By Oguzhan Bayrak, Ph.D., Dennis Fillip, and Gregory Hunsicker, P.E.

As part of a series of articles on the Concrete Bridge Engineering Institute (CBEI), an article in the Winter 2022 issue of ASPIRE® explored the institute’s Concrete Materials for Bridges program. The article also presented collaboration efforts with the National Concrete Bridge Council (NCBC) and the support provided by its members. This article presents details of the Post-tensioning Laboratory (PT Laboratory) program.   

PT Laboratory

Previous articles in this series discussed the three “pillars of learning”—concrete materials, bridge deck construction inspection, and post-tensioning laboratory —of CBEI’s initial training and certification programs. More information on the content of this PT Laboratory program and its importance to the industry are provided in this article.  As with the other programs, in addition to the training and certification programs, the PT Laboratory will also offer technical services through formats ranging from workshops to one-on-one support for post-tensioning related topics under the Concrete Solutions umbrella.  The PT Laboratory, as with the other programs, is seen as a hub for information sharing and standardization of procedures and relevant training programs as well as facilitating implementation of new technologies. 

Workforce Development

Many fields in the construction industry have expressed the need for more robust workforce development programs.  Attracting people and providing new resources for training personnel is an ongoing industry-wide discussion, for every facet of the industry. Additionally, it is recognized that post-tensioning installation also requires a specialized technical skill set and workmanship which warrants the need for intensive training.  Training to the current standards and requirements in the industry is critical in ensuring the intended durability of post-tensioned structures is achieved.  In the USA, the need for qualified personnel and effective training programs has been recognized for decades.  Programs such as those offered by the Post-tensioning Institute (PTI) and the American Segmental Bridge Institute (ASBI) required by Owners around the country, have been instrumental in increasing the available training offered in the industry. These robust programs have continually evolved with the changes in industry requirements over the last 20 years and trained over two thousand attendees.  These programs have had a very positive impact.  Collectively stakeholders have expressed that an increase in hands-on training and “next level” training for personnel would be an excellent complement to the existing programs and further increase the effectiveness of the training. The continual goal is improved performance of post-tensioned structures. This goal can only be achieved if all individuals involved in planning, designing and constructing post-tensioned structures can uniformly be educated and/or trained to a high level of rigor, consistent with the expressed needs of the industry.

Personnel

The targeted audience for the training and certification programs is the installation and inspection personnel directly involved in the construction on project sites.  It is anticipated there will also be interest in attending the programs from project managers, engineers, materials specifiers, and various other roles involved with bridge projects. The PT courses at CBEI are intermediate and advanced level courses with most courses requiring a pre-requisite of having successfully completed the PTI Multistrand and Grouted PT Specialist Level 1 Certification and the ASBI Grouting Certification.  Through these certifications and any other specific requirement by course, the intent is attendees already have a working understanding of post-tensioning concepts and can maximize the time in the PT Laboratory with hands-on exercises and demos, with only short time in the classroom. Throughout the program, the goal is to establish the importance of following the best practices through demonstrations and hands-on exercises.  This includes exercises of both the correct way and examples of lessons learned when things are done incorrectly, and the potential impact on the structure.  The experience of “doing” and “seeing” is typically an impactful one.  The experience of “doing” is also anticipated to accelerate the experience level of those involved in the program.  By demonstrating a “problem”, such as a grout void, the attendee is exposed to a wide variety of situations that they may not otherwise encounter directly in the field for a substantial time.  This program is designed to present as many of these problems as possible, primarily how to avoid them, and provide troubleshooting information on how to approach them if encountered.   

Many of the programs through the PT Laboratory are planned to offer a certification.  The certification requirement of these programs requires both hands-on practical exams and written exams.  Demonstrating the ability to properly perform a given task or test is often a good indicator of competence.  The requirements for certification, by this program or equivalent programs, can be established in the specifications and/or contracts to ensure field personnel are equipped with an understanding of the latest industry requirements.  Most programs are valid for four years with renewal either through an in-person or online short program depending on the content. The renewals will primarily highlight and bring awareness of any changes since the previous certification.  Most of the certifications for the courses held at CBEI are anticipated to be part of the PTI and ASBI Certifications in addition to the programs they currently deliver and administer.  The courses are designed to be individual modules that can be offered individually or grouped together in different customized blocks as needed.         

Curriculum Development 

The overall curriculum includes both existing traditionally offered topics as well as new ones.  One of the themes emphasized throughout the modules is their respective importance on the overall durability of the structure and the connection with other operations.  For example, the initial installation of all of the materials, including the duct, anchorage, and grout vent installation has a large impact on the success of the subsequent strand installation, stressing, and grouting operations, and this will be emphasized.  Another module will specifically be dedicated to finishing, including the proper surface preparation and filling of blockouts, finishing of grout ports at the deck, proper installation of elastomeric coatings, and similar details which often represent a critical first line of protection for the post-tensioning.  The trainings will also cover traditional topics covered by the existing PTI and ASBI certification courses such as stressing and grouting, however the goal will be to complement the existing courses and avoid redundancy.  There will be a focus on the “why”s and “how”s through the use of hands-on exercises and demonstrations.  One example of this is demonstrating a failing pre-grout air-test and what steps are taken to remediate the issue prior to grouting on an actual element. Specific modules will also be introduced for topics and new procedures and materials as needed.  An example of some initial modules that are anticipated are a one-day program for each PL3 Monitorable Tendons (i.e. Electrically Isolated Tendons or EIT) and Replaceable Tendons.  These courses will help provide guidance in a visual and hands-on approach of the details and equipment required for each.  The courses are designed to match the number of students with the infrastructure and number of instructors to ensure appropriate access to the content.   

