| It is a policy to promote the removal of high strength reinforcing bars and low strength reinforcing bars.In order to give full play to the performance of high strength reinforcing bars,activated powder concrete with higher compressive strength is needed.However,the high cost of activated powder concrete restricts its wide application.At the same time,there is a large amount of iron tailings deposit,which has caused serious pollution to the natural environment.Using iron tailings to prepare active powder concrete can not only reduce the production cost,but also achieve the purpose of environmental protection and energy saving by consuming iron tailings stock.At present,there are few researches on the preparation of active powder concrete by using iron tail sand,and there is a lack of test data on the application of active powder concrete of iron tail sand to beam structure.In this thesis,iron tail sand is used to replace quartz sand 100% as the aggregate of active powder concrete to make iron tail sand active powder concrete that meets the strength requirements.Combined with different strength reinforcement bars,9 steel reinforced iron tail sand active powder concrete beams are prepared,and the following research is carried out:(1)Normal section failure test of reinforced concrete beams was carried out on 9test beams.By analyzing the failure form,load-deflection curve and crack distribution of the beam,the flexural performance of the reinforced iron tail sand active powder concrete beam and the degree of adaptation between the high strength reinforcement and iron tail sand active powder concrete are studied.(2)By analyzing the calculation formulas in three different codes and combining with the test data,the proposed formulas for the ultimate bearing capacity of highstrength reinforced iron tail sand active powder concrete beams are derived.(3)The characteristics of acoustic emission signals were studied by analyzing the relationship curves between acoustic emission event location and acoustic emission ringing count,cumulative ringing count and load.(4)At the same time,ABAQUS software was used for finite element simulation,and compared with the test data,the simulation effect of finite element simulation on reinforced iron tail sand active powder concrete beam was studied.Based on the research conducted,the primary conclusions are as follows:(1)Under the condition of high temperature and high wet steam curing,tail of iron ore,a standard condition maintenance of reactive powder concrete cube compressive strength increased by 4.41% ～8.12%;The bearing capacity of activated concrete beams with iron tailings powder is increased by 3.1%～10.6%.At the same time,the bonding strength of rebar and iron tail sand active powder concrete is improved.(2)The optimization coefficient of the bearing capacity calculation formula of the high-strength reinforced iron tail sand active powder concrete beam is put forward: k of the single-reinforcement rectangular beam with HRB500 reinforcement is 1.24;For the single reinforcement rectangular beam with HRB600 reinforcement,k is 1.35;The k of the double-reinforcement rectangular beam equipped with HRB500 reinforcement is 1.2;The k of the double reinforcement rectangular beam equipped with HRB600 reinforcement is 1.3.The calculated values of ultimate flexural capacity with optimization coefficient agree well with the experimental values.(3)The location of event occurrence obtained by acoustic emission test is in good agreement with the actual fracture development.In the loading process of the test beam,the changes of acoustic emission ringing count and cumulative ringing count present three distinct stages corresponding to the three failure stages of the test beam bending.It is proved from the microscopic point of view that the active powder concrete of iron tailing sand has a good match with the high-strength reinforcement.(4)By comparing the test data and the simulated values of 6 double-reinforced beams,it is found that the simulated values are slightly higher than the test values,and the simulated results are closer to the test beams under the condition of high temperature and high humidity steam curing.In this thesis,finite element software is used to simulate the active powder concrete of iron tailing sand under the condition of high temperature and high humidity steam curing.The simulated value is in good agreement with the test value. |
