## GUIDELINES FOR AN IN-DEPTH INSPECTION OF THE FABRICATION OF PRECAST PRESTRESSED CONCRETE STRUCTURAL MEMBERS

> **PURPOSE**
>
> The purpose of this inspection is to evaluate the adequacy of all the
> materials, fabrication practices and procedures, and State inspection
> associated with the construction of precast, prestressed concrete
> structural members, and to determine whether or not the resultant
> product is satisfactory.
>
> **INSPECTION DATA**

  ----------------------------------- -----------------------------------
  Project No.                         Contract No.

  Project Title                       

  Contract Amount                     Prime Contractor

  Date of Inspection \_\_/\_\_/\_\_   District

  Inspection Made By                  

  In Company With                     

  \% Time Elapsed\                    \% Work Complete
  (Total WD = )                       

  Name of Fabrication Plant           

  Location                            

  Narrative of Work Done:             
  ----------------------------------- -----------------------------------

> **PLANT ORGANIZATION**
>
> Individual In Charge of Plant
>
> Individual In Charge of Production
>
> Individual In Charge of Quality Control

1.  Is QC performed by other than production personnel?

2.  does QC report to? (Please attach a functional organizational chart)

> **MATERIALS**

A.  Concrete Aggregates

    1.  Stockpiles handled to prevent intermingling and segregation?

B.  Cement

    1.  Kept dry and lump free?

C.  Concrete Mix Design

  ------------------------- ------------------------- --------------------
                            **Source**                **Quantity**

  Coarse Aggregate                                     

  Fine Aggregate                                       

  Cement                                               

  Water                                                

  Admixture(s)                                         

  Design Strength:                                     
  ------------------------- ------------------------- --------------------

D.  Reinforcing Steel

    1.  Stored to ensure cleanliness?

E.  Prestressing Steel

    1.  Stored under cover to minimize corrosion?

    2.  Bands on strand packs should not be torched to avoid damaging
        strands.

    3.  Are reels identified with (STA) DOT & manuf. numbers?

> **FABRICATION**

A.  Forming

    1.  Have shop drawings been approved?

    2.  Are forms clean?

    3.  Are side forms steel as specified?

    4.  Do joints prevent significant leakage of paste?

    5.  Does inspector check alignment, end dams, bond breaker
        treatment, & actual length of forms (each beam) before pour?

B.  Steel Placement

    1.  Is steel clean and free from rust?

    2.  Is steel tied securely and in the proper locations?

    3.  Are clearances satisfactory?

    4.  Are the post-tensioning ducts, if any, secured in the correct
        positions?

    5.  Is the inspection provided timely and complete?

    6.  Does the inspector check the placement using the approved shop
        drawings & check the positions of the strands?

C.  Tensioning Prestressed Strands

    1.  What is the setup of the stressing bed?

    2.  Are the strands horizontal or draped?

    3.  Are the strands clean and free from significant rust & form oil?

    4.  Have the jack gauges been calibrated within the last 180 days or
        since repaired or adjusted?

    5.  What are the calculated losses for:

        a.  grip slippage

        b.  movement of anchoring abutment

        c.  friction of hold-downs

        d.  temperature adjustment

    6.  Does the inspector:

        a.  determine the distance from bulkhead to bulkhead?

        b.  have a work chart showing the calculated elongation, the
            pressure the gauge should indicate, the time of tensioning,
            the ambient temperature and the reel number of the strand
            used?

        c.  fill out a pretensioning report?

    7.  Is the elongation calculated from the actual modulus of
        elasticity of the strand used?

    8.  Describe the tensioning procedure. (Example: Tension to gauge
        reading, meas. elong, jack to 1.05 of gauge reading to achieve
        calc. elong.)

    9.  What tensioning method- single or multiple strand?

    10. Is the member cast within 3 days after stressing, or if not, are
        the strands retensioned to compensate for relaxation?

D.  Concrete Placement

    1.  Are concrete batching & mixing procedures & controls adequate?

    2.  Does inspector:

        a.  observe batching & mixing?

        b.  record time required for placement of each load and each
            girder?

        c.  record slump, entrained air (when required) & temp of
            concrete? (What are the requirements?)

        d.  record ambient temp and temp of forms and steel?

