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Testing the Properties of Fiber-Reinforced Geopolymer 3D Printing Material

In a paper entitled “Effect of Polypropylene Fibre Addition on Properties of Geopolymers Made by 3D Printing for Digital Construction,” a group of researchers investigates the effect of polypropylene (PP) fibers on the fresh and hardened properties of 3D printed fiber-reinforced geopolymer mortars. One of the main limitations of extrusion-based concrete 3D printing techniques, the researchers point out, is the difficulty of incorporating conventional steel reinforcement.

“As a possible solution, conventional steel bars might be partly or completely substituted by short-fibre reinforcement, thus minimizing or rendering unnecessary requirements for steel reinforcement with regard to mastering issues of cracking due to shrinkage or temperature changes and, in some cases, achieving particular load-bearing capacity and deformability,” they state.

Another limitation is the limited range of printable concretes, they continue. Conventional OPC concrete is not suitable because of its setting characteristics, as well as its high energy consumption and emissions. An alternative is geopolymer, which can be made by alkaline activation of fly ash and slag. There has not been a great deal of research done to optimize the mixture proportions of 3D printable geopolymers, so the researchers dedicated their work to developing an optimized geopolymer for 3D printing.

To produce a geopolymer mortar, the researchers used fly ash, micron-scale silica sand, an alkaline solution composed of sodium silicate and sodium hydroxide solutions, and sodium carboxymethyl cellulose (CMC) powder. They tested mixtures with different proportions of each ingredient before settling on one that was both extrudable and buildable. Different percentages of PP fiber were then added to the optimized mixture, in volumes ranging from .025% to 1.00%. They tested the mortar by 3D printing it with a custom-made testing device. The printed specimens were then heat treated.

The shape retention ability test setup

Rheological behavior of the mixtures was tested, as were the mechanical properties of the hardened mortar. Tests were also run for apparent porosity and interlayer bond strength.

“Fibre addition seems to influence compressive strengths positively only when the loading is perpendicular to the interface plane,” the researchers state. “This is due to the preferential fibre alignment parallel to the direction of extrusion. The addition of fibre significantly enhanced the flexural performance of the printed samples. The use of fibre dosages of 0.75 and 1.00 vol % caused deflection-hardening behaviour of the 3D-printed geopolymers and, hence, a significantly higher fracture energy in comparison to specimens without fibre or with lower fibre content.”

An increase in fiber volume did cause some minor reduction in interlayer bond strength. Higher fiber volumes, however, caused better shape retention ability in the printed samples, as well as ductility. A strong correlation between porosity and compression strength was found in the 3D printed material, similar to that of cast concrete.

The interlayer bond strength test

“The results indicate the possibility of printing fibre-reinforced geopolymers which meet all the necessary properties in both the fresh and hardened states,” the researchers conclude.

Authors of the paper include Behzad Nematollahi, Praful Vijay, Jay Sanjayan, Ali Nazari, Ming Xia, Venkatest Naidu Nerella and Viktor Mechtcherine.

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Indian Institute of Technology Madras Develops 3D Printed Homes That Take Three Days to Build

As 3D printing just continues to gain traction around the world—contributing enormous benefits and innovation to a wide range of industries—India has been embracing the technology and making strides with many different applications. Now, faculty and alumni at the Indian Institute of Technology Madras have developed a new program for 3D printed construction technology and have fabricated their first building.

Meant to act as a start-up for a ‘re-envisioned construction process,’ the academic team is currently developing a 3D printing process that will allow them to create 320-foot, one-story homes within three days each. They are working from a progressive prototype that has already been created at the Institute, offering a concept that allows them to use all the benefits of 3D printing to fulfill the demands for housing in India. Affordability is a huge factor, along with speed in production time, less need for construction labor, and less challenge in transporting more expensive, and dense, materials.