The courses are planned to follow the guidance in the PTI/ASBI M50.3-19 Specification for Multistrand and Grouted Post-tensioning and PTI M55.1-19 Specification for Grouting of Post-Tensioned Structures, as well as the program manuals for the CRT-70 Post-tensioning System Certification program. The courses will also make use of references from Owners and other industry groups, such as Replaceable Grouted External Post-Tensioned Tendons Publication No. FHWA-HIF-19-067 October 2019. https://www.fhwa.dot.gov/bridge/concrete/hif19067.pdf Throughout the courses, the different Protection Levels (PL) will be referenced recognizing that different environments and structure types warrant use of different types of post-tensioning. Protection Levels (PL) are a key concept presented in the PTI/ASBI M50.3-19 Specification for Multistrand and Grouted Post-tensioning. 

A sampling of the initial modules planned is listed below, and includes both certification modules and learning modules.  Additional modules will be added based on input from stakeholders.       

• Installation   
• Stressing
• Grouting
• Finishing 
• PT System Inspector 
• Grout Testing 
• PL3 Monitorable Tendons (EIT)
• Replaceable Tendons
• PT Repairs 
• PT Spliced Girder Details
• Segmental Details     

Two new modules to be introduced include the PT System Inspector module and Grout Testing module.  The PT System Inspector module will provide a training and certification focused on understanding the requirements for certification and approval of a post-tensioning system (PTS) per the PTI/ASBI M50.3-19 Specification.  It will review the topics and issues encountered in the field including defects, substitutions, material certifications, storage, and initial project qualification for a PTS. Upon completion, the attendee will be able to demonstrate through hands-on trials identification of conforming and non-conforming PTS components such as defects or substitutions.  The module will also cover such topics as material certification QC tests and traceability requirements, acceptance criteria for various components due to corrosion or UV exposure, typical variances by type of structure and region, the various Protection Levels (PL’s), and a sample quarantine and disposition procedure for non-conforming parts.  The Grout Testing Certification module will look to build upon the information provided in the current ASBI Grouting training and require the attendee to demonstrate, themselves in the presence of a proctor with the testing equipment and grout, their competence in performing grout field quality control tests such as: Wet density (ANSI/API Mud Balance Procedure), Modified Flow Cone (Modified ASTM C939 per PTI M55.1-19 § 4.4.7), Schupack Pressure Bleed Test (ASTM C1741), Wick Bleed Test (Modified ASTM C940, per PTI M55.1-19 § C4.4.8.1), Sampling for a Compressive Strength test, Temperatures of mixed grout, ambient, water, and bag material, Spot checking bag weights and Verifying expiration date, and Chloride Test (Sampling only) (ASTM C1152).  The module will cover proper recording of the quality control information on a standard grout log.  The module will also cover, primarily through demonstrations, potential causes of test values outside of the acceptable range and typical remediation measures.  Both courses will provide the attendee with a certification upon successful completion.  

Stations / Infrastructure

The PT Laboratory will be outfitted with infrastructure to allow for efficient demonstrations and hands-on activities.  Several stations will be arranged at the CBEI facility focused on the various modules.  The stations include an over one-hundred-foot-long reaction beam for stressing and grouting operations and a parallel “pre-concrete” beam with a reinforcing cage for duct, anchorage, and grout vent placement operations (Figure 1).  The reaction beam is planned to allow configuration for different profiles and details, including replaceable tendons. The pre-concrete beam (Figure 2) will allow for such activities as measuring support heights, viewing and remediating damaged ducts, maintain proper angles and avoiding kinks at anchorage to duct transitions, proper placement of grout vents, illustrating congestion at anchorage zones, and many other activities.  Stations specifically focused on grouting will include a grout testing, grout inspection and remediation, and vacuum grouting station. There is also a station dedicated to finishing including pourbacks, grout vent finishing, elastomeric coatings and will focus on material installation including proper surface preparation. Another station will be dedicated to inspection and non-destructive evaluation techniques.  One station will be dedicated to post-tensioning systems (Figure 3).  This station will include different types and sizes of post-tensioning systems including both strand (Figure 4) and PT bar systems.  It will also include non-conforming and substituted parts that are used as part of the exercises during the PT System inspector module (Figure 5). 

While the infrastructure represents a significant tool, there has also been an ongoing effort to make as many of the modules as possible in a mobile format and it is planned to utilize a train-the-trainer program to disseminate the information as widely as possible.  There have also been considerations for other regional centers to incorporate some of the larger infrastructure in an effort to expand the footprint of the training. In effect, the training programs are intended to address the needs of the industry by educating and training all individuals vertically (from installers to engineers and designers) and horizontally (by establishing satellite training centers and opportunities all across the Nation, in addition to the core training facility that will be built in Austin, TX).

Closing

Efforts under a current contract with FHWA are ongoing in the planning for a PT Laboratory.    This is the fourth article in a planned series of articles about CBEI and its impact on the construction industry.  The article in the previous issue presented the CBEI Concrete Materials for Bridges program and collaboration with NCBC.  Articles in the next issues of ASPIRE will explore other technical programs, including the Bridge Deck Construction Inspection program, in greater detail and an update on the status.  Please visit CBEI’s website at www.cbei.engr.utexas.edu for more information.