# Experimental Investigation of TR-UHPC Composites and Flexural Behavior of TR-UHPC Composite Slab
## 1 Introduction  
China has the largest number and scale of bridges in the world [1]. However, many of these bridges were constructed in the 1980s and 1990s, and as a result, they have been in service for too long to the end of their service life as well as outdated design specifications. Pedestrian walkway slabs, as subsidiary components of bridge decks, are often constructed using reinforced concrete (RC). However, issues such as spalling, the delamination of protective layers, and corrosion of reinforcement commonly occur in RC slabs. These degradation problems are particularly pronounced in marine environments [2, 3]. Severe deterioration can significantly impact the overall structural integrity of bridges, while other structures such as galvanized steel pedestrian walkway slabs have a longer lifespan. However, when the steel plates are thin, the structure exhibits low stiffness, resulting in significant deflection and reducing the comfort and safety of pedestrians. On the other hand, increasing the thickness of the steel plates incurs higher economic costs, and the added self-weight significantly reduces the structural safety. Ultra-high-performance concrete (UHPC), as a new generation of building material emerging in the late 20 th century, possesses outstanding properties such as ultra-high strength [4, 5] and high toughness [6]. Its exceptional durability is particularly noteworthy, enabling it to effectively adapt to corrosive environments [7]. In recent years, UHPC hasgradually been adopted in China as a primary construction material for main bridge structures [8; 9], pedestrian walkway covers [10; 11], bridge decks [12; 13], and other applications, showcasing broad prospects for its usage. By leveraging existing research, applying UHPC with its high strength, toughness, and durability to pedestrian walkway slabs can address the issues of corrosion and insufficient durability commonly associated with conventional RC slabs. Research indicates that the self-weight of pedestrian walkway slabs accounts for approximately 7% in the long-term loads of railway bridges and about 15% for highway bridges [14]. Using UHPC to make ribbed pedestrian walkway slabs is capable of reducing the thickness and self-weight of slabs [15]. According to JTG D62-2018 [16], the prefabricated concrete pedestrian walkway slab should possess a thickness no less than 60 mm. In this thickness, UHPC ribbed slabs can reduce the self-weight by more than 50%, which can improve the long-term performance of main girders by reducing the long-term stress and thus the creep effect. Simultaneously, the high durability of UHPC can reduce the maintenance cost of the bridge and facilitate transportation, emphasizing an economic advantage. However, unreinforced UHPC slabs are susceptible to cracking, low-load bearing capacity, and brittle failure when subjected to external loads [17; 18]. If two or more layers of rebars are arranged in the slab and subjected to both positive and negative bending moments, the slab thickness must be increased to satisfy the requirement on durability, thus increasing the slab's cost and the self-weight of the whole bridge. Fiber textiles have the advantages of high strength, light weight, and excellent durability [19; 20]. Fiber textile reinforced cementitious materials such as textile reinforced UHPC (TR-UHPC) can improve the ductility and enhance the toughness of UHPC. The multi-layer fiber fabric is arranged in the UHPC matrix, which is conducive to the directional distribution of short fibers, and the two cooperate to exert better mechanical properties. [21]. [PERSON] et al. [22] investigated the vertical tensile mechanical properties of a layer-casted textile reinforced concrete (TRC) composite. The results indicated that defects during casting have little impact on the tensile mechanical properties of the TRC composite when the textile reinforcement ratio is high. Additionally, the test results showed low dispersion. [PERSON] et al.