Concretes are broadly used for civil engineering structures because of their great adaptability and limited cost. The constant extension of the duration of the operating life of these structures (up to 120 years for current engineering structures) raises the question of the durability of these structures (i.e. the physico-chemical interactions between the concrete making up the structure and its environment) as well as the need for monitoring and assessment of the "health" of these structures. Today, the main tools available to structure managers are visual inspections and sampling for analysis. There is therefore a strong need for durability-oriented instrumentation. However, concrete is a porous material whose solution contained in the porosity is in chemical equilibrium with the minerals present in the solid skeleton. Thus, any mineralogical change in the solid has a consequence on the pH value of the pore solution. It is therefore possible to carry out long-term monitoring of the "health" of the structure on the basis of a pH measurement in the concrete. In this context, the objective of this post-doc is to develop a pH sensor using an optical fibre (optode) that can be used for concrete. The prototype recently developed at CEA for basic solutions will be used for this purpose. It should be noted that particular care has been taken to ensure the durability of the sensor by using an innovative method of fixing the active layer by covalent grafting (patented method).