Experimental Study on a Novel Modified Magnesium Phosphate Cement Mortar Used for Rapid Repair of Portland Cement Concrete Pavement in Seasonally Frozen Areas

In this study, basalt fiber-reinforced and polymer-modified magnesium phosphate cement (BFPMPC) mortar, a novel rapid repair material, is proposed for portland cement concrete pavements (PCCP). A practical mixture design was selected from the orthogonal experiments. The properties of this mixture under different environments were studied. Considering the horizontal load of vehicles, the bonding mechanism between magnesium phosphate cement (MPC) mortar and PCCP was studied through shear strength tests. The experimental results show that the BFPMPC mortar proposed has not only reliable compressive and flexural strengths but also good water resistance in the interfacial transition zone (ITZ) and good bonding performance with the old cement concrete. Additionally, the ITZ between the BFPMPC mortar and old concrete has good freeze-thaw resistance. Then, the salt freeze-thaw cycles were found more destructive to the repair interface than freeze-thaw cycles. The addition of the styrene-butadiene copolymer (SBC) emulsion in BFPMPC mortar was formed without new hydration components, which was observed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The ability to enhance the bonding strength with the addition of SBC was found by scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS). In summary, the BFPMPC mortar can be used as a rapid repair material for PCCP in seasonally frozen areas.