3D Concrete Printing Research Articles

Assessing the Load-Bearing Capacity of 3D-Printed Concrete at Early Ages: An Innovative Approach

Assessing the Load-Bearing Capacity of 3D-Printed Concrete at Early Ages: An Innovative Approach

Applicability of 3D concrete printing technology in building construction with different architectural design decisions in housing

3D Printing (3DP) technology, one of the layered production methodologies where design and construction configurations can be made with increasing digitalization and Industry 4.0, is one of the leading techniques of the period. 3D Concrete Printing (3DCP) also comes to the fore in the construction industry. The study aims to observe the impact of architectural design decisions on the 3DCP process by developing controlled and consistent design alternatives. Architectural designs developed with different geometric forms in the housing function were subjected to digital planning, 3DCP preparation, and 3DCP prototype final product stages. In the integration of design and 3D concrete printing (3DCP), two key aspects were investigated: (i) the impact of different geometric forms (square, rectangle, hexagon, octagon, circle, and ellipse) on the buildability performance of 3D-printed structures, and (ii) how variations in design details influence printing time, material consumption, cost, and the feasibility of mass production in architectural applications. For the 3DCP process, 3D-printable cementitious mixture was developed, and a 3D printer with dimensions of 100 x 100 x 40 centimeters was used. The results obtained during the printing process were analyzed in comparison with the building evaluation parameters. As a result, the house with circular geometry showed the optimum behavior according to the parameters of buildability, cost, and mass producibility. The circle geometric form provides a 4.2% advantage over the octagon in terms of buildability, a 16.6% advantage over the ellipse in terms of cost, and a 20% advantage over the ellipse in terms of mass producibility.

Early age time-dependent mechanical properties of 3D-printed concrete with coarse aggregates

Incorporating coarse aggregate into 3D-printed concrete is essential for promoting its practical application, yet the impact on the early age time-dependent mechanical properties, crucial for the multilayer structure stability and quality, is underexplored. In this study, 3D-printed concrete with coarse aggregate (3DPCA) with varying mortar-to-coarse aggregate ratios (M/A) and coarse aggregate gradations were prepared, of which uniaxial unconfined compression and direct shear performance were experimentally investigated. The fundamental formulations between the early age mechanical parameters and the resting time of 3DPCA were characterized and then utilized in a digital model simulating actual printing. Results indicated that the 3DPCA early age mechanical properties, including compressive strength, Young's modulus, cohesion, and friction angle, increased with longer resting time and decreasing M/A, and higher proportions of aggregates above 9.5 mm. High coarse aggregate content caused three distinct compressive strength-displacement curve stages and complicated strength eigenvalue extraction. Coarse aggregate gradation affected shear properties more than content, with larger aggregates improving cohesion and friction angles. The failure mode prediction model based on ABAQUS could accurately predict the maximum collapse layer of 3DPCA that occurred in overall unstable collapse and over-expansion failure but was incapable of localized deformation.

Data-driven models for predicting compressive strength of 3D-printed fiber-reinforced concrete using interpretable machine learning algorithms

3D printing technology is growing swiftly in the construction sector due to its numerous benefits, such as intricate designs, quicker construction, waste reduction, environmental friendliness, cost savings, and enhanced safety. Nevertheless, optimizing the concrete mix for 3D printing is a challenging task due to the numerous factors involved, requiring extensive experimentation. Therefore, this study used three machine learning techniques, including Gene Expression Programming (GEP), Multi-Expression Programming (MEP), and Decision Tree (DT), to forecast the compressive strength of 3D printed fiber-reinforced concrete (3DP-FRC). The dataset comprises 299 data points with sixteen variables gathered from experimental research studies. For training the model, 70 % of the dataset was used, while the remaining 30 % was reserved for model testing. Several statistical metrics were utilized to evaluate the accuracy and applicability of the models. In addition, SHapley Additive exPlanations (SHAP), partial dependence plots, and individual conditional expectations approach were employed for the interpretability of the models. The proposed GEP, MEP, and DT models indicated enhanced efficacy, exhibiting correlation coefficient (R) scores of 0.996, 0.987, and 0.990, with mean absolute errors (MAE) of 1.029, 4.832, and 2.513, respectively. Overall, the established GEP model demonstrated exceptional performance compared to MEP and DT, showcasing high prediction precision in assessing the strength of 3DP-FRC. Moreover, a simple empirical formulation has been devised using GEP to predict the compressive strength, offering a simplified and efficient approach for predicting 3DP-FRC strength. The SHAP approach identified water, silica fume, fiber diameter, curing age, and loading directions as leading controlling parameters in predicting strength of 3DP-FRC. In summary, the proposed models can potentially minimize both the computational workload and the need for experimental trials in formulating the mixed design of 3D-printed concrete.

