| Researches on corrosion protection of marine concrete structures based on cathodic protection technology have drawn intensive interests.It is of great significance to develop high performance cathodic protection mortar to improve the corrosion protection effect of marine structures.Carbon nanotube(CNT)and nano-Zn O(nZnO),which respectively have excellent mechanical toughness,thermal/electrical conductivity and semiconductor thermoelectric properties,are doped into the mortar,and the temperature difference power generation and piezoresistive intelligent sensing properties of corresponding nano-modified protective mortar are developed.The study has a good scientific and research significance on the corrosion protection effect of the steel in concrete structure and the good self-monitoring efficiency.In this paper,the surfactant sonication dispersion method was firstly used to investigate the dispersibility of two kinds of nanomaterials(CNT,nZnO)in aqueous solution under different types and different sonication time.Then,under the aid of water-reducing agent,the well-dispersion CNT/nZnO suspension pouring was adopted.CNT or /and nZnO modified protective mortar(CNT/nZnO-RM)was prepared by cast molding method,and SEM microstructure and EDS element analysis was used to evaluate the dispersion efficiency of CNT/nZnO and fiber bridging effect;the resistance performance of CNT/nZnO-RM was tested by four-electrode method and AC impedance method,and the thermoelectricity under different temperature differences condition was measured by thermocouple testing and constant temperature water bath method.The piezoresistive intelligence behavior of CNT/nZnO-RM under different loading rates and different cyclic loads were further explored.The results of the study are analyzed as follows:(1)The optimal dispersion process of CNT/nZnO is found by the static sedimentation method of the dispersion,high-speed centrifugal layering method and spectrophotometric multiple dispersion evaluation method: CNT/nZnO is mixed with 5% polyvinylpyrrolidone(PVP),the ultrasonic treatment of n CNT/nZnO in water for 70 min and 60 min,respectively,has the best dispersion effect and high stability.SEM & EDS microstructure reveal,CNT/nZnO can be well dispersed in cement mortar,and CNT can play the role of fiber bridging effect.(2)The CNT-RM resistivity is as low as about 3.6 k?·cm when the CNT content is 1.5%,which well satisfies the percolation mechanism of the conductive filler;and the resistivity of nZnO-RM increases with the increase of nZnO content and the resistivity continues.This may be due to the semiconductor characteristics of nZnO and PVP dispersant forming hydrogen bonds,forming an insulating barrier.The thermoelectric coefficient of CNT-RM doped with 2% CNT reaches the maximum(1785.0 ?v/?)),and the thermoelectric coefficient of CNT-RM doped with1% nZnO can reach(1283.0 ?v/?),while CNT-RM doped with 2% CNT and 1% nZnO simultaneously The thermoelectric coefficient of nZnO-RM does not achieve a synergistic enhancement effect.This may be because nZnO and PVP dispersant form hydrogen bonds,which affects the probability of physical overlap of CNT and nZnO in the mortar matrix,which greatly reduces its electronic heat conduction effect.(3)The corresponding CNT/nZnO-RM exhibits bad piezoresistive intelligent effect perhaps due to hydrogen bond forming resulting the insulating characteristics of CNT and nZnO;whether at 60N/s or 100N/s loading rate,under the peak load of 5k N,7k N and 10 k N.The CNT-RM with2% CNT shows good piezoresistive intelligence: its resistivity change rate changed uniformly with cyclic load,and the corresponding change difference is 7.3%?10.01%?12.28%,respectively.The load sensitivity and linearity are accordingly(1.32±0.06)%/k N?(3.8±1.74)%?(2.8±1.3)%,respectively.Obviously,CNT-RM with high thermoelectric coefficient and piezoresistive intelligence would be used as protective mortar in marine concrete structures to exert its cathodic protection and damage self-monitoring functions. |
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