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Fresh and hardened properties of 3D printable cementitious materials for building and construction
Abstract
The main advantage of 3D concrete printing (3DCP) is that it can manufacture complex, non-standard geometries and details rapidly using a printer integrated with a pump, hosepipe and nozzle. Sufficient speed is required for efficient and fast construction. The selected printing speed is a function of the size and geometrical complexity of the element to be printed, linked to the pump speed and quality of the extruded concrete material. Since the printing process requires a continuous, high degree of control of the material during printing, high performance building materials are preferred. Also, as no supporting formwork is used for 3DCP, traditional concrete cannot be directly used. From the above discussion, it is postulated that in 3DCP, the fresh properties of the material, printing direction and printing time may have significant effect on the overall load bearing capacity of the printed objects. The layered concrete may create weak joints in the specimens and reduce the load bearing capacity under compressive, tensile and flexural action that requires stress transfer across or along these joints. In this research, the 3D printed specimens are collected in different orientations from large 3DCP objects and tested for mechanical properties. For the materials tested, it is found that the mechanical properties such as compressive and flexural strength of 3D printed specimen are governed by its printing directions.
... The rheological characteristics of pastes, in particular their thixotropic behavior, have been the subject of several investigations, and they have been shown to be crucial [63]. As the printing process requires constant material control, high-performance construction materials must be given priority [64]. ...
... Therefore, the initial curing time is considered essential for 3D printing. Furthermore, The printing direction may affect factors like the nozzle's form, which affects the samples' mechanical characteristics [63]. ...
... In another test, Paul et al. [63] employed three alternative mixing systems for flowability characteristics, two using cement as a binding agent and one with GP mortar (see Table 1). Mixture 1 also consisted of fly ash and slag as binders. ...
Due to the need of the construction industry to implement structures with special and complex designs, mass customization with the lowest cost, especially reducing the labor cost as well as the amount of waste and materials used, the use of concrete 3D printing can be the appropriate solution to these requirements fulfill these options. As a result, a comprehensive and practical study of the major 3D printing methods and their development in the construction industry was carried out in this study. In addition, the use of OPC-based materials and geopolymer-based materials was reviewed and compared due to the development of the materials industry and the advantages and disadvantages of using different types of cementitious materials in the 3D printing of concrete.
... Initial rigidity of the mix in fresh state is related to its shape retention capability which is required prior to the structural build-up to maintain the balance between the structural build-up and layer deposition speed to achieve high buildability. If the rate of layer deposition exceeds the structural build-up rate, the structure fails [101]. Note that the structural build-up rate is affected by the thixotropy of printable mix. ...
... Note that the printing duration increases with the scale of the element. Paul et al. [101] examined the effect of nozzle size and shape on the overall printability and reported that if the size of the nozzle is increased, extrusion pressure has to be enhanced to synchronize with the speed of the print head. They also reported that the voids in the printed concrete with circular nozzles leads to a decrease in strength in comparison to the concrete printed with square and rectangular nozzles as they provide more contact area between the filaments. ...
... This time-gap should not be too short such that the element collapses or too long such that it leads to poor interfacial bonding [143]. To optimize the quality of the printed structure, the fresh properties, and print parameters have to be tailored according to the final scale and geometry of the element [26,101,216]. Tripathi et al. [217] suggest that buildability in concrete printing can be enhanced through the set-on-demand technique which can be possible by employing Accelerator intervention [111,218], Magnetorheological control [219,220], Ultrasonication at the print head [219], and Microwave heating [221,222]. We envision that the use of set-on-demand techniques could reduce the high yield stress requirement while concrete is being pumped which would be helpful in improving pumpability for large scale applications. ...
3D printing of concrete is a rapidly growing additive manufacturing technology, bringing advantages like freedom of geometry, formwork-free construction, reduced construction time, and wastage, contributing towards a sustainable built environment. The technology also has the potential to mimic bio-inspired material archi-tectures with enhanced performance. Among the available additive manufacturing techniques, the scalability and the speed of construction motivate the adaptation of extrusion-based concrete 3D printing technology. For conventional concrete pumping, the rheological behaviour and the mix design have been well established. However, for 3D printing, the pumpability of the mix which is governed by its rheology and the flow mechanism has to be viewed in conjunction with the extrudability, shape-retention, and buildability. This study provides a review of significant rheological properties, the effect of various material mixes, and printer configurations on the pumping of conventional as well as printable concrete, and a general comparison between them. The requirements of a pumpable concrete mix based on rheology and the optimal hardened properties for the 3D printing application are discussed. The significant rheological properties affecting the printability of concrete are plastic viscosity, static yield stress, thixotropy, and open time. A detailed review of various factors affecting the pumpability of a printable concrete mix is presented. The key constituents of a concrete mix affecting pump-ability identified here are the type of binder(s), chemical admixture, the inclusion of nano-fillers, aggregate shape, size and grading, and aggregate-to-cement ratio. The range of yield stress and plastic viscosity are discussed for the 3D printable mixes. Recommendations are provided to improve the process and quality of 3D concrete printing. State-of-the-art applications and the potential of this technology to manufacture nature-inspired material architectures with superior toughness is highlighted.
... The material in this case is known as a Printable Fiber Reinforced Concrete (Printable FRC) [23,57]. The fibers can be of different origins, such as natural flax and sisal [59][60][61][62], steel [23,29], basalt [23,63], glass [23,39], carbon [23], or polymer like polypropylene fibers [22,36,37,40,42,46,48,64,65]. This technique does not require any modification of the printers, except when fibers are added just before the extrusion stage [58]. ...
... The mixture is subjected to a shear rate profile composed of an increase followed by a decrease (Figure 16) [38,47,90]. This protocol of shear rate variation can either be with an incremental step [21,91], with a threshold process [39,44,80], or with a preshear ( Figure 16) [9,92,93]. With these protocols, the static and dynamic yield stress and thixotropy can be adequately evaluated. ...
... The mixture is subjected to a shear rate profile composed of an increase followed by a decrease (Figure 16) [38,47,90]. This protocol of shear rate variation can either be with an incremental step [21,91], with a threshold process [39,44,80], or with a pre-shear ( Figure 16) [9,92,93]. With these protocols, the static and dynamic yield stress and thixotropy can be adequately evaluated. ...
Citation: Arrêteau, M.; Fabien, A.; El Haddaji, B.; Chateigner, D.; Sonebi, M.; Sebaibi, N. Abstract: The field of 3D printing is in rapid evolution. The 3D printing technology applied to civil engineering is a promising advancement. From equipment and mixture design to testing methods, new developments are popping up to respond to specific demands either for the fresh or hardened state. Standardizing methods are still at an early age. For this reason, there is a multitude of 3D printers with different capabilities to print cementitious materials. In addition, norms are not applicable in 3D printing material science. Advances are being made to create new methods of testing. The key parameters of this new 3D printing process based on stratification, multiple uses of binders, and measurement at fresh and hardened states are being perfected to achieve an industrial application. This article gives an overview of how 3D-printed structures are made along with critical parameters that influence their performances. Our review suggests that the quality of the 3D prints is determined by the printing method, key printing parameters, and the mix design. We list different tests to help characterize these 3D-printed cementitious materials at the fresh state and to assess their performances at the hardened state. We aim throughout this work to give a state-of-the-art of recent advances in 3D printing technology. This could help for a better understanding of cementitious materials 3D printing for current and future related research work.
... Assembling formwork, preparing, pouring, and demolding concrete is highly time-consuming, laborious, and suspectable to errors [41][42][43]. Formwork accounts for 60% of total construction cost, 10% percent of formwork material, and 50% is labor used to design, install, and remove temporary formwork construction [44]. A detailed distribution of the cost of conventional construction is shown in Figure 1. ...
... Assembling formwork, preparing, pouring, and demolding concrete is highly timeconsuming, laborious, and suspectable to errors [41][42][43]. Formwork accounts for 60% of total construction cost, 10% percent of formwork material, and 50% is labor used to design, install, and remove temporary formwork construction [44]. A detailed distribution of the cost of conventional construction is shown in Figure 1. ...
... This study comprehensively analyzed 77 mix designs to generate a model for flexural strength [44,107,[152][153][154][155][156][157][158][159][160][161][162][163][164][165][166][167]. Additionally, 49 mix designs were examined to develop a model for tensile strength [117][118][119][120][121][122]129,[132][133][134][135]. ...
