## 1 Introduction  
Ultra-high-performance concrete (UHPC) stands out among construction materials as an extraordinary marvel that surpasses conventional constraints [1]. UHPC has key characteristics like a high particle packing density (0.825-0.855), a low water-to-binderratio (0.15-0.25), steel fiber content exceeding 2%, and suitable chemical admixtures [2]. In this respect, UHPC has transformed the construction sector by offering attributes like outstanding strength, excellent durability, acceptable ductility, and crack resistance, enabling the construction of lighter, more flexible, and visually appealing structures [1; 3]. The outstanding performance of UHPC has resulted in its use in various construction projects, ranging from bridges and high-rise buildings to architectural marvels [4; 5; 6]. Over the past three decades, UHPC has undergone four phases of evolution [2]: (1) laboratory-only production with vacuum mixing and heat curing (before the 1980s), (2) the use of MDF and DSP cement to reach a compressive strength of 200 to 345 MPa (in the early 1980s), (3) the addition of steel fibers to reduce the fragility of this kind of concrete (in the mid-1980s), and (4) the introduction of superplasticizers and the creation of RPC, which marked a significant advancement for UHPC (in the 1990s). The production of UHPC has shown a new trend since 2000, which includes reducing CO\({}_{2}\) emissions and reducing initial costs. The rheological properties of UHPC, such as viscosity and yield stress, are critical to its performance and are often evaluated using methods like the squeeze flow test. This test is particularly effective for assessing mortars under compression, with studies demonstrating strong correlations between squeeze flow and rotational rheometry results [7; 8]. Because of the low water-to-binder (w/c) ratio and the high quantity of fine particles like silica fume, quartz sand, and fibers, UHPC is more viscous than normal concrete [9]. This makes the particles stickier and more resistant to flow, resulting in a stiffer and less fluid mixture [10]. The high viscosity can have negative effects on the workability, fiber distribution, and curing of UHPC, so it is essential to use appropriate additives, such as superplasticizers, to make the mixture more fluid and dispersed [11]. Superplasticizers are generally classified into four groups based on their chemical structure [12]: (1) lignocellulosic (SP), (2) sulfonated naphthalene formaldehyde condensate (SNF), (3) sulfonated melamine formaldehyde condensate (SMF), and (4) polycarboxylates (PCE). Figure 1 depicts details on the mechanism of action, chemical structure, and generation of each Superplasticizer. Beyond superplasticizers, advancements in material science--such as nano-absorbers for electromagnetic wave shielding [13; 14; 15] and sustainable low-carbon composites [16; 17]--highlight the broader potential of tailored material design in enhancing UHPC performance. Figure 1: Types of superplasticizers based on chemical structure. The tests used to assess concrete's mechanical properties can be problematic due to their time-consuming nature, high costs, and reliance on laborious, intensive work [18; 19; 20]. Moreover, the results might be uncertain because of varying laboratory conditions or human error [18; 21]. In this regard, to more precisely assess the mechanical properties of concrete, the focus has been placed on techniques like artificial neural networks (ANNs) and fuzzy logic (FL). Various researchers have demonstrated the effectiveness of ANNs and FL in studying the mechanical properties of UHPC [22; 23; 24]. ANN, inspired by the biological nervous system, aims to process information similarly to the human brain [25; 26; 27; 28; 29]. ANN allows the modeling of nonlinear relationships between input and output [30]. The three layers of ANN are the input layer, the hidden layer, and the output layer [30]. In the ANN modeling process, determining the number of hidden layers and neurons is a crucial stage.