“Building Technology and Construction Management Division at IIT Madras is a unique Research Group in the country which has the expertise in materials as well as construction technologies which is relevant to this effort,” said Prof. Koshy Varghese, Department of Civil Engineering, IIT Madras.

“We have been working on developing 3D printing technology in the area of Construction from 2016 and have conducted International Workshops and awareness sessions for this in Chennai. In addition, the institute is exploring automated construction methods and novel formwork systems for rapid housing construction.”

Along with this current startup, IIT Madras is working with other government divisions to encourage education about—and the use of—technologies like 3D printing.

“3D printing of concrete gives a new dimension to construction. This technology can best meet the complex demands of modern architecture with concrete. The use of a combination of binders and optimally proportioned and sized aggregates, along with suitable chemical additives, the concrete mixture is fine tuned to achieve the rheological characteristics that make it possible for extrusion of the material and shape retention after placement,” said Prof Manu Santhanam, Department of Civil Engineering, IIT Madras.

The government realizes the need for innovation in construction processes as housing issues become further pressing:

“It is very heartening to see that institutions like IIT Madras and new startups such as Tvasta building technologies like 3D printing for construction sector in India from the ground up under the ‘Make in India’ platform,” said Kranthi Valluru, Assistant Secretary, MoH UA. “Such technologies help in expediting construction with optimal use of resources. They help in bringing a paradigm shift in construction sector which is very much the need of the hour.”

Aside from prototypes, it is expected that Tvasta will produce the first 3D printed homes within a year.

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[Source / Images: The Hans India]

Indian Institute of Technology Madras faculty and alumni have developed the country’s first 3D Printing Construction Technology and have successfully built India’s first 3D Printed Structure.

Researchers Evaluate 3D Printability of Different Types of Concrete

To 3D print concrete, several parameters must be met. It must be able to be extruded through a nozzle, hold its shape once deposited, and also be able to hold up under the weight of successive layers. In a paper entitled “Evaluation of workability parameters in 3D printing concrete,” a team of researchers measured the workability of fresh concrete for 3D printing according to four different tests: “flow table, ICAR rheometer, Vicat and an experimental applied in the laboratory by measuring the electric power consumption of the motor that rotates the screw extruder.”

For their materials, the researchers used crushed limestone, siliceous river sand and a combination of half and half of each. They developed a prototype 3D printing system to test the materials.

“Concrete mixtures produced with different aggregates, binders and different amount of water and superplasticizer were produced, tested for workability according to four different tests and printed in order to have available a wide data range of measured workability parameters and finally define their threshold values that characterize a concrete mixture as printable,” the researchers state.

The researchers established four criteria of printability and buildability:

The mixture can be extruded through the nozzle
Good print quality meaning no voids, no dimensional variations of extruded material
Five layers of printing material can be achieved without collapse
Height of 1st layer versus height of 5th layer ~ 1

It was difficult to find a mixture that met all four criteria. A mixture with limestone as aggregate and cement as binder was adjusted to achieve three different workability levels, high, moderate and low, but none of them were considered printable because none met all four of the established criteria.

The researchers also evaluated the loss of workability with time. Expansion of mixtures with the three different aggregates (limestone, river sand and the mixture of both) was measured 0, 15 and 30 minutes after mixing.

“Concrete with limestone filler lost workability in a higher rate than ones with river sand or combination with limestone and river sand,” the researchers state. “This can be explained by the granulometry of aggregates. Limestone filler has more fines that absorb more water from the mixture.”

Many of the river sand and combination aggregates could be 3D printed successfully, while most of the limestone-based mixtures were proven to be not printable. The limestone mixtures also required higher amounts of water and super-plasticizer to achieve the same level of workability as the other mixtures, which led to lower values of compressive strength.

“The use of alternative cementitious materials such as fly ash and ladle furnace slag as a replacement of cement
(20wt.%) results to average reduction of compressive strength by 30% and density by 10%, compared to mixtures with 100% cement as binder,” the researchers conclude. “It should also be mentioned that in most cases during printing, it was observed that fly ash mixtures showed reduced values and higher loss rate of workability with time compared to other mixtures. However, lower cost and volume stability of hardened concrete are expected to be the advantages of using fly ash or ladle furnace slag in concrete for 3D printing.”