The additive manufacturing of concrete, also known as 3D-printed concrete, is produced layer by layer using a 3D printer. The three-dimensional printing of concrete offers several benefits compared to conventional concrete construction, such as reduced labor costs and wastage of materials. It can also be used to build complex structures with high precision and accuracy. However, optimizing the mix design of 3D-printed concrete is challenging, involving numerous factors and extensive hit-and-trail experimentation. This study addresses this issue by developing predictive models, such as the Gaussian Process Regression model, Decision Tree Regression model, Support Vector Machine model, and XGBoost Regression models. The input parameters were water (Kg/m3), cement (Kg/m3), silica fume (Kg/m3), fly ash (Kg/m3), coarse aggregate (Kg/m3 & mm for diameter), fine aggregate (Kg/m3 & mm for diameter), viscosity modifying agent (Kg/m3), fibers (Kg/m3), fiber properties (mm for diameter and MPa for strength), print speed (mm/sec), and nozzle area (mm2), while target properties were the flexural and tensile strength of concrete (MPa data from 25 literature studies were collected. The water/binder ratio used in the dataset ranged from 0.27 to 0.67. Different types of sands and fibers have been used, with fibers having a maximum length of 23 mm. Based upon the Coefficient of Determination (R2), Root Mean Square Error (RMSE), Mean Square Error (MSE), and Mean Absolute Error (MAE) for casted and printed concrete, the SVM model performed better than other models. All models’ cast and printed flexural strength values were also correlated. The model’s performance has also been checked on six different mix proportions from the dataset to show its accuracy. It is worth noting that the lack of ML-based predictive models for the flexural and tensile properties of 3D-printed concrete in the literature makes this study a novel innovation in the field. This model could reduce the computational and experimental effort required to formulate the mixed design of printed concrete.
... It is well-known that the formwork cost in reinforced concrete (RC) construction takes away a significant share of the budget. According to Paul et al. [2], the formwork costs up to 60% of the overall cost, further differentiated into 10% (material cost) and 50% as formwork labor expenses. Another issue is formwork preparation time, which consumes 50% to 70% of the total construction span [3,4]. ...
... It is an extrusion-based technique where the printer nozzle extrudes the concrete, and for efficient and smooth extrusion, the rheological properties of the mix are critical. Rheology of the concrete influences the ease of pumpability before extrusion and shape retention of layers after extrusion without any deformation of the layers, which need to hold the weight of subsequent printed layers [2,20]. The viscosity of concrete needs to be maintained using various specialized admixtures to ensure the flowability during extrusion and the hardening of layers after extrusion. ...
... Therefore, 3DPC must show thixotropic nature where it should show high yield stress in rest (static yield stress) and lesser viscosity when in the flow state. The 3D printing of concrete should have smooth extrusion from the transportation pipe and be feasible to hold the weight of subsequent layers needed for shape stability [2,32,38,40,41]. 3DPC requires deposition in layers; the yield stress of any layer placed on top of another layer should increase according to its weight. ...
This study presents a detailed assessment of current technical obstacles and the potential for newly developed 3D printing concrete technology. This novel construction strategy will transform the building geometry features while saving time and money, but it still faces several technical, environmental, and operational obstacles. This study combines the knowledge of the most recent publications with the author’s view to address and explore the significant operating aspects, practicality, and possibilities for novel three dimensional printed concrete (3DPC) technology. This paper is organized into seven main categories: prominent parameters for 3DPC, raw materials, mix design methodology, the effect of concrete ingredients on the properties of 3DPC, 3DPC microstructure, reinforcement in 3DPC, field applications and sustainability of 3DPC are covered. Furthermore, solutions for the problems, scope, and economic and environmental challenges have been presented. It was found that this technology needs maturity at different levels, such as technical, economic, and environmental before implementation for practical applications.
... Set of trial experiments done in past has indicated a flow value of 50-60 % suitable for designing the printable mixtures. Similar flow values are reported in the literature for printable concrete [10][11][12][13][14][15]. The rheological measurements with granular suspensions like cementitious mixtures are prone to effects like particle migrations and solvent drying. ...
... The rheological measurements with granular suspensions like cementitious mixtures are prone to effects like particle migrations and solvent drying. These factors may have an influence on the results and are some of the limitations on performing rheological measurements with cement-based materials [14][15]. While a highly workable material is needed for 3D concrete printing to ensure easy transportability (usually by pumping) to the printing head, the extruded material is required to be relatively stiff to ensure that the deposited filaments retain their shape [16]. ...
... The initial obtained shear stress of printable mix is given in Table 6. The influence of superplasticizers on the viscosity has been investigated before by past researchers [10][11][12][13][14][15], and there exists a general agreement on the fact that, although superplasticizers decrease the yield stress, it does not decrease the viscosity of the cementitious mixtures significantly. It was seen that the increase in yield stress with increase in a/b is not significant as compared to the increase observed for the plastic viscosity. ...
The printing process is a novel digitally-controlled additive manufacturing method which can build architectural and structural components without formwork, unlike conventional concrete construction methods. The most important fresh properties are extrudability and buildability, which have mutual relationships with workability and open time. These properties are greatly influenced by the mix proportions and the presence of superplasticiser, retarder, accelerator and polypropylene fibres. The present study is about optimisation of material quantity to obtain a 3D printable mix with 3D printer. Cement, fly ash, silica fume, fine aggregate, water and chemical admixture are used for developing a 3D printable mix and optimum dose of chemical admixture such as PC base chemical admixture and Viscosity Modifying Admixture (VMA) is used to optimise the 3D printable mix. The study indicated that the dosage of superplasticizer needed to achieve the similar flow value increases as a/b increases. The plastic viscosity increased by about 35 % when a/b increased from 0.75 to 0.9. The flow was ranging from 160 to 225 mm which indicates dependency on the material type and packing density. Study also highlighted that yield stress of mix is important to achieve buildability and low yield stress value can lead to collapse of layers and will also prevent layer wise buildability. The optimum dose of polypropylene fibre was found to be 0.1 % to achieve 3D printable mix without clogging or shrinkage crack. The open time is found to be about 12—15 minutes for the materials. Studies reported in this paper highlights that both mix optimisation with different combination of cementitious binders and selection of optimum dosage of superplasticizer and VMA are very critical in achieving a 3D printable concrete.
... 18,19 One of the main disadvantages of 3D concrete is that it has anisotropic properties, unlike conventional concrete with isotropic properties. [20][21][22] As it is known, in structures produced with 3D technology, a monolithic material is formed by connecting the layers to each other. It was reported that the horizontal interface is formed between the layers as a result of extrusion perpendicular to the casting direction. ...
... Compared to conventional concrete mixtures, it was reported that the risk of shrinkage is higher in 3DPC mixes as a result of the absence of coarse material and the use of formworks (increased air contact surface). 20 Therefore, it was declared that there is a need to investigate methods such as the use of sulfoaluminate cement, the use of pozzolan, and the use of fiber in order to reduce shrinkage cracks in 3DPC mixtures. 17 For the development of 3DPC, it is important that the interlayer bonding strength is strong, as well as high compressive and flexural strength. ...
... In addition to these parameters, it was stated that the interlayer adhesion of 3DPC varies depending on parameters such as the rheological properties of the mixture, the interlayer interval time, the contact area between successive layers and the standoff distance. 20,59 It was found that splitting tensile, direct tensile and flexural tensile tests are used to determine interlayer adhesion. 136,137 In a study by Moelich et al., 85 the interlayer adhesion was determined using Equation (1): ...
In this study, the strength and durability performance of 3D printing concrete mixtures (3DPC) were examined in terms of the materials used in their pro- duction and printing process parameters (interlayer interval time, printing speed, and nozzle shape). Due to the anisotropic nature of 3DPC, it was under- stood that the compressive strength depends on the loading direction. It was emphasized that it is necessary to control the shrinkage behavior of 3DPC mix- tures due to the lack of formwork and the high dosage of binders. It was reported that the interlayer adhesion of 3DPC is highly dependent on the inter- layer interval time and printing speed parameters. It was understood that noz- zle shape and standoff distance affect the mechanical properties and surface roughness of 3DPC specimens, and this effect is more pronounced in mixtures with high static yield stress values.
... Many studies focused on the forming of these voids which have a harsh influence on the hardened properties of 3D printed structures Paul et al., 2018). According to (Le, Austin, Lim, Buswell, Law, et al., 2012a), the formation of these voids is dependent on the pump pressure and print quality which can reduce the volume of voids inside filaments (known as intra-filament voids), providing benefits to printed filaments' microstructure. ...
