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Purpose – This research explores the role of concrete 3D printing (C3DP) in the development of culturally appropriate housing in Indigenous Reserves in Canada through the design, building and evaluation of the Star Lodge project located in the Siksika Nation of Alberta, Canada. The project aims to assess the potential of C3DP in addressing the escalating housing demands in Indigenous communities in Canada. Design/methodology/approach – The research involved a collaborative and multidisciplinary approach, engaging Blackfoot Elders, Knowledge Keepers from the Siksika Nation, Siksika Housing and Nidus3D. Central to this was the design, build and documentation of the Star Lodge project to analyse the advantages and challenges, guided by weekly meetings and site visits. Findings – The project harnessed C3DP to streamline construction, enhance durability, reduce maintenance costs and enhance the energy performance of the homes. Notable time savings were achieved compared to conventional construction methods. Challenges included developing strategies to overcome extreme cold weather conditions, achieving a consistent concrete mix and integrating conventional construction elements such as drywall construction in interiors. The project served as a platform for collaboration and community participation, shaping the design and construction process while raising awareness of innovative construction techniques in the community. Originality/value – This study provides an evidence-based framework for the evaluation of C3DP technology by analysing the Star Lodge Project, the first C3DP project in Alberta and the largest of its kind in Canada. By addressing housing challenges in Indigenous communities, the research holds broader implications for sustainable development and Indigenous empowerment across Canada.

This paper aims to provide a global snapshot of concrete 3D-printed buildings and to uncover robotic-oriented large-scale fabrication strategies. Therefore, an extensive internet search and literature review was carried out to investigate 3D-printed buildings. In this study, 154 construction projects with 204 buildings were systematically recorded and evaluated from 2013 up to 2023. Using an exploratory mixed-methods approach and a comparative case study analysis, a total of 88 3D-printed buildings were first evaluated descriptively. Thereafter, different existing printing strategies for in situ, on-site, and off-site production were identified, using an iterative approach. In addition to the geographical distribution, the descriptive evaluation also showed the key players as drivers for the spread of the 3D-printing technology and the correlations between printer type, fabrication strategy, and the building size. With regard to the printing strategy, three different approaches for in situ and off-site fabrication can be defined, depending on the printer types and their characteristics (work size and mobility): print-in-one-go, horizontal or vertical segmentation, and the multi-element vs. full-scaled wall strategy. However, the study showed that the data quality was sometimes difficult due to a lack of information and essential details of the printing process and segmentation. [ABSTRACT FROM AUTHOR]

This paper aims to provide a global snapshot of concrete 3D-printed buildings and to uncover robotic-oriented large-scale fabrication strategies. Therefore, an extensive internet search and literature review was carried out to investigate 3D-printed buildings. In this study, 154 construction projects with 204 buildings were systematically recorded and evaluated from 2013 up to 2023. Using an exploratory mixed-methods approach and a comparative case study analysis, a total of 88 3D-printed buildings were first evaluated descriptively. Thereafter, different existing printing strategies for in situ, on-site, and off-site production were identified, using an iterative approach. In addition to the geographical distribution, the descriptive evaluation also showed the key players as drivers for the spread of the 3D-printing technology and the correlations between printer type, fabrication strategy, and the building size. With regard to the printing strategy, three different approaches for in situ and off-site fabrication can be defined, depending on the printer types and their characteristics (work size and mobility): print-in-one-go, horizontal or vertical segmentation, and the multi-element vs. full-scaled wall strategy. However, the study showed that the data quality was sometimes difficult due to a lack of information and essential details of the printing process and segmentation.

