Preparation and properties of a layered double hydroxide deicing additive for asphalt mixture

Abstract

Mg-Al Cl− layered double hydroxide (LDH) was prepared from Mg-Al CO32− LDH by the calcination recovery method. Energy-dispersive spectroscopy spectra show that Cl− anions replace CO32− anions in the LDH structure. X-ray diffraction patterns and scanning electron microscopy images show that the intercalation spacing and platelet thickness of Mg-Al Cl− LDH are larger than those of Mg-Al CO32− LDH. This increase in the structural dimensions occurs partially because a larger quantity of monovalent Cl− anions than divalent CO32− anions is required to balance the positive charges of the LDH metal cations. The results of melting ice point (MIP) tests indicate that Mg-Al Cl− LDH is more effective than Mg-Al CO32− LDH in decreasing the MIP of water. Freezing points (FPs) of asphalt mixtures show that Mg-Al Cl− LDH can reduce FPs. At temperatures below the FPs of asphalt mixtures containing Mg-Al Cl− LDH, the adhesion forces between ice and asphalt mixtures show that Mg-Al Cl− LDH can facilitate ice removal. Immersion tests were conducted to investigate the effect of rain on the melting ice properties of asphalt mixtures. FPs and adhesion force for Mg-Al Cl− LDH do not change after immersion, indicating that rain should not affect the properties of melting ice of Mg-Al Cl− LDH. Conductivities of immersion liquids show that Mg-Al Cl− LDH enables Cl− anions to be retained in asphalt mixtures without adversely affecting the surrounding environment and pavement.