Research On Smartness Of Multiphase Conductive Concrete

In the service process,the architectural structure will be affected by adverse factors such as load and environmental degradation,resulting in different degrees of deformation and damage of the structure.Therefore,it is very important to conduct health monitoring for the building structure.Conductive concrete is a kind of intelligent material which can reflect deformation and damage by its own resistivity change and has a very broad application prospect.In this thesis,composite conductive concrete was prepared by adding functional materials such as carbon fiber(CF),multi-walled carbon nanotubes(MWCNTs)and graphene oxide(GO)into cement-based materials.The CF content was 0.3wt%-1.2wt%,and the MWCNTs content was 0.1wt%-0.5wt%.GO content was selected as 0.03wt%-0.09wt% to study the pressure-sensitive and bending-sensitive properties of multiphase conductive concrete.The specific research contents and conclusions are as follows:(1)The influence of functional materials on the compressive strength and electrical conductivity of concrete is studied.With the increase of CF content,the compressive strength of CF doped conductive concrete increases first and then decreases,and the resistivity decreases gradually.When CF content is 0.7wt%,concrete has the best compressive performance,but the resistivity of concrete is still high at this time.With the increase of CF content,the resistivity of concrete continues to decrease.When CF content is 1.2wt%,the resistivity of concrete drops to the lowest,but at this time,the compressive performance of concrete decreases.When CF content is 0.7wt%,0.25wt% MWCNTs and 0.06wt% GO are added,the composite conductive concrete has the highest compressive strength,which is24.37% higher than that of ordinary concrete.Meanwhile,the conductivity of composite conductive concrete is significantly improved.With the increase of functional materials,the resistivity of the composite conductive concrete decreases,but its compressive strength also decreases.(2)By mixing CF,MWCNTs and GO into cement-based materials to prepare multiphase conductive concrete,the effect of functional materials on the pressure-sensitive properties of multiphase conductive concrete was studied.Under constant amplitude cyclic load under low compressive stress,when CF content is 1.2wt%,the average resistance change rate of conductive concrete with CF content is-18.16%,and the pressure sensitive performance is the best.However,the compressive strength of concrete decreases at this time.Therefore,MWCNTs,GO and CF are mixed into cement-based materials to improve the compressive strength of concrete and ensure that concrete has good electrical conductivity.When CF was added to 1.2wt%,MWCNTs to 0.25wt% and GO to 0.09wt%,the average resistance change rate of the composite conductive concrete was-20.38%,indicating the best pressure-sensitive performance.There is a good correspondence between the stress and the resistance change rate of the composite conductive concrete under different loading modes.(3)The bending resistance and bending sensitivity of composite conductive concrete were studied by four-point bending test.When CF was added to 0.7wt%,MWCNTs to 0.25wt%and GO to 0.06wt%,the flexural performance of the composite conductive concrete was the best.With the increase of functional materials,the flexural performance of the composite conductive concrete decreased.The composite conductive concrete specimens all have good bending sensitivity,and the maximum resistance change rate is 45.73%.The deflection-resistance change rate curve is established and fitted,and the correlation coefficients are all greater than 0.96.