Concrete is the most used human-made material in the world, and it is responsible for around 8% of the total greenhouse gas emissions worldwide. Hence, efficient concrete construction methods are one of the main foci of research in architecture, civil engineering, and material science. One recent development that promises to achieve this goal is the use of digital fabrication for building components. Most investigations focus on direct extrusion 3D printing with concrete, which has already been covered in several review articles. Conversely, this article reviews a different approach, which focuses on the indirect digital fabrication of concrete through 3D printed formworks. This approach is under investigation for structural and nonstructural, as well as for on- and off-site applications, with a number of projects having already been built, but a comprehensive review of 3D printed formworks has not yet been compiled to synthesize the findings. This article provides a comprehensive map of the state-of-the-art of five different 3D printing technologies used for the fabrication of formworks so far. The aim is to serve as a fundamental reference for future research, provide a basis for consistent language in this field, and support the development of construction standards. The article further discusses the new geometric possibilities with 3D printed formworks and their potential for making concrete construction more sustainable. In addition, the opportunities and challenges of 3D printed formworks are evaluated in the context of other traditional and digital fabrication tools. A synthetic classification in five functional typologies is proposed and illustrated with 30 representative case studies. Finally, the article concludes with a brief reflection on the role of 3D printing in the broader context of formwork innovation and a possible outlook for this technology. However, very few consider the use of 3D printing, a fabrication process that has the potential to radically improve conventional formworks in several key respects.Formworks are the single largest cost component in the construction of a concrete structure.2 However, concrete is responsible for roughly 8% of the total greenhouse gas emissions worldwide.3 This significant contribution is due to the sheer quantity of concrete produced, concrete being the most widely used construction material in the world.4Concrete is one of the most sustainable materials available for construction, averaging a specific embodied energy of only 0.75 MJ/kg.One of the reasons for the wide use of concrete is that the raw materials are readily available locally at low costs in most parts of the world. Due to this, concrete elements are often oversized to keep the construction process quick, simple, and cheap. This paradox of using more material to reduce costs is explained by a fundamental step in the production of concrete: the fabrication of the necessary formwork.5 To be more economical, formworks must be simple to fabricate, transport, install, and reuse. Hence, most of the commercially available formwork systems today are based on standardized, mass-produced, reusable, modular flat panels, which put a hard limitation on the shapes that can be achieved in concrete constructions.Formwork is the temporary structure used to retain fluid concrete in its designated shape until it hardens. Formworks alone account for more than half the resources necessary for concrete structures, more than cement, aggregates, admixtures, labor, and reinforcement combined. For particular building elements, such as slabs, the formwork can even represent up to 80% of the total costs.Standardized formwork systems often result in oversized, monolithic concrete components. Nevertheless, the overall cost of standard parts is still lower, because the cost of bespoke formworks outweighs the extra cost of raw materials. Furthermore, bespoke optimized geometries incur significantly higher design and engineering costs as opposed to relying on a catalog of standard parts. As a typical example, concrete columns in high-rise buildings are usually sized identically, even if the structurally required section area decreases progressively for upper floors. As a further example, slabs have flat horizontal soffits to be economical. Nevertheless, dropped column heads, ribbed, and waffle slabs are materially more efficient, but can be more expensive to fabricate.Oversized building elements have a knock-on effect on the substructures of the building. For example, thicker slabs have a larger dead-load and require thicker columns and walls, which, in turn, require deeper foundations. More material means a bigger carbon footprint. Furthermore, the implications do not stop at the construction phase, but impact the end-of-life strategies for the oversized concrete buildings too.To address the challenges of the formwork, two different approaches that involve advanced or digital fabrication are currently being investigated. The first approach looks into the direct digital fabrication of concrete (DDFC), which completely eliminates the need for formwork. The second approach looks into the digital fabrication of formworks (DFF), which radically expands the geometric possibilities with concrete.7 as well as by articles focusing on specific methods.8 Wangler et al. identify three types of DDFC: layered extrusion, slip forming, and binder jetting.6 These processes share several challenges that currently prevent them from being used in structural applications.9 The main limitation of DDFC concerns the reinforcement. While short fiber reinforcement is possible to a certain extent, the inability to integrate continuous rigid reinforcement bars is a significant penalty for the bending strength of DDFC. This limitation, along with the material discontinuity inherent in layer-based fabrication processes, prevents DDFC from being certified for compliance with the statutory requirements of building standards.DDFC has been covered in recent years by extensive reviews,Furthermore, even if DDFC does not require formworks, it still has significant geometric constraints, limiting build heights and volumes, cantilevers for the extrusion-based processes, inner voids for binder jetting, and resolution for slip forming. DFF aims to address these limitations.10 Recent research has shown that flexible, lightweight formworks can have nondevelopable shapes as well, through numerically controlled knitting.12At the end of the 19th century, the early attempts to break away from the constraints of the flat panel formwork used patterning and stitching of flexible materials to create new concrete shapes. Flexible materials such as geotextiles can be used for ultra-light developable formworks.14 Inflatable formworks have also been used in conjunction with robotic fabrication for a thin carbon fiber bespoke shell with a span of 8.5 m.16 This suggests that the limited geometric possibilities of pneumatic formworks for concrete can also be expanded through the use of digital fabrication.Pneumatic formworks are another one of the earliest methods for creating nonstandard concrete shapes, especially long-span shells. It relies on flexible membranes that can be inflated either before or after the concrete is applied. The method was introduced in the 1920s and it became more prominent in the 1970s and 1980s with the work of Heinz Isler and Werner Sobek.17 Variations of this method, such as robotic hot-wire cutting,18 hot blade cutting,19 and spatial wire cutting,20 have been used to extend the geometric capabilities of CNC wire cutting beyond ruled surfaces. CNC cutting of flat sheet materials such as plywood and plastics has also been actively used to create moderately curved concrete shells.21Further geometric freedom can be achieved with subtractive fabrication processes. Computer numerically controlled (CNC) hot wire cutting of extruded polystyrene blocks is one of the most used commercial methods to fabricate formworks with nonstandard shapes.22–24 CNC folding of thin sheet materials has been successfully used to produce minimal plastic formworks.25Formative fabrication is another category of processes that is intensely researched and occasionally used in building projects. Processes such as CNC thermoforming and molding of glass-fiber-reinforced polymers (GFRP) produce reusable formworks, but with significant geometric constraints. Land forming is another process in the formative fabrication family, which has only been used experimentally for the fabrication of formworks so far. It relies on casting, spraying, or extruding concrete on a mechanically or robotically shaped reusable granular substrate, such as earth, sand, or gravel.26 A final example of formative fabrication are actuated molds that deform a thin sheet of lining material, either before or after the concrete placement.28Another formative process, Mesh Mold, produces a functional stay-in-place formwork by robotically bending, cutting, and welding steel reinforcement rods on-site.In contrast to DDFC, which eliminates formworks altogether, all the DFF processes rely on formworks, the most expensive aspect of concrete construction. Nevertheless, formworks have in this case their own advantages. DFF allows the precise control of the concrete surface quality, does not require special concrete mixes, and allows the use of regular rigid reinforcement. DFF relies on conventional concrete casting techniques that are familiar to the building industry and can be easily certified for the use in constructions. However, all the processes described so far still have geometric limitations. High-resolution details and surface features are generally not easily achievable. Most methods have process-specific limitations: ruled surfaces for CNC hot-wire cutting, developable surfaces for CNC folding, anticlastic surfaces for fabrics, undercut-free shapes for milling, and limited principal curvatures for formative processes.8Therefore, despite all the advances in DFF, the geometric potential of concrete is still latent due to the various limiting factors, such as tool accessibility , material constraints , and economic constraints . These geometric limitations can be overcome by using 3D printing for the fabrication of formwork. While not fully unconstrained geometrically, 3D printing can produce significantly more complex geometries with higher precision and resolution.29 Out of these, binder jetting, material extrusion, and material jetting have been used so far for the fabrication of formworks  for fabricating easily removable and fully recyclable formworks