2015-03-31 I&S Committee - Item 5 - Attachment 1 - Munna Pt Bridge Repairs Level 3 Bridge Report

    •   Core drilling into mid-sides of pilecap beams revealed that side reinforcement
        (ligatures/stirrups, side bars and main steel at corners) has significantly corroded,
        to the point of being ineffective. Side reinforcement was measured at 89-93mm.
    •   Core drilling into side near bottom of pilecap beam (Pier 4) revealed that the main
        bar in the bottom corner has corroded moderately but would still be 60-80%
        effective. Side reinforcement cover to main bar was measured at 105mm.
    •   Pilecap beams for Piers 3, 4 and 5 had wide longitudinal cracks in the sides,
        which appear to have worsened since the 2009 Opus report.
    •   Pilecap beams for Piers 1, 2 and 6 were in better condition with smaller cracks,
        but these appeared to have worsened since Opus’ 2009 report.

o   Piles
    • Pile 3 (Pier 1) and Pile 8 (Pier 1) had no signs of corrosion in the prestressed
        strands, spiral wire and head bar reinforcement, where a small area of concrete
        was removed in each pile.
        Notes: This was despite being directly where cracks were in the concrete from the
        surface to the reinforcement level. The holes were filled with underwater repair
        plastic-filler.
    • ASR cracking of the piles appeared to have slowed since TMR and Opus
        reported the problem. A inspection using pole mounted underwater camera of
        Piles 3 & 8 (Pier 1); Piles 2, 3, 8 & 9 (Pier 4); and Piles 2, 8 & 9 (Pier 5); did not
        reveal any cracks exceeding 1-3mm on the sides that could be viewed.
    • Piles 2 & 3 (Pier 4) had a steel band around them near the top, indicating earlier
        repairs.

2.1 Laboratory Test results

NSC commissioned ALS Industrial to take material tests on the same days as Tod
Consulting’s site inspections. Their report can be seen in Appendix E. A summary of ALS
Industrial’s results follows:

o   Columns
    • Carbonation was at safe levels (0 to 6mm penetration, so nowhere near
       reinforcement).
    • Chlorides were well below corrosion threshold in one tested column (Pier 2),
    • Chloride levels were higher but inconclusive in the other tested column (Pier 4).
       The test (50mm depth) did not extend to the likely reinforcement depth (assumed
       to be 75-80mm). By extrapolation of the results, it appears that the chloride levels
       would be at, or just below, the corrosion threshold at the likely reinforcement
       depth. Note that the original drawings do not include the notes about
       reinforcement depth (cover), and no jackhammering of the columns was carried
       out to confirm the reo depth (cover) on site.
       Tod Consulting recommends that the reo depth be confirmed on site (for the Pier
       4 column), and the chloride level be retested from surface to measured reo depth.
       This will help to confirm if cathodic protection of the columns is required or not.



                                        Page 16 of 31