Non-destructive Testing of Concrete Cubes Under Various Curing Conditions: The Inaccuracies and Flaws

Abstract

AbstractIn this study, the author’s experience in the estimation of concrete strength by rebound hammer (RH) and ultrasonic pulse velocity (UPV) test is summarized and compared with destructive laboratory tests. In the destructive testing of concrete, only the impact resistance, ductility, yield strength can be obtained, whereas through the non-destructive techniques (NDT) testing, discontinuities such as voids, cracks, and differences in material characteristics such as high strength materials or low strength materials can be more effectively attained and material under test can still be utilized after inspection. A various selection of NDT testing is available which can be used to provide information regarding the condition of the material and several other approaches can be used to derive the strength of a material through NDT testing. To perform the test, samples of concrete blocks were prepared and kept under various curing conditions for assorted periods of time. Multiple tests were carried out under various conditions of various aged samples. Measurements and results from NDT are indicative of the properties of concrete such as porosity, complexity of the pore network, water content, and strength. Samples that returned with the highest rebound number and peak compressive strength values using the RH test came from samples that was left for the first 14 days under adequate curing conditions with additional 14 days dry conditions. Another condition that obtained peak results was the samples that buried in the earth for 14 days as a means of curing. In the UPV testing, the strength depends on the aging of the concrete rather than the total curing days. In comparison with samples contained voids tested, it is found that as the voids is larger the UPV reading was more accurate which is indicative that NDTs have flaws which need to be taken into considerationKeywordsNon-destructive testingVaried curingBuried moisture curingHammer testPulse velocity