The Application Research of Microwave Imaging in Nondestructive Testing of Concrete Wall

The examination of concrete walls is an important schedule in civil engineering. For these opaque and uncontinuous object, microwave technique is an effective method to realize nondestructive testing (NDT). A series of data coming from different frequencies and positions can be used to reconstruct an image of the section of the concrete wall. The equipment for microwave NDT is a small-size radar, which is consisted of an oscillation source, four PPLs, a four-way power distributor, power amplifiers, a coupler, a power detector, an common antenna, a signal collecting system and some control circuits. The design scheme and the working principle were stated. The algorithm for image reconstruction was introduced. Several concrete models with steel bars in them were under testing. The results of two models were given with one and two steel bars respectively. The reconstructed images showed the existence of the steel bars with depths and positions clearly. Further more research and plenty information are needed to determine the sizes of the steel bars