Multi-Mode Concrete Scanner

A light-weight hand-held scanner is needed that can rapidly make a non-destructive assessment of concrete slabs that are up to six feet thick. The Army's stated goals are to measure material strength over the range 3 to 30 +/-3 ksi, estimate thickness to +/- one foot, and locate metal objects inside the structure. The device should also estimate the density of steel reinforcement (rebar) as well as fiber reinforcement. The time required to make the scan should be less than 10 minutes, and results should be obtained while in the field within a few minutes of the scan. The research team designed a new Multi-Mode Scanner and they built a prototype that incorporates both radar and stress wave sensors. An existing hand-held ground penetrating radar (GPR) scanner that is currently sold for concrete inspections was used as a basis for the new scanner. The power emitted by the commercial GPR system was increased by nearly 5 times in order to increase the penetration depth. Experiments show that the back side of a 6.5 foot thick concrete structure can be readily detected with GPR. Additionally, it was demonstrated that thin metallic objects like rebar can be detected at depths of four feet.