Fracture Parameter Analysis Of Concrete Subjected To Calcium Leaching

The durability and service life of concrete structures under erosive water environment will be greatly affected due to the calcium leaching of concrete.Therefore,the calcium leaching issues on concrete should be addressed,especially for the calcium leaching model and the degradation of mechanical properties.To evaluate the service performance of concrete structures under erosive water environment,the following contents were studied in this paper.Firstly,a two-dimensional calcium leaching model was established to describe the concrete degradation in the erosive period on the basis of the leaching mechanism of concrete subjected to soft water and nitric acid.Then,a damage model was proposed to reflect the chemo-mechanical damage interaction on the mechanical properties of concrete.Furthermore,based on the fracture mechanics,the distribution of the closing force in the precritical crack propagation zone was defined and the deterioration regularity of double-K fracture parameters of concrete under different calcium leaching periods was analyzed.Finally,the fracture process of three-point bending concrete beams with different erosion depths were simulated by the extended finite element method(XFEM)with the aid of ABAQUS.The results show that the leaching depths of concretes subjected to soft water and nitric acid are proportional to the square root of time,and the simulation results are in good agreements with the experimental results.Calcium leaching is a continuous process,and it reduces the mechanical properties of concrete.Compared with the intact concrete,the distribution of the closing force in the precritical crack propagation zone of concrete after the calcium leaching is changed obviously.The fracture toughness of concrete decreases with the erosion period,but the the unstable fracture toughness is more sensitive to calcium leaching than the initial fracture toughness.The cohesive toughness of concrete also decreases with the erosive period because the calcium dissolution deteriorates the mechanical properties of concrete.When the main crack propagation zone passes through the erosion part of concrete,the closing force decreases and eventually leads to the decrease of cohesive toughness.When the extended finite element method is adopted to analyze the fracture process of erocded concrete,the simulation results are in good agreement with the experimental results,which shows that this method is effective to predict the fracture properties of concrete subjected to calcium leaching.