... From the author's perspectives, there are three loading directions: perpendicular, longitudinal, and lateral directions as many studies suggest following this approach when analyzing the anisotropic property (G. Ma et al., 2018Ma et al., , 2019Panda, Chandra Paul, et al., 2017;Paul et al., 2018;Wolfs et al., 2019). Figure 22 shows the testing directions that were followed in testing the flexural strength of the cutprinted filaments. ...
... The relationships between nozzle size (i.e. maximum dimension of rectangular or circular nozzle of 30 mm, 20 mm and 4 mm) and position corresponding to their compres- Fig. 5 that the lower compressive and flexural strengths can be obtained for smaller nozzle size [28][29][30]. The strength increases with increase in nozzle size. ...
... Relationship between nozzle size, compressive and flexural strength of geopolymer concrete[28][29][30]. ...
In the last centuries when the Additive Manufacturing (AM) started, the major focus was on mostly plas-tic and metal printing process. Using AM, the production of goods made of plastic and metal increased alot. Nowadays concrete is also produced by printing commonly known as Three Dimensional ConcretePrinting (3DCP). 3DCP is a process where a concrete like materials are extruded through a designated sizeand shape of the nozzle. The nozzle can be placed on a gantry or just connecting with a robotic arm andextruded any designated shape according to their digital design input. The aim of this paper is at summa-rizing the effect of mix design and printing parameters on the compressive and flexural strength of 3Dprintable geopolymer concrete. The results are collected from the published literatures from differentparts of the world specifically on 3D printable geopolymer mortars. Various relationships are developedfor mixing parameters such as activator to binder ratio, mix density, viscosity and compared with theircorresponding compressive and flexural strengths at 7 and 28 days. Similarly, strengths for printingparameters such as nozzle types, position of nozzle and loading direction are also investigated. A statis-tical data analysis (ANOVA) has been performed at the end to correlate the effects of these factors onstrength. It is found that the strength of 3D printable geopolymer mortars is greatly influenced by itsmix design and printing constraints.
... This leads to different degrees of compaction based on the orientation of the filament [12,13] and voids that tend to form between filaments since no vibration is employed after extrusion. Several authors [14][15][16][17][18] have performed flexural, compressive, and tensile bond strength tests to evaluate anisotropy in the hardened state of 3DCP specimens, considering three loading directions: longitudinal, perpendicular, and lateral. It has been shown that printed concrete exhibits anisotropic behavior with specimens loaded in the longitudinal direction display larger strength, which is explained by the higher pressure and consequent compaction during extrusion, This compaction results in fewer voids and less interfacial slip between filaments in the other directions. ...
... Compressive strength in cast cubes was 38%-82% higher than in printed cubes, which can be explained by the existence of inter-and intra-voids ( Fig. 23) in printed specimens that result from the printing process. These results are in accordance with other studies that reported larger compressive strength in cast specimens and attributed the differences to the distribution and existence of inter-and intra-gaps [14,16], and differential water evaporation [51]. On average, printed cubes reached a compressive strength close to 20 MPa after seven days, while cast cubes exceeded 25 MPa. ...
... However, in most experimental and industrial production installations for 3DCP, the concrete is pumped by an extruder and flows usually through a conical or rectangular nozzle which is significantly different from ram extrusion through a round orifice. 8,[12][13][14][15] Paul et al. 16 20 measured the rheological properties of two fine-grained concretes for 3D printing, using a Couette type rotational viscometer, where the inner cylinder remains stationary and the outer one rotates at specific speeds. In the study by Alghamdi et al. 9 , a parallel plate rheometer was employed to carry out rheological analysis of several 3D-printable alkaliactivated fly ash-based binders. ...
The additive manufacturing technology of extrusion of concrete mixtures through a nozzle and deposition layer-by-layer is commonly called three-dimensional concrete printing (3DCP). Such materials are rheologically characterized by yield stress and viscosity. The Bingham model is a good approximation of their rheological behavior. We have developed approximate expressions for determination of pressure for flow through slightly tapered tubes and wedge-shaped extrusion dies, starting from the Buckingham–Reiner equation for flow of a Bingham fluid in a straight tube. The predictions are compared to numerical simulations for convergence half-angles (taper) from 0° to 30° and to analytical solutions available in the literature. Good comparison has been obtained for taper angles up to 15° but the agreement deteriorates as the angle increases. Some experimental data available in the literature have been analyzed, and the challenges for prediction of pressure drop in flow of concrete mixtures through tubes and dies, including entry flow losses, are discussed.
... According to (Camacho et al., 2018), cementitious materials, metallic materials, and polymer materials are the most often used materials in 3D printing. The current research on 3D printing focuses on other materials like cementitious materials (Huang et al., 2013;Paul et al., 2018;Soltan & Li, 2018), polymer materials (Ju et al., 2017;Panda et al., 2017;Yao et al., 2019) and metal materials (Buchanan & Gardner, 2019;DebRoy et al., 2018;Frazier, 2014). The 3D printing process involves the input process of fresh materials into the 3D printing machine and the output process of a 3D-printed object. ...
The need to implement sustainability in construction has given birth to 3D printing innovation. It is also a potential construction technique by which the construction industry contributes to sustainable development. 3D printing has recently gained more interest in construction, thereby promising automation of building processes with its advantages in faster production, cost reduction, material minimization, and greater environmental soundness. However, numerous barriers have limited the adoption of 3D printing in construction in various parts of the world. Little consideration has been given to assessing empirical studies of current knowledge of barriers to 3D printing adoption. This paper provides a comprehensive literature review on the key barriers to 3D printing in construction. In this study, the Preferred Reported Item for Systematic Review and Meta-Analyses (PRISMA) guideline was adopted to report the systematic review of the relevant past empirical studies on the barriers hindering the implementation of 3D printing in the construction industry. A total of 36 barriers were identified during the review and classified into six (6) categories. Thirteen key barriers hindering 3D printing implementation in the construction industry were identified and discussed. This study contributed to the knowledge of the barriers hindering the adoption of 3D printing. It will enable the built environment professionals to make the right choice when it comes to how 3D printing can improve the sustainable delivery of buildings.
... Produced ceramic objects using extrusion-based AM processes are prone to such limitations [328]. These defects can be minimized by loading high solid in the feedstock, accurate control of the feedstock viscosity, temperature of the built environment, and changing the nozzle design [329]. The same inconvenient and solutions to limit them can be reported for DLP, with the exception of the nozzle design. ...
... Last but not least, the rheology plays very important role during the design process of any concrete or concrete-similar materials. In the literature, we can find, for instance, Feys [4] and Paul [5], who were dealing with this phenomenon. ...
In this paper, information about cementitious composite materials for further 3D processing is discussed and supplemented. Many of the research in this area focuses primarily on cement composites suitable for 3D printing. Nevertheless, 3D printing is not the only robotic processing technique. Another such a technology is modelling with the help of a robotic arm, which can be used to create various elements that fulfil their original but also aesthetic function. The robotic arm creates, using a variety of sculptural or hand tools, a final unique relief of a given element. Three different cement composite mixtures are discussed and their mechanical, physical and thermophysical properties are evaluated. The research aims to investigate and optimise these composites for robotic sculpturingand 3D printing.
... Thus, the direction in which the printed samples were tested did not have much influence on the strength of the mixtures. This finding coincides with that of Wolfs et al. [78], who found a minor influence of layer orientation with respect to the applied load, in contrast to other studies that reported a clear influence of load direction on the strength properties of printed specimens [79][80][81][82]. ...
Concrete 3D printing is one of the newest technologies in the field of construction. However, despite the various opportunities that this technique offers today, it still has a high environmental impact, as most 3D-printable materials contain high amounts of cement. On the other hand, due to the large volumes of soil excavated each year across the world, there is a pressing need for proper management to dispose of it or reuse it efficiently. This study aims to develop sustainable and resistant 3D-printable materials with low environmental impact using excavated soil. Firstly, a series of tests were carried out to find the most appropriate superplasticizer and the amount required to develop the printable mixtures. Next, the extrudability and buildability were evaluated and verified to validate the printability of the developed mixtures. A 3D laboratory printer was also used to validate the printability of the mixtures on a larger scale. Then, the fresh and hardened properties of the printable mixtures were investigated. Three printable mixtures were developed, with the most environmentally friendly mixture having a soil content of 1602 kg/m3 and a cement content of 282 kg/m3. The mixtures demonstrated satisfactory characteristics and properties in both fresh and hardened states. On the one hand, the mixtures were extrudable and buildable at two laboratory scales. On the other hand, the mixtures presented sufficient compressive strengths, ranging from 16 MPa to 34 MPa, despite their high soil content and low cement content. In addition, their compressive strengths were found to be higher than the minimum strength required for structural concrete. Consequently, this study highlights the possibility of developing ecological, sustainable and resistant mixtures that can be used in 3D-printing construction applications using excavated soil.
