The Role of Reinforcement Density in the Capacitance Based Self-Sensing Behavior of Concrete Elements

This study explores the self-sensing capabilities of reinforced concrete elements with a coplanar electrode system, without using conductive fillers. Specimens with different tensile reinforcement amounts (2 and 4 bars) were subjected to four-point tensile loading, and capacitance was measured throughout the process. The initial (with no load) capacitance value for the element with two tensile reinforcements was approximately 215 pF, and for the element with four tensile reinforcements, it was 282 pF. Capacitance decreased with increasing vertical beam deflection, with the reduction more pronounced as the load and reinforcement density increased. At loads of 36 and 72 kN, capacitance reduction was 39% for the two-reinforcement specimen and 49% for the four-reinforcement specimen. Stress sensitivity was approximately 1.92×10−8 Pa−1, indicating minimal influence of reinforcement density at low loading levels (0–20 kN). The study confirms that reinforced concrete elements have inherent self-sensing capabilities for stress and deformation, regardless of reinforcement density. Capacitance-based monitoring systems were shown to be effective for detecting microstructural changes, offering a promising method for real-time structural health monitoring in critical infrastructure.