INVESTIGATION OF CRACKS IN SELF COMPACTING CONCRETE BY USING ULTRASONIC PULSE VELOCITY

Abstract

This paper describes the reliability of Ultrasonic Pulse Velocity (UPV) method in detecting horizontal cracks and flaws inside self compacting concrete (SCC) and also to know more about if ultrasonic pulse velocity effective for measuring horizontal cracks in SCC. Thirty beams was prepared in order to study the results of this research, sixteen beams for crack examinations for indirect UPV method and eight beams for detecting compressive strengths of beams with horizontal construction joint by direct method of UPV and by fracture methods also. Horizontal cracks were simulated using lower acoustic impedance material (plastic sheet) inserted at a known distance while casting the specimens. Three mixes of SCC were designed in order to prepare a new calibration curves for ultrasonic pulse velocity for detecting the compressive strength of SCC with horizontal cracks. Results indicated that horizontal cracks induced to SCC may be detected by UPV if the transducers were in limited distance depending on the position and direction of readings and also the position of the cracks. In addition, compressive strength of SCC with one and two horizontal cracks was detected and a new calibration curves were prepared for detecting compressive strength of SCC with horizontal cracks. Results indicated that UPV is reliable for investigation the horizontal cracks and flaws of SCC in addition to the compressive strengths of the defected SCC which helps the investigators in repair works but with some limitations of the distances and positions of receiver and transmitter. Experimental results also indicated that taking care should be taken into consideration for construction joint erection of SCC where a reduction of compressive strength of SCC with a construction joints was reduced by (9-14%) whereas the reduction was about (10-17%) for cracked SCC.