Maricopa Community Colleges  CON204   20052-20086 
Official Course Description: MCCCD Approval: 07/22/08
CON204 20052-20086 LEC 1 Credit(s) 1 Period(s)
Post-Tensioning Field Problems
Delivery, acceptance, handling and storage of post- tensioning materials. Installation procedures, concrete placement, stressing tendons, trouble-shooting and "lift off" testing.
Prerequisites: (Registered apprentice status and CON105) or permission of the apprenticeship coordinator.
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MCCCD Official Course Competencies:
 
CON204   20052-20086 Post-Tensioning Field Problems
1. List and describe terms associated with post-tensioning of concrete. (I)
2. Explain the importance of document control in the construction of projects using unbonded post-tensioning tendons. (II)
3. Describe procedures for the delivery, acceptance, handling and storage of post-tensioning material. (III)
4. Describe the process of installing a post-tensioning system. (IV)
5. Describe specific requirements for placing concrete to be used with post-tensioning systems. (V)
6. Explain the steps necessary for stressing and finishing tendons. (VI)
7. Describe procedures for determining and recording the amount of elongation during post-tensioning. (VII)
8. Describe steps involved in troubleshooting on the job site. (VIII)
9. Explain how to conduct a "lift-off" test on post-tensioned concrete. (IX)
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MCCCD Official Course Outline:
 
CON204   20052-20086 Post-Tensioning Field Problems
    I. Trade terms
        A. Anchorage
        B. Coating
        C. Coupler
        D. Jack/ram
        E. Pocket former/grommet
        F. Prestressing steel
        G. Sheath
        H. Tendon
        I. Unbonded tendons
      II. Document control
          A. Shop drawings
            1. number, size and location of tendons
            2. tendon support plan
            3. bursting steel requirements
            4. changes
          B. Shipping lists
          C. Material certifications
          D. Jack calibrations
          E. Stressing records
        III. Delivery, acceptance, handling and storage
            A. Delivery and acceptance
              1. protecting material integrity
              2. discrepancy reporting
            B. Handling and storage
              1. sheathing damage
              2. dry storage
              3. identification by pour and/or floor sequence
              4. dam and gauge unit
              5. calibration records
              6. limit access
          IV. Installation
              A. General installation procedures
                1. experienced crews
                2. vertical deviation limits
                3. watertight integrity
              B. Slabs and flat plates
                1. location marking
                2. installing anchorage assembly
                3. placing reinforcing bars
                4. placing tendons
              C. Beams and slabs
                1. preassembled beam cage
                2. tendon support
              D. Inspection
            V. Concrete placement
                A. No calcium chloride
                B. Inspection completed
                C. Tendon position unchanged
                D. Anchorage zones
                E. Care during placement
                  1. truck
                  2. crane
                  3. pump
                  4. vibration
              VI. Tendon stressing and finishing
                  A. Curing - minimum compressive strength
                  B. Preparation
                    1. clean anchor cavity
                    2. check concrete integrity
                    3. check tension alignment
                    4. install wedges
                    5. mark tendon
                    6. check stressing equipment
                  C. Tensioning
                    1. inspection personnel- on site
                    2. secure jacks and pumps
                    3. position jack
                    4. operate pump to achieve specified pressure
                    5. check elongation + or - 7%
                    6. record gauge pressure and elongation
                    7. burn or cut strand ends
                  D. Slab-on-ground tendons
                  E. Safety procedures
                    1. safe working distances
                    2. detensioning
                    3. never "piggy back" jacks
                  F. Pre and post-tensioning inspection
                VII. Elongation recording
                    A. Mark reference point with spray paint
                    B. Stress
                    C. Measure - nearest 1/8th inch + or - 7%
                    D. Record
                    E. Check causes if out of tolerance
                  VIII. Troubleshooting
                      A. Wedge slippage
                      B. Ram hung up
                      C. Honeycomb
                      D. Blowouts
                      E. Tendon breakage
                      F. Short tendons
                      G. Splicing tendons
                      H. Cracked wedges
                      I. Equipment
                        1. ram fails to extend/retract
                        2. ram leaking
                        3. ram damages strand
                        4. ram will not grip
                        5. seating loss over 1/4"
                        6. ram mot obtaining stressing pressure
                        7. pump operating too slowly
                        8. gauges
                    IX. Lift-off test
                        A. Procedure
                        B. Force determination
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