Non-Linear Non-Destructive Evaluation of Concrete

This paper explains non-linear non-destructive evaluation of concrete aimed at examining the occurrence of non-linearity under non-linear wave propagation through the concrete. Standard cubic concrete sections in damaged and undamaged conditions were investigated. The specimen was first damaged under compression testing and then subjected to non-linear ultrasonic evaluation in two directions i.e., perpendicular and parallel to the direction of compression loading. For observing non-linearity the ultrasonic pulse was transmitted at high power level through 100 kHz broadband frequency transducer. The obtained test results for the concrete cube both in damaged and undamaged conditions were plotted and compared. The ratios of harmonic generations in decibels were calculated and plotted as normalized frequency spectrums. It was shown that the wave propagation in damaged specimen in a direction perpendicular to compression loading is more sensitive to cracking in concrete than in a direction parallel to compression loading.