This paper investigates the Near‐nozzle Mixing (NNM) technique for 3D printing cementitious mortar, focusing on achieving continuous and homogeneous material properties. The NNM's ability to print Natural Sand Mortar (NSM), Recycled Aggregate Mortar (RAM), and Lightweight Mortar (LWM) was assessed. Fresh and hardened properties of each mortar were examined, emphasizing standard deviation (STD) and coefficient of variation (CV) to measure material homogeneity. Fresh properties included slump flow, yield stress, air void volume, density, and water‐to‐cement ratio, while hardened properties covered compressive strength, flexural strength, hardened density, and thermal conductivity. Results showed low CV values for all mortar types, indicating high consistency and homogeneity. NNM showed is capability to print of various materials with customized properties. NSM showed the highest compressive strength, RAM balanced strength and sustainability, and LWM provided the best thermal insulation. The study highlights NNM's versatility and potential for construction applications requiring tailored properties, proving it a promising additive manufacturing solution. The research serves as a foundation for future studies on graded multi‐material printing. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) with concrete, also known as concrete 3D printing, is one of the most interesting approaches for disrupting the construction industry and is currently subject to numerous research activities worldwide. AM has great potential to decrease labour costs and increase the material efficiency and geometric complexity of non-standardised building components. Although prior investigations have shown various fields of application for AM with concrete, the full potential with respect to different structural component types has not been covered yet. With this paper, an up-to-date review of fabrication strategies for the main structural components, (1) walls, (2) columns, (3) slabs, and (4) beams, is provided to identify trends and existing challenges. Therefore, firstly, AM methods and their underlying principles and characteristics for concrete components are presented, and secondly, fabrication strategies for each AM method are shown. The investigation uncovers different AM strategies (direct part vs. indirect "permanent formwork"; in situ, on-site, or off-site), which are currently being used. As a result, future applications of AM will require a hybrid manufacturing strategy combining conventional and additive manufacturing to fully explore its potential. [ABSTRACT FROM AUTHOR]

The trending methodology in 3DCP is accompanied by extensive trial and error methods, leading to the final product's more expensive and time-consuming development. The specific printable combination of design, materials properties, and process parameters for successful 3D concrete printing (3DCP) process resembles a “secret recipe”. This study explores the design capabilities of numerical tools for 3DCP, understands its limitations and challenges, and provides an overview for future research direction. Different analytical and numerical models have been developed in the literature as a function of material properties, printing parameters, and the geometry of the final printed structures. These models serve to optimize the printing parameters and predict the performance of the printed product and rheological responses, hence, offering a safer and more economical solution. The analytical models provide the first-degree approximation and can be used for simple shapes such as straight or tilted walls; however, numerical methods are needed for more complex structures. The literature review shows an apparent delay in the progress of computational technology to catch the pace of interest of the construction industry in 3DCP. The prediction of 3DCP structure performance is not straightforward for complex geometries, variable process parameters, or multi-materials printing. Due to involving multi-physics phenomena at each sub process, the developed numerical models are limited to a specific sub-process range. The study presents a plan to integrate different sub-processes to build a single computational model from material mixing to final buildability.

Additive manufacturing (AM) with concrete, also known as concrete 3D printing, is one of the most interesting approaches for disrupting the construction industry and is currently subject to numerous research activities worldwide. AM has great potential to decrease labour costs and increase the material efficiency and geometric complexity of non-standardised building components. Although prior investigations have shown various fields of application for AM with concrete, the full potential with respect to different structural component types has not been covered yet. With this paper, an up-to-date review of fabrication strategies for the main structural components, (1) walls, (2) columns, (3) slabs, and (4) beams, is provided to identify trends and existing challenges. Therefore, firstly, AM methods and their underlying principles and characteristics for concrete components are presented, and secondly, fabrication strategies for each AM method are shown. The investigation uncovers different AM strategies (direct part vs. indirect “permanent formwork”; in situ, on-site, or off-site), which are currently being used. As a result, future applications of AM will require a hybrid manufacturing strategy combining conventional and additive manufacturing to fully explore its potential.

This article discusses the application of additive manufacturing (AM), also known as 3D printing, in the construction industry. The use of AM technologies in construction can reduce material waste, increase design flexibility, and contribute to resource efficiency. The article highlights various materials that have been tested for AM processes, such as concrete and rammed earth, and explores their potential for reducing environmental impact. The article also discusses the integration of computational design and digital fabrication methods in the construction process. Challenges and advancements in AM techniques, including data-driven models for quality control and the improvement of thermal insulation in AM-produced walls, are also addressed. The authors provide insights and recommendations for further research and development in this field. [Extracted from the article]

• W1.5 shows superior interlayer bonding and flexural strength. • Optimal stand-off distance is 13.5 mm to 15 mm. • Lattice beam achieved a failure load of 49.01 kN with flexural failure. This paper presents the optimal selection of cable reinforcement for concrete 3D-printed lattice beam. It also addresses key challenges associated with interlayer bonding and flexural strength of 3D printed elements. Three different types of reinforcement including 1.6 mm and 2 mm diameter rebar, (R1.6 & R2) and 1.5 mm wire (W1.5) with seven strings were evaluated with different stand-off distances of 10–20 mm. The interlayer bonding and flexural strength were investigated to determine the most effective reinforcement configuration. Results show that W1.5 reinforcement exhibited higher interlayer bonding and flexural strength as compared with R1.6 and R2. Subsequently, the optimal reinforcement configuration (W1.5) was embedded in a concrete 3D-printed lattice beam. The lattice beam was structurally evaluated using four-point testing, demonstrating an ultimate load-carrying capacity of 49.01 kN with a mid-span displacement of 2.99 mm. Moreover, it exhibited flexural failure with no premature failures such as inter-layer delamination. [ABSTRACT FROM AUTHOR]

