# Effect of Characteristics of Different Types of Bauxite Clinker on Adhesion
## 1 Introduction  
Bauxite clinker is obtained by calcining raw bauxite in a rotary kiln or up-draft kiln at a high temperature to achieve a certain porosity ratio, water absorption ratio and volume density, and then to form relatively stable phase composition and microstructure [1]. Refractory material taking bauxite clinker as aggregate is widely used in steal making, iron smelting and other industries. Based on the fact that bauxite clinker has small thermal conductivity [2] and excellent skid resistance and wear-resisting property [3; 4; 5], it can be used in HFST(high friction surface treatment) or the abrasion layer of asphalt mixture to replace or partly replace the existing aggregate [6]. Bauxite clinker is the only aggregate that can provide long-term anti-skid performance [7; 8; 9]. It has important practical significance to apply bauxite clinker to replace some or all aggregates in asphalt mixtures to improve the long-term skid-resistance performance of asphalt mixture. The interfacial adhesive property between aggregate and asphalt varies with different aggregate types and the effect of aggregate on water sensitivity is greater than that of asphalt [10]. Therefore, it is necessary to study the adhesion characteristics between bauxite clinker and asphalt. Several studies have been conducted to evaluate the adhesion of asphalt and aggregate; especially in recent years, with the intersection and integration of multiple disciplines, new evaluation methods emerge, including water-boiling method, static flooding test [11], dynamic oscillation stripping test [12], rotating bottle test [13], SHRP net adsorption method [14], surface energy test [15], ultrasound method [16], pull-out test [17] and peeling test [18]. In addition, the influence of adhesive factors has been studied extensively, especially the influence factors of aggregate properties on adhesion. The aggregate characteristics affecting adhesion majorly include: the shape feature, chemical composition and structural parameters (porosity, density, and pore volume) of aggregates.Zhang [PERSON] et al.studied the effect of mineralogical composition of aggregates on adhesion. The results show that the clay, calcite, soda feldspar, quartz and potassium feldspar contained in aggregate have adverse effects on adhesion, while the calcite has positive effects [7]. [PERSON] analyzed the effects of the mineralogical composition of aggregate (limestone and granite) on the interfacial bond property and pointed out that the bond property of limestone-asphal interface mainly depends on the chemical composition of aggregate having been transferred to asphalt, while bond property of granite-asphal interface mainly depends on the physical bonding between aggregate and asphalt [19]. [PERSON], [PERSON] et al., [PERSON], [PERSON] et al. and others studied the effects on water sensitivity from the angularity of coarse aggregate [20; 21]. [PERSON] reported that the geometry of aggregate has an important effect on the adhesion property, especially under the low temperature and aging conditions, and the effect is quite obvious [22]. [PERSON] studied the effect of aggregate morphology on the adhesion property of asphalt-aggregate [23]. [PERSON] studied the effect of structural characteristic parameters of aggregate, such as the effect of pore structure, porosity, average pore size and others on the adhesion property of asphalt-aggregate [24]. When the aggregate type changes, it will inevitably affect the adhesion, and thus the thermal stability, of asphalt mixture. Bauxite clinker has been classified into aiz categories, generally based on the content of Al\({}_{2}\)O\({}_{3}\), Fe\({}_{2}\)O\({}_{3}\), TiO\({}_{2}\), CaO and MgO contained in the bauxite clinker [25]. The higher is the content of Al\({}_{2}\)O\({}_{3}\) and the lower are the contents of other components, the higher is the grade of bauxite clinker. The key research questions were: What grade of bauxite clinker exerts the best adhesion with asphalt?