This document summarizes various non-destructive testing (NDT) methods used to evaluate concrete structures without damaging them. It discusses the need for NDT to assess structures for things like strength and durability. Several common NDT methods are described, including ultrasonic pulse velocity testing, rebound hammer testing, rebar detection testing, and rebar corrosion detection testing. The document provides details on how each method works and how results are used to evaluate concrete quality. In conclusion, NDT is considered an important technique for assessing existing concrete structures in a non-destructive manner.