Physical And Mechanical Properties Of Steel Slag Metakaolin Based Polymer Conductive Gel

Conductive concrete is a kind of multi-functional composite material,with the characteristics of structural engineering materials,electrical conductivity and voltage sensitivity,and can be used for road signal collection,ice melting and snow removal,and damage monitoring.Compared with cement,since the pore solution contains rich ions,geopolymer has better conductive performance.At present,geopolymer is mainly studied as a substitute for cement,while there are few studies on geopolymer-based conductive gel,especially on its piezoresistive properties.Therefore,the mechanical,electrical and piezoresistive properties of the geopolymer-based conductive gel are studied by changing the curing temperature,steel slag mixing amount,water-binder ratio,alkali mixing amount and fiber mixing amount.On this basis,the optimal mixture proportions of the geopolymer composite is determined.The main conclusions are as follows:(1)With the growth of curing age and the increase of curing temperature,the compressive strength of specimen is somewhat increased,and the compressive strength of specimens is the highest when the steel slag mixing amount is 30%.Another,at different curing temperatures,the more the steel slag is mixed,the lower the electrical resistivity of specimen.Increase of curing temperature leads to accelerate the reaction rate of raw materials and improves early physical and mechanical properties of specimen.However,with the growth of curing age,the effect of curing temperature on the electrical resistivity of specimen becomes weaker.In addition,under the stress of cyclic compression load,the optimal strain sensitivity of steel slag-metakaolin based geopolymer conductive gel is 40.35～50.31.Among them,when curing temperature is 40℃ and steel slag mixing amount is 30%,the correlation coefficient R2 between FCR and cyclic compression stress is as high as 0.95258,and the piezoresistive stability is optimal.At last,microscopic analysis shows that at the same curing temperature,with increase of steel slag mixing amount,the structure density of specimen is first enhanced and then weakened,and the SS-30 group specimen is optimal,which is in good agreement with the strength results.(2)With the decrease of water-binder ratio,the fluidity of SS-30 and SS-60 decreases,while the compressive strength and resistivity of SS-30 and SS-60 increase.Under the same water-binder ratio,the fluidity of SS-60 is higher than that of SS-30,and the compressive strength of SS-30 is higher than that of SS-60.Another,with the increase of alkali content,the compressive strength of SS-60-0.39 specimen increases gradually,but the electrical resistivity decreases gradually.The piezoresistive properties of conductive gel tend to be better as the decrease of water-binder ratio,and the piezoresistive properties of SS-30 sample are greatly affected by the change of water-binder ratio.In addition,the rate of electrical resistance change is unstable with the increasing number of loading times,while the piezoresistive behavior of the SS-60 conductive gel has good sensitivity and reproducibility.The piezoresistive behavior of SS-60-0.39 specimen is greatly affected by the alkali mixing amount,and becomes better as the increase of the alkali mixing amount.Finally,the micromorphology of SS-60 conductive gel is greatly changed as the decrease of water-binder ratio,showing better compactness.(3)The fiber incorporation has a great influence on the degree of fluidity for the conductive gel,which gradually decreases with the increase of the fiber incorporation.Among them,the degree of fluidity for the carbon fiber conductive gel is less than that of the basalt fiber conductive gel under the same fiber content.Another,The compressive strength of the fiber conductive gel increased first and then decreased,and the maximum compressive strength was reached when the content of fiber is 0.4%.The flexural strength of the fiber conductive gel was higher than that of the reference group,indicating that the toughness of the material was enhanced with the increase of the content of fiber.In addition,when the content of carbon fiber is 0.3%,the infiltration phenomenon occurs,while the content of basalt fiber has little effect on the electrical resistivity of specimen.With the increase of fiber content,the electrical resistance change of carbon fiber specimen decreases first and then increases,where CF-0.3 has the highest compressive sensitivity and CF-0.2 has the best piezoresistive repeatability.However,the electrical resistance change rate of basalt fiber specimen is not sensitive to pressure.With the increase of fiber content,the fiber spacing shortened,and began to contact.