Durability of reinforced concrete (RC) structure is strictly connected to the capacity of concrete mass to protect the embedded reinforcement from corrosion. As cracks are almost inevitable, crack width is a fundamental parameter that needs to be controlled during the serviceability stage of RC members. In fact, not only the direct ingress of aggressive agents, such as oxygen and water, is a function of crack width, but also concrete carbonation and the chloride ion penetration are accelerated by the presence of wide cracks. Accordingly, the aim of present research project is to assess the width by using a new system, based on the optical conoscopic holography. It provides the non- contact measure of crack profile, taken at the end of each loading cycle, in ties subjected to sets of repeated loads. Both in plain and fiber-reinforced concrete (FRC), more than one crack width can be measured for the same crack.