1. A contractor fabricated 0.5 m thick concrete slab foundation to support a load testing machine. The owner had some concerns about the fabrication quality, primarily the concrete strength. What NDE method(s) do you recommend for this investigation?
2. A 0.25 m thick concrete panel is fabricated and tested using the impact echo test method. The measured peak frequency for the slab is 8.42 kHz. a) Calculate the P-wave velocity Vp for the solid slab. b) The impact echo test results in a defected location gives a peak frequency of 16.32 kHz. Calculate the depth of defect.
3. Contractor proposed to use an ultrasonic pulse velocity (UPV) equipment to measure the quality of a floor casted over soil. The contractor has access only to the top surface. What is the suitable method to measure the slab thickness?
4. An intern performed the resistivity test according to AASHTO T358 on two sets of 4 × 8 in. cylinder specimens at 28-day of concrete age. One set of specimens (ASTM) were wet cured through the testing ages. Other set of specimens (Field) were wet cured for seven day following specimen fabrication, then dry cured. The average resistivity results of two sets of specimens are 89.8 and 14.9 kO – cm. However, the intern forgot to document the curing conditions. What is the result of average resistivity for the ASTM and Field specimens? Justify your answer. What is the likely corrosion rate for both sets of specimens according to the recommendation of CEB-192?