Research And Microstructure Analysis Of Cement Asphalt Mortar In Extreme Weather Conditions

As the key functional material of CRTS type ballastless track,CA mortar can be seen as a semi rigid cementitious material.Its mechanical properties are highly sensitive to temperature.Our country has a wide range of climate and regional temperature difference.CA mortar is mostly in the diversity temperature environment in operation.Many scholars have done research on cement asphalt mortar at different temperatures,but most of them are qualitative and macroscopic.In this paper,the mechanical properties of cement asphalt mortar under extreme climatic conditions are studied from two aspects of qualitative and quantitative.The changes of the internal components of CA mortar under the action of temperature cycling are analyzed from the view point of meso scale.Draw the following conclusions:(1)Read a large number of domestic and foreign literature and contact the actual situation of CA mortar and design the mechanical properties test and temperature cycling test of CRTS Ⅰand CRTS Ⅱ type CA mortar specimens under extreme temperature.The experimental results show that with the increase of temperature,the compressive strength and elastic modulus of CRTS Ⅰ CA type mortar decrease,the brittleness decreases and the plasticity increases.CRTS Ⅱ type CA mortar is similar to ordinary cement mortar,and has low temperature sensitivity.With the increase of the number of cycles,the compressive strength and elastic modulus of CRTS Ⅰ type CA mortar increased and then decreased.The compressive strength and elastic modulus of CRTS Ⅱ type CA mortar increased slightly at the beginning of the cycle,and then it is in a stable state.(2)Starting from the angle of energy transformation,analyzes the transformation process of CRTS Ⅱ type CA mortar under uniaxial compression test at different temperature.The analysis showed that with the increase of temperature(-50℃-80℃),the total power is more and more small,elastic energy is more and more small,the power dissipation is accelerated and the better damping performance in the same strain level.(3)By CT scanning technology,analyzed the changes of the internal components of the two types of CA mortar in the process of temperature cycling.Test results show:With the increase of the number of temperature cycles,the volume fraction of emulsified asphalt in CRTS ⅠCA type mortar increases,the porosity increases,and the emulsified asphalt is changed from dispersed state to network type.The porosity of CRTS Ⅱ type CA mortar increased initially,and then remained unchanged,The main factor that influences the macroscopic mechanical properties is the formation of the emulsified asphalt network and little correlation with porosity variation.Analysis results of CT gray value of section profile show:with the increase of the number of temperature cycles,the gray value stability of the edge zone of CRTS Ⅰ and CRTS Ⅱ CA mortar is not as good as that of the middle zone.The density change of the edge zone is larger than that of the middle area,and the aging phenomenon is larger than that of the middle zone,and the aging delamination phenomenon of CA mortar occurs.