Isocyanate-Functionalized Layered Double Hydroxides for Simultaneous Enhancements of Asphalt Storage Stability and Low Temperature Performance

Layered double hydroxides (LDHs) can significantly improve the aging resistance of asphalt, but the poor storage stability and low temperature performance of LDHs modified asphalt (LDHs-MA) restrict its large-scale application in asphalt pavement. In order to simultaneously improve the storage stability and low temperature performance of LDHs-MA, isocyanate-functionalized LDHs (I-LDHs) were prepared by surface treatment with isocyanate. Then, I-LDHs-MA was prepared, and the effects of I-LDHs on physical properties, storage stability, high and low temperature properties, and aging resistance of asphalt were studied. The results showed that isocyanate that could react with the active groups in asphalt was successfully grafted onto LDHs surface, and thus the compatibility between asphalt and isocyanate surface modified LDHs was improved. When the I-LDHs content was 2%, 4%, 6%, and 8%, the softening point difference of I-LDHs-MA was reduced by 71.43%, 36.36%, 40%, and 47.62%, respectively, compared with LDHs-MA. I-LDHs-MA also has better physical properties and high and low temperature properties than LDHs-MA. The low temperature properties of 6% I-LDHs-MA at -18°C can still meet the requirements of the specifications. Meanwhile, I-LDHs-MA showed better antiaging properties. In comparison to LDHs-MA, the softening point increment of I-LDHs-MA with 2%-8% contents of I-LDHs all decreased to some extent after pressure aging vessel aging and ultraviolet aging. This study lays a foundation for the preparation of asphalt with good storage stability, high and low temperature performance, and aging resistance.