... The composite showed orthotropic properties. The uniaxial compressive strength in the direction of layer stacking was lower than that of the direction perpendicular to it, by 42.6% in the case of net reinforcement without heat treatment, 42.9% in the case of net reinforcement followed by the freeze-thaw test, and 29.8% without net reinforcement and heat treatment [15,41,46]. ...
The increasing popularity of additive manufacturing technologies in the prototyping and building industry requires the application of novel, improved composite materials. In this paper, we propose the use of a novel 3D printing cement-based composite material with natural, granulated cork, and additional reinforcement using a continuous polyethylene interlayer net combined with polypropylene fibre reinforcement. Our assessment of different physical and mechanical properties of the used materials during the 3D printing process and after curing verified the applicability of the new composite. The composite exhibited orthotropic properties, and the compressive toughness in the direction of layer stacking was lower than that perpendicular to it, by 29.8% without net reinforcement, 42.6% with net reinforcement, and 42.9% with net reinforcement and an additional freeze–thaw test. The use of the polymer net as a continuous reinforcement led to decreased compressive toughness, lowering it on average by 38.5% for the stacking direction and 23.8% perpendicular to the stacking direction. However, the net reinforcement additionally lowered slumping and elephant’s foot effects. Moreover, the net reinforcement added residual strength, which allowed for the continuous use of the composite material after the failure of the brittle material. Data obtained during the process can be used for further development and improvement of 3D-printable building materials.
... However, study on the use of this technique in the construction industry is still lacking as compared to the manufacturing industry (Furet et al., 2019). Moreover, a research database is limited to studying the performance and mechanical properties of 3DP mortar material and the behavior of the material during the printing procedure (Paul et al., 2018), (A. S. J. Suiker, 2018), (A. S. Suiker et al., 2020), (Wolfs et al., 2019), (Panda et al., 2017). Although the technique is unique and has several benefits, the study of 3D printed (3DP) walls as structural members are still to be explored. ...
This study reports an experimental and numerical examination performed on a 3D printed (3DP) wall subjected to vertical axial compression. A detailed investigation of material property and full-scale testing of the 3DP plain wall was performed to explore the structural performance of the 3D printed wall. To obtain the mechanical properties of mortar, test prisms obtained by printing mortar as layers resulted in undesirable failure modes. Hence, this study proposes a unique methodology to obtain the mechanical property of mortar with an assumption of mortar material as isotropic. However, to consider the effect of the interface within the printed layers, interface strength tests in terms of normal and shear strength were performed. Likewise, the behavior of 3DP wall being anisotropic, a unique analysis concept was adopted in a current study comprising of modelling the printed layers as in actual thickness and cross-section and providing material property obtained from an assumption of mortar material as isotropic. Moreover, orthotropic material properties of the printed material were provided to FE models via testing of the 3D printed specimens parallel and normal to the interface. The full-scale test specimen was modeled as layers in a numerical tool and results from the test and simulation were compared in terms of load-displacement behavior, distribution of strain on the wall surface, and damage pattern of the wall. Moreover, recommendation on the selection of the suitable material model and contact algorithm is provided in the current study for simulating the behavior of 3DP structures.
... Previous studies have proved the feasibility of this new LCM, which exhibits good performance at an early stage and continuous performance improvement at a later stage [31][32][33]. The layer-by-layer process and absence of vibration in 3D printed mortar result in more pores compared to cast mortar [16,[34][35][36][37][38][39]. However, the coupling effect of GGBS and CBP on pores in 3D printed mortar is not yet clear, and the printability of 3D printed mortar may also be affected by GGBS and CBP. ...
... The amount of deformation in the concrete samples with the weight increment is shown in Fig. 5. In most cases, the deformation value of geopolymer concrete is 2-6 %, which is measured immediately after mixing the concrete [19,20]. A similar deformation value was obtained in this study after 10 and 6 minutes of setting time by adding heat. ...
This research study is primarily focused on evaluating the fresh properties of industrial-based 3D printable geopolymer concrete by adding glass wool strings and glass fibers activated by sodium silicate solution with a molar ratio of 2.4-2.6 (31 % SiO 2 and 13 % Na 2 O). The glass wool strings, and recycled glass fiber are added to industrial-based geopolymer concrete at a dosage of 1 % to 5 % by volume of the concrete. The fresh concrete properties such as open time, setting time and shape stability of industrial-based geopolymer concrete (GPC) with glass wool and glass fibers were compared with those of industrial-based GPC without glass wool strings and glass fibers. The results show that the addition of glass wool increases the setting time of the concrete mix at room temperature. The deformation of the specimens at room temperature decreased by 39 %. The addition of glass fiber in geopolymers also increases the stiffness by 74 % compared to GPC without glass fiber.
... Studies show that there is no relationship between yield stress and thixotropy. A minimum of 10,000 N mm rpm of thixotropic value is necessary for 3DCP [67]. All the above rheological properties that are studied are interlinked with the mix design of the concrete. ...
Rapid construction with an energy-efficient approach is a major challenge in the present construction industry. Cement, a carbon-intensive material, is mainly used in the construction industry and hence increases the sector's carbon footprint on the environment. The current review focuses on the study of 3D concrete printing (3DCP), in which cement is partially replaced with industrial byproducts such as ground granulated blast furnace slag (GGBS), fly ash, and silica fume. Walling material is primarily targeted in 3DCP. There is a need to include energy efficiency to achieve a thermally comfortable environment. The life cycle assessment (LCA) of concrete is studied to discover the potential conflicts affecting the environment. The sand-to-binder ratio is pivotal in determining the performance of concrete. The content of the supplements is decided based on this factor. The rheological, physical, and mechanical properties of 3DCP are studied further and analysed. GGBS demonstrates better performance in the compressive and flexure strength of concrete. The usage of fly ash and silica fume has reduced the thermal conductivity of the material, whereas GGBS has increased it. An LCA study shows that 3DCP can be made sustainable with the use of these supplementary cementitious materials.
... Among all methods in the 3DCP technology, the one which is most widely used is extrusionbased 3DCP [7], where the fresh state cementitious material is extruded layer by layer via a pumping system without any formwork [8]. Since the cost of formwork and corresponding labor accounts for a significant part of the total cost [9], the 3DCP can save the total cost of construction [10]. Additionally, same as the 3D printing technology in other fields, the ...
Recently, 3D printing technology has become more popular in the field of construction. For the extrusion-based 3D concrete printing (3DCP) process, the cementitious material needs to be strong and flowable enough to ensure buildability and pumpability. Nanostructured silica, a kind of additive, has been used to modify the 3DCP concrete to meet these requests. However, most previous studies focused on the effect of nanostructured silica on rheological properties and failed to link the obtained rheological properties of nanostructured-silica-modified cementitious materials to the performance in 3D printing. In this paper, the 3DCP mixture based on premix cement, river sand, silica fume, and water was modified by different dosages of nanostructured silica (from 0.25% to 1.00% by the total weight of the 3DCP mixture). The effects of nanostructured silica on the rheological, hydration, printing, and microstructural properties were determined by rheological tests, stress growth tests, setting time tests, printing tests, and scanning electron microscopy (SEM) tests, respectively. This paper revealed that the nanostructured silica has a positive effect on 3DCP buildability but negatively affects the printing quality, which fits the effect of nanostructured silica on the rheological properties. Hence, the determined rheological properties can qualitatively evaluate the printing performance of nanostructured-silica-modified cementitious materials.
... Несмотря на большой объем исследований и разработок [1][2][3][4][5][6][7][8][9], сегодня 3D-печать в строительной практике применяется только для возведения оболочки вертикальных конструкций, преимущественно стен, армирование и отделка которых осуществляется традиционным ручным способом. Изменить данную ситуацию можно двумя способами. ...
