Comparative relationships of direct, indirect, and semi-direct ultrasonic pulse velocity measurements in concrete

An experimental study is conducted to compare direct, indirect and semi-direct ultrasonic pulse velocity (UPV) measurements on a total of 30 concrete blocks 30 × 30 × 25 cm³ in size that came from different mix batches and have cube compressive strength grades varying between 18.8 and 79.9 MPa. The correlations are established between the direct UPV and indirect UPV in the concrete casting direction as well as in the horizontal direction and semi-direct UPV measurements via statistical analysis. The statistical analysis reveals that the average value of direct UPV is 9%, 4%, and 4% higher than the average of indirect UPV in the casting direction, indirect UPV in the horizontal direction, and semi-direct UPV, respectively. The average value of indirect UPV in the horizontal direction is 5% higher than that in the casting direction. The text was submitted by the authors in English.