The ultra-sonic test allows us to find out defects that cannot be discovered under other testing methods. This method works best with deep elements and wide-diameter piles. For this test, at least two water-filled 2-inch-diameter iron or plastic tubes must be fixed into the pile during pouring. A greater number of tubes will yield better coverage of the tested pile’s cross-section (depending on the diameter of the pile itself).
During the test, a transmitter and a receiver are lowered to the base of the tubes installed inside the pile. While the two are pulled simultaneously back up, the transmitter emits ultra-sonic pulses, and those are picked up by the receiver. A cables-operated pulley gauges the pile’s depth, and the transmitter and receiver data are transmitted, via the cables, to a computer. The data is converted into a graph representing the pulses’ arrival time and their energy through the concrete in relation to test depth. In case a defect is discovered during the test, the equipment also allows for a tomographic survey, mapping the defect area and gauging its exact location and size. The tomographic survey also allows a gauging of the concrete’s strength at any given cross-section. The greater the number of installed tubes is, the more detailed the information received through the test.
The tomographic test is carried out on large-diameter piles, used mainly in larger construction such as bridges and tall buildings. Its main aim is to show a defect’s precise size and location, thus minimizing as much as possible any repair costs.
The test may be administered after the concrete has somewhat hardened, usually about five days after pouring. Reported depth is the depth gauged to the bottom of the shortest test tube, not the depth of the actual pile.
Q-Basing carries out the ultra-sonic test using Piletest.com’s CHUM (Cross Hole Ultrasonic Monitor) technology.