Introduction. As part of the solution for the problem of creating a new class of materials for building additive technolo�gies, cement composites reinforced with high-strength fiber, this work presents the results of experimental studies of the strength of the adhesive bonding between cement matrices and reinforcing fibers with different chemical compositions, diameters, and tensile strength. Materials and methods. Rheological properties of cement systems were studied using shear and squeeze rheometry, the method of micromechanical testing for determining the strength of the adhesive bonding “cement matrix – reinforcing fiber” based on the pull-out test, which involves pulling out the fiber from the cement matrix layer; after the pull-out test for all the studied systems, the microstructure of the contact surface “cement matrix – reinforcing fiber” was assessed using a Thermo Scientific™ Phe�nom™ Desktop SEM scanning electron microscope; the compressive strength of hardened cement paste-samples was determined using an INSTRON Sates 1500HDS testing machine. Results and discussions. It was established that the combination of strength characteristics of matrices, fibers, and adhesive strength at their interface allowed securing the required strength characteristics of reinforced construction composites. In the “cement matrix – carbon fiber” systems, the value of adhesive strength was 9 – 11 MPa; in the “cement matrix – steel wire” systems, the value of adhesive strength was 3 – 4 MPa. Conclusions. Matrices with viscosity modifiers containing nano- and micro-sized particles of SiO2 (complex nano-sized additive and metakaolin) are reasonable options for combinations of the “cement matrix – reinforcing fiber” components. Carbon fiber and steel wire are recommended to be used as reinforcing fibers.
... Buildability is the ability of the printed mixture to retain its geometry under the loads brought from the upper layers [87]. Buildability mainly depends on the static yield stress [14], which is affected by OPC replacement level, water content, and calcined clay grade. ...
The rapid development in 3D printing applications requires exploring a sustainable printable mixture to decrease the environmental impact induced by the existing Ordinary Portland Cement (OPC) mixtures and enable 3D printing technology to reach its peak efficiency. The high-volume substitution of OPC with supplementary cementitious materials (SCMs) is of significant interest as a promising solution for developing low-carbon feedstock for 3D printing. Yet, those materials share the problem of limited availability. The combination of limestone and calcined clay could be a promising alternative, offering various benefits, including replacing OPC in high ratios. This paper reviews 3D printable limestone calcined clay cement (LC3) mixtures, compositions, and chemical behaviour. The effect of different sand-to-binder ratios, additives content, OPC replacement levels, clay grade and calcination, and admixtures on the fresh, hardened and printing properties of the 3D printed mixtures are critically discussed. The environmental impact and production cost of the LC3 system compared to OPC and other systems are also critically evaluated along with the applications, future directions and research gaps in this field. The findings of this review show that 3D printed LC3 has a similar hardened performance and better microstructure than OPC system. Moreover, cast LC3 system has 30–50% lower environmental impacts depending on the replacement level and better economic feasibility than OPC. Therefore, making it a suitable feedstock for the innovative manufacturing technology of 3D printing.
... It has been demonstrated that 3D printing technology has advantages, including high efficiency, flexibility, and environmental benefits, when used for both conventional right-angle wall printing and complex-shaped buildings [159]. Numerous laboratory studies have been conducted on the performance and characterization of concrete containing fine aggregate printed with 3D printers [160][161][162]. Concrete with coarse aggregate has recently been used in 3D printing technology. ...
Natural fibers or their derivatives have gained significant attention as green fillers or reinforcement materials due to their abundant availability, environment-friendly nature and biodegradability for sustainable development. Despite the availability of modern alternatives such as concrete, glass-fiber/resin composites, steel, and plastics, there is still considerable demand for naturally occurring based materials for different applications due to their low cost, durability, strength, heat, sound, and fire-resistance characteristics. 3D printing has provided a novel approach to the development and advancement of natural fiber-based composite materials, as well as an important platform for the advancement of biomass materials toward intelligentization and industrialization. The features of 3D printing, particularly fast prototyping and small start-up, allow the easy fabrication of materials for a wide range of applications. This review highlights the current progress and potential commercial applications of 3D printed composites reinforced with natural fibers or biomass. This study discussed that 3D printing technology can be effectively utilized for different applications, including producing electroactive papers, fuel cell membranes, adhesives, wastewater treatment, biosensors, and its potential applications in the automobile, building, and construction industries. The research in the literature showed that even if the field of 3D printing has advanced significantly, problems still need to be solved, such as material incompatibility and material cost. Further studies could be conducted to improve and adapt the methods to work with various materials. More effort should be put into developing affordable printer technologies and materials that work with these printers to broaden the applications for 3D printed objects.
... These flat voids can be observed in all the printed samples (see Figures 12d, 13d, 14d and 15d). These flattened voids may have caused the anisotropic properties in the printed samples, as mentioned by Suvash et al. [36]. Figure 13 shows the cast and printed samples containing cenosphere aggregate replacement. ...
Concrete 3D printing is a sustainable solution for manufacturing efficient designs and creating less waste, and selecting the optimal materials to use can amplify the advantages of this technology. In this study, we explore printing lightweight concrete by replacing normal weight aggregate with lightweight aggregates such as cenospheres, perlite, and foam beads. We adopt a systematic approach to investigate mixtures using different formulation methods such as the specific gravity and packing factor methods to improve the printing and mechanical performances of the mixtures. The rheological results showed significant improvement in the flow characteristics of the different mixtures using both the specific gravity method and the packing factor method to formulate the mixtures. Furthermore, a statistical tool was used to achieve optimal performance of the mixtures in terms of high specific compressive strength, high flow characteristics, and good shape retention capability by maximizing the specific compressive strength ratio, slump flow, and the static yield stress, while minimizing the slump, dynamic yield stress, and plastic viscosity. With the above design objectives, the optimal percentages of the aggregate replacements (cenosphere, perlite, and EPS foam beads) were 42%, 68%, and 44%, respectively. Finally, the optimized results also showed that the mixture with cenosphere aggregate replacement had the highest specific strength.
... Since Pegna's groundbreaking work, there has been a general trend toward expanding applications of 3D printing in architectural design all across the world [9]. Due to the limitation of these technologies, 3DPC is generally unable to install a reinforcing steel bar [10,11]. In addition, 3DPC is exposed to quick shrinkages, which are drying, self-drying and especially plastic shrinkage in the early hours after printing [12][13][14][15]. ...
Three-dimensional printed concrete (3DPC) is emerging as a new building material. Due to automation, this method dramatically decreases construction time and material wastage while increasing construction quality. Despite the mentioned benefits, this technology faces various issues. Among these issues, the inability to use steel bars for reinforcement and early age cracking because of the low water-to-binder ratio and high amount of binders can be mentioned. In this regard, due to the superior properties of fiber-reinforced concrete (FRC), such as high first crack strength, tensile strength, improvement ductility, and resistance to shrinkage cracking, one of the effective ways to reinforce the mixture of the 3DPC is to use fibers instead of steel bars. Regarding the mentioned issues, the effects of different fibers, such as steel, carbon fibers and so on, on fresh and mechanical properties and dimensional stabilities of hardened concrete have been reviewed. It is predicted that using fibers, especially hybrid fibers, not only covers the deficiencies of initial cracking of 3DPC, but also can be used instead of steel bars; therefore, this material can play a pivotal role in the construction industry's future.
... AM is in contrast to subtractive manufacturing, as seen in sculpting, and casting, where materials are poured into molds. A large number of materials can be 3D printed, including polymers [39,76], metals [77,78], ceramics and glass [79,80], cement [81], carbon materials [82], magnets [83], elastomers and nanoparticles [84]. Even electronic structures have been 3D printed [84,85]. ...
... This situation can be challenging for large-scale construction projects [38]. In addition, additive manufacturing uses a filament which could impact material load-bearing capacity and strength properties [39]. This setting is due to the directional dependency used in layered manufacturing. ...
Three-dimensional (3D) printing, or additive manufacturing (AM), is a production can be utilised to fabricate 3D shapes from a simulated file. This technology has gained global popularity in the construction industry since 2014 due to its wide range of applications. AM promotes a more automated, innovative, flexible, and sustainable construction method, making it an integral part of the Construction Industry 4.0. However, there need to be more detailed studies regarding the effectiveness of AM as the future direction in the construction industry. This paper investigates the application of the finite element method (FEM) in assessing 3D-printed structures to get insight into the performance of these structures. Three leading 3D-printed structures were selected, including Dubai Future Foundation in the United Arab Emirates, Apis Cor house in Russia and PERI house in Germany. Structural and thermal analyses, including linear static, natural frequency, spectral response, and steady state heat, were performed using Strand7 to assess the effectiveness of AM in construction and the reliability of FEM in analysing 3D-printed structures. Although there are limited standards and regulations for 3D-printed structures in most countries, it was concluded that 3D-printed structures presented a similar strength to traditional ones. Moreover, FEM can be used to provide a reasonable analysis of the performance of these structures, while complying with the relevant standards. This paper presents a novel numerical procedure to assess the performance of small-scale 3D-printed structures under various mechanical and thermal loadings by checking against the relevant standards.
