Research On Mechanical And Volume Stability Properties Of Steel Slag Concrete

The large number of steel mills in the country has brought about a large amount of waste solids in the form of steel slag,which has the problems of low utilization,waste of land resources and environmental pollution.At present,there is a shortage of natural building materials at home and abroad,rising prices and other problems,the application of steel slag as aggregate in the preparation of concrete,not only to a certain extent to alleviate the pollution of the natural environment,but also to explore the steel slag alternative to natural aggregates to solve the problem of shortage of raw materials for concrete.Steel slag across the country is affected by different treatment processes,making it different in appearance,composition and content,and reflecting different patterns in performance.Therefore,this thesis firstly tested the chemical composition and physical properties of steel slag produced and treated by Baotou steel Group after passing the test,and then carried out concrete preparation and related performance tests.Based on the existing research results of the group,the blending rates of steel slag coarse aggregate and steel slag fine aggregate were adjusted in the range of 25%-45%,and in order to study the influence of steel slag concrete in terms of work-ability,basic mechanical properties and volumetric stability,steel slag concrete with different volume replacement rates of strength C40（25%,35%and 45%for steel slag stone and 25%,35%and 45%for steel slag sand）were tested for fresh mix performance,cubic compressive strength,splitting tensile strength,axial compressive strength and volumetric stability.In order to further investigate the mechanism of poor volumetric stability of steel slag concrete,microscopic and XRD analyses were carried out,in addition to the stress-strain intrinsic structure relationship of steel slag concrete.The tests yielded that the incorporation of steel slag can adversely affect the fresh properties of the concrete,improve the strength of slag concrete to a certain extent,but adversely affect the volumetric stability of the slag concrete.With the increase of steel slag aggregate admixture,the work-ability of steel slag concrete gradually decreases,the fluidity and cohesiveness become poor,while the cubic compressive strength,splitting tensile strength and axial compressive strength keep increasing.The incorporation of steel slag improves the ability of the concrete to resist early plastic cracking,but can cause poor stability problems in the concrete.The internal product of steel slag concrete after compression steaming is mainly Ca（OH）₂,which causes damage to the steel slag concrete because the expansion stresses generated exceed the maximum strength that the concrete structure can withstand.Under uni-axial compression,the damage modes of both ordinary concrete and slag concrete are oblique shear damage;the curve of ordinary concrete appears fuller,while the curve of slag concrete appears elevated with the increase of slag replacement rate;the peak strain of slag concrete increases,while the modulus of elasticity becomes larger with the increase of slag content,which improves the deformation resistance of concrete to a certain extent;using the slag Concrete model fitting curves,the fitting accuracy are above 0.94,which has a good analysis of its force behaviour under uni-axial compression.A comprehensive analysis of the properties of steel slag concrete,in order to ensure its safe application in practical engineering,it is recommended that steel slag sand and steel slag stone are optimal when the equivalent volume replacement ratio is 25%.