A rapid-hardening cement emulsified asphalt (CEA) mortar prepared from magnesium phosphate cement

Cement emulsified asphalt (CEA) mortar is the key component material of high-speed railway track slabs, and it is prone to damage under the coupling effect of environment and load. For severely damaged CEA mortar, the strategy of replacing the filling layer is required. However, the daily idle period of high-speed railways is extremely short in China, which makes Portland cement-based CEA mortar unable to meet the time and material performance requirements of high-speed railway maintenance. Therefore, a novel magnesium phosphate cement-based CEA (MEA) mortar is prepared in this study, and the effects of key parameters on its fresh properties, strength, and durability are systematically investigated. A MEA mortar with a setting time within 30 min and a compressive strength of 15–45 MPa is developed. Increasing the emulsified asphalt to cement (EA/C) ratio reduces the strength, water resistance, and frost resistance of MEA mortars, mainly because increasing the EA/C ratio leads to decreased reaction products and increased porosity. Meanwhile, increasing the EA/C ratio also leads to a higher volume expansion of the MEA mortar. In addition, adding an appropriate amount of emulsified asphalt with low water content can increase the setting time and failure strain of the MEA mixture compared with the plain magnesium phosphate cement component, and it performs better than emulsified asphalt with high water content. This study demonstrates acceptable performance of MEA mortar prepared with appropriate EA/C ratio and type of emulsified asphalt, which provides an alternative material for track slab maintenance.