... Ma et al. [20] conducted various mechanical tests on aligned fiber reinforced composites for extrusion-based 3DPC and observed anisotropy in such materials. Paul et al. [21] extracted samples from large 3DPC structures in various orientations and tested their mechanical properties. The mechanical properties were found to be governed by the printing orientations. ...
In-situ printing leads to distinctive features of 3D printed concrete (3DPC) to conventional casting concrete, and the temperature of its service environment has significant impacts on the performance development of 3DPC. This emphasizes the importance of investigating the relationships between the structural strength and temper-tures considering the characteristics of 3DPC. A maturity model that is suitable for 3DPC was therefore established via tests and least squares regression analysis of the tested results in this paper. The maturity model was verified and calibrated by examining the mechanical properties of 3DPC cured under both fixed and varied environmental temperatures. The anisotropy of the specimens with different temperatures and curing ages was also examined and discussed. It was observed that the proposed maturity model might be able to be applied to the in-place evaluation of early age mechanical properties of 3DPC, with a maximum error of 6.67% for compressive strength and 3.27% for flexural strength under outdoor temperature curing conditions. With the increase of age and curing temperature, the anisotropy parameter of compressive strength tends to approach the limit value obtained by S u. It was also found that there are no significant mechanical-anisotropic behaviors for flexural strength between Y and Z directions.
... Most current research is focused on the 3D printing of concrete [2][3][4], studying its properties when both fresh and hardened [5], looking at how to optimize it [6,7], how to reduce waste and how to make it more environmentally friendly [8]. Work is being conducted on the life cycle adapted to 3D printing in concrete [9], while materials such as clay are undervalued. ...
Clay is of great interest as a 3D printing material thanks to its ease of use, recyclability and reusability. This paper analyses the technical aspects of the whole printing process. The behaviour of 3D printing clay is studied with respect to the environment and its specific application as a temporary or definitive formwork system for cement parts. The study addresses the performance of clay and the loss of its properties and characteristics according to the type of protection, whether it is in direct contact with air or cement, or protected with plastics, metal sheets, or combinations of both. A 3D printing system with various printers and 3D models has been considered, observing a direct relationship between the prototype shape, extrusion process and resulting material. The most important variables in 3D printing have been considered: layer height, line thickness, base definition, total model height, overhang angles, overlap between layers, etc. The main technical aspects have been analysed such as raw material properties, kneading, process control, post-treatments and material hardening. As a natural material, clay can be reused indefinitely under certain conditions to be part of a circular economy with low energy consumption and minimal resources. It is concluded that the option of using ceramics in 3D printing for very diverse uses in the architecture, engineering & construction (AEC) sector is very promising due to their ease of implementation, recycling capability and suitability to different environments.
... Therefore, many researchers have concentrated on mixture designs or the strength of 3D printed concrete. Paul et al. [7] introduced a 2 of 5 mixing ratio for 3D printing using cement, and the 28 day compressive strength of the produced concrete was measured, 36-57 MPa, and the bending strength was 10 MPa. Le et al. [8] designed a high-strength fiber-reinforced concrete with a compressive strength of 92 MPa and a flexural strength of 11 MPa. ...
Three-dimensional (3D) printing applications have emerged as a new production method in the construction industry. The materials that are to be used in 3D production process play an important role for a sustainable built environment. The main objective of this study is to design a suitable mixture to produce 3D printed concrete paving stones. In this respect, a unique 3D printer was also developed. The results show that the setting time of cement-based mortars was shortened by increasing the ratio of the added accelerator admixture. However, the optimum mixture proportions for 3D printed concrete paving stones were not reached. The results of the study are expected to develop a sustainable method of paving stone production.
... This phenomenon is undoubtedly true when the object is more extensive, and printing takes longer. The mechanical characteristics of the specimens taken from the various positions of the object would also be varied dramatically for the same reason [164]. ...
This study reviews the essential aspects of implementing Additive Manufacturing in the construction sector by highlighting the key benefits and challenges. A comparative review allows identifying the leading technologies and prospects that have been utilized in this particular area. In recent years, research into the application of 3D printing in the building industry has increased significantly worldwide. Moreover, various systems and robotic arms have been investigated to enhance buildings’ productivity. Even though there are various manufacturing methods, this article reviewed current material extrusion technologies widely used in this field. The article critically evaluates the materials used in printed structures, polymer, and cementing. The problems of reducing carbon dioxide emissions through the introduction of geopolymers are also considered. The paper focuses on four areas or directions or dimensions. First, the central concept and classifications of AM and the crucial advantages of utilizing its technologies in the construction sector are discussed. Second, material extrusion techniques and their types, including cementitious and polymer materials and large-scale 3D printing technologies are examined. Third, the ways of reducing negative impacts on the building industry by implementing geopolymers and their current development are described. Fourth, the crucial challenges of using 3D printing approaches and their future direction should be focused on are put forward. Moreover, this article provides lists of companies that produce modern 3D printers from all over the world.
... The viscoelasticity theory, which combines the viscous and elastic characteristics, can be used to explain how viscoelastic materials react [14]. To assess the elastic material behaviour, several testing techniques, including the unconfined uniaxial compression test [13,[15][16][17], direct shear test [18], rotational rheometer [5,19], and ultrasonic wave transmission test have been used [20]. These techniques allow for the experimental derivation of the green strength, yield stress, and pulse velocity, providing the fundamental material characteristics related to elastic and plastic deformation for structural deformation prediction. ...
3D printing concrete technology is an integration of material preparation, geometric modeling, structural design, and construction with the essential advantages of green, low-carbon, and intelligent construction, which had a booming development in recent years. Due to the specificity of printing materials and printing technology, 3D printing concrete exhibits unique macroscopic anisotropy, and the research on the constitutive relation of 3D printing concrete is still insufficient. Although there are numerous engineering cases of 3D printing concrete, mature structural reinforcement enhancement methods as well as quantitative structural bearing capacity analysis theories and methods are still needed to be studied. To adapt to the specific requirements of materials and printing processes, and achieve the efficient usage of materials, the optimal design is essential for 3D printing concrete structures. The field of optimal design of 3D printing concrete is currently in its infancy. Finally, the printing, connection, and construction methods of the slab, shell, beam, and arch structures provide a multi-faceted reference for 3D printing concrete structures. In general, the selection of 3D printing concrete materials and structures as well as the design and construction of structures are problematic. Based on the above-mentioned, this paper reviews four aspects which include mechanical properties of materials, structural forms, optimal design, and connection construction methods in the context of engineering examples.
The interest and knowledge in the research field of 3D concrete printing are vastly increasing. With the rise of more established printing methods and materials, larger elements with a higher degree of geometric complexity can be printed. This allows to shift the research focus towards the structural application of 3D printed concrete. The need for numerical modelling of these printed structures arises, wherein insight into the elastic properties of the material is essential. Multiple sources report about a certain degree of anisotropic behavior in the failure state, but researchers fail to reach a consensus concerning the degree of anisotropy in the elastic range in the hardened state of the homogenized material. During an exploratory experimental study, the directional dependency of cylindrical printed specimens is investigated based on uniaxial compression tests and optical displacement measurements. Cast cylinders and 3D printed cylinders in two different orientations are compared. Quasi-static moduli of elasticity are quantified in accordance with the concrete standard EN 12390-13, after which a preliminary conclusion concerning the degree of anisotropy of 3D printed concrete is presented. With this information, a new step is taken towards the numerical modelling of 3D printed concrete in order to use it for structural applications.Keywords3D Printed ConcreteAnisotropyHardened PropertiesOptical Displacement MeasurementUniaxial Compression Test
This paper proposes a machine learning (ML) model to predict the 3D printed polypropylene fiber-reinforced concrete (3DP-PPRC) rheological properties, in which dynamic yield stress (DYS) plays a vital role. ICAR rheometer is used to measure the yield stress of the concrete mixture, where 41 mixtures were used to compile the data. In this research, four machine-learning models have been used to predict the DYS of the 3DP-PPRC, accounting for different water binder ratios (W/B) and polypropylene (PP) fiber content. The code has been generated in Python scripts. Several ML models such as random forest (RF), support vector machine (SVM), extreme gradient boosting (XGBoost), and light gradient boosting machine (LightGBM) have been used to predict the DYS, considering 80% and 20% data for training and testing, respectively while the model’s accuracy, MSE, RMSE, MAPE, and R2 were also calculated for 3DP-PPRC. The influence of each rheological parameter in the ML-based of 3DP-PPRC, Shapley additive explanations (SHAP) are also accompanied. The outcomes proved that utilizing an ML model to estimate the yield stress of 3DP-PPRC using PP fiber is a dominant approach.