for columns.53–56A patent for using a more conventional layer-based polymer extrusion 3D printing for flexible formworks was filed in 2014. The proposed method, named Additive formwork, was demonstrated in a series of small-scale prototypes.te canoe .52 An in57 Submillimeter formworks were also used to fabricate the Funicular Slab prototype for the World Economic Forum 2020 in Davos  air ducts formed with 3DPF. MAS Stairs is a project based on two master students' theses, who used submillimeter polymer 3DPF to produce large concrete structures in discrete prefabricated segments. MAS Stairs focused on structurally optimized post-tensioned stairs assembled from precast individual steps.59Another innovation was proposed in Eggshell formworks, which are based on a simultaneous casting and 3D printing process to tackle the challenges of the fragile Submillimeter formworks developed earlier.in Davos .58 The s60 Later, NOWlab used the same approach for a refurbishment project, in which arched lintels were cast in concrete based on reusable 3DPF.61 Furthermore, in 2018, a patent was filed by BigRep for using this method for the fabrication of a flat-panel 3DPF system structurally optimized according to the hydrostatic load.62 This development goes back toward the standardized flat-panel formwork systems that were initially challenged by 3DPF.Instead of minimal disposable formworks, another approach to achieve material efficiency proposes a robust, heavy-duty formwork system that can be reused multiple times. The method was used by NOWlab and Immensa Labs for a conceptual prototype of a functional wall with integrated lighting.63 BAAM was able to reuse formworks up to 190 times with minimal maintenance work.A similar approach, aiming to 3D print robust and reusable formworks, was also implemented with the Big Area Additive Manufacturing (BAAM) facility for a high-rise apartment building in the Domino Sugar Refinery complex in New York.64 A different approach was taken by a Aectual, a Dutch company based in Amsterdam, relying on robotic 3D printing of complex 2D patterns for terrazzo floors. Aectual also experimented with polymer extrusion for a stair.65 Another recent project from CREATE, University of Southern Denmark, investigated the fabrication of informed textures with polymer 3DPF and measured the deviations of the resulting concrete parts and formworks compared to the designed digital model.66Several other projects addressed new, experimental approaches to 3DPF. The Vulcan Pavilion used small prefabricated polymer 3DPF modules that were partly filled with concrete to increase the stability and integrate an opacity gradient in a large-scale vaulted structure.Material Jetting is an additive manufacturing process in which drops of feedstock material are sprayed by one or more nozzles on a substrate from a distance . The sprThe process involves a hot wax in liquid state that is jetted onto a support surface from a relative distance. The distance controls a cone of dispersion and implicitly the width of the deposited material bead. The structural buildup of the deposition comes from the change in phase of the wax material from liquid to solid. The waxes used in this process have relatively low melting points 40–70°C, require little energy to be melted, and transition quickly back to the solid state at room temperature.67 The method, called FreeFab, uses wax jetting for achieving the rough outline of the formwork, which is subsequently milled to a precise tolerance using a rotating numerically controlled spindle.68 The wax is soft, requiring little energy to be milled, while the subtracted material can be easily recyclable. The concrete is sprayed and the smooth milled surfaces of the formworks facilitate an easy demolding process. After the concrete cures, the wax can be crushed, melted at low temperatures, filtered, and reused. FreeFab was used for a series of infrastructure projects in London: Tottenham Court Road, Bond Street, and Liverpool Street. Around 1400 unique wax formwork panels were made using FreeFab for the bespoke geometry of the prefabricated concrete lining for the underground tunnels.693D printed wax was proposed as a solution for achieving zero-waste formwork due to its potential to be recycled with little energy and reused multiple times.Foams constitute another class of materials used in material jetting, as well as in extrusion 3D printing. They are dispensed through a numerically controlled nozzle in a liquid state and a blowing agent triggers the foaming process through the formation of gas bubbles. The stabilization of the deposited foam is a result of chemical cross-linking that increases the viscosity and eventually leads to solidification. By controlling the blowing agent, foams with different properties can be obtained, from soft to tough, from elastic to rigid, and from lightweight foams with large open pores to foams with fine dense closed pores. These properties can be useful in creating architectural qualities such as transparency or insulation properties.71 According to the patent, the main application for this compound fabrication method is to produce formworks for concrete walls in residential buildings.Spray Foam is a foam jetting 3D printing method patented in 2013. The patent describes a nozzle that sprays foam layer by layer, followed by a subtractive tool that corrects the layer irregularities to fabricate an object according to a CAD model.in situ fabrication of lightweight large-span structures, but the idea of using it as formwork for concrete was abandoned. In 2016, a similar technique to Spray Foam was demonstrated for the fabrication of the walls for a social house in Nantes, France. The new system, named Batiprint3d™, proposed the use of the same robotic arm to 3D print the foam and to extrude the concrete infill.72This research on foam 3D printing was continued in the direction of 73 Moreover, this process has the advantage that geometric complexity is decoupled from printing time and production cost. On the downside, the process often requires time-consuming postprocessing steps for cleaning loose powder and stabilizing the printed parts, such as microwave curing or surface infiltration treatments.In binder jetting (BJ), a liquid binder is selectively applied on successive thin layers of powder . Its sig74 The formwork consisted of 252 binder-jetted parts, coated and assembled to create the 1.9 × 1.6 × 0.9 m structural lattice that optimizes the use of high-performance concrete.75 The 9-m-long by 6-m-high space was defined by a thin convoluted shell of fiber-reinforced shotcrete with a thickness varying between 10 and 40 mm. Around a third of the 2000 formwork parts were 3D printed with a large-scale binder-jet printer. In the same year, The Smart Take From the Strong, a pair of concrete slab prototypes measuring 1.8 × 1 m showcased how stay-in-place 3DPF can enable the fabrication of topologically optimized building elements.76 Two years later, the prototypes were followed up by the Smart Slab, which used a disposable formwork system to prefabricate a 15-tonne cantilevering structural slab . However, even less dense materials can have a positive effect by partially offsetting the magnitude of the hydrostatic pressure. To this extent, the Concrete Canoe project has proposed the use of sand as counter pressure material, and Submillimeter formworks have suggested the use of water , the inverse of resolution. The y axis maps the maximum build volume (V). The data are compiled from available commercial specification sheets obtained from manufacturers. One to five different manufacturers are cataloged for each of the 30 different technologies. Assuming a minimum volume (Vm) of at least 1 m3 is required, the performance index (Pvr) can be expressed as follows:3D printing allows more geometric freedom than subtractive and formative processes. However, the various 3D printing processes have different specific geometric limitations and constraints. Taking the log of both sides and rearranging the terms, this givesVm = 1, (2) is an equation of the form y = p × (x − 1), which is a parabola with the apex in x = 1 in a log–log plot. The desirable processes are found to the right of this performance curve.For The graph highlights to the left of the performance curve the 3D printing processes that are not suitable due to their limited print bed sizes: material jetting, lamination, stereolithography, and metal filament printing. These would require extensive discretization for large formwork parts and implicitly, puzzles with many pieces, difficult to assemble.Extrusion-based processes and binder jetting are situated to the right of the performance curve, and therefore they enable a significant improvement in geometric complexity for concrete at large scale. With these processes, the formwork is no longer a bottleneck for the geometric complexity of concrete. The geometric limitations are now imposed by other constituents of concrete construction, such as provisions for reinforcement fabrication and placing, accessibility for casting, rheology of concrete, size of the aggregates, concrete processing, and directional demolding.in silico and the reality of physical fabrication. The Smart Slab demonstrates the capabilities of 3DPF well, exhibiting a convoluted, ornamented surface with digitally designed organic features with varying amplitudes and widths in the range of only a few millimeters. The Smart Slab further demonstrates how a complex macro topology, with openings above the supporting wall, allows natural light to penetrate deep inside the space, thus contributing to the overall atmosphere of the unit  construction, which consists of lightweight hollow insulating interlocking blocks that act as formwork for reinforced concrete, and can achieve between 5 m2K/W (Logix ICF panels) and 6.67 m2K/W (BASF Neopor with graphite), depending on the material used for the insulation.Thermal insulation is the only type of integration that has already been investigated in depth and prototyped in large scale. The Yhnova system is a sandwich wall with two 80-mm-thick external layers of foam and a 150-mm-thick concrete core that achieves a thermal resistance of 6.75 mThe integration of services in building elements originates from lean manufacturing, a concept borrowed from the automotive industry, where components are preassembled with all the necessary subcomponents and then put together in assembly lines. This approach increases productivity, reduces waste, and facilitates serviceability and incremental improvements.100In buildings, this