Effect of hydration process on the interlayer bond tensile mechanical properties of ultra-high performance concrete for 3D printing

It is crucial to reveal interlayer interface characteristics for fully analysing the mechanical properties of 3D printed ultra-high performance concrete (3DP-UHPC). Despite its significance, the interlayer bonding behaviour of 3DP-UHPC has not been fully explored. To fill this gap, this study adopted different curing times and conditions to investigate the effect of hydration process on the interlayer microstructure and mechanical properties under different interlayer interval times. As the result show that, the interlayer microstructure remained dense for interval times less than 5 minutes, but interlayer gaps became increasingly apparent as the interval time exceeded this threshold. Promoting hydration, however, helped heal interlayer defects in 3DP-UHPC. Additionally, the interlayer bond tensile strength gradually decreased with increasing interval time but remained almost unchanged when the interval time exceeded 1 day. Notably, hot water bath curing enhanced the bond tensile strength of specimens with interval times within 60 minutes, but its improvement was insignificant for interval times exceeding 1 day. Based on these experimental results, a preliminary interlayer bond tensile stress-strain equation of 3DP-UHPC was derived. The findings of this study offer promising avenues for the improvement and promotion of 3DP-UHPC technology.

Rock fragmentation of simulated transversely isotropic rocks under static expansive loadings

Rock fragmentation is a critical process for mineral extraction and for mitigating overstressed rock in geotechnical applications. In this study, 3D-printed concrete was used to simulate the stratified rock mass, and experimental and numerical methods were employed to investigate crack propagation under static expansive loadings in transversely isotropic rocks. Two types of cracks were observed in the experiments: P-type (a crack propagates primarily along the weak layer) and T-type (a crack propagates across the weak layers) cracks. The findings revealed that the orientation of layers significantly influenced the initiation and propagation of cracks, with P-type cracks commonly observed in simpler P-P mode fragmentations and more complex P-P-T modes emerging under higher expansive loadings. P-T-T modes were characterized by the simultaneous presence of the T-type crack after an initial P-type crack. The AE energy levels in the P-P-T and P-T-T modes were much higher than those in the P-P mode. 2D-DDA models were further built to understand the effects of the loading scales, layer angles, and locations of weak layers on the cracking sequences. The results provided detailed insights into stress evolutions and the impact of expansive loadings on crack initiation and propagation.

Triaxial compressive behavior of 3D printed PE fiber-reinforced ultra-high performance concrete

The layered deposition process of 3D concrete printing can lead to reduced mechanical properties at the interfaces between filaments. To address this limitation, external confinement devices, such as fiber-reinforced polymer (FRP) wrapping, have been proposed to enhance the strength of 3D-printed concrete concrete. Achieving this requires a solid understanding of the triaxial mechanical performance of 3D-printed concrete. This study presents an experimental investigation of the triaxial compressive behavior of 3D-printed PE fiber-reinforced ultra-high performance concrete (3DP-PEUHPC). A total of 16 pairs of concrete cubes were prepared, including mold-cast and 3D-printed specimens, and subjected to uniaxial and triaxial compression tests. The results revealed that the 3D-printed specimens exhibited either column-type or diagonal shear failures under triaxial compression. Weak bonding was observed at both filament-fusion and layer-fusion interfaces, with these weaker bonding interfaces, particularly when aligned parallel to the axial load, showing susceptibility to stress concentration and crack initiation. This led to a reduction in load-bearing capacity of the 3D-printed specimens compared to the mold-cast specimens. Importantly, as confining stresses increase, the difference in compressive strength between 3D-printed and mold-cast specimens decreases, highlighting the effectiveness of confinement in mitigating the directional weaknesses inherent in 3D-printed concrete. This paper also presents a modified model for predicting the axial stress-strain relationship of 3DP-PEUHPC under confinement, providing insights into the mechanism of FRP confinement on the compressive strength of 3D-printed concrete structures.

