The senses of asphalt: a new era in road safety with capacitance-based sensing

This study investigates the use of capacitance-based self-sensing for monitoring stress in asphalt pavements. Asphalt samples with maximum aggregate sizes of 12.5, 19 and 25 mm undergo cyclic loading (1-5 and 9-45 kPa) and continuous loading. A strong and reversible relationship consistently emerges between applied stress and changes in capacitance, indicating that the material stays within the elastic deformation range. Regardless of aggregate size, all samples exhibit reliable and repeatable self-sensing behaviour. Under low stress, capacitance typically decreases by 2-6%, while at higher stress levels, this change increases by 7-20%. The stress sensitivity measures about 1.7 x 10-(5) Pa-(1) at low stress and decreases to 0.4 x 10-(5) Pa-(1) under higher loads. This sensing method does not require conductive fillers, making it cost-effective and scalable. The results support the practical use of capacitance-based sensing for real-time monitoring of stress and deformation in asphalt materials. This approach enhances the potential for smart infrastructure systems and contributes to improved durability, safety and sustainability of asphalt pavements.