Study On The Performance Of Conductive Mortar With Single-wall Carbon Nanotube And Carbon Fiber

Conductive cement-based composite materials(CCCMs,adding conductive components to the cement matrix to give the electrical properties of the cement-based materials without losing its basic characteristics)as an intelligent building functional material,can be used to melt snow and ice,building heating,intelligent Monitoring,etc.The excellent properties of single-walled carbon nanotube(SWCNT)and carbon fiber(CF)undoubtedly provide more effective ways for people to improve the performance of cement-based composite materials.Therefore,under the premise of meeting the workability requirement,conductive mortar mixes with varied SWCNT and CF contents were made,the combined effects of SWCNT and CF on the properties were studied,and the relevant mechanism was analyzed,so as to provide a reference for the development and application of CCCMs.The main work and conclusions are as follows:(1)Research on workability.Through mini-slump cone test,preparing conductive mortar that meets workability requirements,and analyzing the factors that affect its workability.Compared with CF,SWCNT would significantly deteriorate the workability of the mortar.However,superplasticizer can effectively compensate the decrease in the workability due to the adding of CF and SWCNT..(2)Research on electrical performance.Through volume resistivity and surface resistance tests,it was found that water/cement ratio,humidity,age,and conductive admixture content all have effects on the conductive properties of the mortar.Among them,CF can greatly reduce the volume resistivity of the mortar,but maginally reduce the surface resistance.SWCNT can signicantly reduce the volume resistivity and surface resistance of the mortar,and its percolation threshold is 0.05% ～ 0.15%.At certain contents of CF and SWCNT,adding both has an additive effect on improving the electrical properties.According to the conductivity requirements,the conductive mortar containing CF and SWCNT can be used for static dissipation,heat generation,shielding,etc.(3)Research on mechanical performance.Through compressive strength and flexural strength tests,it was found that a proper amount of SWCNT can improve the mechanical properties of the mortar,whereas CF can improve the flexural strength,but but maginally increase the compressive strength.At certain contents of CF and SWCNT,the addition of both provides synergistic effect on the mechanical properties of conductive mortar,that is,the super-superposition effect of "1 + 1 > 2".(4)Research on dimensional stability.Through 180-day dry shrinkage test,it was found that both SWCNT and CF can effectively reduce the shrinkage strain of the mortar,especially the early shrinkage strain,and can delay the development of shrinkage strain.Such reduction in shrinkage can prevent the CCCMs from cracking.Adding CF together with SWCNT has an additive effect on dimensional stability of the mortar.In addition,reducing the water/cement ratio can also reduce the shrinkage strain of the mortar.(5)Analysis on the mechanism of action.Through scanning electron microscopy,it was found that an appropriate amount of SWCNT can improve the properties of the mortar by its nano-scaled filling effect and fiber bridging effect.CF is mainly used to improve mortar performance through its fiber bridging effect.Using both SWCNT and CF can improve the microstructure of the mortar in multiscale.However,at excessively high contents,due to the agglomeration phenomenon of SWCNT and CF,the performance of the mortar would decrease,and there exists optimal content for optimizaiton of performance attributes of conductive mortar.