Effect of synchronous surface grafting and intercalation bentonite on properties of SBS modified bitumen
To better enhance the improvement effect of natural bentonite on the comprehensive performance of styrene-butadiene-styrene thermoplastic elastomer modified bitumen (SMB), in this study, 3-(trimethoxysilopropyl) dimethyl octadecyl ammonium chloride (DC5700) was used for synchronous surface grafting and intercalation of bentonite (DC5700-Bentonite). Meanwhile, γ-(2,3-epoxypropoxy)propytrimethoxysilane (KH560) surface grafting bentonite (KH560-Bentonite) and octadecyldimethylbenzylammonium chloride (ODBA) intercalation bentonite (ODBA-Bentonite) were used as comparison samples. The structure and properties of the bentonite and organic bentonites (DC5700-Bentonite, KH560-Bentonite and ODBA-Bentonite) were tested by X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FTIR), ultraviolet-visible spectrometer and contact angle measurement . The effects of bentonite and organic bentonites on physical, rheological and aging properties of SMB were investigated. FTIR and XRD results showed that KH560 was chemically grafted onto the surface of bentonite, ODBA was organically intercalated into the bentonite, while DC5700 achieved synchronous surface grafting and intercalation on the bentonite. Compared with KH560-Bentonite and ODBA-Bentonite, DC5700-Bentonite had the best lipophilicity and ultraviolet shielding ability. When the bentonite content was 4 wt% , KH560-Bentonite, ODBA-Bentonite and DC5700-Bentonite could increase the rutting factor of SMB by 2.9 ℃, 4.9 ℃ and 6.5 ℃, respectively, and reduce the ductility of SMB by 6.5 cm, 4.2 cm and 3.1 cm. Meanwhile, compared to SMBs containing KH560-Bentonite or ODBA-Bentonite, the SMB containing DC5700-Bentonite had the smallest creep stiffness at − 12 ℃, − 18 ℃, and − 24 ℃. The results indicated that DC5700-Bentonite was more conducive to increasing high-temperature performance of SMB than KH560-Bentonite and ODBA-Bentonite, and its adverse effects on low-temperature ductility and low-temperature cracking resistance of SMB were also significantly reduced. After thermal and ultraviolet aging, the deterioration extent of physical and rheological properties of SMB containing DC5700-Bentonite was significantly smaller than that of SMB containing KH560-Bentonite and ODBA-Bentonite. FTIR revealed that DC5700-Bentonite was more beneficial than KH560-Bentonite and ODBA-Bentonite in inhibiting the increase of carbonyl index and the decrease of butadiene index in SMB during aging. The comprehensive results revealed that compared to KH560 surface grafting bentonite and ODBA intercalation bentonite, DC5700 synchronous surface grafting and intercalation bentonite were more conducive to improving the physical and rheological properties, and aging resistance of SMB.
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