Enhancing thermo-mechanical and moisture properties of 3D-Printed concrete through recycled ultra-fine waste glass powder

This paper presents a novel approach to enhancing 3D printed concrete (3DPC) by incorporating ultra-fine glass powder (UFGP), focusing on its mechanical properties and high-temperature resistance. Investigation like fresh properties, basic physical properties, residual compressive strength after exposure to 400 °C and 800 °C, hygric properties such as water vapor diffusion resistance, liquid water transport, and moisture buffering capacity were performed the observe the effect of UFGP replacement ratio on 3DPC, which demonstrates significant improvements, highlighting the potential of UFGP to elevate 3DPCs’ performance. Results showed significant improvements, particularly with a 20% UFGP mix, which showed the lowest compressive strength loss (9.0% at 400 °C and 53.7% at 800 °C). Additionally, the water vapor diffusion resistance factor for the 20% UFGP mix was measured at 65.03. These results suggest that incorporating UFGP in 3DPC enhances thermal resilience and mechanical properties, offering a solution for high-temperature construction. This study contributes to sustainable construction by emphasizing the importance of mechanical resilience for structural integrity under extreme temperatures.

Research on Mechanical Properties of a 3D Concrete Printing Component-Optimized Path by Multimodal Analysis

Three-dimensional concrete printing (3DCP) technology with solid wastes has significant potential for sustainable construction. However, the hardened mechanical properties of components manufactured using 3DCP technology are affected by weak interlayer interfaces, limiting the widespread application of 3DCP technology. To address the inherent limitations of 3DCP technology, conventional improvement strategies, such as external reinforcement and the optimization of material properties, lead to increased production costs, complex fabrication, and decreased automation. This study proposes an innovative spatial path optimization method to enhance the mechanical performance of 3D-printed, cement-based components. The novel S-path design introduces additional printed layers in the weak interlayer regions of the printed samples. This design improves the spatial distribution of fiber-reinforced filaments in continuous weak zones, thus enhancing the functional efficiency of fibers. This approach improves the mechanical performance of the printed samples, achieving compressive strengths close to those of cast samples and only a 20% reduction in average flexural strength. Compared to using a conventional printing path, the average compressive strength and flexural strength are improved by 30% and 55%, respectively, when the S-path layout is employed in 3DCP. Additionally, this method significantly reduces the anisotropy in compressive and flexural strengths to 26% and 28% of samples using conventional printing paths, respectively. Therefore, the proposed method can improve the mechanical properties and stability of the material, reducing the safety risks of printed structures.

Assessing the Prospects and Risks of Delivering Sustainable Urban Development Through 3D Concrete Printing Implementation

The article presents the results of a comprehensive study of the use of 3D Concrete printing (3DCP) technology to create urban infrastructure facilities according to sustainable development principles. The work includes a study of scientific articles on the subject area under consideration, a survey of additive construction market participants, as well as an analysis and generalization of promising areas for technology development and methods for improving the quality of objects erected using 3DCP. As part of the conducted literature review, publications included in the Scopus database for the period 2015–2024 were selected for analysis using the keywords ‘Sustainable development + 3DCP’ and ‘Sustainable construction + 3DCP’. The following conclusions were made: (i) the most popular publications are review articles about the development of materials and technologies for 3DCP and (ii) the most sought-after are the studies in the field of partial application of 3DCP technology, existing equipment and materials for 3DCP, and assessment of the effectiveness and cost-effectiveness of 3DCP use. For this purpose, a questionnaire was developed consisting of three blocks: equipment and technologies; structures and materials for 3DCP; the ecology and economics of 3DCP applicability. As a result, four main risks have been identified, which represent promising areas for 3DCP development.

Load transfer behavior of 3D printed concrete formwork for ribbed slabs under eccentric axial loads

