# Wireless Strain Gauge for Monitoring Bituminous Pavements
###### Abstract
The authors collected the relevant literature on wireless sensor networks and pavement monitoring. This study delved into the essential aspects of networks designed for pavement monitoring with a focus on damage detection. These fundamental characteristics include energy supply (battery power, energy harvesting techniques, or energy efficient designs to ensure operational longevity), detection methods (accelerometers, strain gauges, or acoustic sensors), network architecture (sensors, communication protocols, data aggregation, etc. ), but also performance validation procedures (laboratory tests, field experiments, simulation studies, comparison with existing systems). [PERSON] et al. [9] and [PERSON] et al. [25] have set up measurement or detection systems whose transmission is wireless. The deformation and temperature sensors are connected to self-powered acquisition units. Other researchers, like [PERSON] et al. [26] or [PERSON] et al. [27], proposed smart sensing technology based on the use of self-powered piezoelectric sensors that could be distributed in the pavement for continuous monitoring. The approach proposed by [PERSON] et al. [28] for the health monitoring of pavement systems involves a self-powered sensing system for the evaluation of damage detection performance. Numerical simulations are used to model the behavior of the pavement system under different conditions and to assess the effectiveness of the approach in detecting damage. Experimental studies were performed by implementing the wireless sensor pavement in pavement cores and testing its performance under various scenarios, as well, the damage localization and quantification are investigated and their methodology is based on relative damage. It is therefore not necessary to directly measure the absolute deformation of the pavement. [PERSON] et al. [29] highlighted the importance of continuous, long-term monitoring for pavement structures and presented a novel approach involving self-powered wireless sensors and advanced data analysis techniques. The authors present the feasibility and effectiveness of the proposed monitoring system; however, they also discuss the limitations and challenges encountered during the development and validation process, which may include issues related to sensor accuracy, data transmission, or computational complexities in strain distribution estimation. [PERSON] et al. [30] present the development of a detection system capable of being applied to the long-term monitoring of roadway structures and determining damage and their lifespan. The module consists of a miniaturized, battery-free system with a wireless piezoelectric sensor capable of detecting the long-term deformation history of the pavement structure. The authors also studied the feasibility of integrating the sensor into the roadway, the survival of the sensor under construction conditions, and its longevity. Aware of all these difficulties, in this paper we propose to produce and test a novel miniaturized wireless strain sensor that we instrumented on a pavement core. This pavement core is then re-established in the structure by gluing. The main advantages of this device are that it is post-instrumented (without fear of destroying the sensor during pavement construction), wireless, with relatively reduced size, low cost, and low energy. This could be a useful device for monitoring pavement evolution. This paper is organized as follows: Section 2 presents the electronic design of the sensor, Section 3 provides some details on sensor installation in the pavement surface layer, Section 4 shows the validation of the measurements process in laboratory and the in situ sensor test with mobile load simulator, Section 5 presents some in situ results and discusses results and improvements.