approach implies the integration of building services, such as electrical conduits, HVAC ducts, light fittings, and fire sprinklers, in the prefabrication stage, rather than fitting them on site. This approach ensures better quality control and reduces construction time on-site. Nevertheless, there are concerns regarding the serviceability of integrated building systems, and the shorter life cycles of building services (15–20 years), as opposed to structures (50 years).With the complex geometries facilitated by 3DPF, standard off-the-shelf parts are not adequate for the necessary building services. In these instances, building services can be integrated in the structural concrete and custom designed to fit the complex geometry. The custom design opens an opportunity toward efficient and optimized building services, tailor made for the particular space to reduce the amount of energy.3DPF can facilitate a partial integration, in which only the provisions, voids, and openings for building services are defined in the concrete volume, while the ducts and pipes are installed after casting. Lighting features, electrical conduits, and water pipes were integrated in this way by projects such as the NowLab Wall and the Smart Slab.58 The stay-in-place thin plastic formwork defined two inlets: a duct bringing in fresh air and an internal inlet directed through a heat exchanger. Six air outlets were also defined to distribute the flow of air uniformly toward the internal space. The shape of the network of ducts was optimized through CFD software to minimize air pressure loss. The resulting geometry could not have been fabricated with standard off-the-shelf parts.A further step in integration relies on the stay-in-place formwork itself to act as air duct or cable tray. This full integration concept was demonstrated in the Funicular Slab, in which the integration of an innovative chilled beam HVAC system was enabled by polymer extrusion 3DPF .58 The s57Typically, formwork manufacturing for bespoke parts requires a relatively large component of labor. Some 3DPF also require a series of postprocessing steps to prepare them for concrete casting. Binder jetting is a typical example, in which process-specific desanding, as well as infiltration and coating steps are necessary for stabilizing the parts and for ensuring a smooth surface. Nevertheless, processes like contour crafting, BatiPrint, clay formworks, and to a certain extent polymer 3DPF produce ready-to-use formworks that can be cast straight away. Such an example is the Eggshell formwork, for which the fabrication of formwork and casting are done simultaneously.101–105Digital design and fabrication have the potential to automate construction fully. Computational design tools can integrate all the project-specific processes, such as segmentation for prefabrication, formwork design to fabrication, toolpath generation, collision detections, demolding, and construction sequencing. Recently, computational methods for developing functional molds for complex geometry have been developed, focusing on discretization methods, geometric approximations of free-form geometries for casting, and calculating optimal demolding directions.61 The Smart Slab further demonstrates mass customization, illustrating it through 11 similar, but unique segments that each respond efficiently to the asymmetrical loading conditions (The implications of this automation opportunity are beyond the typical scenario of an unsupervised production line. Digital fabrication allows cost-effective mass customization and production, in which each piece of formwork can be unique, allowing the concrete components to respond optimally to their spatial, structural, and functional conditions. Mass customization is demonstrated by BigRep, who propose in their patent the gradual variation of formwork thickness, in response to the height-dependant hydrostatic pressure.nditions .106 Self-Aligning Molds,107 Mold Carriers,108 Tunnel Formwork,109 Slip Forming,110 Flying Formwork,111 Sliding Formwork,112 Self-Climbing Formworks,113 Insulated Concrete Forms,114–116 Self-Supporting Forms, Hinged Formwork,118 Battery Formwork,119 and Butterfly Formwork.120Historically, the main driver in formwork innovation has been to improve cost efficiency through modularity, reusability, serialization, rationalization, and preassembly. The most significant innovations in formwork construction focus directly on improvements of the construction process that have quick commercial benefits. Any improvement of the concrete structure itself is generally incidental, indirect results of the formwork systems innovations. Some of the major innovations in the field of formwork include Sequential Molds,121These efficient and simple-to-use formwork systems are up to three times more expensive than conventional formwork. However, they result in savings in labor and a remarkable increase in productivity, as well as important financial savings from reusability, with the most performant systems reaching more than 700 concreting cycles with minimal downtime for maintenance.The new 3DPF systems reviewed in this article generally contradict the previous trend of innovative commercial formwork systems. 3DPF are generally disposable or limited-reuse systems and aim to enable bespoke optimized structures and one-of-a-kind designs, tailored for a specific context, rather than mass-produced building element serialization. Although the early attempts are expensive, less robust, and time-consuming, they can also potentially become commercially competitive through automation.59Some types of building elements have specific suitable 3D printing technologies. The hydrostatic pressure of concrete during the casting of tall parts is one of the critical considerations. Slabs and horizontal concrete elements, such as beams and arches, generate the smallest stresses on the formwork, and therefore, binder jetting and polymer extrusion have been favored due to their excellent surface quality. For tall elements, such as columns and walls, concrete and foam extrusion have been the most successful methods, due to their higher strength. Polymer 3DPF through the Eggshell and Dissolvable PVA approaches have also successfully produced objects up to 3 m in height. Finally, intrinsically complex elements, such as stairs and space frames, are generally more suitable for polymer extrusion and binder jetting, technologies that enable more geometric freedom than the other extrusion processes.35 There are, however, niche applications for concrete extrusion that can be implemented sooner, such as nonstructural elements and compression-only structural systems.Are 3DPF just a stepping stone along the way to fully integrated form-free DDFC? Research has shown that 3DPF are ready for implementation in load-bearing building elements. In contrast, the limitations of reinforcement are still far from being resolved for DDFC. Even projects that claim to have fully 3D printed entire buildings are in effect 3DPF made of concrete in most cases.Two aspects concerning the sustainability of 3DPF need to be considered: the sustainability of the formwork itself, and the indirect impact on the sustainability of the resulting concrete parts.Among the 3DPF materials, concrete and clay perform very well due to their minimal specific embodied energy, while at the other end of the spectrum, foams, plastics, and organic binder sandstone have embodied energies higher than steel. The main handicap of most 3DPF systems is their intended one-time use. For unique parts, each cast inherits the entire energy footprint of the formwork.122With careful designs and adequate postprocessing and coating, reusability is a viable solution. However, so far, there is limited research in this direction. The material generally used for coating polymer and binder jet formwork is polyester, which provides a smooth and mechanically and thermally durable surface, also used as a matrix for the fabrication of GFRP. GFRP formworks can achieve upwards of 200 reuses with little to no maintenance work in between casts. This figure has been confirmed by BAAM, who coated ABS 3DPF and reused them 190 times without reaching their end of life.51 Furthermore, minimal 3DPF can be combined with standard reusable scaffolding systems for stiffness.97 Another strategy to alleviate the adverse impact of one-time use is the integration of the formwork in the permanent architecture, as a functional, structural, or aesthetic constituent part of the building. For example, foam formworks achieve this by essentially doubling as permanent insulation for concrete walls.One way to mitigate the high embodied energy per cast of one-time-use 3DPF is to minimize the formwork thickness .51 Furth77 This reduction in concrete use outweighs the increase in embodied energy coming from the 3D printing processes.The embodied energy of disposable 3DPF is measurably higher compared with reusable formwork systems. However, 3DPF can have a further indirect impact on the embodied energy of the concrete parts, as well as on the long-term operational energy of buildings overall. The indirect benefits stem from the material-efficient designs based on topology optimization enabled by 3DPF. Several projects have demonstrated how the weight of slabs can be reduced by up to 70% .58,76,7758 The functional hybridization has been shown to shorten the lifecycle of a building, but even taking this into account, the integrated concrete elements still outperform conventional components regarding their operational energy.100The second important aspect is the saving in operational energy of a building that can be achieved through smart geometries. Operational energy can constitute up to 80% of the total lifecycle energy of a building, and therefore even small improvements can make a big impact. Optimized building systems integrations, efficient HVAC systems, as well as spatial and material savings from integrating services within the structural bounding box of building elements, can all have a positive impact on the operational energy of a building. The integration of such systems has already been demonstrated in the Funicular Slab.in situ, or disposable strategies, approaches that are generally avoided in commercial formwork systems due to their incompatibility with the economy of scale. However, 3DPF projects manage to reinvent the formwork typologies and put forward clever solutions to construction challenges. These new formwork typologies trigger more freedom in design thinking and allow novel architectural solutions to be implemented.3DPF challenge the status quo in which rationalization for mass production and modular reusable assemblies are dominating the market to cut costs. 