Authors of the paper include M. Papachristoforou, V. Mitsopoulos, and M. Stefanidou.

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NTU Singapore Researchers Continue Development of Concurrent Mobile 3D Printing Construction Robots

NTU Assistant Professor Pham Quang Cuong (3rd from left) with his multidisciplinary team of researchers consisting of roboticists, civil engineers, mechanical engineers and material scientists, with the concrete structure 3D printed by the two robots concurrently in a single print.

In August, a multidisciplinary team of researchers from Nanyang Technological University Singapore (NTU Singapore) published a paper in the Automation in Construction journal for civil engineering about their work in developing a smart robotic construction method, in which two robots work simultaneously to 3D print a concrete structure. Large-scale 3D printing of objects, like buildings, is possible, but volume constraints and length of time can still be issues…unless, of course, you enter mobile robots capable of synchronized concrete 3D printing into the equation.

The NTU Singapore Centre for 3D Printing (SC3DP) team developing the technology is led by Assistant Professor Pham Quang Cuong with NTU’s School of Mechanical and Aerospace Engineering, who also worked on a collaborative project this spring where two autonomous robotic arms put together an IKEA chair in less than 9 minutes.

NTU Assistant Professor Pham Quang Cuong (R) working with PhD student Ms Zhang Xu to develop faster, more efficient ways of 3D printing concrete structures.

Professor Pham explained, “We envisioned a team of robots which can be transported to a work site, print large pieces of concrete structures and then move on to the next project once the parts have been printed.

“This research builds on the knowledge we have acquired from developing a robot that can autonomously assemble an Ikea chair. But this latest project is more complex in terms of planning, execution, and on a much larger scale.”

The team’s method of concurrent, or swarm, 3D printing is laying the groundwork for mobile construction robot teams to 3D print even larger structures, like full buildings, in the future. At the moment, large-scale 3D printers that are bigger than the objects they’re building are required to make big concrete structures. As most construction sites have space constraints to deal with, this isn’t really a feasible method of manufacturing.

“Scalability is a problem common to most existing 3D printing processes, where the size of the design is strictly constrained by the chamber volume of the 3D printer. This issue is more pronounced in the building and construction industry, where it is impractical to have printers that are larger than actual buildings,” the abstract of the team’s paper explains.

But using several mobile robots to 3D print at the same time means that larger structures, such as special facades and architectural features, can be built anywhere, provided that the work site has enough room for the robots to move around. It will also be possible to produce structures on demand at a much faster rate of speed.

In just eight minutes, the NTU Singapore team’s robots were able to 3D print a concrete structure, using a specially formulated cement mix, that measured 1.86 x 0.46 x 0.13 m. It took two days for the structure to harden, and a week to achieve full strength before it was deemed ready for installation. The team’s 3D printable cement mix also makes it possible to create unique designs that could not be completed using traditional casting methods.

It’s obviously not easy to use two mobile robots to concurrently 3D print a concrete structure. Both robots need to move into position and begin printing without bumping into the other one. Additionally, it wasn’t feasible to print the structure in separate segments, since joints between parts wouldn’t properly bond if the material didn’t overlap during 3D printing.

The team’s multi-step process begins with using a computer to map out the design and assign each robot a specific portion of 3D printing. Then, a special algorithm is used to make sure that the robots won’t collide during printing. For optimal consistency, the specialized liquid concrete mix has to be blended evenly, at the same time, during mixing and pumping.

Once the material is ready, the robots then move into place with precise location positioning and begin 3D printing the parts, making sure the alignment is correct and the joints properly overlap.

When you combine disruptive Industry 4.0 technologies such as 3D printing with others like AI, robotics, materials science, and green manufacturing methods, it’s possible to advance all of them even further.

