Study On Mechanical Properties Of Composite Limestone Powder Concrete And Small Eccentric Compression Column

In the production process of limestone and machine-made sand,with the production of limestone powder,it causes environmental pollution and waste of resources.Industrial production also produces a large amount of industrial waste residues such as fly ash and slag.If the mineral admixtures such as limestone powder are partially substituted for cement,on the one hand,it can make full use of natural resources and reduce pollution;on the other hand,it can give full play to its respective advantages and improve the work and mechanical properties of concrete.On the basis of the existing results,In this paper,based on physical tests and numerical calculations,the basic mechanical properties,bonding properties and compressive properties of the composite limestone powder concrete are studied.Composite limestone powder concrete includes limestone powder-slag double-mixed concrete and limestone powder-fly ash-slag triple-mixed concrete.The main conclusions and innovations are as follows:1.On the premise of meeting the working performance of concrete,according to the preliminary test results of the research group and relevant specifications.The fixed amounts of limestone powder,fly ash and slag are divided into two mixing methods,the first is 20%limestone powder and 20%slag;the second is 20%limestone powder,15%fly ash and 15%For slag,0.49,0.40,0.35 and 0.25 water-binder ratio concrete mix ratios were selected;2.The change rule of strength of composite limestone powder concrete was revealed,and the calculation model of compressive strength was obtained.For strength development benchmark concrete and composite limestone powder concrete,cube compressive strength and splitting tensile strength are positively correlated with age,that is to say,they increase with age.For the compressive strength of 6L₂₀F₁₅S₁₅ concrete,the average compressive strength reached 75%of L₀F₀S₀ concrete strength at 3 days,90%of L₀F₀S₀ concrete strength at 28 days,and 93.6%of L₀F₀S₀ concrete strength at 90 days.Splitting tensile strength has similar laws.The growth rate is faster in 3-28 days and slower in 28-90 days,and the compressive strength of the specimen cube can reach the strength design value at 28 days.The most reasonable calculation model of compressive strength of composite limestone powder concrete isf_cu=f_{cu,2 8}?t?A+Bt??,And the formulaf_ts=?t??+?t??f_cu can well express the relationship between cube splitting tensile strength and cube compressive strength of composite limestone powder concrete.3.The change law of bond performance between composite limestone powder concrete and steel bar was obtained,and the bond-slip constitutive equation was established.Parameter a=0.47,parameter b:0<b<2.4.The effects of different water binder ratio,different auxiliary cementitious materials and different bonding length on the ultimate bond stress,peak slip and bond slip curve of composite limestone powder and steel bar were obtained.The smaller the water-binder ratio of the composite limestone powder concrete and the smaller the bonding length,the corresponding composite limestone powder concrete and steel bars have higher ultimate stresses,the smaller the corresponding peak slip,the greater the bond stiffness in the rising section of the bond-slip curve,the less regular the falling section of the bond-slip curve is.The incorporation of fly ash has an adverse effect on the development of the ultimate bond stress between concrete and steel bars,the slag in concrete can improve the ultimate bond stress between concrete and steel bars,However,with the addition of fly ash,the ultimate bonding stress decreases with the increase of the bonding length and the speed increases.5.Based on the research on the compression performance of composite limestone powder concrete columns,the development and failure mode of cracks in small eccentric columns are obtained.The ultimate bearing capacity of the three-mixed limestone powder concrete column decreased by about 4%-8%compared with the double-mixed limestone powder concrete column;The normal cross-section strain of the composite limestone powder concrete small eccentric compression column during loading basically complies with the flat section assumption.6.The law of lateral deformation of small eccentric compression columns of composite limestone powder concrete with concrete strength was revealed.That is to say,under the same load,the higher the concrete strength grade of the composite limestone powder concrete small eccentric compression column is,the smaller the lateral deformation of the column is,indicating that the lateral stiffness of the column is positively related to the concrete strength grade.7.The calculated of small eccentric compression column of composite limestone powder concrete during eccentric compression can be calculated by the current concrete specification.8.The results of ABAQUS analysis are in good agreement with the test results.The ABAQUS software can be used to simulate the bearing capacity of composite limestone powder concrete small eccentric columns.The paper has58figures,37 tables and 101references.