3DPF can be used in stay-in-place, 75Radical creative solutions based on 3DPF can challenge fundamental principles of architectural design, such as the archetypical building elements and the right angle. The ubiquity of the right angle in architecture is partly a result of fabrication constraints, which no longer apply to 3D printing. The Incidental Space is a relevant example in this direction, where conventional building elements blend into a continuous shell that illustrates not only a radically new esthetic but also a viable structural solution .753 at up to 75 kg of metal per hour. While the costs of this technology are still relatively high to justify single-use formwork fabrication, it is promising for custom rigid reinforcement cages that could synergize with 3DPF. Other hybrid methods are also expected to follow up, combining 3D printing with complementary digital or nondigital fabrication methods.The analysis of the state-of-the-art presented in this article has shown that the available hardware is one of the major limiting factors for 3DPF. Technological advancements should focus on providing faster fabrication times, more robust and reliable processes, and more sustainable materials suitable for architecture. New research streams are expected to cover other 3D printing methods that are relevant at large scale, such as stereolithography and metal welding 3D printing, as highlighted by the Ashby plot in Furthermore, a critical research topic in this field should continue to be sustainability, both for formworks and the resulting concrete parts. Reusable 3DPF are underrepresented in current research. Along with the development of new sustainable and recyclable materials suitable for disposable 3DPF, reusability can have a positive impact on the sustainability of concrete constructions.Finally, the potential of stay-in-place formworks needs to be explored further as well. Initial research projects have mapped out possible performative aspects that can be covered by 3DPF, such as fire protection, acoustic diffusion, and radiant heating and cooling. However, these aspects should be further explored quantitatively in full scale prototypes.Beyond their direct implications for the construction sequence, formworks can leave their mark on architecture on a deeper semantic, aesthetic, and functional level. This article has shown how different types of formwork have meaningful architectural implications on the possible geometries, structural schemes, building services, functionality, esthetics, surface quality, and finishes.This article further mapped the domain of 3DPF in both academic research and pioneering industry endeavors. 3DPF have already been investigated for more than 25 years, and research has matured from early patents and small-scale experiments to prototypical pavilions and finally to functional large-scale architectural applications. While recent projects demonstrate a clear potential in commercial architecture and infrastructure projects, it has so far only been used in test applications.3DPF have to compete with commercial solutions that are currently faster, more robust, reusable, adjustable, modular, and relatively flexible within a certain standardized typology. However, these often result in oversized components due to the lack of versatility, and sacrifice variety and design freedom for resource economy. On the contrary, 3DPF enable bespoke, optimized building elements that are already being used occasionally for one-of-a-kind showcase buildings. Weight reduction, sustainability, functional integration, a new esthetic, and automation are the key opportunities of 3DPF for concrete that are difficult to achieve otherwise.


Antibiotic resistance is a major health threat. Inappropriate antibiotic use has been shown to be an important determinant of the emergence of antibiotic resistance. Decision support systems for antimicrobial management can support clinicians to optimize antibiotic prescription.The aim of this systematic review is to identify factors influencing the implementation of decision support systems for antibiotic prescription in hospitals.A systematic search of factors impeding or facilitating successful implementation of decision support systems for antibiotic prescription was performed in January 2022 in the databases PubMed, Web of Science and The Cochrane Library. Only studies were included which comprised decision support systems in hospitals for prescribing antibiotic therapy, published in English with a qualitative, quantitative or mixed-methods study design and between 2011 and 2021. Factors influencing the implementation were identified through text analysis by two reviewers.A total of 14 publications were identified matching the inclusion criteria. The majority of factors relate to technological and organizational aspects of decision support system implementation. Some factors include the integration of the decision support systems into existing systems, system design, consideration of potential end-users as well as training and support for end-users. In addition, user-related factors, like user attitude towards the system, computer literacy and prior experience with the system seem to be important for successful implementation of decision support systems for antibiotic prescription in hospitals.The results indicate a broad spectrum of factors of decision support system implementation for antibiotic prescription and contributes to the literature by identifying important organizational as well as user-related factors. Wider organizational dimensions as well as the interaction between user and technology appear important for supporting implementation.The online version contains supplementary material available at 10.1186/s12911-023-02124-4. The rise of antibiotic resistance is widely acknowledged to be an increasing threat to global public health. Worldwide 700.000 people die because of antibiotic-resistant infections . The devProviding antibiotic therapy indicates constant decision making, which requires responsibility and conscientiousness, because it can have a significant impact on patients´ health . Due to Information technology has become increasingly prevalent in all industries, especially in healthcare. The development of a wide variety of information systems employed to aid clinicians in decision-making . One sucMany studies demonstrate that DSSs can potentially offer considerable support for many aspects of the appropriate use of antibiotics  and advaThe search, systematization and analysis of literature follows the recommendations of the PRISMA statement .An extensive search of literature was performed in the databases PubMed, The Cochrane Library and Web of Science from May 2021 to January 2022. A search syntax was developed based on relevant search terms. Various search techniques as well as different operators and combinations  were used when entering the search terms  and second author (JH). The inclusion criteria comprised (1) DSSs for prescribing antibiotic therapy, (2) DSSs used in hospitals for clinical practice, (3) studies in English with a qualitative, quantitative or mixed-methods study design, (4) published between 2011 and 2021 and (5) examining DSS implementation factors. Exclusion criteria were (1) studies analyzing the technological development of DSSs without practical relevance and (2) DSSs in outpatient care. Studies that seemed to meet the inclusion criteria were selected for a full text review. Second, the full papers of the resulting set of publications was retrieved and reviewed, again by the first (PT) and second author (JH). Any disagreement about the inclusion of a publication between the two reviewers was resolved thorough discussion and, if required, the third author (CD) was consulted.Authors and publication yearCountryFunding of the studyStudy designSample sizeTargeted groupCharacteristics of the DSSMethodological qualityThe articles were extracted using standardized table formats with the following parameters:Despite diverse approaches explaining the implementation of DSSs, the interface between technology-organization-user has been insufficiently considered. To describe and categorize the identified implementation factors, the Human-Organization-Technology-fit-model (HOT-fit model) of Yusof et al.  was chostechnology, human and organization and maps their relationships and possible interactions, as well. The three domains comprise subdomains, so that the factors can be mapped onto seven interrelated dimensions: System use and user satisfaction in the human domain, structure and environment in the organizational domain and system quality, information quality and service quality in the technological domain. The framework is completed with the dimension net benefits, which comprises the potential negative and positive impacts on individual, organizational or societal level. All these dimensions influence each other in a temporal and causal way. This model has been developed and validated for the implementation and evaluation of innovations in organizations, especially in hospitals [It focuses the fit between the three domains ospitals , 25. On A critical evaluation of the methodological study quality was performed using the Mixed Methods Appraisal Tool (MMAT) version 2011 . This scIn total, 975 publications were identified through the databases The Cochrane Library, PubMed and Web of Science Fig. . DuplicaA total of five publications were identified from Australia –31, two In the majority of publications (n = 11) the DSS was fully embedded in existing systems, such as the electronic health record , 39, 40.A total of 61 factors were identified Tables , 4. Of tWithin the technology domain, with 76% the majority of factors refers to system quality (n = 19/25) and with approx. 