“This multiple robot printing project is highly interdisciplinary, requiring roboticists to work with materials scientists to make printable concrete. To achieve the end result of a strong concrete structure, we had to combine their expertise with mechanical engineers and civil engineering experts,” said Professor Chua Chee Kai, the Executive Director of the Singapore Centre for 3D Printing.

“Such an innovation demonstrates to the industry what is feasible now, and prove what is possible in the future if we are creative in developing new technologies to augment conventional building and construction methods.”

The NTU Singapore team will now be focusing on integrating more robots to 3D print larger structures, in addition to improving the concrete material to ensure faster curing and further optimizing their 3D printing algorithm for consistent performance. The National Research Foundation, Singapore (NRF Singapore) and Sembcorp Design and Construction, an important industry research partner of SC3DP, are supporting the project.

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[Images: NTU Singapore]

How Economically Viable is 3D Printing Concrete For Construction?

3D printed concrete construction is becoming a practice that is being taken more seriously than ever before, as bridges, houses and other structures are being printed and shown to be effective. A new study entitled “Practice-oriented buildability criteria for developing 3D-printable concretes in the context of digital construction” takes a look at the process of digital construction (DC) and presents what it calls buildability criteria, taking various process parameters and construction costs into consideration.

“A systematic basis for calculating the time interval (TI) to be followed during laboratory testing is proposed for the full-width printing (FWP) and filament printing (FP) processes,” the researchers state. “The proposed approach is validated by applying it to a high-strength, printable, fine-grained concrete. Comparative analyses of FWP and FP revealed that to test the buildability of a material for FP processes, higher velocities of the printhead should be established for laboratory tests in comparison to those needed for FWP process, providing for equal construction rates.”

Full-width printing is defined as a process in which “the breadth of the extrudate is equal to that of the target element,” while in filament printing “the breadth of the extrudate is many times smaller than the the breadth of the target element.” For both processes, three primary requirements are defined: pumpability, extrudability and buildability. Buildability is the ability of the concrete material to retain its shape and size under sustained or increasing loads. It’s a complex property, according to the researchers, that depends on material composition as well as process parameters such as layer geometry.

Three process parameters define buildability criteria:

the height of the wall to be printed
the height of each layer or the total number of layers to be printed
the time interval (TI) between subsequent layers

“The height of the experimental wall was calculated using the aspect ratio of the target construction element,” the researchers explain. “Maximum time interval was determined considering the minimum printing velocity needed for DC to be economically viable in comparison with conventional construction.”

The buildability of an experimental 16-layer wall was validated with a maximum time interval of approximately 52 minutes. The buildability of any given material, the researchers explain, depends not only on the target structure but on the applied printing process or approach. Analysis showed that the buildability of a material for FP processes should be tested at higher velocities of the printhead than for FWP.

Over the course of the paper, the researchers take several factors into consideration, including machine, labor and material costs to quantify the economic viability of digital construction processes. They also name several issues as potential for ongoing research, such as validation of the approach with full-scale printing tests, as well as simplification of the proposed approach and direct buildability tests at various ambient conditions, including temperature, humidity and wind velocity.

For example the team looks at printing full width or using filament to print a line at a time and conclude that higher speeds would be needed for the filament method to equal the total build speed of a full width approach. They also look at concrete drying times and what the required interval would be between layers for those layers to be buildable. For their experiments the team calculated a construction cost of 130.00 €/m3. This means that, “the material costs are 70 % higher in comparison to the material costs for ordinary concrete of the strength 535 class C25/30 in conventional construction.” Based on a test object they also calculate which build speeds would be needed in order for 3D printing to be more economical than regular construction methods. In their case their test printer could be cost efficient in time and money at less than 540 m/h. This takes into account the higher material cost and two operators for the machine (three if multistory construction is required). The machine costs of their printer were estimated at 140 Euro per hour. The team also looked at Travelling Salesman Problem trype solutions to make their toolpaths more efficient.