• The dummy layer reduces geometry deviations and maximizes interlayer bonding. • The dummy layers significantly enhance the interlayer bonding of the top layer. • After introducing a dummy layer, geometrical deviation notably reduces. This paper presents the effect of dummy layers in concrete 3D printing to enhance interlayer bonding and reduce geometrical deviations. The specimens were printed by varying numbers of dummy layers at different layer heights using the optimized printing parameters. The impact of dummy layers on interlayer bonding was determined using a split tensile test and the geometrical deviations were analyzed using a 3D-scanning technique. Results demonstrate that significant improvement was found in interlayer bonding, notably at the top layer. For instance, by adding two dummy layers in specimen H10D2, the difference between the top and middle layers bond strength was reduced from 42.57% (i.e., for specimen H10D0) to 0.79%. Moreover, the dummy layers effectively minimized the geometrical deviations by achieving the desired layer dimensions in the top layer of specimens. [ABSTRACT FROM AUTHOR]

The control of mortar rheology is of paramount importance in 3D printing concrete by extrusion. This is particularly sensitive for two-component (2K) processes that use an accelerator to switch the printed mortar very quickly from a liquid behavior to a sufficiently solid behavior to be able to be printed (i.e. structuration). After some main key points about measuring the structuration of printed mortars, we propose an original and simple inline test using a pocket shear vane tester. The test is able to measure over several decades of yield stress range, mobilizes small quantities of mortar and enables in-situ measurements on freshly printed layers. The results highlight the difference of structuration between a benchtop-prepared printable material and a truly printed material, fostering the importance of inline measurements, and demonstrating the quality of the method. This pocket shear vane test appears as good contender for a light and affordable rheometer for 2K printable mortars. • A 3DCP inline pocket vane test that suits fast structuration (100 Pa/s) is proposed. • A linear model fits early structuration of mortars accelerated by aluminum sulfate. • Potential of 2K strategies in adjusting structuration on the fly is demonstrated. • Inline and laboratory measurements differ : Inline testing is a necessity. • A methodology to choose and qualify 3DCP structuration tests is proposed. [ABSTRACT FROM AUTHOR]

• Interaction between inter-filament void, bonding, & geometric deviation is studied. • Investigated the influence of different printing parameters using RSM. • High speed & low extrusion with 1/8N d overlapping are optimal printing parameters. This study presents the effect of different printing parameters including printing speed, extrusion rate, and inter-filament overlapping distance on inter-filament bonding, inter-filament voids, and geometrical deviation in concrete 3D printed structures using Response Surface Methodology. Moreover, this study adopts a central composite design to generate a set of experimental runs and develop a second-order polynomial equation to quantify the effect of printing parameters. Results show that high inter-filament bonding with minimal inter-filament void and geometrical deviation can be achieved at high printing speed and low extrusion rate with 1/8N d (2.5 mm) inter-filament overlapping distance. [ABSTRACT FROM AUTHOR]

Additive manufacturing and in particular, concrete 3D printing has been suggested as one of the interesting solutions to unlock remote development, enhance the strength and capability of the local and national manufacturing and construction industries, and offer fast recovery in post-disaster scenarios. In this study, the remote housing construction challenges with a particular focus on Australian Northern Territory (NT) are reviewed and the feasibility and efficiency of using concrete 3D printing to tackle those challenges have been discussed. Besides the advantages of 3DP for remote housing, it's limitations and concerns have also been presented. Finally, some completed 3D-printed construction projects in remote locations were introduced. According to the findings of this review, to establish whether 3D printing is practicable and desirable in remote locations, trade-offs between several aspects, including materials, structural design, process efficiency, logistics, labour, and environmental impact, must be taken into consideration. In the case of using local materials that meet the printability, buildability and robustness requirements, 3DP could be considered a cost-effective solution for remote housing. However, researchers, designers, and decision-makers should consider the options, such as remote on-site fabrication, available local materials and their quality, and the large-scale manufacturing process and concrete 3DP limitations when evaluating the feasibility of using 3DP in comparison to conventional construction methods. [Display omitted] • Concrete 3D printing as a solution to overcome remote housing challenges has been investigated. • Advantageous and disadvantageous of concrete 3D printing for remote housing have been discussed. • Case studies on using 3D printing for remote applications have been reviewed. [ABSTRACT FROM AUTHOR]