24% to information quality (n = 6/25). No factor could be assigned to the area of service quality. The compatibility of the DSS with already existing systems , 37, 39 About 87% of the organizational factors (n = 13/15) can be assigned to structural conditions and about 13% to the organizational environment (n = 2/15). With 57% the majority of publications (n = 8/14) examines factors related to participation and the integration of potential user groups in the planning, development and implementation phases as facilitating for implementation , 38, 39.In the human domain, about 91% (n = 10/11) of the factors relate to system use and only two factors to user satisfaction (about 9%). In this context, a positive attitude towards technologies is positively associated with the use of the technology , 37, 38 Apart from these three domains, twelve publications examine positive and negative effects of DSS implementation , 34–40. In undertaking this review, we have provided an overall picture of the current evidence surrounding existing factors to promote the implementation of DSSs for antibiotic prescription in hospitals. Multiple factors could be identified that might affect the success or failure of DSS implementation. According to the HOT-fit framework, the majority of factors could be assigned to the domain of technology and organization.Clearly, a successful DSS is dependent on the completeness and accuracy of the evidence base used to support it and the technical design of the system modalities. However, DSS is not just about technical content or technical design; DSSs involve workflow. DSSs are as much an organizational as a technical intervention, and organizational, professional and other challenges to implementing DSSs may be as daunting as the technical challenges . The finThus, factors concerning the potential impact of implementing DSSs, such as the time required or integration into existing workflow are assessed as fundamental to the implementation process. A disrupted workflow can lead to increased cognitive effort, more time required to prescribe and less time face-to-face with patients . How to This work can be taken forward as a basis for designing and integrating DSSs for antibiotic prescription in a hospital setting, since central components of such interventions need to build on the existing literature, as identified in this work and on existing guidance surrounding the development and evaluation of complex interventions . IdeallyIn relation to systems design there are various options that can help to promote the appropriate use of antibiotics. These include the availability of large volumes of electronic data, which allows the provision of reliable recommendations and so increases the trustworthiness of the DSS. Moreover, an easy access to the DSS and understandable provision of relevant data are crucial. As described in the most of the publications , 37, 39 In any case, appropriate organizational and social components will need to play an essential part. For this reason, it is important to identify stakeholders that support implementation and a multidisciplinary team to achieve realization, distribution and continuation. The literature synthesis also showed that training with the new system and the availability of educational material are important contributors to successful implementation . In lighSociotechnically guided work can also help to ensure the improvement in clinicians’ performance regarding antibiotic prescription effectively. Here, examination the interaction of technical features and user interfaces as well as organizational aspects such as training will be crucial. User perspectives and needs are equally important factors in DSS implementation, which are closely related to the requirement to involve potential user groups early in the development process. For the successful development and implementation of new technical systems it is also essential that various stakeholders are able to integrate their different knowledge and perspectives in this process. By involving relevant target groups, a positive attitude towards advantages and the benefits of DSSs can arise .As highlighted in this review, DSS facilitates decision-making and thus reduces the burden on clinicians. However, when used regularly, the degree of reliance or trust on DSS can also generate a form of dependency. Additionally, the user’s ability to act may be limited, when the system fails . Also, tThe likely difficulty for any future work in this area is the complexity of DSSs. These are likely to consist of multiple components accompanied by organizational characteristics. This justifies the high importance of future research integrating the user perspective. Embedded qualitative designs can help to facilitate insights into which components are potentially transferable between settings for antibiotic prescribing. Such work is also needed to gain deeper insights into the impact on time and reservations amongst users as well as other reasons as to why DSS implementation for antibiotic prescription is not successful .The mixed method synthesis approach, which has been used to identify factors for DSS implementation has several strength. First, due to the large variety in the methods used in research, combining the results of quantitative, qualitative and mixed methods studies was well suited for this review. The multilevel approach chosen for this review was expedient, since different types of factors, which are important for DSS implementation for antibiotic prescription in hospitals, were considered. We, however, considered publications published in the last decade, so that only studies on current generation of DSSs were included. Third, we applied a systematic approach for data extraction with two independent researcher assessing the inclusion criteria per publication, extracting implementation factors and mapping these to the dimensions of the HOT-fit framework. However, several of the identified factors- impeding as well as facilitating- are not unique to DSSs for antibiotic prescribing. Nevertheless, findings from this review also highlight factors that are specific to antibiotic prescription in hospitals and should be considered. For instance, guidance and recommendations for antibiotic treatment require in most cases more detailed information about patient history, previous antibiotic exposure, local resistance patterns and proper examination of microbiological test results. The provision of flexible and comprehensible recommendations appears to be an important factor to increase the uptake of DSSs like highlighted in this review. Indeed, several studies have reported a correlation between DSS adoption and their impact on antibiotic prescription , 58, whiThe interpretation of the results of this review and their representativeness requires the consideration of some methodological limitations. Despite the intensive efforts, it is possible that not all relevant studies have been identified as some may not be available in the public domain, and others may be published outside the peer-reviewed academic literature. Furthermore, the MMAT has been used to assess the methodological quality of the studies. One advantage of this assessment tool is the easy applicability, since criteria are assessed, which are only dichotomously differentiated. However, this leads to the major disadvantage that only a rough differentiation of the quality assessment of the included studies can be made. Final limitation of this review is that the HOT-fit framework was considered useful; the mapping of factors to the HOT-fit framework was a subjective undertaking of two independent researchers. Some factors proved to be difficult to map to one specific evaluation measure of a certain dimension, because these evaluation measures were sometimes not clearly defined or ambiguous. Additionally, the mapping does not reflect the level of interaction between the various factors and their relative importance. Importantly, the findings may not necessarily indicate the significance of a particular issue. Rather, the relative weight of these factors should be determined in developing and implementing DSSs. Nevertheless, the consideration of the HOT-fit framework was expedient to systemize implementation factors and to highlight the importance of paying attention to technical components and the users as well as the surrounding environment for the implementation process all together . FurtherThere is yet inconclusive evidence about the factors influencing the implementation of DSSs for antibiotics prescription in hospitals. The wide range of identified impeding and facilitating factors contribute to the understanding of the implementation process and suggest that there is no “one size fits all approach”. In future, there is a clear need to pay closer attention to social as well as human components and with a broader organizational focus when developing and implementing DSSs for antibiotic prescription in hospitals.Additional file 1. Table S1. Search strategy.Additional file 2. Table S2. Appraisal of the methodological quality.Additional file 3. Table S3. Study characteristics.


One of the leading causes of reinforced concrete degradation is chloride attack. It occurs due to the penetration of chlorides through pores and cracks into the concrete cover. This phenomenon becomes more dangerous if reinforced concrete elements are subjected to cyclic temperature changes. The concrete cover protects against corrosion. This paper presents research, the primary purpose of which was to determine the effect of the addition of steel fibers to concrete on the development of corrosion of the main reinforcement. The tests were carried out on three types of reinforced concrete specimens made of ordinary concrete and concrete with different amounts of steel fibers (0.25% and 0.50%). In order to initiate corrosion processes, specimens were partially submerged in a 3% sodium chloride solution and were subjected to freeze–thaw cycles. The electrochemical polarization galvanostatic pulse method was used for analyzing the reinforcement corrosion activity. Moreover, it was verified whether the corrosion of reinforced concrete elements affects the acoustic emission wave velocity. The addition of steel micro-reinforcement fibers increases the corrosion resistance of reinforced concrete. In addition, a strong linear correlation between the AE wave velocity and the values of the corrosion current density was revealed. OtherIt is worth adding that, in the case of corrosion caused by chlorides, we are dealing with the so-called pitting corrosion ,11,12,13The key factor in protecting the reinforcement against corrosion caused by the synergy of chloride ions and frost is a properly designed and made concrete cover, which should be of appropriate thickness, characterized by high tightness, preventing the penetration of ions ,15 and eResearch on concrete with dispersed reinforcement, i.e., fiber-reinforced concrete, has been conducted for decades, and many of its properties have already been recognized and described ,21,22. VFiber-reinforced concrete is a “quasi-plastic” and “quasi-homogeneous” material, having better adhesion, deformability, tightness and higher early