water-cement ratio on all mixes by 0.05.

While placing concrete in the tunnel lining by use of the pumpcrete machine, an excessive slump loss occurred that caused considerable trouble. The water-cement ratio was reduced to 0.40 with an increased slump in an attempt to overcome the excessive loss and this seemed to help while still maintaining the required strength. The use of transit mixers seemed to be one of the major causes of the slump loss because of the length of time required to obtain a uniform mix throughout the batch.

The laboratory at Prineville Dam was equipped for testing earth and concrete materials. In the control of concrete, periodic tests were run on gradation, specific gravity, moisture, and absorption of sand and each size of aggregate being used. Efficiency tests were made on all mixers in use. The scales at the batching plant were checked every month. The watermeters were kept in good working order. Test cylinders were cast, and slump and air content tests taken on each shift. The test cylinders were cured in a water tank that was equipped with an electric heating unit thermostatically controlled to maintain a water temperature of 72° F. Test cylinders were broken on a 200, 000-poundcapacity compression testing machine. This machine was calibrated by laboratory personnel using the proving ring2/ furnished by the Denver laboratory. Table 2 is a summary of the concrete control tests.

During cold weather the concrete was mixed using hot water and 1 percent calcium chloride. Water was heated by a propane gas heater through which the water circulated. An attempt to heat the aggregate piles by placing corrugated-metal pipes through the pile and heating with wood fire did not prove satisfactory.

"Concrete Manual," sixth edition, Bureau of Reclamation, 1956. pp. 466-471

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E. Concrete Placement

68. Tunnel, Adit, and Access Shaft. Placement of concrete lining in the diversionoutlet tunnel was started on March 24, 1959, using a concrete pump to place the invert section. The invert was placed in alternate sections with a metal water stop in each joint. After the invert was placed to the gate chamber, the arch section was started using metal forms. The concrete was pumped into the forms and vibrated through inspection windows by internal vibrators and form vibrators.

Concrete in the tunnel lining from station 8+04 to station 11+60 was placed by two methods. The invert (fig. 65) was placed using power buggies to transport the concrete from a receiving hopper to the section that was being placed. The invert was placed in alternate 25-foot sections. The concrete had a maximum size aggregate of 3 inches. The arch and sidewalls were also placed in alternate 25-foot sections using steel forms. Concrete was pumped into the forms by a pumpcrete machine through an 8-inch-diameter line (fig. 66) which was connected to the forms by pin valves. The concrete was consolidated using both internal and form vibrators. Figure 67 shows the concrete-lined horseshoe-shaped section of the diversion tunnel.

Concrete in the gate chamber, station 7+70 to station 8+04, was placed by the pumpcrete method as was the concrete in the adit. Concrete in the access shaft was placed by using a crane and a 1-cubic-yard concrete bucket. The placing started at the bottom of the shaft and progressed in 10-foot lifts. During placing operations the crane operator and the placing foreman were in contact by telephone. This method was slow because of the small size of the shaft and the depth to which the bucket had to be lowered.

69. Spillway and Stilling Basin. The concrete in the spillway including the spillwayoutlet works stilling basin was all placed by a crane and 1-cubic-yard bottom-dump bucket (fig. 68). It was transported from the batching plant in transit-mix trucks which discharged directly into the bucket. All concrete in the floors and the bottom 8 feet of the walls had a maximum size aggregate of 3 inches and a water-cement ratio of 0.50. This mix gave an average strength of 3, 600 pounds per square inch at 28 days. The walls above the bottom lift had a maximum size aggregate of 1-1/2 inches and a water-cement ratio of 0.50, except for the top 2 feet of wall which had a water-cement ratio of 0.45.

In the stilling basin, the excavation was below the line required; it was filled with concrete giving a much thicker slab than specified.

The spillway crest structure (fig. 69) was placed in the same manner using the same equipment as for the rest of the spillway. The maximum size of aggregate was 3 inches and the water-cement ratio 0.50. The sloping walls were placed using the same mix as used for the spillway walls. These sections were very hard to place because of the steep slopes. Anchor holes were drilled into the rock on approximately 4-foot centers and steel bars were grouted in place. The concrete was placed on the slope using 4-foot sections of steel forms which were raised and anchored in position as each lift was placed.

The bridge over the spillway crest (sec. 21(c)) is a concrete slab with a designed. loading of H 15-44 (fig. 69). The concrete had a maximum size aggregate of 1-1/2 inches and a water-cement ratio of 0.45 which gave an average strength of 4, 000 pounds per square inch at 28 days. Concrete was placed using the same equipment as used for the spillway.

70. Intake Structure. The concrete in the intake structure of the outlet works (fig. 70) was placed using two methods. The foundation slab was placed by pumpcrete machine and the remainder of the structure was placed by crane and bucket.

71. Second-Stage Placements. Concrete for the inlet elbow of the outlet works was placed from the outside using transit mixers which discharged directly into buggies that in turn discharged into a hopper directly over the inlet at elevation 3112. From this hopper, elephant trunks were used to place the concrete behind the forms. This proved to be quite difficult, especially up toward the top of the second-stage concrete, as the openings were small.

Figure 65. --Concrete invert for horseshoe-shaped section of diversion-outlet tunnel downstream from station 9+00. Some of the poorer tunnel rock was found in this area. P113-129172, May 23, 1959.

Figure 66. --Lined 11-foot-diameter diversion-outlet tunnel downstream from station 3+00. Pumpcrete line is on the left side of the catwalk. P113-129-171, May 23, 1959.

Figure 67.--Horseshoe-shaped section of the diversion-outlet tunnel downstream from station 7+50, showing the temporary protective timbering in the gate chamber. Timbering was later removed and second-stage concrete was placed for conversion of the tunnel from diversion to outlet works use. P113-129-285, October 26, 1959.

Figure 68. --Spillway and outlet works stilling basin during construction. Bottom-dump bucket and crane are being used to place concrete in the left wall. P113-129-238, August 14, 1959.