THE CONCRETE BRIDGE MAGAZINE

WINTER 2017

ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.

Issue link: http://www.aspiremagazinebyengineers.com/i/768999

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Timely inspection of PT installation and grouting before a contractor leaves a jobsite generally means that corrective action, when necessary, will be easier than later when the structure is in service. For example, inspecting tendons shortly after grouting will identify voids, if any, that can be filled using vacuum grouting techniques while the grouting crew is still onsite. Furthermore, when problems are discovered early and a contractor must correct errors before being paid, it serves as a powerful economic incentive to do it right in the first place. Education and Training Qualified personnel are the “grease” that makes the construction process run smoothly. Having installers who know what they are doing, designers who are familiar with PT construction and related details, and inspectors who know what to look for and why, are essential to achieving quality with a high level of reliability. PTI Quality Efforts The mission of the Post-Tensioning Institute (PTI) is to promote quality and advance the state-of-the-art of post-tensioned concrete design and construction. PTI has several activities that are intended to enhance quality of PT installation, including the following. Standards and Specifications The joint PTI/ASBI M50.3-12: Guide Specification for Grouted Post-Tensioning and the PTI M55.1-12: Specification for Grouting of Post-Tensioned Structures provide consensus-based standards that represent the latest state-of-the-art in PT bridge construction. These specifications are being continually updated by PTI’s technical committees, with membership representation from industry, academia, and owners. In addition, PTI is developing a new program to evaluate and qualify multistrand and bar PT systems. Updated editions of both specifications as well as the launch of the PT System Qualification Program are expected in early 2017. Education and Training PTI and ASBI certification programs provide education and training for field personnel. The existing PTI Bonded PT Field Installation and the ASBI Grouting Certification courses provide in-depth training on installation and grouting of PT tendons. A new companion program focused on inspection of bonded PT systems is being developed by PTI and will be available in early 2017. Once in place, it is planned that a provision be added to the M-50 specification which would require a contractor to hire a certified third party inspector to oversee PT installation and grouting QC unless waived by the owner. This self-policing requirement would greatly strengthen contractor QC and minimize problems that go undetected and uncorrected. Research In 2017, PTI will sponsor research with a two-fold objective: • First, study the suitability of using cement that meets the American Petroleum Institute’s API 10-A, Specification for Cements and Materials for Well Cementing, as PT grout. API well cements are produced to a much tighter specification standard with frequent QC testing, which may lead to reduced variability and improved reliability. • The second phase of the study will be to evaluate the effectiveness and accuracy of in-line density meters in PT grouting. Automatic in-line density meters are widely used to monitor soil slurries, and have the potential to provide continuous, realtime monitoring of water content in PT grout. Summary Experience has shown that perfection in construction quality is probably not possible, but our goal should be to come as close as possible and realize a degree of reliability consistent with the owner’s needs. With a team approach where all parties—the PT installer, the general contractor and related subcontractors, the designer and the owner—take responsibility to pursue and achieve quality, a high degree of reliability and performance is not only possible, but likely. Theodore L. Neff is the executive director of the Post-Tensioning Institute in Farmington Hills, Mich. Keys to maximizing quality of PT installation • Train personnel. • Use standard specifications and details. • Require contractor/supplier quality control. • Require acceptance testing and inspection. • Enforce contract requirements. • Identify problems and take timely corrective action. • Communicate.

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