# Safety Performance Evaluation of Ultra-High-Performance Concrete Semi-Assembled Barrier
## 1 Introduction  
As a critical component of road safety facilities, barriers contribute to preventing vehicles from crossing central dividers or breaching roadside barriers, thereby mitigating potential harm to occupants. Among the various types of barriers, concrete barriers stand out for their robust protective abilities and cost-effectiveness, which effectively reduce casualties and property damage. Generally deployed along highways, concrete barriers serve as essential protective structures, which effectively contain vehicles within road boundaries following collisions. Numerous scholars have extensively researched the optimization of structural designs and materials for concrete barriers to improve their protective performance [1, 2, 3]. [PERSON] et al. [4] proposed a movable concrete barrier, surpassing traditional concrete and W-beam barriers, thereby effectively reducing occupant injuries. [PERSON] and [PERSON] [5] proposed the new concrete barrier, comprising expanded polystyrene concreteas the outer material and plain concrete as the inner material. Their verification met the collision requirements for concrete barriers through experiments and simulations. [PERSON] et al. [6; 7] embedded foam concrete and recycled foam concrete as buffer materials in reinforced concrete barriers. This demonstrated buffer capacity in simulations and numerical calculations. The investigations discussed herein primarily utilized ordinary reinforced concrete as the main barrier material. These barriers are typically installed using cast-in-place or prefabrication processes. Cast-in-place concrete barriers involve the cumbersome process of installing scaffolding, formwork, steel bars, and on-site pouring, which leads to slow construction progress and quality challenges. Prefabricated concrete barriers have been developed to address these shortcomings. This can significantly improve construction efficiency and material quality [8; 9]. However, the weight of prefabricated barriers poses transportation and assembly challenges, particularly for longer sections such as the 4 m SB-level barrier, which can weigh up to 4 tons. This results in increased costs and on-site assembly difficulty. Moreover, ordinary reinforced concrete lacks sufficient resistance to salt corrosion, freeze-thaw cycles, and carbonation, which leads to reduced durability, particularly in coastal areas and snowy regions [10]. Additionally, the higher repair costs of concrete barriers further compound these challenges. Therefore, developing new semi-assembled concrete barrier products with extended lifespans and simplified installation processes is imperative. In 1994, [PERSON] and [PERSON] [11] proposed the groundbreaking concept of ultra-high-performance concrete (UHPC). He achieved this by utilizing a low water-binder ratio of 0.14, resulting in a compressive strength of 236 MPa after steam curing for 4 d at 90 \({}^{\circ}\)C. UHPC has garnered widespread attention owing to its exceptionally high mechanical properties [12; 13; 14], extremely low porosity [15; 16], remarkable durability [17; 18; 19; 20], and superior impact resistance [21], which far exceed those of normal concrete. It thereby exhibits profound application prospects in infrastructure (bridge, municipal, power, water) engineering applications, construction applications, structural repairs and strengthening et al. [22; 23; 24]. Based on the aforementioned research, it is evident that integrating UHPC into the prefabrication process of semi-assembled barriers as the barrier shell material can fully exploit its characteristics, such as high strength, exceptional toughness, and outstanding durability. The prefabricated construction method involves fabricating the barrier shell offsite and then transporting it to the construction site for splicing. Filling the interior of the UHPC shell with NC significantly reduces the barrier's weight and transportation costs.