Study On The Basic Mechanical Properties And Bending Properties Of Composite Limestone Concrete

With the increase of infrastructure investment,the corresponding amount of cement is also increasing.In order to relieve the pressure of cement consumption and the increasing environmental pollution,it is very urgent to seek mineral admixtures to replace cement.Mineral admixtures are often used to improve the performance of cementitious materials or concrete.Admixture can reduce the cement content of cement-based materials,improve workability,reduce the temperature rise of hydration,improve strength and many other advantages.Commonly used admixtures include fly ash,slag and limestone powder.Fly ash and slag have hydration activity and are commonly used as admixtures of concrete,but their content must be determined by test.The pulverized limestone powder can fill the pores of concrete and make concrete more dense.In this paper,based on this background research Double lime stone powder+slag and Three limestone powder+fly ash+slag of the basic mechanics performance,uniaxial compressive performance and the mechanical properties of bending beam and of the two kinds of materials from the block to the macroscopic properties of components has a comprehensive understanding,for the promotion of the new materials to provide theoretical support and technical guidance.The main research results obtained are as follows:（1）The law of strength variation of double-lime stone powder+slag concrete and ordinary concrete under the influence of water-binder ratio,auxiliary cementing material and age is obtained.Both compressive strength and splitting strength increase with age and water-binder ratio decrease.A 3d fitting model of concrete compressive strength and splitting tensile strength under the influence of water-binder ratio and age is established.The relationship between compressive strength and splitting tensile strength of composite limestone powder does not meet the requirements of the specification.According to the characteristics of composite limestone powder,the relation between them is put forward as follows:f_ts=0.1209f⁰_cu⁸⁵⁶⁵.Double mixing limestone powder+slag concrete cube compressive strength and splitting tensile performance are lower than that of ordinary concrete,but as the growth of the age,the strength of the limestone powder+slag concrete on the growth rate faster than normal concrete,and smaller and smaller,and the strength of ordinary concrete difference each water-binder ratio of strength design value can satisfy the requirement of specification;（2）The peak stress,peak strain and elastic modulus of double-doped limestone powder+slag and three-doped limestone powder+fly ash+slag concrete are positively correlated with compressive strength,and the indexes of double-doped limestone powder are better than those of three-doped limestone powder.The relationship between the prism and cylinder and the peak stress of cube specimens is established:f_c=0.78f_cuand f_c=0.78f_cu。according to the uniaxial compression strain-strain relationship proposed by guzhenhai,the prism specimens with double lime admixture of stone powder+slag and tri-lime admixture of stone powder+fly ash+slag concrete are fitted,and the fitting results are good;（3）Tests were carried out on 12 flexural beams of double-doped limestone powder+slag and tri-doped limestone powder+fly ash+slag concrete.The strain of concrete loaded by 12 bending beams conforms to the assumption of flat section.The water-binder ratio and auxiliary cementing materials do not affect the failure process and final failure state of the test beam.The load-concrete strain of the 12 bending beams conforms to the assumption of flat section.Under the same load,the strain of the steel bar of the double-admixture and triple-admixture concrete beams with the same water-binder ratio is less than that of the triple-admixture concrete beams.After cracking load appears,for the concrete beam with the same proportion,the rate of increase of steel bar strain of the test beam with small water-binder ratio is less than that of the test beam with high water-binder ratio.For the same test beam water-binder ratio,double mixing limestone powder+slag yield displacement less than three mixing lime stone powder,fly ash and slag of the yield displacement,for different water-binder ratio,the same test beam auxiliary cementitious materials,water/cement ratio smaller than the water-binder ratio of the yield displacement test beam the big test beam of the yield displacement,and ultimately the destruction of the displacement is higher than that of water-binder ratio big test beam;（4）Using ABAQUS software,numerical simulation analysis was carried out on the flexural beam of double-doped limestone powder+slag and three-doped limestone powder+fly ash+slag concrete.Selected through the calculation of the test beam model,including the analysis of the model of the tested beam,the selection of unit type and material parameters and load-reinforced strain curve and load is established-span deflection curve simulation values,by comparing the test curve analysis and simulation curve,is an accurate reflection of the reinforcing steel bar and deflection with load,the change rule of use ABAQUS can accurately reflect the compound of the limestone powder concrete flexural failure process（5）By bending beam,the experimental data and numerical simulation results with the calculated value of"concrete structure design code"comparative analysis to get:to standardize the calculation of the cracking load and ultimate load values than the lime stone powder,fly ash and slag and limestone powder+slag concrete beam test values,with the specification of experimental beams cracking load and ultimate load calculation is feasible.Through the comparison and analysis with the mid-span deflection value calculated by the specification and the test value,the deflection value calculated by the specification value is relatively small,so it is modified,and the modified curve is in good agreement with the test curve.The paper has 72 figures,43 tables and 94 references.