Research On Smartness Of Cement-based Materials Mixed With Functional Fillers

The conductive functional filler reinforced cement-based material not only has good physical and mechanical properties,but also has agile characteristics(pressure sensitivity,bending sensitivity and temperature sensitivity).The agility gives the material many intelligent properties,which can be widely used in intelligent buildings,health monitoring,disaster prevention and other fields.In addition,conductive cement-based materials generate heat when energized.If applied to pavement snow melting and deicing,it can achieve complete environmental protection and no pollution.In order to enhance their power-electricity sensing ability and power-on heating ability,researchers usually add a variety of functional fillers in the preparation process.In this paper,the pressure-sensitivity,bending sensitivity,temperature-sensitivity and electro-thermal properties of the compound conductive cement-based materials are studied.The specific research contents and conclusions are as follows:The effects of carbon fiber on the fluidity of cement paste,compressive strength of concrete,and electrical conductivity were studied.The addition of carbon fiber significantly reduced the fluidity of cement paste and the compressive strength of concrete.The trend is that the optimal dosage is between 0.8% and 1.2%.Through comparative experiments,the effect of different functional fillers on the pressure sensitivity of smart concrete was studied.Under different loading amplitudes,the mixed mixed smart concrete has a larger loading amplitude and a greater resistance change rate.Under different loading rates,the faster the loading rate,the smaller the resistance change rate.When the content of Multi-walled carbon nanotubes is greater than 0.25%,it has a negative effect on sensitivity.The addition of a certain amount of copper-plated steel fiber has a positive effect on the sensitivity of smart concrete,and the optimal content is 4% Around,the incorporation of low-doped nano-graphene piles can significantly reduce the resistivity and at the same time improve the pressure sensitivity.Under 16 MPa,the resistance change rate can reach74.92%The mechanics,electrical conductivity and bending sensitivity of the mixed-type smart concrete were studied.Studies have shown that carbon fiber and steel fiber are the most critical factors affecting resistivity and flexural strength,respectively.The incorporation of carbon black will reduce the mechanical strength.The compound mixed smart concrete has good bending sensitivity.When the deflection is 4mm,the maximum resistivity change is 158%.Under the three-point bending state,the fitted correlation coefficient of the resistance change rate and deflection is greater than 0.95.The mechanics,electrothermal and temperature sensitivity of mixed conductive mortar were studied.Both steel fiber and carbon nanotube can improve the flexural strength of mortar to a certain extent.Carbon fiber powder can reduce the resistivity to a certain extent.The temperature of the conductive mortar with different mixing ratios increased after 2 hours of energization,and the maximum temperature of the outer surface of the test piece increased to 33.4 ?.The resistivity of conductive mortar showed a decreasing trend with increasing temperature,showing a negative temperature effect.By using ABAQUS to simulate the temperature field distribution of the conductive mortar specimen,the temperature distribution can be obtained along all directions.The research shows that the temperature at the center of the upper surface is the highest,and the deformation of the test piece is mainly the linear deformation of the lateral length.The maximum thermal deformation is at the corner of the upper surface.The maximum equivalent thermal stress reaches 0.25 MPa at about 3 cm at both ends of the test block.