strength ,26,27,28Moreover, adding fibers to the concrete mix affects its air entrainment, which improves frost resistance . Randoml3 [One of the most commonly used fibers, due to their multiple effectiveness aspects and relatively low price, is steel. These types of fibers are produced in various shapes and sizes. The content of steel fibers in the concrete mixture usually ranges from 0.25 to 2% (by volume) per 1 m3 ,21,22,233 ,36.The purpose of adding steel fibers to the concrete is to increase the composite’s strength and mechanical properties, including tensile strength, fatigue strength, impact strength, crack resistance and abrasion resistance ,21,22,23Some researchers suggest that concretes with dispersed steel micro-reinforcement are not resistant to corrosion ,24. OtheNevertheless, considering the above discrepancies in the corrosion resistance of fiber-reinforced concrete with dispersed steel reinforcement, it is worth analyzing in laboratory conditions.TM measuring set [This article presents research aimed at evaluating the effect of adding steel fibers to concrete on the development of the corrosion process of ordinary reinforcement in specimens exposed to chloride ions and frost. Two non-destructive methods were used in the tests: the electrochemical polarization galvanostatic pulse method using the GP-5000 GalvaPulsering set  and the 3 of concrete are listed in The components of the concrete mixture and their quantity per 1mThe specimens were made in three series. The first series consisted of “witness specimens” made of the base concrete mixture (marked with the symbol C). The specimens in the two other series were made from a mixture to which randomly dispersed steel fibers were added in various amounts. The specimens with 0.25% fibers by volume of the mixture were marked SF_0.25, and those with 0.5% were marked SF_0.5. In the tests, straight fibers with hooked ends of the BauMix 60/1 type, 60 mm long and 1.0 mm in diameter, were used a.3 were prepared  were also prepared to determine the compressive strength according to ,39.All specimens were made under identical laboratory conditions at 20 ± 2 °C and relative humidity 50 ± 5%. The specimens were removed from the molds the next day after concreting. − ions were transported with the liquid directly into the concrete. In the specimen parts above the surface of the solution, the chloride ion migration was due to capillary action and the action of salt fog. The specimens were immersed for 50 days in a 3% NaCl solution. After this time, the specimens (still immersed in the solution) were placed in a freezing chamber and subjected to 100 cycles of freezing and thawing. Freezing cycles were carried out in a frost resistance test chamber with an automatically controlled research program. The temperature range was +18 ÷ −18 °C. There were ~3 cycles per day. The course of the test is shown in In order to reflect the influence of an aggressive corrosive environment and initiate corrosion processes, the specimens were placed in a plastic tub in a 3% sodium chloride solution, which was tightly wrapped with foil. The immersion of the specimens was partial—it covered only half of each specimen with one reinforcement bar, which was to assess the impact of ambient conditions on the activation of the corrosion process. In the immersed parts of the specimens, ClReference measurements using the GalvaPulse method were made before immersing the specimens in the solution at a constant temperature, while measurements using the acoustic emission method were made before placing the specimens in the freezing chamber. These results were reference measurements for later measurements. The arrangement of the measurement points is shown in In order to assess the corrosion activity of the main reinforcement bars, the specimens were subjected to semi-destructive tests using the galvanostatic pulse method. To assess the impact of an aggressive environment on concrete and fiber-reinforced concrete, the non-destructive acoustic emission method was applied. In addition, tests accompanying the assessment of the compressive strength of the specimens were performed.TM measuring set was used in the described studies. It enables determining the probability of corrosion based on measurements of the stationary potential of reinforcement and resistivity of the concrete cover, estimating the reinforcement corrosion activity and predicting corrosion rate based on the measurements of the corrosion current density. The scheme of operation of the device in connection with a reinforced concrete element is shown in The galvanostatic pulse method belongs to the electrochemical polarization research methods group—the essence of its application results from the electrochemical process of corrosion of reinforcement in concrete. Concrete has a porous structure with pores filled with liquid, so it is a kind of electrolyte. The steel rebar is an electrode placed in an electrolyte. As a result of differences in the concentration of ions in the electrolyte and possible micro-defects in the steel, local anode and cathode areas are formed on the surface of the rod—microcells that initiate the flow of electrons—and the liquid-filled concrete is a carrier of ions. When such a cell is connected to a device equipped with an electric meter and a reference electrode, and the current flow is induced correctly, it is possible to obtain data on corrosion probability and estimate the corrosion activity. The GP-5000 GalvaPulseTM device, the most effective and reliable in the case of the presented tests were the measurements of the corrosion current density. In the case of the other two parameters, the obtained results could lead to their incorrect interpretation. This resulted from the influence of steel fibers, disturbing the measurements of the stationary potential of reinforcement [Of the three parameters measured with the GP-5000 GalvaPulseorcement , and froorcement . Therefocor) measurements were performed for three series of reinforced concrete specimens  in two stages. The first stage included measurements on specimens before they were immersed and frozen in a 3% NaCl solution. The second stage concerned the measurements of specimens after 100 cycles of freezing and thawing in a solution. Measurements were made on the surface of each specimen at four measurement points located on the line of the reinforcement bar , and at one point, the current density increased to icor = 10.68 µA/cm2 (moderate corrosion activity of the tested rod). In all tested specimens, the corrosion activity of the reinforcement bars increased due to the action of chloride ions and cyclic freezing and thawing of the specimens.As seen from the graphs, the reference measurements (stage I) were in the range of ited bars . They prcor = 10.68 µA/cm2), the average of the results was presented in two variants: including this result and omitting it .In addition, cor = 3.63 µA/cm2 (for non-immersed parts) and icor = 3.42 µA/cm2 (for immersed parts). Lower corrosion current density values were recorded in the specimens with the addition of fibers. In the specimens of the SF_0.5 series, the average values of the current density were icor = 3.34 µA/cm2 (for non-immersed parts) and icor = 2.65 µA/cm2 (for immersed parts), and the specimens of the SF_0.25 series (excluding the result of the SF_0.25-point series 7) were, respectively, icor = 3.14 µA/cm2 and icor = 2.72 µA/cm2. However, considering the value of the corrosion current density at point 7 in the SF_0.25 series specimen (icor = 10.68 µA/cm2), it should be assumed that a corrosion center was formed in the tested area. It could have resulted from micro-defects in the concrete cover (cracks caused by stresses in the concrete), which led to increased diffusion of Cl− ions.Analysis of the results obtained from the tests (excluding the result of the SF_0.25 point 7 series) indicates that the corrosion activity of the main reinforcement bars after 100 cycles of freezing and thawing in 3% NaCl solution was the highest in the specimens of series C (concrete without fibers), with the highest increase in the average corrosion current density i− ions into the lagging. The percentage of micro-reinforcement fibers dosed to reduce shrinkage in concrete is, therefore, significant, taking into account the effectiveness of the cover in protecting the reinforcement against corrosion.Analysis of the values of standard deviation and coefficient of variation  shows thcor = 1 (µA/cm2) corresponds approximately to the depth of loss of the cross-section of the reinforcing bar equal to 11.6 (µm/year) [The measurements of the corrosion current density made it possible to determine the corrosion activity of the reinforcement and estimate the corrosion rate. For this purpose, Faraday’s law was used to estimate that the corrosion current density with the value of iµm/year) . The maxIt is also worth noting the differences in the corrosion current density values that occurred depending on whether the measurement points were located in the non-immersed (air) or immersed (solution) part of the specimens. In most of the obtained results, the corrosion current density was lower for some of the specimens immersed in the solution . Therefore, the bars immersed in the solution were characterized by lower corrosion activity than those above the solution. This is probably related to the essence of the corrosion process. Although the concentration of chloride ions in the solution was probably higher than in the “salt mist” (not measured in this study), oxygen was necessary to develop reinforcement corrosion, thereby making chloride ion migration in the concrete above the solution easier than in the immersed parts of the specimens, whose capillaries were filled with liquid ,21.The reference measurement using the acoustic emission method was made before the freeze–thaw cycles in the chamber, i.e., after 50 days of specimen care in a 3% NaCl solution. Measurements were made in two specimen zones b. The fiThe recorded wave parameters show that each immersed part of the specimens (100% care) had higher wave velocity values compared with those recorded in the part of the specimen treated in the air. In both cases, the maintenance time was the same (50 days). Therefore, immersion of some of the specimens in the solution positively affected the course of the cement hydration process, which was complete in relation to the part of the specimens left in the air.In the second part of each specimen (non-immersed part), an increase in the velocity of the AE wave was observed, which may