Extrusion-based concrete 3D printing is at its infancy and many aspects of this new technology need to be thoroughly investigated to pave the way for its widespread use in construction. Since the inherent drying shrinkage of the hardened cement paste is the source of the drying shrinkage of 3D printed concrete, the shrinkage behavior of cementitious 3D printing materials with very high cement to fine aggregate ratios is one of the major challenges for researchers working on this innovative technology. Besides, due to the absence of formwork in this technique, an outdoor 3D printing environment causes excessive moisture loss and drying shrinkage cracking. This paper presents the first comprehensive investigation on the effects of different outdoor environmental conditions i.e. relative humidity (RH) and temperature on the moisture loss, drying and autogenous shrinkage of cementitious 3D printing materials, considering different sand to cement (S/C), and surface to volume (S/V) ratios of free-formed specimens. Mass loss and length change of mortars which were cured for up to 168 days under standard condition (24 ̊C-50%RH with 24 h of sealed initial curing) were compared with those at 24 ̊C-50%RH, 35 ̊C-85%RH and 35 ̊C-45%RH (free-formed specimens without initial curing) to investigate the effect of outdoor printing environment and the absence of formworks on the deformations caused by shrinkage. The drying shrinkage results indicate that 28 days free-formed specimens under different non-standard curing conditions show a length change up to 30% lower than specimens in the standard environment. Moreover, increasing the sand to cement ratio from 0.8 to 1.0 results in a 10% decrease in the drying shrinkage strain. This study also discusses the higher susceptibility of free-formed specimens to carbonation shrinkage and demonstrates that printed specimens have higher shrinkage deformation in the longer term compared to conventional casting specimens. The results of nitrogen adsorption-desorption analysis also prove that the total porosity in free-formed specimens in all environmental conditions reduces and reaches a finer pore structure after 112 days compared to conventional casting specimens. These results point to the importance of internal or external curing for reducing shrinkage in concrete 3D printing. [ABSTRACT FROM AUTHOR]

Foundation piles that are made by concrete 3D printers constitute a new alternative way of founding buildings constructed using incremental technology. We are currently observing very rapid development of incremental technology for the construction industry. The systems that are used for 3D printing with the application of construction materials make it possible to form permanent formwork for strip foundations, construct load-bearing walls and partition walls, and prefabricate elements, such as stairs, lintels, and ceilings. 3D printing systems do not offer soil reinforcement by making piles. The paper presents the possibility of making concrete foundation piles in laboratory conditions using a concrete 3D printer. The paper shows the tools and procedure for pile pumping. An experiment for measuring pile bearing capacity is described and an example of a pile deployment model under a foundation is described. The results of the tests and analytical calculations have shown that the displacement piles demonstrate less settlement when compared to the analysed shallow foundation. The authors indicate that it is possible to replace the shallow foundation with a series of piles combined with a printed wall without locally widening it. This type of foundation can be used for the foundation of low-rise buildings, such as detached houses. Estimated calculations have shown that the possibility of making foundation piles by a 3D printer will reduce the cost of making foundations by shortening the time of execution of works and reducing the consumption of construction materials. [ABSTRACT FROM AUTHOR]

Developments in the automation of construction processes, observable in recent years, is focused on speeding up the construction of buildings and structures. Additive manufacturing using concrete mixes are among the most promising technologies in this respect. 3D concrete printing allows the building up of structure by extruding a mix layer by layer. However, the mix initially has low capacity to transfer loads, which can be particularly troublesome in cases of external components that need to be placed on top such as precast lintels or floor beams. This article describes the application of additive manufacturing technology in the fabrication of a building wall model, in which the door opening was finished with automatic lintel installation. The research adjusts the wall design and printing process, accounting for the rheological and mechanical properties of the fresh concrete, as well as design requirements of Eurocode. The article demonstrates that the process can be planned precisely and how the growth of stress in fresh concrete can be simulated, against the strength level developed. The conclusions drawn from this research will be of use in designing larger civil structures. Furthermore, the adverse effects of concrete shrinkage on structures is also presented, together with appropriate methods of control. [ABSTRACT FROM AUTHOR]