Experimental Study On Mechanical Properties And Bond-slip Relationship Of Self-compacting Concrete Filled Steel Tube

Concrete filled steel tube due to its excellent mechanical performance and ease of construction, more and more applied to practical engineering. Therefore, in recent years, concrete filled steel tube has become the research focus of the engineering sector. The current research has focused on the components of carrying capacity and seismic performance of concrete filled steel tube. Concrete shrinkage deformation on the impact filled steel tube concrete performance to study less. The paper investigates the expansive agent performance impact on high-strength self-compacting concrete mechanical properties and shrinkage, study on axial compressive strength and the bond slip behavior of concrete filled steel tube. Specifically includes:(1) Under the current "technical specifications for self-compacting concrete application "to determine the initial mix ratio of self-compacting concrete, through different types of the admixture composite test, Optimize the preparation of the expansive agent with different contents of high-strength self-compacting concrete. Mixed with expansive agent, Improve the stability of self-compacting concrete mixture, but the fluidity of the mixture is slightly reduced. Appropriate increase in the dosage of superplasticizer, it could improve the concrete mixture mobility.(2) Through the test studied on the impact of the expansive agent dosage to self-compacting concrete cube compressive strength, splitting tensile strengths, axial compressive strength and modulus of elasticity of the basic mechanical propertie. The results showed that: with the expansive agent dosage increases, self-compacting concrete cube compressive strength, splitting tensile strength and axial compressive strength are first increases and then decreases, there are peaks, the expanders content on the impact of self-compacting concrete modulus of elasticity is not obvious; mixed with expansive agent, improve the self-compacting concrete compressive strength, splitting tensile and axial compressive strength.(3) Through the test studied on the impact of the expansive agent dosage to the contractile properties of the self-compacting concrete. The results showed that: compared with the benchmark self-compacting concrete is not mixed with expansive agent,â‘ with the expansive agent dosage increases, reducing the shrinkage rate of self-compacting concrete;â‘¡In the 28d before and after, mixed with expansive agent of self-compacting concrete have different shrinkage growth rate;â‘¢In the 180 days of age, mixed with expansive agent, the low shrinkage of self-compacting concrete, with expansive agent dosage increases, the shrinkage gap of self-compacting concrete is first reduced and after Increased, there is the lowest point; Return the relationship of shrinkage and age of the self-compacting concrete, and in good agreement with the measured values. (4) Axial compression tests of 12 self-compacting concrete filled steel tube are showed: with the increase of the expansive agent dosage, the axial compressive strength of concrete filled steel tube is slight increase.(5) Through the push out test of four self-compacting concrete filled steel tube, studied on the impact of expansive agent dosage to self-compacting concrete filled steel tube bond slip performance. The results showed that:â‘ Bond destruction strength of self-compacting concrete filled steel tube is increase with the increase of the expansive agent dosage;â‘¡In the bond failure load, the P-S curve of self-compacting concrete filled steel tube appear abrupt change or inflection point,the mutation or inflection point before and after, with load increase, the slip value of the concrete filled steel tube have different increased amplitude, and expansive agent dosage has little effect on Slippage;â‘¢core self-compacting concrete strain increases with increasing load, increasing the core concrete height with strain is decreased, the expanders content has little effect on the core concrete strain;â‘£Steel pipe strain increases as the load increases, longitudinal strain increased with the steel pipe height increases,transverse strain is reduced with increasing height, mixed with expansive agent, the core concrete is passed to the steel pipe stress increase.This paper can provide a reference for theoretical research and practical engineering applications of steel pipe high-strength self-compacting concrete.