    3.  Are placement, consolidation and finishing of the tops of the
        girders satisfactory? (2 layers for beams not more than 3\'-4\"
        deep, 3 layers for deeper beams)

    4.  Are an adequate number of cylinders made and protected next to
        the girder?

E.  Curing

    1.  What type of cure is being used?

    2.  Is a temperature sensor being used and is a continuous log of
        the temperatures available?

    3.  What are the minimum & maximum temperatures experienced? (60 F
        min, 175 F max)

    4.  Are heating & cooling rates less than 25 degrees F/hr?

    5.  If steam cured, concrete should attain initial set before steam
        is applied (2 hrs required by the spec\'s). Is it?

    6.  Is top of girder kept continuously wet per Std Spec\'s?

    7.  Are cylinders being properly cured? (Girder cure for release
        strength & standard moist cure for 28-day strength)

F.  Detensioning

    1.  What is the required concrete strength for release of the
        prestressing force?

    2.  the forms that restrain deflection removed prior to
        detensioning?

    3.  It is recommended that detensioning be done immediately
        following the curing period. Is this being done? Is the
        temperature of the member held reasonably constant for the
        latter part of the curing period to prevent undue stresses or
        cracking?

    4.  What is the sequence of cutting strands? Does this procedure
        minimize eccentricity and shock loading? Does the inspector
        record the releasing procedure in his field book? Has it been
        approved by (STA) DOT? (If burned, the first wire in a strand
        should not be cut until at least 5 seconds after the torch has
        been applied.)

    5.  Does the inspector record the camber while the girder is still
        on the bed?

G.  Finishing

    1.  Is the surface of the concrete adequately finished?

    2.  Are extensive honeycombed areas evident?

    3.  Does the inspector measure the length of each member?

H.  Handling & Storage

    1.  Are members handled only by approved pickup points?

    2.  Are they properly stored to prevent damage & supported at
        bearing points?

> **TESTING & REPORTING**

A.  Testing

    1.  Concrete cylinders:

        a.  Is concrete sampled from 1/3 & 2/3 parts of pour and bucket?

        b.  Are they made within 15 minutes of sampling & consolidated
            properly?

        c.  If heat cured, allowed to cool 1/2 hour before capping for
            testing?

        d.  Are sulphur caps allowed to cure 1/2 hour before testing?

        e.  Are the actual dimensions of the cylinder measured (within
            1/16\" diameter, 1/4\" length)?

        f.  Is the loading rate satisfactory (20 to 50 psi/sec for
            hydraulic system, 0.05\"/min for screw system)? (For 6000
            psi conc., time from midpoint of load to failure should be
            from 60 to 150 seconds.)

        g.  Is the strength test an average of 2 breaks & does any one
            break fall below 95% of the required 28-day strength?

    2.  Is the concrete aggregate being tested at a sufficient frequency
        (at least 2 times weekly)?

    3.  Horizontal alignment:

        a.  Is it checked upon removal from casting bed & within the
            tolerance of 1/8\" per 10\' of length?

        b.  Is it checked during storage & just prior to shipping to
            conform to 1/4\" per 10\' of length?

B.  Reporting

    1.  Does the inspector\'s diary contain instructions to the
        fabricator, an account of work accomplished, description of
        inspector\'s actions & an discussion of problems encountered?

    2.  Are the appropriate forms filled out & complete?

> **COMMENTS**
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> **FINDINGS/RECOMMENDATIONS/RESOLUTIONS**
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> **CONCLUSION**
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> **Applicable Specifications**
>
> 6-02.3(25)E Prestressed Concrete Girders (Construction Requirements)\
> 9-19 Prestressed Concrete Girders (Materials)\
> 9-03.1 Aggregates for Portland Cement Concrete\
> 9-25.1 Water for Concrete\
> 9-01 Portland Cement\
> 9-23.7 Air-Entraining and Chemical Admixtures for Precast\
> Prestressed Concrete\
> 9-07 Reinforcing Steel
>
> **References**

1.  Manual For Quality Control For Plants and Production of Precast and
    Prestressed Concrete Products; Prestressed Concrete Institute; 3rd
    Edition, 1985.

2.  Tentative Standards For Prestressed Concrete Piles, Slabs, I-Beams
    and Box Beams For Bridges and an Interim Manual For Inspection of
    Such Construction; AASHTO/Prestressed Concrete Institute; 1963.

3.  Prestressed Concrete Inspectors\' Manual; Prestressed Concrete
    Manufacturers\' Association of California; 1975.

4.  Inspector Guide For Prestress Plant Inspection and Quality Control;
    (STA) DOT; 1982.

5.  Construction Manual; (STA) DOT; 1984.

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