NLA Diagnostics (NLAD) introduces the NLAD Pioneer™, a nondestructive concrete characterization system designed to estimate concrete compressive strength and wall thicknesses.
The NLAD Pioneer™ is controlled by a smart phone and utilizes sound wave propagation and impact resonance to evaluate the condition and wall thickness of a concrete structure. The apparatus is pressed against a concrete structure by a single operator using two hands and the proposed tests are performed automatically with a single press of a button.
The ultrasonic pulse velocity test method in the pitch-catch configuration is used to determine the compressive strength of the concrete specimens. The pitch-catch method allows the operator to covertly test the concrete wall from one side contrary to the through-transmission or the semi-direct methods. The pulse travels through the concrete and undergoes multiple reflections at the boundaries of the different material phases within the concrete.
A complex system of stress waves which includes both longitudinal waves (P-waves) and shear waves (S-waves), develops and propagates through the concrete. The first wave to reach the receiving transducer is the P-wave followed by the S-wave which are converted into an electrical signal. Compressive strength is calculated by using the measured P-wave and S-wave time of travel with the pitch-catch method of ultrasonic testing.
Wall thickness of a concrete structure is calculated by using the P-wave velocity obtained through the pitch-catch method of ultrasonic testing in conjunction with the resonance frequency obtained through the impact resonance test method controlled by an electromechanical impact hammer.