## 1 Introduction  
Concrete mixed with lightweight aggregates (LWAs) instead of normal-weight aggregates is called lightweight aggregate concrete (LWAC). Since most LWAs are porous and have a low specific gravity, LWAC is lightweight and has better seismic resistance than traditional normal-weight aggregate concrete (NWC) [1]. Taking structural LWAC as an example, its main benefit is to reduce the weight of the structure so the size of columns, foundations, and other stress-bearing members can be reduced. Therefore, the inertial force generated by an earthquake due to the structure is relatively small, and the design load can be reduced to save on construction costs. Moreover, LWAC has very good thermal insulation performance, and its thermal conductivity is only half that of ordinary NWC. However, LWAC usually has higher levels of brittleness and worse mechanical properties compared with NWC, which has the same compressive strength [2]. With the innovation of modern science and technology, on the one hand, the production technology used for artificial lightweight aggregates (LWAs) has been continuously improved. On the other hand, nanosilica, nanoscale titanium oxide, and various fibers have been appropriately mixed into LWAC [3; 4; 5; 6]. Therefore, fiber-reinforced LWAC with a high strength and good toughness has emerged as the times required, making its application in structural concrete more common [7; 8; 9; 10]. In reinforced concrete (RC) members, most researchers agree that the bond behavior between the rebars and the concrete mainly consists of three resistance mechanisms: adhesion, friction resistance, and rib support [11; 12; 13; 14; 15; 16; 17]. In terms of exploring the bond behavior between concrete and rebar, pull-out tests are generally used. Many studies have explored the bond behavior of rebar to LWAC at room temperature. Previously, the strength of LWAs was lower, resulting in LWAC having a worse bond strength than NWC at the same level of compressive strength [18]. However, some studies have shown the opposite result, namely, that LWAC has a better bond strength. The research conducted by [PERSON] et al. [19] showed that the peak bond stress of a well-confined LWAC could be expressed as \(3.5\sqrt{f_{c}^{\prime}}\). This is significantly larger than the value of \(2.5\sqrt{f_{c}^{\prime}}\) suggested by the CEB-FIP standard [20]. [PERSON] et al. [21] established a theoretical analysis model for the bond stress slip between rebar and LWAC. [PERSON] et al. [22] studied the bond-slip behavior between corroded bars and LWAC. [PERSON] et al. [23] proposed a bond-slip relationship of rebar in LWAC under the influence of additional embedded rebar around the central rebar. [PERSON] [1] studied the uniaxial bond stress-slip behavior of reinforcing bars in LWAC. The results showed that the larger the rib height to the diameter ratio of the rebar, the greater the peak bond stress. In contrast, there is relatively little research on the bond behavior between rebar and LWAC after being exposed to high temperatures. The chemical composition, physical structure, and water vapor moisture content of LWAC change when it is exposed to high temperatures. This results in a severe decrease in its mechanical properties, thereby affecting its bond behavior with steel bars. [PERSON] et al. [24] pointed out that the failure of RC members exposed to fire mainly arises due to the reduction in the bond strength between the embedded rebar and concrete. [PERSON] et al. [25] conducted experimental studies on the bond-slip behavior of rebar in fiber-reinforced LWAC at ambient and elevated temperatures, respectively. Their experimental results showed that exposure to high temperatures changed the failure mode from a more ductile pull-out mode to a brittle splitting mode. As a result, the peak bond strength and toughness of the specimen's bond-slip behavior were reduced. [PERSON] [26] studied the effects of steel fiber and polypropylene fiber blending on the bond strength of LWAC after being exposed to high temperatures.