- Published: Sunday, 01 June 2008 08:00
- Written by CP Staff
One of the nation's largest contractors working in what arguably has ranked among the world's fastest-paced high-rise construction markets Û Las Vegas Û cannot gamble on concrete pumping services. Not long ago, Sylmar, Calif.-based Tutor-Saliba Corp., undertaking both traditional and design/build construction projects, added high-rise concrete pumping to its capabilities. Accordingly, it enlisted Construction Forms, Inc., in 2006 to provide engineering assistance for concrete pumping services on the $2 billion Wynn Las Vegas Encore Resort and Casino.
Part of the Wynn resort complex, the Wynn Las Vegas Encore Resort and Casino sits on more than 15 acres and rises 700 feet. Tutor-Saliba recently topped off the 52-story Encore Tower, after successfully placing 120,000 yd. of concrete.
Mike Cetnar, concrete pumping foreman for Tutor-Saliba, notes that the project's year-long timetable was in keeping with the local pace of high-rise construction: the goal was to complete at least one floor per week, each requiring 1,600 to 2,000 yd. of concrete. Because even minor delays in pumping would jeopardize the building's timely completion, Tutor-Saliba selected Con Forms to provide concrete pumping equipment.
Two significant mix placing challenges were identified early in the construction process. The greatest of these was the Encore building's curved design, offering no straight pathways for pipe and concrete pumping equipment. Consequently, the building was divided for pumping into three horizontal sections per floor; and, concrete was placed in a three-part rotation, requiring multiple pipe lines to access each section of every floor. A flier system spanning the outer columns enabled movement among the floor sections to place the 10-in. deck mat, as well as walls and interior columns.
Con Forms engineers specified ∫-in., heat-treated pipe for its abrasion resistance and durability. They also designed vertical lines, braced and clamped, leading up to each floor, plus horizontal lines snaking their way to each floor's sections. The lines featured bends and turns as needed to course through corridors and hallways on each level.
Access for concrete pumping lines posed another challenge during construction. The building area was surrounded by demolition debris and various fixtures that, combined with necessary avenues cleared for material staging, left no room for lines from the pump to the building. The boom pump located on the site's far west side was unable to reach the point of placement.
A Putzmeister T14000 boom pump and Schwing 32-meter placing booms were selected for the Wynn Encore project on the basis of the contractor's previous experience with the equipment. To achieve their ends with the available resources, Con Forms engineers established a 1,000-ft.-long, underground base line from boom pump to building, utilizing three high-pressure diversion valves that directed concrete to the desired section or stopped the flow for pipe maintenance. Each section's line could be closed off and maintained, while concrete was directed to another section.
The diversion valves were designed specifically to withstand the vertical pressure of high-rise pumping, Con Forms representatives assert. Because they allowed pipe replacement in sections, the valves saved considerable time, effort and expense by preventing systemwide shutdowns.
In addition, the quarter-wall pipe proved effective, as the underground base line showed wear life remaining at the time of replacement, after 50,000 yards of concrete had been pumped through it. Con Forms officials emphasize that the replacement was part of a scheduled maintenance plan, not the result of pipe failure. Moreover, three vertical pipe lines on the tower Û each conveying 30,000 yards of concrete Û never needed replacing.
Also designed specifically for the project were PBX elbows. At half-inch thickness (rather than the standard quarter-inch) to extend service life, the customized elbows never failed.
Tutor-Saliba's Cetnar affirms that the equipment supplier's willingness to adapt products to accommodate special requirements was a boon on the project. Further, as construction progressed, the company kept him fully supplied with necessary pumping-system components, including Con Forms 4-in. and 5-in. wire-reinforced placing hose. That collaboration will continue with Tutor-Saliba's next Las Vegas high-rise project, at the Planet Hollywood Casino and Hotel down the Strip.