## 1 Introduction
The results showed that the blending method of using one type of fiber or mixing two types of fiber had no significant effect on the residual bond strength of LWAC after being exposed to a temperature of 800 \({}^{\circ}\)C.  
Due to many unavoidable factors, RC members often exhibit cracks or local damage. If these cracks or local damage are not repaired in time or are handled improperly, it will further lead to the loss of bond strength between the rebar and concrete [27]. Therefore, repairing damaged concrete to ensure the performance of RC components has always been a research focus in academic circles. General repairs use commercially available chemicals and polymers, which are sources of health and environmental risks [28]. In addition, these methods of repairing damaged concrete structures are less than satisfactory. In view of this, many researchers have changed their approach to biomineralization technology [29; 30; 31; 32; 33]. The use of insoluble compounds produced through microbial metabolism to fill cracks in concrete materials is a developing self-healing technology for concrete [34; 35; 36]. Therefore, research on microbial-induced calcium carbonate precipitation (MICP) to repair concrete cracks is gaining prominence. However, if unprotected bacteria are added directly to concrete, which is highly alkaline in nature, it can easily lead to bacterial death. This resultsin a substantial reduction in bacterial populations [29]. [PERSON] et al. [30] confirmed that alkali-resistant spore bacteria have the ability to repair cracks in concrete. To avoid the reduction in or disappearance of the bacterial population, appropriate carriers must be used to protect the bacteria [31]. [PERSON] et al. [32] used bacteria to repair concrete cracks caused by high temperatures and improve concrete properties. Their test results showed that specimens repaired using Saccharomyces pasteurianus and Bacillus sphaeroides showed a 31-93% increase in compressive strength. [PERSON] et al. [33] explored the feasibility of using biomineralization technology to repair the performance of fiber-reinforced LWAC after exposure to high temperatures. The test results showed that, in the absence of nutrient sources, the bacterial mineralization rate of the test specimen was slow. [PERSON] et al. [9] applied biomineralization technology to improve the bond strength of fiber-reinforced LWAC damaged in pull-out tests. Their test results show that biomineralization technology could effectively improve the residual bond strength of the damaged specimens. The principle of MICP technology is to use the bacteria found in nature that can produce urease through their own metabolic activities to decompose carbon sources in the surrounding environment [37]. It then undergoes a biomineralization reaction with the calcium source material to form dense calcium carbonate precipitation with a cementing effect. The minerals formed are naturally pollution-free and have high cementing properties. They can better replace the traditional cementing building materials currently on the market, such as epoxy resin, polyurethane, cement, etc., effectively avoiding chemical erosion of the environment [38]. The concept of this technology was proposed in the early 21 st century and is still being improved. Research directions include the selection and culture of bacteria and the effects of changes in temperature, acid, liquid concentration, injection rate, and other conditions on cementation strength during the mineralization process. At present, this technology can be realized relatively stably under certain experimental conditions, and it is mainly used in four applications: solidifying soil, repairing concrete cracks, impermeabilizing building materials, and controlling heavy metals or radioactive metals. From this point of view, MICP technology contributes to the sustainability of building materials [39; 40]. This study aims to apply MICP technology to improve the bond strength of fiber-reinforced LWAC after high-temperature and pull-out damage.