Three-dimensional Cementitious materials Printing (3DCP) is a cutting-edge technology for the construction industry. Three-dimensional printed buildings have shown that a well-developed automated technology can foster valuable benefits, such as a freeform architectural design without formworks and reduced human intervention. However, scalability, commercialization and sustainability of the 3DPC technology remain critical issues. The current work presents the ecological fragility, challenges and opportunities inherent in decreasing the 3DCP environmental footprint at a material level (cementitious materials and aggregates). The very demanding performance of printable mixtures, namely in a fresh state, requires high dosages of cement and supplementary cementitious materials (SCM). Besides the heavy carbon footprint of cement production, the standard SCM availability might be an issue, especially in the longer term. One exciting option to decrease the embodied CO 2 of 3DCP is, for example, to incorporate alternative and locally available SCM as partial cement replacements. Those alternative SCM can be wastes or by-products from industries or agriculture, with no added value. Moreover, the partial replacement of natural aggregate can also bring advantages for natural resource preservation. This work has highlighted the enormous potential of 3DCP to contribute to reducing the dependence on Portland cement and to manage the current colossal wastes and by-products with no added value, shifting to a Circular Economy. Though LCA analysis, mixture design revealed a critical parameter in the environmental impact of 3DCP elements or buildings. Even though cement significantly affects the LCA of 3DCP, it is crucial to achieving adequate fresh properties and rheology. From the literature survey, mixtures formulated with alternative SCM (wastes or by-products) are still restricted to rice husk ash, Municipal Solid Waste ashes and recycled powder from construction and demolition wastes. Natural aggregate replacement research has been focused on recycled fine sand, mine tailing, copper tailing, iron tailing, ornamental stone waste, recycled glass, crumb rubber, rubber powder and granules, recycled PET bottles and steel slag. However, flowability loss and mechanical strength decrease are still critical. Research efforts are needed to find low-carbon cement replacements and mix-design optimization, leading to a more sustainable and circular 3DCP while ensuring the final product performance.
The construction sector is responsible for significant CO2 emissions, especially due to the production of ordinary Portland cement (OPC). One option to decrease CO2 emissions is to print mortar made from an alternative binder. A precursor was used consisting of mainly non-ferrous metallurgical Fe-rich slag and a minor amount of OPC (<16 wt%), which forms upon alkali-activation a hybrid binder. A 3D-printable hybrid mortar was developed in a step-by-step performance-based approach, with a focus on the fulfilment of criteria relevant for 3D printing: shear-thinning, high yield stress, and stiffness development. The criteria to be met were determined using a commercially available 3D-printable OPC-mortar. Several raw materials were introduced to develop a hybrid mortar with a particle packing that positively influenced the pumpability and buildability. The effect of the precursors and superplasticizer on reactivity was investigated. The final mortar met the printing criteria, offering a suitable alternative to 3D-printable OPC-mortars.
In recent years, both academically and industrially, additive manufacturing (AM) has experienced rapid expansion because of its capability of producing customized products of intricate shapes. 3D printing has evolved as a promising technology for the creation of engineering parts or applications, as it is an additive technique, unlike traditional manufacturing techniques. The advantages of 3D printing include reduced material waste, easiness in manufacturing, minimal human participation and post-processing, and efficiency in energy, which make it a viable option for industrial application. The chapter provides a brief introduction to additive manufacturing and also addresses a variety of 3D printing techniques, as well as their benefits and drawbacks. A detailed discussion of the various materials that are suitable for each type of 3D printing procedure is discussed along with the application of AM and the challenges associated with it.
Extrusion is a plastic-forming method whereby several structural shapes are manufactured under high shear and compressive forces. Extrusion moulding introduce advantages in cement product processing of fibre reinforced Engineered Cementitious Composites (ECC). The introduction of extrusion moulding in cement product processing generate materials that are formed under high shear and high compressive forces. The extrusion process through its plastic-forming action under high shear and compressive forces, has the potential of producing products of superior geometrical tolerance. Furthermore, the extrusion process has a beneficial influence on the fibre orientation. There is evidence that short fibres are aligned by the extrusion, leading to significantly improved mechanical properties of the material. The objective of this paper is to corroborate the effectiveness of fibre reinforced cementitious composites with respect to the extrusion process, using different fibres in combination with some common chemical additives.
Different manufacturing processes demand appropriate materials processing adjustments. This holds true for concrete materials that have versatility in processing, including normal mixing and casting in the construction industry; spraying or so-called shotcrete application in soil stabilization for mining or construction excavations, extrusion in pre-casting factories for structural elements intended for the construction industry; and spinning manufacturing processes for concrete pipes. Recent innovation in 3D printing for construction demands yet another adaption of the mix design and manufacturing process. This paper presents an overview of required adaptions in terms of mix ingredients and mixing process and equipment to produce the appropriate rheology in the fresh state, rate of viscosity change for dimensional stability, sufficient adhesion/cohesion for interlayer bond, and appropriate, specified hardened and fresh rheology. Attention is given to fresh rheology and the chemical additives to prevent ingredient segregation during mixing and processing, despite a range in fluidity required by the various processes from highly workable for pumping, to dough-like consistency for extrusion and 3D printing.
3D printing (3DP), commonly known as additive manufacturing (AM), is a promising technology that can fabricate three dimensional complex shape prototypes directly from computer-aided design (CAD) model without any tooling and human intervention. Owing to its peculiar characteristics, AM is widely used in many industries to assist in the design, manufacture and commercialization of a product. More recently, this technology has been extended to building and construction (B&C) application in order to mitigate some of the critical issues such as shortage of skilled labour, high production cost and construction time, health and safety concerns of the workers in the hazardous environment etc. However for successful implementation, proper selection of materials and their mix design is highly recommended, which is a challenging task. This paper summarizes the current available 3DP systems from literature and the respective materials that have been used thus far by various experts, industries for B&C purposes. Finally, the benchmarking properties of theses material and potential research directions are briefly discussed
3D printing (3DP), commonly known as additive manufacturing (AM), is a promising technology that can fabricate three dimensional complex shape prototypes directly from computer-aided design (CAD) model without any tooling and human intervention. Owing to its peculiar characteristics, AM is widely used in many industries to assist in the design, manufacture and commercialization of a product. More recently, this technology has been extended to building and construction (B&C) application in order to mitigate some of the critical issues such as shortage of skilled labour, high production cost and construction time, health and safety concerns of the workers in the hazardous environment etc. However for successful implementation, proper selection of materials and their mix design is highly recommended, which is a challenging task. This paper summarizes the current available 3DP systems from literature and the respective materials that have been used thus far by various experts, industries for B&C purposes. Finally, the benchmarking properties of theses material and potential research directions are briefly discussed.
Development of formwork free 3D-Concrete-Printing opens many thresholds into the future of construction technology. Implementation of such construction process will provide immense flexibility in terms of structural geometry while drastically reducing formwork costs (which amounts up to 28 % [1] and in some cases half of total concrete structure cost [2]) as well as construction time. In this paper current approaches of 3D-Concrete-Printing are briefly presented and a novel approach, in which, a concrete boom pump is adapted to place fresh concrete with geometrical precision is proposed. This new construction process inherently requires construction materials with good pumpability, extrudability and adequate very-early-strength (" green strength "). In addition, fresh concrete rheological properties have to be optimized in correspondence with process parameters such as printing rate and print scenarios. Authors propose a holistic approach for testing and characterizing printability – as a combination of pumpa-bility, extrudability and buildability – of cement-based composites using fresh concrete rheology as a tool with the objective of optimizing 3D-Concrete-Printing process.
The three dimensional (3D) printing technology has undergone rapid development in the last few years and it is now possible to print engineering structures. This paper presents a study of the mechanical behavior of 3D printed structures using cementitious powder. Microscopic observation reveals that the 3D printed products have a layered orthotropic microstructure, in which each layer consists of parallel strips. Compression and flexural tests were conducted to determine the mechanical properties and failure characteristics of such materials. The test results confirmed that the 3D printed structures are laminated with apparent orthotropy. Based on the experimental results, a stress-strain relationship and a failure criterion based on the maximum stress criterion for orthotropic materials are proposed for the structures of 3D printed material. Finally, a finite element analysis was conducted for a 3D printed shell structure, which shows that the printing direction has a significant influence on the load bearing capacity of the structure.
