Effects of Loading on Concrete Quality Through Ultrasound Testing

Considering the importance of non-destructive testing in inspecting existing structures, this study aims to analyze the effects of external loading on the quality of concrete using the ultrasonic pulse velocity (UPV) test. To this end, a multidirectional UPV measurement is proposed on concrete samples under compressive stresses, considering their porosity and anisotropy. Twenty cylindrical specimens measuring 10 × 20 cm (diameter × height) were made from low-strength concrete (< 20 MPa). Compressive strength (fc), tensile strength (fct), porosity (P), and UPV were then measured in the direction of the height of the specimen and also radially, under increasing compressive stresses in this case. Scanning electron microscopy (SEM) was also carried out. The results (UPV = 3716.20 m/s) made it possible to classify the quality of the low-strength concrete (fc = 17.48 MPa, fct = 1.65 MPa) as "good", which is attributed, among other things, to its high porosity (P = 6.73%) and quantity of macropores, confirmed via SEM. However, under increasing compressive loads, the curve fitting the data (R2 = 79.42%) revealed a reduction in the UPV in the radial direction, significantly reducing the quality of the concrete.