Study On Corrosion And Bonding Property Of Steel Bar In Geopoltmer Concrete

In order to meet the requirements of green development,the research and development of green cementitious materials has become one of the most important goals in the field of building materials.The greenhouse gases are released and fossil energy is consumed in the production process of Portland cement,a traditional cementitious material.In order to contribute to the sustainable development of environment,the exploration and development of cementitious materials with low energy consumption and high environmental protection become extremely important.Alkali activated slag cement,as a new type of cementitious material,has attracted the attention of scholars at home and abroad for its advantages of energy saving,environmental protection and high performance.In this study,the corrosion of steel bars in gopolymer concrete(GPC)and ordinary concrete(OPC)is studied by means of electric accelerated corrosion test of steel bars in concrete.Aiming at the problem of bond performance between corroded steel bars and GPC and OPC,the central pull-out test was carried out,and the finite element simulation was used to modelling the bondslip relations.The main research work is listed below:1.Through the electrical accelerated corrosion test of reinforcement in concrete,the corrosion of steel bars in GPC and OPC was studied.It was found that the steel bars rusted earlier in OPC;when the corrosion rate of ordinary concrete specimens was about 1%,the corrosion cracking occurred.GPC specimens showed corrosion cracking later when the corrosion rate was 2%,and it was found by chloride titration test and mercury pressure test that,compared with OPC,GPC is better than OPC in terms of the kresistance to chloride ion erosion and the compactness of pore structure.2.Through the pull-out test,the bond performance between corroded steel bar and two kinds of concrete is studied.It is found that at the initial stage,the bond stress and the relative slip between steel bar and concrete will first increase and then decrease with the increase of the corrosion rate.The bond stress at the initial stage and the ultimate stage will decrease when the corrosion rate is about 0.5%,when the stress climbs to the pick.3.The bond strength between the two kinds of concrete and steel bars is similar when the steel bars are not corroded or at a low corrosion level.For OPC specimens,when the corrosion rate is larger than 0.5%,the bond strength decreases obviously;for GPC specimens otherwise,when the corrosion rate is greater than 1%,the bond strength starts to decrease.When the specimens are corroded and cracked,the bond stress of both steel GPC and steel OPC specimens decreases sharply,while the slip of steel increases.4.Based on the pull-out test results observed in this study,ABAQUS is used to simulate the pull-out test,and the finite element model of the pull-out specimen is established.The bond between steel bar and concrete is defined by using contact action and restraint action.Finally,the feasibility of simulating the bond between corroded steel bar and GPC is confirmed by verifying the simulation results using the test results.