3D printed concrete (3DPC) has primarily been used for non-structural applications, with limited exploration into its potential for structural load-bearing applications. This is mainly due to the layered structure of 3DPC and the lack of compatibility of conventional reinforcement strategies to be integrated within the 3D concrete printing process. The post-tensioning of 3DPC structures presents an effective solution to improve the load-carrying capacity and cracking behavior of 3DPC. However, understanding the load transfer behavior and failure modes of 3DPC structures under a particular post-tensioning configuration are crucial to determine the permissible post-tensioning load for a structure without premature failure and to understand the distribution of stresses within the concrete structure under post-tensioning loads. The current study aims to investigate the load transfer behavior and failure mode of a 30 mm thick 3DPC formwork designed for one-way ribbed slabs when subjected to end-anchorage post-tensioning. For this purpose, a series of mechanical characterization and load transfer experiments were conducted on ribbed 3DPC formwork. The mechanical characterization investigations involved examining the compressive and flexural strength, as well as the elastic modulus of 3DPC, under various loading orientations relative to the print path. In the load transfer experiments, the end anchorage post-tensioning system was simulated by applying the axial load to the specimen via end plates bonded to the specimen. The variable parameters of the load transfer experiments were the boundary conditions, the eccentricity of the axial load from the neutral axis, and the topology of the ribbed 3DPC formwork. A digital image correlation system was used to study the axial and transverse strain evolution during the load transfer experiments. The experimental results showed that, regardless of the eccentricity of the applied load, the ribbed 3DPC formwork specimens exhibited higher axial load capacity when the load was applied near the bottom flange rather than the top flange. This was because of the reduced effective cross-sectional area for compression when the load was positioned near the top flanges, a consequence of the selected formwork topology, where top flanges were discontinuous to allow for pouring of the cast concrete within the formwork.

Fire resistance of 3D printed ultra-high performance concrete panels

Ultra-high performance fiber-reinforced concrete (UHPFRC) is highly suitable for 3D concrete printing (3DCP) due to its high flexural strength, thereby reducing the need for reinforcements. However, UHPFRC is susceptible to spalling under exposure to fire, limiting its application as structural members. In this paper, the effect of 3D printing process on the fire behavior of UHPFRC is studied, benchmarking against mold-cast panels. The insulation, integrity, and structural adequacy of the panels are investigated using the heat transfer mechanisms, failure modes, and the post-fire compressive strength of the panels, respectively. The presence of interlayers reduced the spalling of UHPFRC under fire and improved the structural integrity of 3D printed specimens compared to mold-cast specimens. Further, the addition of 0.5 % polypropylene (PP) fibers eliminated the interlayer delamination and spalling in 3D printed UHPFRC panels. Similarly, 3D printed panels showed improved structural adequacy than mold-cast specimens. The residual compressive strength of 3D printed UHPFRC panels after being exposed to fire was observed to be above 50 % of the initial mean compressive strength. However, the insulation property of 3D printed panels was reduced compared to that of the mold-cast counterparts due to the high rate of heat transfer via the porous interlayers. The addition of PP fibers improved the insulation resistance of the interlayer region and surface of the 3D printed panels. The strength anisotropy of the 3D printed UHPFRC reduced significantly following the fire exposure. Further, the thermal bowing of 3D printed panels was higher with an increased dosage of PP fibers due to the increase in the thermal strain of UHPFRC. Therefore, adequate care must be given in the design of 3D printed structures for potential fire resistant wall, slab, and façade elements.

Micro/nano additives in 3D printing concrete

3D concrete printing has attracted burgeoning interest in the construction industry for its ability to offer cost-effectiveness, architectural design flexibility, efficient use of energy and materials, as well as significant time savings in the construction process. However, conventional cement-geopolymer-based materials cannot be used directly for printing due to their lack of printability. This review explores the utilization of inorganic micro/nanomaterials to modify the rheological and mechanical performance of fresh-state and post-hardening cementitious composites, respectively, offering an in-depth analysis of the mechanisms underpinning their effects. This paper discusses a wide range of inorganic micro/nanomaterials, including carbon-based nanomaterials, silicon-based nanomaterials, metallic oxide nanomaterials, nano-calcium carbonate particles, and other micro/nano-materials. Those materials have been utilized in 3D printing concrete or show considerable potential for future applications in this field. Furthermore, this work provides insights into the multiple applications that arise from the synergistic combination of 3D printing construction techniques with the distinctive properties of different nanomaterials.

Testing Mortars for 3D Printing: Correlation with Rheological Behavior

Three-dimensionally printed concrete is a transformative technology that addresses housing shortages due to population growth and enables innovative architectural designs. The objective of this study is to investigate the connection between a conventional test and the rheological properties of 3D-printed concrete. A more precise assessment of material quality based on traditional evaluation techniques is proposed. Standard tests are conducted to evaluate the consistency of 3D-printed concrete materials. Complementarily, a rheometer is employed to accurately measure key rheological properties, thereby establishing a link with empiric testing methodologies. The correlation between the flow table test and rheological coefficients, such as yield stress and viscosity, has been identified as the most effective in basic experiments for evaluating material behavior. This approach allows for a preliminary assessment of printability without the need for additional complex equipment. The study has successfully established a relationship between flow table tests and rheological parameters. However, further research involving a broader range of materials and print-test experiments is essential to enhance the correlation between other conventional testing methods and rheometer results.

