## 1 Introduction  
The optimized monitoring of a structure must be considered from the design of the structure and carried out as soon as it is built. One of the phenomena to be monitored to ensure its physical durability is the mechanical strength of the concrete structure [1]. Thus, the delayed attribute formation, deleterious to mechanical properties of thick structures, is provoked by an excessive temperature increase at an early age and by a high ambient water content [2] which must be measured for effective durability modeling [3]. Meanwhile, corrosion of the reinforcements is the main degradation factor of reinforced concrete structures and is a consequence of a number of causes which may not always be independent. These can be carbonation, the penetration of chloride ions, or internal swelling reactions. The parameter conditioning their development is the water content of the concrete; therefore, this is considered as one of the main parameters governing the durability of reinforced concrete structures [1]. Several non-destructive techniques, such as electromagnetic methods, are used to characterize the water content in concrete [4; 5; 6; 7; 8]. Among these methods, the DC-electrical resistivity technique [9; 10; 11] is proven to be highly sensitive to the water content as described by [PERSON]'s law [12]. Other factors can affect the electrical resistivity measurements, among which we can cite the formulation and microstructure of the concrete (pore structure, connectivity and tortuosity of the porosity, water-cement ratio, cementitious content, etc. ), the presence of metallic reinforcements [13; 10; 14; 15], and the variations in environmental measurement conditions (temperature, relative humidity, etc.) [16; 17; 14]. [PERSON] and [PERSON] [18] showed that the temperature has a notable effect on concrete resistivity; thus, controlling the temperature is necessary [19]. The temperature of the concrete influences the concentration and mobility of the ions and the ion-ion and ion-solid interactions [20]; therefore, it affects the measured resistivity [21; 22], as well the electromagnetic permittivity [23]. These interactions can be different for cements of different chemical composition (e.g., slag or fly ash). This influence varies according to the concrete water content [14]. For a constant relative humidity (RH), an increase in the temperature of the concrete implies a decrease in the resistivity [14]. For simplicity, it can be assumed that, in the range of temperature between 0 \({}^{\circ}\)C and 40 \({}^{\circ}\)C, the resistivity doubles when temperature decreases by 20 \({}^{\circ}\)C, or that the resistivity varies, either from 3% to 5% per \({}^{\circ}\)C (per 1.8 \({}^{\circ}\)F) [21; 24] or from 1.8% to 2.2-3% per \({}^{\circ}\)C in geophysical applications [19; 25]. In controlled laboratory conditions, resistivity is affected by the temperature at which the measurement is taken. On site, seasonal changes lead to temperature variation in the concrete structures exposed to various environmental conditions, affecting the resistivity of the structures. Therefore, it is necessary to consider the temperature effect to enhance the relevance of the resistivity measurement in thick concrete structures. This article presents a study of the effect of concrete temperature on the electrical resistivity measurement using a novel multi-electrode embedded sensor. This sensor was developed by [PERSON] et al. [26] in order to monitor the water content gradient through the thickness of radioactive waste storage tunnels for the French national radioactive waste management agency (Andra). The coupled influence of the temperature and the degree of saturation on the resistivity measurements is studied for the sensor embedded along the entire structure thickness. For this purpose, several experiments were carried out on cylindrical specimens having a diameter of 11 cm and a length of 22 cm (standard specimen geometry) and made from the same concrete formulation and procedure.