Apparatus and method for non-destructive testing of concrete

Abstract

A device and method for determining characteristics of a concrete sample includes the use of multiple transducers. The transducers may couple to the concrete surface so that they can impart or receive mechanical waves from the sample. An area within a plane in the concrete sample is bounded by a collective extent of mechanical waves that pass through the plane and has a dimension at least as long as a distance between reinforcing bars in the concrete.

What is claimed is: 
     
         1 . A device for determining characteristics of a concrete sample, comprising:
 a frame;   a plurality of first transducers secured by the frame at predetermined positions with respect to each other and so that coupling surfaces of the first transducers are disposed linearly with respect to each other and generally coplanar with each other;   a plurality of shear wave transducers secured by the frame at predetermined distances with respect to each other and so that coupling surfaces of the shear wave transducers are generally coplanar with each other and the coupling surfaces of the first transducers;   a plurality of primary wave transducers secured by the frame at predetermined distances with respect to each other and so that coupling surfaces of the primary wave transducers are generally coplanar with each other and the coupling surfaces of the first transducers; and   a control device in communication with the first transducers and configured to
 actuate at least one of the first transducers so that the at least one first transducer imparts a mechanical wave in the concrete sample, 
 receive at least one output signal from respective at least one other of the first transducers in response to reception of the mechanical wave by the at least one other first transducer, 
 based on the received at least one output signal, determining a depth of a characteristic of the concrete sample, 
 actuate at least one of the shear wave transducers so that the at least one shear wave transducer imparts a shear wave in the concrete sample, 
 actuate at least one of the primary wave transducers so that the at least pone primary wave transducer imparts a primary wave in the concrete sample, 
 receive at least one output signal from respective at least one other of the shear wave transducers in response to reception of the shear wave by the at least one other shear wave transducer, 
 receive at least one output signal from respective at least one other of the primary wave transducers in response to reception of the primary wave by the at least one other primary wave transducer, 
 determine, in response to the at least one output signal from the respective at least one other of the shear wave transducers, a velocity of the shear wave, and 
 determine, in response to the at least one output signal from the respective at least one other of the primary wave transducers, a velocity of the primary wave, 
   wherein the first transducers are arranged in the frame so that an area
 that is within a plane parallel to the coupling surfaces and in the concrete sample and 
 that is bounded within the plane by an extent of said mechanical wave of the at least one first transducer that passes through the plane and that is receivable by respective at least one of the first transducers 
 has a dimension parallel to the coupling surfaces of at least about two feet. 
   
     
     
         2 . The device as in  claim 1 , comprising:
 an impact device for imparting a second mechanical wave to a concrete sample so that a standing wave is established in the concrete sample, and   at least one broadband transducer for detecting the standing wave and responsively generating an output signal,   wherein the control device is in communication with the at least one broadband transducer and is configured to
 receive at least one said output signal from the at least one broadband transducer, 
 based on the at least one broadband transducer output signal, determine a resonant frequency of the standing wave, and 
 based on the velocity of the primary wave and the resonant frequency, determine a depth of the concrete sample.