Post-tension Cables – Locating to Support Safe Coring

Post-tension Cables – Locating to Support Safe Coring
September 3, 2015

Background

Coring of bridge deck with post-tension cables required for condition assessment.

Methodology

Ground Penetrating Radar (GPR) used to locate depth and lateral position of all post-tension cables and rebar. Initial large scale survey performed to locate all targets on deck.  The initial survey was performed with the SmartCart and 103m x 8m grid with 0.5m line spacing. Follow up surveys performed at time of coring to clear areas for cores.

Findings

Figure 1 is a plan view drawing displaying embedded rebar in a concrete slab; processed depth slice between 0.10 – 0.30m.  Bright spots at 43m and 60m correspond to the apex of post-tensioned cabling.

post-tension cables

Figure 2 is a processed radar section through a post-tensioned slab, displaying reflections from transverse and longitudinal post-tension cables and regular rebar.

post-tension cables

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