Real-time monitoring of extrudability and buildability in 3D concrete printing based on target detection method

Real-time monitoring of extrudability and buildability in 3D concrete printing based on target detection method

Frontiers in construction 3D printing: self-monitoring, multi-robot, drone-assisted processes

AbstractTo overcome productivity issues and revolutionize the stagnating construction industry, a large amount of research efforts has been devoted to robot-assisted construction technology. The advancements in robotics including mechanical system design, tool design, digital system design, and numerical control systems design enabled engineers to create complex geometries that are infeasible for conventional construction methods. In addition, innovative robotic systems that utilize mobile platforms, multiple robots, and unmanned aerial vehicles have demonstrated significant promise in fully automating the construction process. This work will provide a perspective on the state-of-the-art applications of robotics in the revolution of construction, where a comprehensive review of the current development of the relevant software and hardware, 3D concrete printing (3DCP), robot-assisted assembly of discrete prefabricated blocks, real-time quality monitoring and feedback control systems, and typical innovative robot-assisted structural designs are conducted. Finally, the limitations of existing robot-assisted construction technology are identified, which leads to several recommendations for future research toward fully automatic construction.

Influence of printing parameters on the durability of 3D-printed limestone calcined clay cement mortar: overlap between filaments and nozzle offset

Large-scale cement-based Additive Manufacturing (AM), also known as 3D Concrete Printing (3DCP), is a promising technique to innovate the construction industry. The durability properties of printed specimens have been studied and compared to those of cast samples in the literature. However, no study has evaluated and quantified the influence of printing parameters on the durability of 3DCP specimens. Aspects such as nozzle offset and the overlap between printed filaments, among others, may influence the porosity of the samples and, therefore, the durability properties. This paper aims to investigate the influence of printing parameters on the durability of 3D manufactured mortar samples. The effects of the printing height and overlap between filaments on the durability properties were analysed in the X, Y and Z axes. An experimental investigation of 39 samples was conducted. Printed and cast specimens were subjected to a curing process for up to 90 days in a water tank at a temperature of 20 °C. Durability tests (oxygen permeability, electrical resistivity, and porosity) were performed at 7, 28 and 90 days. Relationships between the printing variables and durability properties with time were derived. Based on this study, it is concluded that the long-term properties of concrete are significantly sensitive to the overlap between filaments and the nozzle offset. In general, the durability properties were enhanced by modifying the printing parameters. In particular, an overlap of 4 mm showed the most promising results in this regard.

Nature-inspired approach for enhancing the fracture performance of 3D printed strain-hardening cementitious composites (3DP-SHCC)

3D printing technology enhances design flexibility, enables the creation of complex geometrical structures, facilitates rapid prototyping, and allows the fabrication of micro- and macroscopic structures. This study investigates the use of 3D concrete printing to create Bouligand structures inspired by mantis shrimp. Bouligand-printed strain-hardening cementitious composites (SHCC) with different pitch angles (15°, 30°, 45°, 60°, 75°, and 90°) are fabricated and compared with traditional parallel-printed and mold-cast SHCC. The fracture behavior of these specimens is investigated through three-point bending tests on notched beams. The results reveal that Bouligand-printed specimens exhibit enhanced flexural strength, fracture energy, and fracture toughness, ranging from 0.97 to 1.29 times, 0.99 to 1.63 times and 0.87 to 1.47 times that of the mold-cast specimens, respectively. Bouligand-printed specimens with a pitch angle of 30° exhibits the highest flexural strength, fracture energy, and fracture toughness. The Bouligand-printed SHCC enhance toughness through the synergistic effects of crack twisting and bridging. A finite element model integrating cohesive elements with the concrete plastic damage model is developed to numerically replicate the experimental process. This study highlights the potential of 3D concrete printing for the fabrication of biomimetic concrete structures with superior fracture performance.

Exploring the role of 3D concrete printing in AEC: Construction, design, and performance

Exploring the role of 3D concrete printing in AEC: Construction, design, and performance

Effect of fly ash and ground waste glass as cement replacement in concrete 3D-Printing for sustainable construction

Effect of fly ash and ground waste glass as cement replacement in concrete 3D-Printing for sustainable construction