hould Be on Owners’ Radar
and impact-echo testing – can identify these issues, even when there is no visible evidence of damage.
Ground-Penetrating Radar GPR can detect the depth and spacing of reinforcing steel,
and the thickness of concrete slabs. It’s able to detect subsur- face deterioration of a slab from changes in the radar signal through the concrete. GPR also can pick up on elevated levels of moisture or chloride in a slab, signaling early stages of dam- age or deterioration. These resultsmake GPR a useful tool in planning preventive
maintenance and avoiding severe and costly structural issues down the road. In addition to detection of deterioration, GPR is used to
locate rebar for determining as-built conditions and construction quality assurance. Handheld ground-coupled radar systems may be used to focus on subsurface conditions in one specific area or to scan hard-to-reach locations.
Impact-Echo Test In addition to GPR surveys, impact-echo testing (IET) is an
NDE technique used to determine slab thickness and to identify
areas of delamination and substandard concrete. By generating an elastic wave with an impact source and measuring its return frequency, the impact-echo test provides a resonant frequency associated with the thickness of the deck slab. If the slab is intact, the thickness data show a single clear
peak that should correspond with the expected slab thickness. If the slab is damaged by a delamination, the thickness data are unclear and do not correspond to the thickness of the slab. Impact-echo tests may be used in conjunction with GPR to
detect areas of the slab that have begun to deteriorate and meas- ure the extent of the deterioration. Nondestructive evaluation (NDE) techniques allow for rapid
and economical assessment of the condition of parking struc- tures. This information then enables owners to better allocate their maintenance funds to ensure that the areas of significant damage are repaired, and eliminates the costs and risks of per- forming unnecessary maintenance.
Ken Maser, P.E., President of Infrasense Inc. of Arlington, MA, can be reached through
www.infrasense.com.
PT
Parking Today
www.parkingtoday.com
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