indicate the influence of humidity on the concrete sealing.The waves recorded in the SF_0.25 in the second stage of the research, after 100 freeze-thaw cycles, had a lower amplitude than the amplitude recorded in the specimen in Stage I. In the immersed part, the amplitude decreased from 115 mV a to appr2.Analysis of the test results shows that the corrosion activity of the main reinforcement bars after 100 cycles of freezing and thawing in 3% NaCl solution was the highest in the C series specimens (concrete without fibers), in which the average increase in corrosion current density was highest, icor = 3.63 µA/cmThe decrease in the wave velocity in the immersed parts during the freezing cycles was most likely due to micro-defect formation in the concrete. However, the bars in these parts of the specimens showed slightly lower reinforcement corrosion activity than the bars in the non-immersed parts of the specimens. It can therefore be assumed that, despite greater losses in the concrete cover, the ambient humidity of 100% contributed to the slowdown of the corrosion process, probably due to the oxygen deficit, which is necessary for the process to proceed.In the non-immersed parts of the specimens, there was no such destruction of concrete resulting from the freezing and thawing cycles. The effect of filling the voids of the concrete pores with corrosion products resulted in the “sealing” of the concrete and increasing the wave velocity. Hence, further tests are planned to supplement the AE wave measurements, the location and quantitative assessment of destructive processes taking place in unloaded concrete in an analogous environment in order to demonstrate the cause of the increased number of destructive processes in the submerged zone compared to the non-immersed zone.The results of the GP and AE tests showed a strong relationship between the tested parameters, i.e., the corrosion current density and AE wave velocity. The Pearson coefficient determined for these parameters for the immersed part of the specimens is 0.85, while in the non-immersed part it is 0.97. This information is important in the context of the possibility of developing a non-destructive method that enables the diagnosis of corrosion in reinforced concrete and fiber-reinforced concrete based on the analysis of the AE wave velocity. Initially, it can be concluded that in concrete elements cured in water containing NaCl, the development of the corrosion process can be signaled based on wave velocity analysis. It was observed that, due to the possible filling of concrete voids with corrosion products, partial sealing of the concrete might occur, corresponding to a local increase in the wave velocity relative to places not exposed to corrosion development. However, this dependence requires further analysis and in-depth research.In particular, the last issues related to the correlation of the longitudinal wave velocity with the degree of rod corrosion and the impact of concrete moisture on the longitudinal wave velocity (stage I) or the effect of cyclical heating and freezing of concrete on the longitudinal wave velocity (stage II) can be considered as a novelty in the conducted tests. However, to fully confirm the observed phenomena, the work in this direction should be continued due to the scope of work carried out so far.For this reason, one of the directions of further work will be verifying the correlation between the wave velocity change and the progressive corrosion of reinforced concrete elements.In addition, tests will be carried out to compare the method of sending a reference source in the form of the Hsu-Nielsen method (wave generated by breaking a pencil lead) and from a sensor, determining the advantages and disadvantages of both methods of generating a longitudinal wave source and measuring its velocity for samples subjected to NaCl and cyclic heating and cooling.These tests will also include comparisons of elastic wave shapes and amplitudes and the impact of the corrosive degradation of concrete on these parameters.The corrosion activity in the specimens with 0.5% fibers was the lowest, and the dispersion of the results was the smallest. The highest corrosion activity was shown by bars in the concrete specimen without fibers. The largest scatter of results was observed in the specimen with the addition of 0.25% of fibers. This indicates that the addition of steel micro-reinforcement fibers to concrete affects the effectiveness of the cover as a layer protecting the reinforcement against corrosion caused by the action of chloride ions and frost. However, the percentage of fiber content in the concrete mixture is of significant importance.The content of steel fibers in the concrete mixture in the amount of 0.25%, defined as the minimum anti-shrinkage micro-reinforcement in concrete, is insufficient to obtain a homogeneous and tight concrete cover protecting the reinforcement against corrosion.The use of steel fibers as micro-reinforcement does not increase the corrosion risk of the main reinforcement in concrete.Randomly dispersed fine steel fibers covered with concrete do not constitute corrosion centers.Corrosion caused by chloride ions is pitting corrosion, which means that in concrete elements, there may be point corrosion centers with high corrosion activity of the reinforcement.Heating and freezing cycles in a 3% NaCl water solution affect the destruction of concrete—the wave velocity and amplitude decreased in this medium.There is a strong linear correlation between the AE wave velocity induced by the calibration pulse from the PK6I acoustic sensor and the values of the corrosion current density recorded in the main reinforcement bars.As a result of the conducted research and analysis, the following conclusions can be drawn:Based on the results and presented conclusions, it can be predicted that further tests will allow for the determination of the procedure for inferring the reinforcement corrosion activity based on the AE tests and their correlation to the GP tests.


The analysis was focused on three different factors: the ligand rigidity and the steric hindrance, the presence of a guest inside the cavity, and the guest dimension. Three different quantum mechanical calculation set-ups  were considered. Comparison between theoretical and experimental outcomes suggests that all calculations correctly estimated the most stable isomer, while the inclusion of the dispersion correction is mandatory to reproduce the geometrical parameters. General guidelines can be drawn: less rigid and less bulky is the ligand and less stable is the helicate, and the presence of a guest can strongly affect the isomerism leading to an inversion of the stability by increasing the guest size when the ligand is flexible.To drive the synthesis of metallo-supramolecular assemblies (MSAs) and to fully exploit their functional properties, robust computational tools are crucial. The capability to model and to rationalize different parameters that can influence the outcome is mandatory. Here, we report a computational insight on the factors that can determine the relative stability of the supramolecular isomers helicate and mesocate in lanthanide-based quadruple-stranded assemblies. The considered MSAs have the general formula [Ln Self-assembly of discrete metallo-supramolecular architectures (MSAs) paves the way towards functional systems such as helicates, grids, wheels, knots, and cages that in the last three decades have shown increasing complexity ,2,3. MSAM or P). However, if the metal centers possess opposite-handedness, the final MSA is achiral and is called mesocate. Helicate and mesocate are hence supramolecular isomers chiral and achiral, respectively. Although these structures have been known for some decades [2L4]2− quadruple-stranded helicates that show interesting supramolecular properties such as ion exchange to produce heterometallic systems 2− , and with the inclusion of the implicit solvent and the dispersion correction (named solvent-D). The cavity containing quadruple-stranded [Ln2L4]2− systems allows evaluation of three main factors: (i) the ligand rigidity and steric hindrance; (ii) the presence of a guest inside the cavity; and (iii) the guest dimension. The MSAs analyzed with DFT calculations have the general formula [La2LX4]2− for the host systems and {NR4⊂[La2LX4]}− for host–guest systems. Systems obtained with eight different ligands, L1−L8, were analyzed. The ligands are bis-β-diketone with the same binding groups, but they display scaffolds with variable flexibility and steric hindrance . For clarity and concision, hereafter, the MSAs [La2L1−84]2− will be labeled as C1−C8 depending on the used ligand. To drive the synthesis and functional properties of new MSAs through a new effective and feasible approach, a robust computational tool is crucial. The computational investigation allows the systematic study of various types of MSAs, by varying the flexibility, steric hindrance, and chemical properties of the organic ligands and connecting these characteristics with specific features. The rationalization of each MSA component will allow building of multifunctional coordination by introducing different ligands with different properties. Among MSAs, coordination-driven cage compounds have surely attracted much attention even for the development of new dedicated computational tools to design new metallo-cages and to model their behavior ,27,28,29iketones , and alsiketones  and the iketones  of the liketones ,32. Hybriketones ,34,35,36ructures . The com [2L4]2−  systems ance see , while t4⊂C1 cage bearing the most rigid ligand and hosting the cation NEt4+. La3+ was used as a metal center, because of its closed-shell electronic configuration—[Xe]4f0—that allows simplification of the level of theory used to opportunely describe the systems. This Ln-substitution was previously successfully applied in smaller complexes 2− (C1–C8) self-assembled with bis-β-diketone ligands. These systems also possess a cavity able to host suitable guests such as NR4+ cations. The supramolecular isomerism helicate/mesocate was computationally studied according to three different factors: (i) the ligand rigidity and steric hindrance; (ii) the presence of a guest inside the cavity; and (iii) the guest dimension. In particular, the accuracy of the quantum mechanical calculations  was taken into account. The relative stability of a structure with respect to other accessible systems, and its structural properties, are crucial aspects for MSAs. Thus, the capability to model these parameters and to