Research On Mechanical Properties Of Steel Slag Concrete Based On Different Levels Method

Compared with the traditional natural sand,steel slag has the advantages of high density,high compressive strength and low grindability index.Steel slag can be used as fine aggregate in concrete to improve the strength of concrete.The research scale of concrete materials can be divided into micro scale,micro scale and macro scale.The basic theory of modern materials science shows that the properties of materials are closely related to their composition and structure.For concrete material,as a kind of heterogeneous composite material,its fine and micro composition determine the complex mechanical properties on the macro level.Concrete is a kind of complex composite material.The research on the failure law of concrete from the macroscopic point of view is less concerned with the nonlinear characteristics of each phase of concrete.Therefore,if we want to study the failure process of concrete,we must consider the structural characteristics of materials in meso scale and micro scale.Based on the micro scale,meso scale and macro scale,this paper studies and analyzes the microstructure characteristics,meso failure process and macro mechanical properties of four kinds of steel slag concrete by replacing the fine aggregate with the volume of granulated steel slag,so as to provide the basis for the application of steel slag concrete in Pavement Engineering.The main research work of this paper is as follows:The cube compressive strength,splitting tensile strength,axial compressive strength and flexural strength of four kinds of steel slag concrete were studied.The variation law of concrete cube compressive strength,tension compression ratio and flexural compression ratio with steel slag content is obtained;The axial compressive stress-strain curves,constitutive relations,deformation properties,ultimate flexural load and peak deflection of different slag contents were obtained.With the increase of steel slag content,the cube compressive strength of concrete first increases and then decreases,and the cube compressive strength reaches the maximum when the steel slag content is 20%.With the increase of steel slag content,the splitting tensile strength of concrete first increases and then decreases,and the splitting tensile strength reaches the maximum when the steel slag content is 20%.With the increase of steel slag content,the axial compressive strength of concrete first increases and then decreases,and the axial compressive strength reaches the maximum when the steel slag content is 10%.When the steel slag content is 10%,the toughness index is the largest,the brittleness index is the smallest,and the deformation performance of concrete is the best.With the increase of steel slag content,the flexural strength of concrete first decreases and then increases.When the content of steel slag is30%,the flexural strength of concrete is the largest.With the increase of steel slag content,the tension compression ratio of concrete first increases and then decreases.When the steel slag content is 20%,the tensile compression ratio of concrete reaches the maximum.With the increase of the steel slag content,the ratio of the flexural pressure decreases first and then increases.When the steel slag content is 30%,the concrete flexural pressure ratio is the largest.The cube compressive strength of four kinds of steel slag mortar was studied.With the increase of steel slag content,the compressive strength of mortar first decreases and then increases.When the steel slag content is 30%,the compressive strength of mortar is the largest.By means of X-ray fluorescence spectrometer,scanning electron microscope,energy spectrum analysis and nano indentation,the microstructure characteristics of mortar with different steel slag content were studied.The results show that the composition of steel slag fine aggregate is complex,and the main mineral phases are Ca O and Si O₂.Steel slag fine aggregate has a certain hydration activity,which makes the hydration products of cement matrix more dense and has less pores.There is an obvious interface transition zone around the slag fine aggregate,and the width of the interface transition zone is about 8μm.The elastic modulus and hardness of the interface transition zone of steel slag fine aggregate are low,which are about 19.298 GPa and 0.602 GPa.Granular steel slag fine aggregate concrete is regarded as a five phase composite material composed of stone coarse aggregate,steel slag fine aggregate,cement mortar,stone coarse aggregate cement mortar interface and steel slag fine aggregate cement mortar interface.In this paper,the method of random generation and placement of aggregate in fine aggregate concrete with granulated steel slag is studied.Using meso numerical simulation method,the granulated steel slag mortar is regarded as a three-phase composite material composed of steel slag,mortar matrix and steel slag cement mortar interface.According to the compressive strength of mortar with different steel slag content,the physical and mechanical properties of mortar matrix are inversed,and the meso numerical model of steel slag concrete is established.The concrete with four kinds of steel slag contents are tested by meso simulation,including cube compressive strength,axial compressive strength,flexural strength and axial tensile strength.The simulation results are close to the experimental results,which verifies the reliability of the meso numerical model of granular steel slag fine aggregate concrete.