Building with concrete in Las Vegas: Le Reve and Mandalay Bay—two casino resorts built with concrete from the ground up

Concrete Construction,  Jan, 2003  by Joe Nasvik

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According to Richard Shea III, the company's vice president, the CFA piles at the Le Reve project will be 1 meter in diameter with lengths ranging from 35 to 50 feet and allowable working loads up to 1500 tons per pile. The CFA pile system requires the use of special drilling rigs. The operator installs the CFA piles by drilling the bit to the proper depth in a single pass. In a process very similar to extracting a cork from a wine bottle, the auger bit is twisted in and extracted without rotation. Simultaneously, 8000-psi concrete is pumped under pressure through the hollow stem of the auger to fill the hole, which ensures that there will be no collapse of the pile walls. An on-board computer monitors the concrete injection to ensure that the proper amount is delivered into the hole. As one might imagine, special rigs are required for this work. As much as 250,000 foot-pounds of torque and 120 tons of extraction force are used to screw in and withdraw the auger.

For reinforcement, a pre-assembled steel rebar cage is lowered into the pile through the plastic concrete. The cage has special spacer wheels wired to the outside of the frame to ensure proper cover for the reinforcing bars.

"The advantage of CFA pile construction is that more `skin friction' is provided between the concrete and the side of the hole. This is possible because the sidewalls of the borehole are less disturbed because the pile is completed in a single pass. Also, concrete is placed under pressure, providing better contact with the sides of the hole," Shea adds.

For both projects, there are two or three caissons to support each column. Therefore, a reinforced concrete pile cap is cast between the building column and the caissons to equally distribute the load.

Building the structure at Le Reve

As previously mentioned, center-to-center column spacing at Le Reve is 36 feet, resulting in a heavy structure. Ceiling heights for the first four floors (the low-rise portion of the resort) will be 18 to 21 feet. Floors will be 11 to 12 inches thick with 10-inch drop panels at the columns and mild steel reinforcement. The column cross sections in this lower portion will be 42x96 inches.

The tower portion of the project has 50 floors. Although the top floor shown on the plans is the 60th floor, there are no floors starting with the number "4," a number regarded as unlucky by Asian gamblers. The tower floors will be 10 inches thick with post-tensioned reinforcement. When the concrete reaches 75% of its design strength, the post-tensioning reinforcement will be tensioned and the formwork removed. The columns for the tower are also larger than the typical column cross section: 24x36 inches for those on the perimeter and 24x96 inches for interior columns. Each deck placement on the tower floor will be 55,000 square feet, requiring 1 week to complete a forming and placing cycle, according to Travis Cubley, Marnell Corrao's project manager.

Claude Trudeau, vice president of Atlas Construction Supply, San Diego, states that his company is providing specialty forms for this project, including wall and column forms and all suspended slab shoring systems. This includes two complete floor levels of flying forms engineered to accommodate both the tower floors and the high shoring heights of 18 and 21 feet for the low-rise portion of the project. The tower has a gentle curve, so the table decks are trapezoidal in shape to allow for curving edges. And, in an effort to allow quick adjustment of column form dimensions and thereby allow Marnell Corrao to stay on schedule despite frequent column height and dimension changes, Atlas is furnishing pre-assembled column forms in four separate increments.