rationalize the factors that can influence the assembly is mandatory to drive their performances and applications. In this study, the attention was focused on a family of Ln-containing quadruple-stranded helicates/mesocates [La4⊂C1 cage to set up the computational protocol shows that all calculations  are able to reproduce the larger stability of the helicate isomer with respect to the mesocate isomer. Indeed, the difference between the three calculation set-ups is evident in the geometrical parameters, where the inclusion of the dispersion correction reduces the average percentage errors from 4 to 0.3%. The rigidity and the steric hinderance of the ligand scaffolds influence the relative stability of the two isomers: the less rigid and less bulky the ligand, the less stable is the helicate isomer. Indeed, for the most flexible ligand (L8), the mesocate becomes the more stable isomer. The direct comparison with SCXRD experimental data for NEt(i)vacuum calculations are adequate;if one is interested in estimating the stability of one isomer with respect to the others, in (ii)if one is interested in good agreement with geometrical parameters (error on distances <0.5%), the inclusion of solvent and dispersion correction is imperative;(iii)the accordance with experimental geometrical parameters depends on the flexibility of the ligands: the more flexible the ligand, the larger the average percentage errors.A more detailed analysis of the outcomes for all calculations suggests that: 8), where the helicate is the most stable isomer for the empty and smallest guest, while the mesocate becomes the most stable with larger guests. Since all trends described for the solvent calculations are also perfectly reproduced for the in vacuum calculations for both cages and both isomers, if one is interested in the geometrical variation trends in dependence on the size/shape of the guest, it is not necessary to include a solvent effect, which has a higher computational cost. In addition to the rigidity and the steric hinderance of the ligand, the presence of a guest with a different size strongly influences the relative stability of the two isomers and the MSA structure. Its importance is particularly evident for the most flexible ligand (L


In this study, ground glass powder and crushed waste glass were used to replace coarse and fine aggregates. Within the scope of the study, fine aggregate (FA) and coarse aggregate (CA) were changed separately with proportions of 10%, 20%, 40%, and 50%. According to the mechanical test, including compression, splitting tensile, and flexural tests, the waste glass powder creates a better pozzolanic effect and increases the strength, while the glass particles tend to decrease the strength when they are swapped with aggregates. As observed in the splitting tensile test, noteworthy progress in the tensile strength of the concrete was achieved by 14%, while the waste glass used as a fractional replacement for the fine aggregate. In samples where glass particles were swapped with CA, the tensile strength tended to decrease. It was noticed that with the adding of waste glass at 10%, 20%, 40%, and 50% of FA swapped, the increase in flexural strength was 3.2%, 6.3%, 11.1%, and 4.8%, respectively, in amount to the reference one (6.3 MPa). Scanning electron microscope (SEM) analysis consequences also confirm the strength consequences obtained from the experimental study. While it is seen that glass powder provides better bonding with cement with its pozzolanic effect and this has a positive effect on strength consequences, it is seen that voids are formed in the samples where large glass pieces are swapped with aggregate and this affects the strength negatively. Furthermore, simple equations using existing data in the literature and the consequences obtained from the current study were also developed to predict mechanical properties of the concrete with recycled glass for practical applications. Based on findings obtained from our study, 20% replacement for FA and CA with waste glass is recommended. In proportion to the increasing urbanization in the world, raw material resources are decreasing and industrial wastes are increasing ,9,10,11.3 in the cement, the mechanical properties are adversely affected. It was also found that with the change in FA conservative, its mechanical properties are up to 20% substitution [In recent years, much research was conducted on the mechanical properties of CWG added concretes. The CWG can be substituted for both fine and CAs . The nattitution . It was titution . Chen ettitution . Khmiri’titution . Letelietitution . Mostofititution . Tamannatitution . Penachotitution . Lee et titution . Corinaltitution . Tejaswititution . Bataynetitution . With a titution . As a retitution . In a sttitution . Walczaktitution .Though several investigations were performed on this topic, as presented in above, there were changes in the consequences gained from the literature. Therefore, there is still a necessity to examine the mechanical productivity of concrete with the fractional replacement of CWG, and the perfect amount of it. For this purpose, an investigational study was performed on some investigation samples. The effects of different production-based features of concrete with different amounts of crushed CWG as replacement of aggregates were studied. More importantly is that empirical equations are developed to predict the capacity of concrete with CWG, considering both the literature and the data obtained from the experimental study.To amount the mechanical belongings of the concrete with recycled CWG, different mixtures were cast. Eight different mixtures were chosen. Four of them were considered for FAs and rest of them were considered for CAs. Four different proportions of 10%, 20%, 40%, and 50% were selected . CAs witIn the mixture, CEM 32.5 Portland cement was utilized. Water-to-cement proportion was selected as 0.5. The proportion of fine to CAs was selected as unity. The proportion of cement to total fine and CAs was selected as 0.2. 2 worth of more than 92%.An evaluation of the relation STS of the numerous concrete proportion mixtures made with the reference, and several proportions of recycled aggregate replacing FA with and without CWG and CA, which were swapped with CWG, is presented in 2 worth of more than 95%.FS of investigational specimens were recognized on specimens after CST. The assimilated types of strength alternated among 5.2 MPa and 7.0 MPa. The result of the FS of the specimens is offered in SEM investigation was achieved with samples taken from some samples of this experimental study. The images are magnified 500 times to show the interaction among binder materials and aggregates. In SEM analysis, there are images of two different mixtures. The first four are images of concrete samples containing only CGW, and the last four are images of samples containing both CGW and glass powder. f) were primary regularized by the strength value of concrete without glass (f′). These normalized strength values (f/f′) were then shown as a function of different replacement proportions. The changes in the normalized strength values were depicted in Since it has the potential to be preferred as aggregate in concrete mixture, the effect of CWG on engineering properties was examined by many investigators. CWG were used as either FA or CA replacement in concrete. To develop empirical equations, strength values  for plain concrete and concrete formed from CWG were collected from previous experimental studies ,78,79,80f = strength values to be calculated ; c1 and c2 = the coefficients given in WGR: CWG proportion (0 < WGR < 50); and Considering both our findings and previous studies, an empirical equation was developed as follows to predict the CS, STS, and FS, respectively:As presented in Equation (1), engineering properties of concrete formed with CWG were identified as a function of the quantity of the CWG. The developed expressions for compressive, flexural, and splitting tensile strength of concrete produced with CWG can be employed in project phases.In this study, the effects of different productions based features of concrete with different amounts of CWG as replacements of aggregates were investigated. For this purpose, fine and CAs were altered for 10%, 20%, 40%, and 50% . Penetrability and slump properties of produced concrete samples were also examined. Then, CS, STS, and FS of the produced test examples were investigated. Furthermore, SEM analyses were also performed to compare the strength consequences obtained from the experimental study. These specifications were then compared with those of reference concrete. Lastly, practical equations were derived to easily estimate the CS, STS, and FS of produced concrete samples. Considering our findings, the following consequences can be obtained from this study:According to the slump test consequences, while the slump value reduces, the quantity of CWG rises. In other words, the workability of concrete reduces when the rate of glass powder as replacement for aggregates increases.In this study, fine and CA for 10%, 20%, 40%, and 50%  were exchanged with CWG, and this tendency was inverted while fractional replacement of CA with CWG decrease the CS of concrete. In other words, while CA was swapped with CWG, a remarkable downgrade in strength was detected when compared with the reference concrete.As mentioned above, the consequences of STS generally follow a similar trend as the CS. The significant progress in STS of the concrete is up to 13% with CWG used as fractional replacement for FA. Upon changing the quantity of CWG, consequences of STS are affected correspondingly to the CA.While aggregates were swapped with CWG, there was an increase in the FS values up to a certain value of the quantity of the CWG. It was observed that with the addition of CWG at 10%, 20%, 40%, and 50% of FA swapped, the increase in FS was 3.2%, 6.3%, and 11.1% and 4.8%, respectively, compared to reference concrete sample.From the SEM analyses, it can be observed that the use of both CWG together for concrete is a good match. Furthermore, similar to the studies in the literature, it is also shown in this study that glass powder with finer particles has a high pozzolanic effect and provides better strength in concrete.The developed empirical equations for the CS, STS, and FS are quite general and they have the potential to be implemented into design guidelines of the concretes with CWG.The use of 20% replacement for fine and CA with CWG is recommended, considering both workability and strength.