A quality control framework for digital fabrication with concrete

The quality control of digital fabrication with concrete has more stringent requirements than traditional casting. Firstly, since formwork is typically absent, or removed at an early stage in production, the material is exposed to external influences that can result in deformations, collapse, or deterioration. Therefore, the evolution of properties during the process has to be controlled. Secondly, the fabrication systems are typically more sensitive to dosing fluctuations, and the produced, optimized objects are more sensitive to defects, which requires the process variations to be controlled at a higher resolution. A framework is presented that categorizes quality control experiments into destructive and non-destructive, according to their systematic error, and according to the location of testing with respect to the process. This framework is applied to the fresh state mechanical performance of concrete and quality control strategies are derived from it. Lastly, research gaps are identified that are critical for the further development and adoption of these quality control strategies in digitally fabricated concrete

A quality control framework for digital fabrication with concrete

The quality control of digital fabrication with concrete has more stringent requirements than traditional casting. Firstly, since formwork is typically absent, or removed at an early stage in production, the material is exposed to external influences that can result in deformations, collapse, or deterioration. Therefore, the evolution of properties during the process has to be controlled. Secondly, the fabrication systems are typically more sensitive to dosing fluctuations, and the produced, optimized objects are more sensitive to defects, which requires the process variations to be controlled at a higher resolution. A framework is presented that categorizes quality control experiments into destructive and non-destructive, according to their systematic error, and according to the location of testing with respect to the process. This framework is applied to the fresh state mechanical performance of concrete and quality control strategies are derived from it. Lastly, research gaps are identified that are critical for the further development and adoption of these quality control strategies in digitally fabricated concrete

Crack width and crack spacing in reinforced and prestressed concrete elements:Data description and acquisition

Existing databases containing measurements of crack width and spacing are usually limited in size and based on isolated experimental studies. These databases are used to develop new formulas to describe crack patterns in concrete structures. A database obtained from multiple sources of experimental programmes is required to quantify the accuracy of those formulas. To this end, a database containing crack width and crack spacing measurements was created, based on 30 different experimental programs described in literature. The results of each program were described in .xlsx format and queried to a database (.csv) using Structured Query Language (SQL). The structural elements considered in the database are reinforced and prestressed ties, beams, and reinforced slabs with varying geometry, concrete and reinforcement properties. From the considered experimental programs, over twenty thousand data points were extracted using a systematic approach. The data points consist of the metadata, materials, structural element preparations, test setups and measured crack widths and spacings. The database's applied structure is robust and valuable: it can be implemented in subsequent research focussing on cracking in concrete, such as assessing existing formulas to describe the crack widths and spacings in concrete structures, or deriving new formulas, potentially improving the prediction of the remaining service life of concrete structures

Double curved concrete printing: printing on non-planar surfaces

It is no secret that there have been some great advances in the realm of concrete additive manufacturing. However, one of the major drawbacks of this fabrication technique is that the elements must be self-supporting during printing. While most other additive manufacturing materials can overcome this by using a secondary printed support structure, alternative strategies have to be developed for materials such as concrete. This 4TU project explores the possibilities of combining concrete additive manufacturing with a temporary support surface. By printing on a free-form surface, more intricate geometries can be realized. A number of potential applications have been outlined, however the principle focus is combining concrete additive manufacturing and casting. The end result is a partially-printed pavilion using a completely digital design-tofabrication workflow

Optimizing 3D concrete printing: exploring potentials and limitations of materials and production

The application of new Computer Aided Manufacturing (CAM), digital fabrication and additive manufacturing techniques in the construction industries is expected to bring major change to these industries. Driven by a foreseen reduction of construction time and labor cost, simplification of logistics and an increase of constructible geometrical freedom, many experiments are performed both at academia and in practice. Beyond these economical and architectural objectives, digital fabrication in construction can be used to reduce the environmental footprint of the industry. The increased level of control offered by digital fabrication enables the use of advanced computational optimisation techniques. With these optimisation techniques buildings can be designed which, for instance, combine an optimal thermal performance with a minimum use of materials, while still complying with all codes and standards. In order to fully utilise this potential of digital fabrication, the capabilities and limitations of the manufacturing process need to be taken into account during optimisation. By combining the concrete 3D printing knowledge of Eindhoven University of Technology, the optimisation expertise of the BEMNext lab at Delft University of Technology and software development by White Lioness technologies, the ‘Optimising 3D concrete printing’ Lighthouse project has made the first steps towards more knowledge on integrated optimisation and manufacturing

Optimizing 3D concrete printing: exploring potentials and limitations of materials and production

