Performance of cement-based sensors with CNT for strain sensing

Strain-sensing functions of Portland cement pastes with different dosages of carbon nanotubes (CNT) are systematically studied. This is one of the relevant functions that multifunctional composites are able to develop when a conductive addition is included in the cement matrix. Strain sensing refers to the ability of a structural material to sense its own condition, such as strain or stress, through the piezoresistive behaviour (change of volume electrical resistivity when it is subjected to a force). CNTs, which possess exceptional electromechanical properties, are considered as a promising addition for practical applications such as structural health and load monitoring. Nevertheless, there is still an important challenge regarding CNT cement composite fabrication: achieving their effective dispersion. This point is addressed by means of a comparison between different physical and chemical dispersion methods. The technique used for that purpose is light-scattering particle size analysis. After selecting the optimal dispersing procedure, the effect on the strain-sensing properties of CNT reinforced cement pastes was studied for the following variables: CNT dosage, curing age, current intensity, loading rate and maximum stress applied. All these parameters are discussed taking gauge factor value as the reference.