Research On The Resistivity Attenuation Law Of Cementitious Conductive Composites Induced By Stress Relaxation And Creep

Creep and stress relaxation of concrete materials can induce structural damage under certain conditions,causing engineering accidents.Researching on creep and stress relaxation can help prevent engineering accidents.In this paper,by incorporating conductive materials into concrete to make it conductive,studying the mechanical and electrical properties under creep and stress relaxation,and the relationship between electric and force was established.Finally,The performance of the material changes during creep and relaxation were characterized by electrical signals.Firstly,designing the optimal mix ratio of cement-based composites with certain strength and high electrical conductivity.Discussing the effects of the types and amounts,the single-mixed and complex-mixed of the onductive materials and mineral admixtures.The final considerations were based on strength and electrical conductivity and material cost.The cement-based composites for stress relaxation experiments were prepared according to the optimal mixture ratios.The law of resistivity change in loading and stress relaxation stages were mainly studied.During the loading phase,it was found that loading at a rate of 0.3 mm/min,through the change in resistivity,the first occurrence of damage was detected to be in the range of 0.7 mm to 0.85 mm of the displacement of the the loading displacement.In the stress relaxation phase,the stress was attenuated by a exponential function.And the three-parameter solid model can describe the stress change well.The experimental data showed that there was a linear relationship between stress and resistivity during stress relaxation,and the two were positively correlated.According to the relationship between stress and resistivity,and the stress variation model,the decay model of resistivity was derived,and the resistivity was also attenuated in exponential form.The model describing the resistivity was also a good fit.In addition,the creep properties of materials at different stress levels were also investigated.Firstly,using the axial compressive test to calculates the average compressive strength,and the stress level was performed at 30%,50%,70%,and 100% of the average compressive strength.During the data processing process,unstable oscillating changes in resistivity were found and the causes were explored.The results showed that the oscillation of resistivity was caused by the change in the pore structure of the cement-based composite.The number of oscillating offsets and the growth rate decreased as the creep stress level increases.At low(30%)and high(100%)stress levels,the strain and electrical resistivity of the material may be unstable.Only at moderate stress levels(50%),the strain and resistivity have obvious regularity.And the strain increased with a very graceful power curve,use the three-parameter solid model to describe strain,which also has good effect.At the same time,a linear relationship between resistivity and strain was found to be negatively correlated.Combining the basic model of strain to derive the attenuation model of resistivity also has a good effect.