The application of new Computer Aided Manufacturing (CAM), digital fabrication and additive manufacturing techniques in the construction industries is expected to bring major change to these industries. Driven by a foreseen reduction of construction time and labor cost, simplification of logistics and an increase of constructible geometrical freedom, many experiments are performed both at academia and in practice. Beyond these economical and architectural objectives, digital fabrication in construction can be used to reduce the environmental footprint of the industry. The increased level of control offered by digital fabrication enables the use of advanced computational optimisation techniques. With these optimisation techniques buildings can be designed which, for instance, combine an optimal thermal performance with a minimum use of materials, while still complying with all codes and standards. In order to fully utilise this potential of digital fabrication, the capabilities and limitations of the manufacturing process need to be taken into account during optimisation. By combining the concrete 3D printing knowledge of Eindhoven University of Technology, the optimisation expertise of the BEMNext lab at Delft University of Technology and software development by White Lioness technologies, the ‘Optimising 3D concrete printing’ Lighthouse project has made the first steps towards more knowledge on integrated optimisation and manufacturing

The realities of additively manufactured concrete structures in practice

Extrusion-based 3D Concrete Printing (3DCP) is rapidly gaining popularity in the construction industry. Trial projects are now being realized at an increasing rate around the world to test the viability of the technology against real-world requirements. This step, from the ‘simple’ deposition of filaments of self-stable concrete to its application in buildings and structures, with all associated requirements and interfaces, comes with challenges. These range from matching the design intent to the manufacturing capabilities (through structural analysis and approval, and reinforcement) to quality consistency (robustness) on large scale, and compatibility with other materials. In many of these areas, much simply remains unknown due to a lack of experimental data or information from projects where 3DCP has been applied. This paper aims at reducing this knowledge gap by presenting a systematic discussion, based on the analyses of eight realized 3DCP projects from around the world. It was found that the structural application of printed concrete is limited, due to a lack of regulatory framework for expedient approval, as well as limited reinforcement options which require to resort to unreinforced masonry analogies. The application of the technology features a host of practical issues that relate to the print process, material, site conditions, building integration and design – or to the 3DCP technology in general. Although some potential risks, such as shrinkage cracking and quality consistency are generally recognized, the measures taken to mitigate them vary considerably, and are largely based on individual expertise. The actual effectiveness is generally unknown. Finally, it was observed that, while the printing itself is fast, the preparation time is generally considerable. This is partially due to a lack of knowledge amongst professionals. In the practical production of a 3DCP project, three expertise areas are crucial: one for the digital part, one for the machine side, and one for the material side. Thus there is a strong need for educational institutions to develop dedicated training courses and incorporate relevant topics into their curricula

Clinical presentation and outcome of invasive mould disease in paediatric patients with acute lymphoblastic leukaemia

Background: Childhood acute lymphoblastic leukaemia (ALL) cure rates have improved, but invasive mould disease (IMD) remains a life-threatening complication. Here, we evaluate the epidemiology, clinical presentation, treatment and outcome of IMD in paediatric patients with ALL. Methods: Patients (1–18 years) treated according to the Dutch Childhood Oncology Group (DCOG) ALL-11 protocol from 2012–2021 were analysed for probable and proven IMD. Data was extracted from the Dutch national registry and the electronic health care system. Results: Among 643 patients with ALL, 47 (7.3%) were diagnosed with a probable (n = 29) or proven (n = 18) IMD. Aspergillosis was diagnosed in 42 (89%) patients. Forty-one episodes (87%) occurred during the induction (n = 20) and first consolidation (n = 21) course. The median age at ALL diagnosis was 5 years [IQR 3–10] in the overall group versus 14 years [IQR 7–16] in the IMD group. Two-third of the patients did not receive mould-active prophylaxis. The most prevalent clinical symptoms at presentation were persistent fever and respiratory symptoms. The lungs were the most common site of infection with involvement in 44 (94%) patients, followed by the CNS in 16 (34%) patients. The 6-week and 12-week mortality rate after IMD diagnosis was 10.6% and 14.9%, respectively. Discussion and conclusion: In our paediatric cohort a notable incidence of probable and proven IMD was observed during the early stages of treatment. Remarkable is the high frequency of CNS involvement. These findings highlight the importance of effective prophylactic strategies and warrant early brain imaging

Endotoxin Induced Chorioamnionitis Prevents Intestinal Development during Gestation in Fetal Sheep

Chorioamnionitis is the most significant source of prenatal inflammation and preterm delivery. Prematurity and prenatal inflammation are associated with compromised postnatal developmental outcomes, of the intestinal immune defence, gut barrier function and the vascular system. We developed a sheep model to study how the antenatal development of the gut was affected by gestation and/or by endotoxin induced chorioamnionitis