Influence of styrene-acrylic emulsion additions on the electrical and self-sensing properties of CNT cementitious composites

Carbon nanotube (CNT) cementitious composite sensors are considered as an effective method for monitoring the health of building structures owing to their good self-sensing properties. However, previous studies have shown that the high electrical conductivity imparted by CNTs to cement-based materials can increase the risk of steel corrosion. To overcome this drawback and further enhance the piezoresistive performance of the material, a new method has been proposed in this study to improve the self-sensing properties of CNT-cement composites by incorporating styrene-acrylic emulsion (SAE) in them. The results show that the electrical resistivity of CNTcement composites increases significantly with the addition of SAE, which is attributed to the polymer film hindering the mutual contact of the CNTs and ion migration. In addition, the piezoresistive properties of the composite sensor are significantly improved owing to the CNT/SAE three-dimensional network structure of the conductive system established in the cement matrix. The CNT-cement composite sensor containing 10 wt% SAE exhibits the best self-sensing properties and can reach a stress sensitivity of 22.1 x 10-3 MPa  1. The utilization of polymers as reinforcement for CNT-cementitious materials presents an economical and efficient approach for fabricating piezoresistive stress sensors intended for SHM applications.