This study explores the feasibility of using transmission tomographic images based on attenuation measures in transmission to detect and estimate the most common materials that are embedded in concrete, reinforcements and natural and artificial voids. A limited set of concrete specimens have been made in which cylindrical objects such as bars/tubes of steel, PVC and aluminium have been embedded to analyse the effect of size and material. The methodology and scope of this study is presented and numerical simulations are carried out to optimize the emitter-receiver configuration and to understand the complex physical propagation phenomena of ultrasonic signals that travel through concrete with embedded inclusions. Experimental tomographic images are obtained by using an ultrasonic tomographic system, which has the advantage of needing only two ultrasonic transducers. Both the software simulation tool and the tomographic inspection system are developed by the authors. The obtained results show that PVC tubes and steel bars of diameters higher than 19 mm and embedded in cylindrical specimens, can be detected and their sizes estimated using segmented tomographic images.