3-D-Printed Piezoresistive Sensor for Real-Time Shrinkage Monitoring of Cementitious Materials

Monitoring shrinkage in mortar and concrete is critical for ensuring structural integrity and durability, as well as for preventing potential cracking through proactive maintenance and design modifications. Traditional methods for predicting shrinkage typically rely on regression techniques based on elapsed time, or on models that incorporate mechanical properties, physical characteristics, and material age. This study introduces an innovative method for real-time monitoring of mortar shrinkage using 3D-printed piezoresistive sensors, with a focus on assessing the effect of metakaolin in high-volume fly ash–cement composites. The sensors, fabricated via fused deposition modelling using conductive thermoplastic polyurethane filament, were embedded within mortar samples to measure volumetric strain by monitoring changes in relative electrical resistance. Theoretical analyses revealed a strong correlation between mortar shrinkage and the piezoresistivity of the embedded sensors, which was experimentally validated with high precision (R² values exceeding 0.9, up to 0.99). To further refine predictions and address any discrepancies, an artificial intelligence model was developed to enhance prediction accuracy. This proposed method offers a promising tool for civil engineering applications, enabling enhanced structural safety, optimized maintenance, and extended lifecycle management.