Integrated self-monitoring of carbon based textile reinforced concrete beams under repeated loading in the un-cracked region

This paper studies the piezoresistive behavior of self-sensory carbon/glass textile reinforced concrete beams under the effect of loading, unloading, and reloading in the un-cracked region. Continuous carbon tows knitted into the textile serve both as the structural reinforcement and as the structural health sensors. The design eliminates the need for additional sensors by taking advantage of a monitoring system that is an inherent part of the load bearing element. The paper faces the challenge of understanding of the correlation between the piezoresistive change of the electrical properties of the carbon tow and the change of mechanical properties under repeated loading representing the response to service live loads. The paper looks into this correlation and explores it through an experimental investigation. It is found that for the un-cracked stage of the beam, the carbon component of the reinforcing textile provides an electro-mechanical sensing capability with gauge factors of 2.4-5.4 for tensile strain. Since the investigation focuses on flexural elements with at least two layers of textile reinforcement, the experiments also reveal negative gauge factors of -2.7 to -6.5 for compressive strains. These observations take a step towards many applications of sensory carbon based textile reinforced concrete elements.