The Geophysics HM Ltd "DELTA" Bridge Ground Penetrating Radar imaging system is a high efficiency and low cost NDT alternative options to chain dragging and visual inspections on the bridge decks since they are reliable, precise, high speed and traffic independent. High resolution GPR scanning can be effectively deployed over the surface of the concrete bridge components to provide information on the deterioration andinternal conditions of the concrete structure and components layout not provided from visual observations. The integration of the GPR, thermal imagery and other nondestructive techniques are necessary to complete a sound and full bridge condition assessment and rehabilitation.
Ground Penetrating Radar carried over concrete structures with embedded corroded steel bars will show very distinctive diffraction responses and high signal attenuation due to cracking, delamination and change of the concrete properties due to the presence of chemical sub-products of the corrosion process. The attenuation of the GPR signal generated from the steel bar is used for estimating the degree of deterioration of the concrete structure and bridge decks.
High resolution image of the location, depth and orientation of steel reinforcement and other imbedded structural elements is accurately obtained with the use of high frequency GPR. Geophysical techniques are useful for mapping and estimating the number of reinforcement bars in the structure. Imaging the position and relationship between the internal elements of thee concrete structure are very important aspects to consider during the design of the concrete structure. The inadequate selection and wrong placement of reinforcement will significantly affect the strength, stability and durability of the concrete structure.
Bridge concrete decks get deteriorated over time due to damages caused by stress, winter deicing process, water and chemicals, fatigue and corrosion of reinforcement. The corrosion process causes internal stress, cracking, delamination and eventually spalling over the reinforcing steel (Nawy, 2008). For estimating the bridge deck deterioration we use the D6087-08 “Standard Test Method for Evaluating Asphalt-Covered Concrete Bridge Decks Using Ground Penetrating Radar”.
"DELTA" Bridge high speed GPR scanning system is used by Geophysics HM Ltd for bridge deck structure imaging, structure integrity assessment, reinforcement and posttension cables mapping, rebar cover depth and concrete deterioration analysis. The scanning system is successfully utilized for a rapid assessment of the bridge deck condition for rehabilitation and renovation without the necessity of line closures. The main advantages of the system are: