Page 42

2017WinterShotcreteEMag

reinforcing bar. Pumping into a blind form could result in voids, poor consolidation, or reduced bonding to the original concrete, thus requiring removal and replacement of the patched areas after form removal. This substantial shotcrete project was the result of the general contractor recognizing the benefits of shotcrete placement as a substitute for the originally specified formand pour method of concrete repair. Proven past experience by ACR with its credentials and qualifications on other highprofile shotcrete projects demonstrated the benefits to using shotcrete on a project, allowing the airport work to be accomplished more efficiently, more safely, with higher quality and significant time savings. Ultimately, the Owner was thrilled about the limited amount of disruption the construction project caused its customers and operations, allowing them to keep the airport fully functional throughout construction. Cathy Burkert received her bachelor’s degree in business management and thereafter started working at American Concrete Restorations, a Chicago-based shotcrete contractor. She joined the laborers’ apprenticeship program to learn the intricate details of the trade. After 2 years in the program, she began running her own shotcrete crews and shortly after earned the title of Field Office Coordinator. In March 2009, Burkert became the first female ACI Certified Nozzleman for the wet-mix, vertical, and overhead processes. She has been involved with two award-winning ASA infrastructure projects: the Abraham Lincoln Memorial Bridge in 2008 and the Dan Ryan Expressway in 2009. Burkert currently serves as Treasurer for ASA. 2016 OUTSTANDING REPAIR & REHABILITATION PROJECT Project Name Structural Bridge Repair at O’Hare International and Midway Airports Project Location Chicago, IL Shotcrete Contractor American Concrete Restorations, Inc.* General Contractor McDonagh Construction Architect/Engineer CARE Plus, LLC Material Suppliers/Manufacturers Spec Mix Inc.* and Putzmeister Shotcrete Technology* Project Owner City of Chicago – Department of Aviation *Corporate Member of the American Shotcrete Association concrete removal, but we also found cleaning of the debris created during the shotcrete operation—for example, from breaking the prepackaged shotcrete bags—was an issue. While the construction workers were protected with proper personal protective equipment including respirators, the pedestrians were not. Therefore, the contractor used water to control the airborne dust and large fans to move the air. In addition, the contractor was challenged with keeping overspray and rebound from attaching to the nearby “obstructions.” While plastic, tarps, and netting were used to try to contain the majority of overspray and rebound, many of our workers’ only task was to continually clean the work area of all debris, overspray, and rebound. Additionally, each night, the entire work area needed to be power-washed to ensure the area was clean and safe when opened back to the public. SIGNIFICANCE TO THE PROJECT As in all projects, time is of the essence. The use of shotcrete and its versatility had many advantages compared with form and pour. The use of prebagged shotcrete material that was mixed on-site for wet-mix placement provided a high-quality, consistent mixture that was fresh and never a problem with being “too old.” Ready mix that would have been used in a form-and-pour approach would have a much shorter open time to work with after factoring in the drive time from the plant. There would have also been risk of a form blowout and the potentially catastrophic impact on the motor and pedestrian traffic below. In comparison, our shotcrete used accelerator in the wet-mix process to ensure that each patch reached a sustainable final set before opening the site back to the public. With only 100 ft (30 m) of area available at any one time, the small area needed for the shotcrete equipment was significantly less than bringing in large ready mixed concrete delivery trucks. Also, if a problem occurred with concrete placement in the middle of a form-and-pour patch, it would require removal of the form. The shotcrete placement by ACI Certified Nozzlemen, provided by a qualified contractor and inspectors, enables constant visual confirmation of full encapsulation of the SUPERIOR GUNITE STRUCTURAL SHOTCRETE & ENGINEERING Steven J. Crawford, AIC, CPC President 12306 Van Nuys Blvd. Lakeview Terrace, CA 91342 www.shotcrete.com steven.crawford@shotcrete.com Main (818) 896-9199 Direct (818) 485- 8812 Cell (503) 709-3204 CA Lic # 370034 40 Shotcrete | Winter 2017 www.shotcrete.org


2017WinterShotcreteEMag
To see the actual publication please follow the link above