Percolation network and piezoresistive properties of ultraductile cementitious monitoring coating with A-POSS modified carbon-based nanoconductors

Abstract

Conventional cement-based sensors are large and often embedded in cast-in-place concrete structures, resulting in poor flexibility, low sensing accuracy, and inability to be replaced after damage. This paper reports a promising health monitoring technology, namely the composite coated sensor (sensing skin) prepared by anionic waterborne polyurethane (WPU)-modified cement, in which N-(2-aminoethyl)-3-amino propyl trime thoxy silane (NAEAPTMS) silsesquioxane modified ettringite (A-POSS) acts as a core modifier. The results showed that a continuous interpenetration polymer network was formed between the WPU and the cement, which greatly improved the crack resistance and balanced the polarisation reaction field. The agglomerated GO-CNT particles self-dispersed into micron/nanometer-sized particles under the co-precipitation of Ca2+/Al3+ and the semi-cage-like POSS structure formed by NAEAPTMS, using AFt as the supporting skeleton. The toughness and bond strength of the sensing skins were improved in the presence of A-POSS and, in particular, the maximum deflection angle exceeded 110°. Meanwhile, the electrical resistivity was reduced by more than 2 orders of magnitude. The effective conductivity inside and outside the interface can be precisely delineated when GO-CNT was perfectly arranged inside WPU-CEMENT. The agreement between the theoretical and experimental results of effective conductivity indicates that the sensing skin had a percolation network with imperfect and tunnel-assisted interfaces. The synergistic effect of WPU and A-POSS gave the sensing skin excellent performance of high sensitivity (80 times larger than strain gauges), low relaxation time (50 ms), and monitoring stability.