Experimental Study On Stress And Damage Self-Induction Of Carbon-Steel Fiber Smart Concrete

With the development and application of reinforced concrete structures,damage accumulation and catastrophic behavior of reinforced concrete structures become increasingly prominent,and the need for long-term monitoring of reinforced concrete structures under important loads becomes increasingly urgent.Fiber smart concrete not only has superior mechanical properties,but also has pressure sensitivity and flexural sensitivity.It can sense the stress change and damage expansion of concrete,which provides the possibility for long-term monitoring of important stressed concrete structures.It can sense the load change and internal damage of concrete,which provides a possibility for long-term detection of important stressed concrete structures.In this paper,the mechanical properties,electrical conductivity,compressive stress self-induction and bending damage self-induction of fiber reinforced coarse aggregate smart concrete with carbon fibers and steel fibers(single or mixed)are studied.The main contents are as follows:?.Study on mechanical properties of carbon-steel fiber smart concrete.The cubic compressive strength and splitting tensile strength of concrete with different fiber content were tested.The results show that both carbon fibers and steel fibers can improve the failure mode of concrete and enhance the integrity of the specimens under the condition of single and mixed fibers.When only one fiber is added,the higher the content of short-cut carbon fibers and steel fibers,the greater the cubic compressive strength and splitting tensile strength of concrete correspondingly.When both fibers are added,they have a positive hybrid effect.?.Study on electrical conductivity of carbon-steel fiber smart concrete.Under the same measuring voltage,the polarization reaction of smart concrete with different fiber content is intense at the initial stage of switching on the circuit.the current decreases rapidly and the resistivity increases correspondingly.Subsequently,the current change rate decreases and the resistance remains basically constant.In addition,when the carbon fiber content is the same,the more the steel fiber content is,the more the current decreases after the polarization reaction is completed,the more the resistivity increases correspondingly,and the more obvious the polarization effect is.?.Study on self-induction of compressive stress of carbon-steel fiber smart concrete.Firstly,the effects of test voltage,fiber content,loading speed,humidity and coarse aggregate size on the stress self-induction performance of carbon-steel fiber smart concrete in the elastic range are studied through experiments.Then,the stability of stress self-induction ability of carbon-steel fiber smart concrete under cyclic loading was studied.The results show that: The relative variation of resistance can be obtained by using lower measuring voltage under the same stress condition.The content of fiber has a great influence on the stress self-induction ability of fiber-smart concrete.When the content of carbon fiber is 0.2% and the content of steel fiber is 0.45%,the smart concrete has the best self-induction ability of compressive stress.Loading speed has little influence on the compressive stress self-induction ability of smart concrete.The stress self-induction ability of smart concrete with high humidity is poor under small stress condition.The stress self-induction ability of smart concrete increases with the increase of coarse aggregate size range.There is a good correspondence between the relative change of resistivity and the change of stress under cyclic loading.?.Bending damage self-induction of carbon-steel fiber smart concrete.The influence of steel fiber content and coarse aggregate size range on the deflection and crack self-induction ability of carbon-steel fiber smart concrete under bending damage was studied by testing the change of resistance with load,mid-span deflection and crack width.The results showed that: Before the maximum load is reached,the mid-span deflection of smart concrete with different steel fiber content and different coarse aggregate size range increases,but the relative variation of crack width and resistance is small.After the maximum load is reached,the resistance of smart concrete increases with the increase of mid-span deflection and crack width.After the load reaches the peak,the resistance of smart concrete increases with the increase of mid-span deflection and crack width.The toughness of flexural members is enhanced by adding steel fibers,which is conducive to the effective monitoring of mid-span deflection changes by detecting the change of resistance of specimens in the case of large deflection and crack width.With the increase of steel fiber content,the change of resistance increases slightly when the same mid-span deflection and crack width are reached;With the increase of coarse aggregate size range,the relative variation of resistance increases slightly when the same mid-span deflection and crack width are reached,and the fitting correlation between mid-span deflection-resistance curve and crack width-resistance curve decreases slightly.However,the relative variation of resistance in different coarse aggregate size range can still reflect the change of mid-span deflection and crack width.