## 1 Introduction  
The concept of ultra-high performance concrete (UHPC) appeared in the 1990s [1], and one of the most widely used is Reactive Powder Concrete (RPC). As a new class of cement-based material, RPC has become the focus on developing cement materials due to its great strength, high tenacity and outstanding durability [2; 3]. Traditional RPC improves the homogeneity and compactness of the matrix by eliminating coarse aggregate and adding active constituents such as silica fume and fly ash [4]. This ultra-compact microstructure results in low permeability and high durability. Previous studies have verified that the compressive strength of RPC can reach 200-800 MPa, together with the ultimate tensile strain on the order of 1% [5]. To further enhance the performance, steel fibers are commonly chosen for reinforcement to promote the ductility and the flexural strength of RPC [6]. Nowadays, RPC is considered as a promising material for use in special pre-stressed and precast concrete components. Although the production cost of RPC is generally high, its ultra-high mechanical properties make it possible to reduce the thickness of concrete members, which results in reducing material consumption. Therefore, it also has economic advantages in practical application. Basalt fiber has been used for many years as a reinforcing material in concrete technology. This fiber is a kind of environmental protection material with high performance and is made of natural basalt. Due to its high tensile strength, excellent elastic modulus and superior corrosion resistance, basalt fiber is a beneficial admixture for concrete. The addition of steel fiber in RPC not only affects the production costs, but also has negative effects on the dead load and may cause corrosion problems [7]. Replacing steel fibers with basalt fibers seems to be a feasible solution to these problems [8]. In addition, incorporation of basalt fibers may positively impact the workability of concrete. [PERSON] et al. [9] found that, when the mass content reaches 12 kg/m\({}^{3}\), the strengthening effect of basalt fiber on the flexural strength and impact strength of concrete is similar to that of steel fiber. It has been validated that the addition of 0.15% basalt fiber and 0.033% polypropylene fiber can increase the flexural and compressive strength of high-performance concrete by 14.1% and 22.8%, respectively [10]. [PERSON] et al. [11] found that the maximum compressive strength could reach 84.08 MPa with a volume content of 2% basalt fiber in UHPC when 10% cement was replaced by silica fume and kaolin. The damage of concrete materials including matrix cracking and the fracture caused by fiber pulling out. If the fracture processes and cracking patterns of concrete can be determined, the structure can be strengthened with appropriate design to enhance the resistance to specific fracture patterns. Meanwhile, it would lead to an early warning to final fracture. Nowadays, there is a technique that has shown enormous potential for real-time monitoring and evaluation of material damage called acoustic emission (AE). The acoustic emission is a non-destructive testing (NDT) technique with the advantages of high sensitivity and full period online monitoring [12]. In recent years, AE technology has been widely used in the construction field, such as crack monitoring and damage assessment of reinforced concrete beam [13], shear wall [14] and short wall [15]. Previous studies have shown that the AE generated by solid fracture is similar to the propagation mode of seismic waves. In reference to the Gutenberg-Richter empirical relation in seismology, the b-value method can be adopted to analyze AE data [16]. [PERSON] et al. [17] established the damage assessment system of fiber-free concrete by Hilbert-Huang Transform processing of AE data, verifying the role of AE technology in the monitoring and health assessment of infrastructure service status. AE technology can also locate the internal damage of the structure. [PERSON] et al.