## 1 Introduction  
Bitumen pavement has been extensively employed in China, in view of its excellent properties such as low noise and good driving comfort [1]. In response to pavement distresses caused by the increasing traffic volume, loads, and other factors in early service conditions, virgin bitumen is usually required to be modified [2]. Polymers are the most commonly used modifier in bitumen, which mainly contain rubbers (e.g., styrene-butadiene rubber (SBR), chloroprene rubber (CR)), thermoplastic elastomers (e.g., styrene-butadiene-styrene (SBS)), thermoplastic resin (e.g., poluethylene (PE), ethylene-vinyl acetate (EVA)), and thermosetting resin (e.g., epoxy (EP)) [3; 4; 5; 6]. In most cases, bitumen properties are dramatically improved by adding a small amount of polymers. However, there are also some deficiencies such as the easy aging and degradation of polymers in the bitumen matrix, and the poor storage stability of polymer-modified bitumens, which results from the physical coexistence between them [7; 8]. In order to overcome these defects, many novel bitumen modifiers have appeared in recent years, and among them, layered silicates have been paid much attention to [9; 10; 11; 12]. As it is well known, layered silicates are characterized by being one dimension smaller than 100 nm in the dispersed phase [13; 14]. It is their small size and large specific surface area that endows them with surface effect, size effect, and barrier effect [12; 14; 15]. Hence, layered silicates with a small content, in general, largely improve bitumen properties [12; 14]. Additionally, they have layered nanostructures in which there are exchangeable cations [16]. Bitumen molecules are able to insert interlayers [9; 17; 18]. It is these characteristics that make bitumen molecules effectively blocked, thereby improving the high-temperature stability and aging resistance of virgin bitumen [19; 20]. The layered silicate chiefly consists of montmorillonite, recrotite, vermiculite, hectorte, saponite, and kaolinite [21; 22; 23; 24]. Generally, before incorporation into the bitumen matrix, the hydrophilic layered silicate is converted into an organophilic material by selecting an appropriate organic reagent to react with exchangeable cations, which improves the compatibility of the layered silicate with bitumen [25]. In addition, the interlayer space of the pristine layered silicates is expanded [20; 26; 27]. Most studies have been conducted regarding montmorillonite (MMT) as a bitumen modifier [18; 28; 29], the main reason of which is that MMT is a 2:1 layered smectite clay with two silica tetrahedral sheets sandwiching an alumina octahedral sheet [29; 30]. There exists a large amount of exchangeable cations (i.e., cation exchange capacity) between the 2:1 layers. Many organic reagent molecules can enter the MMT interlayers, thereby endowing MMT with excellent lipophilicity and great expansibility [31; 30; 32]. Therefore, organic montmorillonite (OMMT) particles with a large specific surface area are capable of effectively blocking the thermal motion of bitumen molecules, leading to the excellent thermal stability and aging resistance of OMMT-modified bitumen [17; 33]. By comparison, rectorite (REC) has a layered structure similar to MMT, which is composed of alternate pairs of a non-expansible dioctahedral mica-like layers and expansible dioctahedral montmorillonite-like layers, in a 1:1 ratio [24; 31; 34]. The exchangeable cations only lie in the interlayers of a 2:1 montmorillonite-like layer, which determines that REC, in most cases, has a lower cation exchange capacity than MMT. Nevertheless, the size (including the interlayer space and layer aspect ratio) of REC particles are larger than those of MMT [24; 35]. As a result, these differences in nature between MMT and REC possibly have an influence on bitumen properties. [PERSON] et al. [36; 37] have reported on the microstructures, aging properties, and flame retardancy of OMMT and organic recrotite (OREC)-modified bitumens.