Study On The Interface Behavior Between Magnesium Phosphate Cement Mortar And Cement Concrete

In addition to the vehicle load,the cement concrete pavement in the seasonal frozen area is also affected by the environmental effects during the service period,and there are many kinds of damage,such as corner cracks,water damage,freeze-thaw cycles damage and salt freeze-thaw cycles damage.In order to minimize traffic delays caused by road maintenance,rapid repair materials need to be developed.Magnesium phosphate cement(MPC)has attracted much attention as a rapid repairing material.In this study,the following aspects are mainly studied in terms of corner fracture of cement pavement in seasonal frozen area:The cement concrete pavement is repaired by basalt fiber reinforced and polymer modified magnesium phosphate cement mortar(BFPMPC mortar)in this research.Considering the stress requirement of pavement structure,the compressive strength and flexural strength tests of magnesium phosphate cement mortar at early age were carried out.Considering that the repairing materials are subject to the horizontal load of vehicles,the shear strength tests on the interface of the repairing materials and the concrete were carried out to evaluate the bonding performance.The strength test,freeze-thaw test and salt freez-thaw test were used to investigate the water damage and frost resistance.Then,the bonding mechanism between magnesium phosphate cement mortar and cement concrete was studied.The results show that the repair material presented in this paper not only has high strength at the early age,but also has good bonding property with the old cement road surface,good water resistance,frost resistance and salt frost resistance.The interfacial transition zone(ITZ),as the weakest area of the structure in mechanical properties,is usually prone to disease.The repaired interface were studied by the reasonable composites specimen with shear strength testing,nano-indentation and interface material properties tests such as scanning electron microscopy(SEM)and Energy Dispersive Spectrometer(EDS)which observe interfacial morphology,micro cracks,the performance and action mechanism.The results show that the MPC pastes was perfectly bonded to the cement paste in the ITZ,according to SEM/EDS,the cracks appeared at 10 μm away from Portland Cement Pastes(PCP)edge and the width after 6h and 3d was around 3~5 μm.The results of Nano-indentation indicate that the elastic modulus varied greatly in the ITZ and the lowest value located 10μm away from the PCP side.Based on the multi-scale method,the finite element model(FEM)was established in this research.Combined with the interface kinematics theory,the interface damage model was introduced.Then,the FEM was utilized by DIGIMAT and ABAQUS to verify the rationality of the interface damage theory and the interface damage model.MPC mortar can be used to repair the corner cracks of cement pavement in the seasonal frozen area,and BFPMPC mortar is better on the repair performance,showed on this research.