Experimental Study On Cyclic Loading And Unloading Of Mechanical Properties Of Reinforced Cement

Cement mortar has been the most important building material in recent years as it always has a large amount of demand.The quality of cement mortar has a great i MPact on the safety of the buildings.Besides,the research on the performance of cement mortar is one of the important topics in the field of civil engineering.Therefore,the research of the mechanical properties of reinforced concrete mortar under cyclic loading and unloading circumstance would have a great iMPact on solving engineering practical problems.A SAW-2000 Microcomputer controlled electro-hydraulic servo rock-testing machine was used by this research.A stress-strain curve was obtained by the cyclic loading and unloading test of the cement mortar and the reinforced concrete mortar.The mechanical properties of the specimen and the image of the hysteresis loop were obtained by using the Origin software to deal with the data processing.Moreover,this study applied the Ansys numerical simulation software to enrich the load gradient of the experiment so that the stress-strain curve,the whole displacement cloud image and the stress cloud diagram of the reinforced cement mortar column under the cyclic loading and unloading condition in an ideal circumstance.This research analysed the stress-strain curve obtained by the cyclic loading and unloading experiment and made a simulation of the stress – strain by means of the Ansys numerical simulation software,so that the mechanical properties are obtained.When we made the fixed load level cycle loading and unloading experiment for reinforced concrete mortar column with a load level of 6MPa,the axial strains of the reinforced cement mortar column are 0.311%?0.323%?0.334%?0.340%?0.348%?0.355%?0.359%?0.361%?0.365% respectively and the amplitudes of each axial strain are 3.86%?3.31%?1.84%?2.39%?1.81%?1.13%?0.75%?1.08% respectively.When the load level becomes 5MPa,the axial strains of the reinforced cement mortar column are 0.303%?0.317%?0.330%?0.337%?0.343% respectively whilst the amplitudes of each axial strain are 4.17%?4.00%?2.31%?3.68%.When the load level becomes 7MPa,the axial strains of the reinforced cement mortar column are 0.317%?0.329%?0.337%?0.342%?0.352%respectively,meanwhile the amplitudes of each axial strain are 4.17%?4.00%?2.31%?3.68%.After nine cycles of loading and unloading experiments for reinforced concrete mortar column,the areas of the hysteresis loop formed by each cycle are 0.08275×106J/m3?0.08009×106J/m3?0.07814×106J/m3?0.07651×106J/m3?0.07629×106J/m3?0.07814×106J/m3?0.07926×106J/m3?0.07172×106J/m3 respectively.The ranges of variation of each new hysteresis loop are-3.21%?-2.43%?-2.08%?-0.28%?2.42%?1.43%?-9.51% respectively.When we made the load gradient incremental loading and unloading experiments for reinforced concrete mortar column with a load level of 1MPa,and reinforced concrete mortar column was under the stress of 3.5MPa?4.5MPa?5.5MPa?6.5MPa?7.5MPa and been destroyed,the axial strains are 0.118%?0.161%?0.240%?0.317%?0.429%?0.822%.The amplitudes of axial strain are 36.44%?49.07%?32.08%?35.33%?91.61%.When the load level becomes 2MPa and the reinforced concrete mortar column was under the stress of 3.5MPa?5.5MPa?7.5MPa and been destroyed,the axial strains are 0.118%?0.241%?0.429%?0.822%.The amplitudes of axial strain are 103.34%?78.25%?91.64%.When an incremental load gradient cyclic loading and unloading experiment was made with a load gradient of 2MPa for prime cement mortar,the areas of the hysteresis loop formed by each cycle are 0.03675×106J/m3?0.07291×106J/m3 and the range of variation of hysteresis loop's area is 98.39%.When an incremental load gradient cyclic loading and unloading experiment was made with a load gradient of 2MPa for reinforced concrete mortar column,the areas of the hysteresis loop formed by each cycle are 0.01868×106J/m3? 0.03217×106J/m3?0.06953×106J/m3 and the ranges of variation of hysteresis loop's area are 72.22%?116.13%.The axial strain of the cement mortar column is proportional to the number of times of cyclic loading and unloading.The overall displacement of the cement mortar column is proportional to the number of times of cyclic loading and unloading.The hysteresis loop in the stress-strain curve would increase with the increasingly number of times of cyclic loading and unloading experiment so that resulting in the total energy loss would also increases.Reinforcement will cause the cement mortar column to withstand greater axial stress and increase the friction of the internal cracks in the cement mortar column during axial compression.The essence of cement mortar column destroy is the uneven pressure inside cement mortar column.The forces are in different directions,resulting in the cement mortar column splitting damage.The process of the initiation,development and the expansion to penetrate of the fine crack is acco MPanied by the absorption and release of the energy.Therefore,the research of the mechanical properties of the dissipated energy dissipated in the reinforced cement mortar from the perspective of energy could link the energy method to the macroscopic characteristics of reinforced cement mortar damage.