Cement-based materials are of enormous technological importance and their satisfactory performance depends on being able to transport and mould them in the freshly mixed state. This article describes the rheology of fresh cement, mortar, concrete and related products in the context of practical situations, and deals with testing and measurement, together with the main features of their behaviour. It explores the links between rheology and technology, and identifies areas where these are weak and could benefit from further experimental and computational effort.
This paper presents the hardened properties of a high-performance fibre-reinforced fine-aggregate concrete extruded through a 9 mm diameter nozzle to build layer-by-layer structural components in a printing process. The printing process is a digitally controlled additive method capable of manufacturing architectural and structural components without formwork, unlike conventional concrete construction methods. The effects of the layering process on density, compressive strength, flexural strength, tensile bond strength and drying shrinkage are presented together with the implication for mix proportions. A control concrete (mould-cast specimens) had a density of approximately 2250 kg/m3, high strength (107 MPa in compression, 11 MPa in flexure) and 3 MPa in direct tension, together with a relatively low drying shrinkage of 175 μm (cured in water) and 855 μm (cured in a chamber at 20 °C and 60% relative humidity) at 184 days. In contrast well printed concrete had a density of 2350 kg/m3, compressive strength of 75–102 MPa, flexural strength of 6–17 MPa depending on testing direction, and tensile bond strength between layers varying from 2.3 to 0.7 MPa, reducing as the printing time gap between layers increased. The well printed concrete had significantly fewer voids greater than 0.2 mm diameter (1.0%) when compared with the mould-cast control (3.8%), whilst samples of poorly printed material had more voids (4.8%) mainly formed in the interstices between filaments. The additive extrusion process was thus shown to retain the intrinsic high performance of the material.
1.0 ABSTRACT The rheology of fresh cement, mortar and concrete is described and selected features of the
An experimental program was undertaken to evaluate the effect of water-cementitious material ratio (w/cm) and type of high-range water-reducing admixture (HRWRA) on the development of formwork pressure that can be exerted when using self-consolidating concrete (SCC). Pressure variation was monitored using an experimental column measuring 2800 mm in height. The tested mixtures were proportioned with a similar initial slump flow consistency of 650 ± 15 mm. Three w/cm of 0.36, 0.40, and 0.46 and three types of HRWRA (polycarboxylate, polynaphthalene sulphonate, and polymelamine sulphonate) were investigated. Variations in lateral pressure were related to the thixotropy of the concrete. Test results show that the variations in lateral pressure and thixotropy of SCC are significantly affected by the w/cm. Irrespective of the HRWRA type, mixtures proportioned with 0.46 w/cm exhibited greater initial pressure and lower thixotropy compared with mixtures made with a w/cm of 0.40 and 0.36. This is related to the higher water content and lower coarse aggregate volume in concrete proportioned with the higher w/cm, which can lead to a reduction in shear strength properties of the plastic concrete. The rate of pressure drop and increase in thixotropy with time, however, were greater in mixtures made with a higher w/cm. This is attributed to the lower HRWRA demand that can lead to sharper fluidity loss with time. For any given w/cm, the type of HRWRA appears to have a limited effect on initial lateral pressure. Compared with naphthalene- and melamine-based HRWRA, the use of polycarboxylate-based HRWRA in SCC resulted in lower rate of pressure drop with time. This is reflected by the greater fluidity retention of the mixtures containing the polycarboxylate-based HRWRA. The incorporation of a water-reducing agent in mixtures made with polynaphthalene sulphonate-based HRWRA is shown to increase lateral pressure development of the plastic concrete over time.
A novel Concrete Printing process has been developed, inspired and informed by advances in 3D printing, which has the potential to produce highly customised building components. Whilst still in their infancy, these technologies could create a new era of architecture that is better adapted to the environment and integrated with engineering function. This paper describes the development of a viable concrete printing process with a practical example in designing and manufacturing a concrete component (called Wonder Bench) that includes service voids and reinforcement. The challenges met and those still to be overcome particularly in the evaluation of the manufacturing tolerances of prints are also discussed.
In this paper, the methods used to measure and model thixotropy of fresh concrete in the civil engineering field are described and a simple thixotropy model is presented. It is shown that this model is in agreement with the experimental observations that can be found in the literature and a classification of SCC according to their flocculation rate Athix is proposed. The predictions of the model are compared with experimental measurements obtained with a concrete rheometer. In the last part, two applications of the model are briefly presented as examples (pressure formwork prediction and multi-layer casting of fluid concretes). It is shown that according to the element to be cast (slab or wall), a non-thixotropic SCC (low flocculation rate) or a highly thixotropic SCC (high flocculation rate) is respectively more adapted.
Additive manufacturing is gaining ground in the construction industry. The potential to improve on current construction methods is significant. One of such methods being explored currently, both in academia and in construction practice, is the additive manufacturing of concrete (AMoC). Albeit a steadily growing number of researchers and private enterprises active in this field, AMoC is still in its infancy. Different variants in this family of manufacturing methods are being developed and improved continuously. Fundamental scientific understanding of the relations between design, material, process, and product is being explored. The collective body of work in that area is still very limited. After sketching the potential of AMoC for construction, this paper introduces the variants of AMoC under development around the globe and goes on to describe one of these in detail, the 3D Concrete Printing (3DCP) facility of the Eindhoven University of Technology. It is compared to other AMoC methods as well as to 3D printing in general. Subsequently, the paper will address the characteristics of 3DCP product geometry and structure, and discuss issues on parameter relations and experimental research. Finally, it will present the primary obstacles that stand between the potential of 3DCP and large-scale application in practice, and discuss the expected evolution of AMoC in general.
This paper reviews published data on the mechanical properties of additively manufactured metallic materials. The additive manufacturing techniques utilized to generate samples covered in this review include Powder Bed Fusion (e.g. EBM, SLM, DMLS, etc.) and Directed Energy Deposition (e.g. LENS, EBF3, etc.). While only a limited number of metallic alloy systems are currently available for additive manufacturing (e.g. Ti-6Al-4V, TiAl, Stainless Steel, Inconel 625/718 and Al-Si-10Mg), the bulk of the published mechanical properties information has been generated on Ti-6Al-4V. However, individual summary tables for published mechanical properties and/or key figures are included for each of the alloys listed above, grouped by the additive technique utilized to generate the data. Published mechanical properties obtained from hardness, tension/compression, fracture toughness, fatigue crack growth, and high cycle fatigue are included for as-built, heat treated and/or HIPped conditions in the tables and figures, when available. The effects of test orientation/build direction on properties are also provided, when available, along with discussion of potential source(s) (e.g. texture, microstructure changes, defects, etc.) of anisotropy in properties. Recommendations for additional work are also provided.
Two rheological tools widely used in the cement industry are compared: the Viskomat rheometer and the spread test. It is shown that proper calibration of the first, and selection of an adequate physical model for the second yield to a quantitative agreement of yield stress values. Such results are important for industrial labs that may translate existing data in arbitrary units into rheologically relevant parameters.
Although automation has advanced in manufacturing, the growth of automation in construction has been slow. Conventional methods of manufacturing automation do not lend themselves to construction of large structures with internal features. This may explain the slow rate of growth in construction automation. Contour crafting (CC) is a recent layered fabrication technology that has a great potential in automated construction of whole structures as well as subcomponents. Using this process, a single house or a colony of houses, each with possibly a different design, may be automatically constructed in a single run, imbedded in each house all the conduits for electrical, plumbing and air-conditioning. Our research also addresses the application of CC in building habitats on other planets. CC will most probably be one of the very few feasible approaches for building structures on other planets, such as Moon and Mars, which are being targeted for human colonization before the end of the new century.
Apparatus for production of three-dimensional objects by stereolithography
- C W Hull
C.W. Hull, Apparatus for production of three-dimensional
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Additive Manufacturing Technologies: 3D Printing, Rapid Prototyping, and Direct Digital Manufacturing
- I Gibson
- D W Rosen
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I. Gibson, D.W. Rosen, B. Stucker, Additive Manufacturing
Technologies: 3D Printing, Rapid Prototyping, and Direct
Digital Manufacturing,
Springer, 2015, http://dx.doi.org/
10.1007/978-1-4939-2113-3-1.
The potential of 3D printing to reduce the environmental impacts of production
- McAlister
C. McAlister, J. Wood, The potential of 3D printing to reduce
the environmental impacts of production, ECEEE Industrial
Summer Study Proceedings (2014) 213-221.
Formwork for Concrete Structures, Tata McGraw Hill Education Private Limited
- K N Jha
K.N. Jha, Formwork for Concrete Structures, Tata McGraw Hill
Education Private Limited, New Dilhi, India, 2012,ISBN 978-1-25-900733-0.