# Augmented Data-Driven Approach towards 3D Printed Concrete Mix Prediction
## 1 Introduction  
The construction industry has witnessed significant progress in recent years with advancements in both construction materials [1; 2] and techniques [3; 4; 5; 6; 7; 8; 9; 10]. This has revolutionized the industry by focusing on cost-effectiveness [11], sustainability [12], and time efficiency [13]. Construction materials capable of energy harvesting are being researched to be the next generation of smart materials. [PERSON]. et al. evaluated the energy harvesting potential of polyvinyl alcohol (PVA) fiber-reinforced engineered cementitious composite (ECC) using surface-mounted polyvinylidene fluoride (PVDF) [14]. One such innovative and advanced construction technique is (three-dimensional) 3D Concrete Printing (3 DCP) [15]. In contrast to traditional construction methods, 3 DCP utilizes an extrusion-based additive manufacturing process. The system employs a computer-controlled nozzle that deposits cementitious material with enhanced rheological properties in layers. The movement of the nozzle is unrestricted across three orthogonal axes (\(x,y,z\)) via a multi-axis robotic manipulator or gantry system. The deposition path is precisely controlled by a pre-programmed digital model, typically generated through computer-aided design (CAD) or building information modeling (BIM) software [16]. Research has shown that printed structures can significantly cut construction costs and simultaneously have the potential for the incorporation of green technology. For example, buildings constructed using this method have achieved cost savings of 33% in China [17], 50% in the UAE [18], and 60%in the Philippines [19]. [PERSON] et al. developed a 3D printed Vertical Green Wall (3D-VtGW) system using concrete 3D printing technology, integrating vertical greenery into the building envelope and demonstrated that the 3D-VtGW system reduced air-conditioning load by 11.20% in summer and 9.12% annually while enhancing yearly thermal comfort and lowering the baseline's lighting power density (LPD) by 10.20% [20]. 3 DCP or \"Construction 4.0\" is extensively being researched as it offers many advantages, including reduced labor involvement, high design flexibility, safer construction, less construction wastage, and environmentally friendly structures [21; 22]. This way of construction holds immense potential for printing structures as evidenced by Figure 1.  
3D concrete printing is being researched for using advanced cementitious mixes to enhance printability, incorporating materials like silica fume [1], fly ash [23], and nano-clay [24]. Material with more fine particles and cementitious properties can improve the overall quality of print; however, they can also affect the hydration rate, increasing the chances of clogging the nozzle [25]. These materials can also improve the mechanical properties and workability of the concrete, making it more suitable for intricate and high-precision construction tasks [26]. It is also being investigated to explain the complex and interrelated effect of printer characteristics such as nozzle diameter [27], extrusion speed [28], and layer height [29] on the quality and durability of the printed structures. However, among all research questions, one major challenge with this technology that hinders its larger-scale application is the easy and quick formulation of a printable mix design [30]. The mix needs to fulfill certain requirements of fresh and hardened properties simultaneously. During extrusion, the mix requires a lower dynamic yield stress characterized by extrudability; however, while being deposited from the printer, it should resist deformation in its shape under the action of gravity and loading caused by subsequent layer deposition [31]. This property is known as buildability. This build-up-ability of concrete is due to the structuration associated with the formation of silica gel with time [32]. The inherent layer-by-layer deposition process in 3 DCP presents an additional challenge of interlayer bonding [33; 34].