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Pazzolen: Trade name (Interground).

Air entraining agent: Tradb new

Colcium chloride: Percent by

Protex

4.2 2688 3351 3444 3678 6.0 3997 4952 3785 3873 3.1 1857 2511 2971 3484

4.1 2852 3618 4209 4.9 3272 4032

3.6 2263 3148

52

58

28

42

239 0.46 2.62 143.8 0.47 2.75 144.5 0.45 1.87

273 604 25 % 947 2014

143.1

Type

Portland

Source Louisville, Nebraska

Specific gravity

Fog Room

Pozzolan

4.5 3033 4105 45454545 5.0 3114 4474

4.0 2953 3625

Source Type II Cement, Specific Gravity with Pozzolan-2.97
Method of curing cylin

Curing temperature renge.

65-78°F

Figure 34.--Typical concrete mix data.

[graphic]

Figure 35.--Workmen using a vibrating screed in finishing a spillway floor slab. Wood floats were used for the final finishing work. P328-701-3634, May 8, 1952.

[graphic]

Figure 36. -- Placing concrete in a spillway pier with a crane and bucket. P328-701-4648, March 18, 1953.

The initial concrete placing operations were restricted to the canal outlet works, the spillway floor and walls between stations 30+80 and 35+55, the foundation for the gate structure, and the left nonoverflow abutment. Spillway floor panels 18 inches high or over were placed in two lifts to assure fresh concrete on the entire surface for finishing. About 2 hours time was needed to place and vibrate one panel, requiring 50 cubic yards of concrete, and one additional hour for finishing operations. Some difficulty was experienced in finishing floor slabs during very warm or windy days. To improve the quality of finishing, these slabs were placed only during night shifts or cool weather. A floor slab finishing operation is shown in figure 35.

Initially, for placement of concrete in spillway wall panels, hoppers and flexible chutes were used. This proved inefficient, and after several wall panels had been placed, the hoppers were discarded and concrete was discharged directly from the bucket into forms. The latter method also proved to be economical for placing concrete in the nonoverflow abutment and piers of the spillway (fig. 36). Because the wall panels were placed monolithically and in a short period of time, the top 6 or 8 feet were revibrated after 1 or 2 hours to settle the concrete as much as possible prior to setting. Concrete in the higher walls of the stilling basin was placed in lifts of 19 feet or less. In general, the height of lifts in the gate structures and nonoverflow abutments was governed by the most convenient elevation for installing metalwork and reinforcement steel or by location of reinforcement steel splices.

Because of anticipated high shrinkage, concrete in the 50-foot-long bridge spans was placed with special care. The concrete had a water-cement ratio of 0.47 and a maximum slump of 2 inches, and was placed in lifts about 12 inches thick. Before a final set had taken place on the bridge span, a warehouse broom was drawn laterally across the surface to produce numerous small parallel grooves.

(a) Cold Weather Operations.

In order to maintain specified minimum temperatures

of concrete placed during freezing weather, several methods were used in addition to heating of ingredients (sec. 53). On small jobs, the concrete was enclosed in prefabricated canvas shelters and heat supplied by airplane heaters. For casting walls about 17 inches thick at the base and 12 inches thick on the top, insulated wall forms and concrete with admixture of 1 percent of calcium chloride were used. The top of the wall was protected with a layer of sand or rock-wool blankets. Insulated forms were also used for bridge piers. Measurement of the concrete temperature after placement indicated a rise of about 30° F during the first 48 hours and a gradual decrease of from 30° to 40° F during the next 5 days.

Floor slabs were placed only in the afternoon when frost had left the gravel beneath the slab. Prior to placing of the slabs, construction joints at the base of wall panels were washed with hot water. After placement and finishing operations were completed, the slab was coated with a membrane curing compound and enclosed in a canvas shelter which was heated with airplane heaters. Heat was applied overnight or until the curing compound had set, when the heating facilities were removed and the slab covered with 6 inches of sand.

56. Curing.

Several methods were used for curing concrete. Construction joints were water-cured with burlap or sand and frequent sprinklings of water. Finished and formed concrete was usually cured by application of a membrane curing compound. The interiors of control houses, gate chambers, stair wells, and spillway gallery were water-cured or cured by leaving the specially coated forms in position.

Dampproofing, consisting of two coats of an asphalt emulsion, was used for curing the outside of the horseshoe conduit, the outside surface of the terminal well, and a portion of the nonoverflow abutment. To keep concrete and embankment work progressing, the contractor was permitted at times to apply only one coat of the dampproofing as a sealing compound until about a day before backfilling operations, when the second coat was applied. Because of temperature and shade requirements for the dampproofing, large volumes of concrete placed at one time presented a critical curing problem with this method of curing.

57. Contraction Joint Grouting.

Two keyed contraction joints, each provided with grout outlets and header and return pipes, were constructed in the spillway crest

structure. Eleven months after completion of concreting work, the joints were washed out, tested with water, and the leaks calked with lead wool. About 42 sacks of cement were forced into the joints, which opened a maximum of 0.002 inch during grouting operations. Low grouting pressures were used because of the low sliding resistance of the shale foundation.

[blocks in formation]

58. High-Pressure Gates. Six high-pressure gates were installed at Trenton Dam. Four gates, 6 feet wide by 7 feet 6 inches high, were installed in the river outlet structure and two gates, 4 by 4 feet, were installed in the canal outlet conduit. All the gates were received from the contractor in good condition in advance of requirements. After installation, the gates and operating systems were pressure tested and trial operating runs were made.

59. Radial Gates. Three radial gates, 30 feet high and 42 feet wide, were installed in the Trenton Dam spillway. The gates were fabricated by Johnson Machine Works, Inc., Chariton, Iowa, under specifications No. 3321. The last gate was delivered to the site in July 1953, and erection of the gates was begun immediately and completed during October of the same year. During installation, the gate parts were handled by two cranes, one of 10-ton capacity and the other of 60-ton capacity. After the bridge over the spillway was completed, the lighter gate members were handled and placed from the bridge deck by the 10-ton crane. As limited by the bridge capacity, heavy gate members were placed by the 60-ton crane from the spillway floor. After installation of the gates, including the gate hoists, counterweights, floats, and control mechanisms had been completed, water was pumped into the gate float wells and the gate operation was tested.

(a) Painting.-- Prior to painting, the radial gates were sandblasted then covered with a rust-inhibitive wash solution and a wetting agent. A coat of zinc-chromate priming paint was next applied. A second coat of priming paint was applied to the upstream side of the gate and, while the paint was still wet, a coat of sand was applied by using low air pressure. After the sand coating was dry, two coats of aluminum-finish paint were applied. The remainder of the gate, including the interior surfaces, was also covered with two coats of aluminum-finish paint, but without a second priming or sand coat.

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