Studies like this one are important in the continuing development of 3D printed concrete construction, as experts work out the best ways to make the technology as economically viable as possible, not to mention safe and effective. Many wild claims about 3D printed construction exist, but when it comes down to it, many factors have to be taken into consideration to ensure that it is, in fact, an optimally effective technology.

Authors of the paper include Venkatesh Naidu Nerella, Martin Krause, and Viktor Mechtcherine.

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NTU Singapore Researchers Develop Mobile 3D Printing Concrete Collaborative Robots

There’s been a lot of talk about 3D printing construction robots recently, and while we’ve seen some of these robots receive help with their task from drones, we don’t often see them working together to build structures…until now.

Large-scale 3D printing of objects, like buildings, is possible, but volume constraints and length of time can still be issues. Robot arms can be used to print anywhere within reach of the arms, and there have been some gantry systems that are able to 3D print structures, so long as the structure is smaller than it is, of course.

“The way to avoid constraints like these is to have a robot that can both 3D print things and move around, and once you’ve decided to go that route, there’s no reason not to use multiple robots to speed things along,” wrote Evan Ackerman for IEEE Spectrum.

Recently, a team of roboticists from Nanyang Technological University in Singapore (NTU Singapore) published a paper, titled “Large-scale 3D Printing by a Team of Mobile Robots,” in the Automation in Construction journal. The paper details how the researchers were able to complete the actual 3D printing, using two mobile robots operating simultaneously, of a single-piece concrete structure.

The team believes they are the first to have achieved this.

The abstract reads, “Scalability is a problem common to most existing 3D printing processes, where the size of the design is strictly constrained by the chamber volume of the 3D printer. This issue is more pronounced in the building and construction industry, where it is impractical to have printers that are larger than actual buildings. One workaround consists in printing smaller pieces, which can then be assembled on-site. This workaround generates however additional design and process complexities, as well as creates potential weaknesses at the assembly interfaces. In this paper, we propose a 3D printing system that employs multiple mobile robots printing concurrently a large, single-piece, structure. We present our system in detail, and report simulation and experimental results. To our knowledge, this is the first physical demonstration of large-scale, concurrent, 3D printing of a concrete structure by multiple mobile robots.”

These aren’t drones, but instead robot arms on mobile bases. So while there are still restrictions as to how high they can reach, they are far more flexible in terms of length and width than most other systems. Additionally, since you can bring in several cooperating robots for one big project, they are a more efficient option – one robot can tackle one problem, while a second can take on another task, and so on and so forth. Multiple robots also means that you can make stronger, more complex structures at an increased rate of speed, because, as Ackerman put it, “you don’t run into the problem of trying to bond wet concrete to dry concrete where two parts intersect.”

Because the mobile robot system developed by the NTU Singapore researchers can move around and thus define its own build volume, it can actually build structures that are essentially arbitrary in size without needing to make many system changes. You can see the system in action below:

There are all sorts of applications that a fleet of moving construction robots could work on. But the team is currently looking at one in particular, as they explain in their paper:

“Using a fleet of mobile robots for construction could have an extreme potential in other non-conventional aspects. One such application is to allow automated construction in hard-to-reach, remote areas, such as underground caves, the Moon or Mars, to which it is inconvenient or even impossible to bring other kinds of machine required for existing cementitious material printing methods.”

Currently, this system is still just an early proof of concept, so no cave construction yet. While the two robots in the video did collaborate to 3D print a structure, they’re not yet moving around during printing. Additionally, a camera array guides the robots during construction, and the existing system is not designed to be used outside…kind of a problem when you’re 3D printing a large building.

But fear not! Quang-Cuong Pham, one of the researchers, explained that it took the team several years to reach this point and that the work is not done yet, so these issues can be sorted out. Pham said that the mobile robotic 3D printing system has been “a multidisciplinary effort, combining both robotics and cementitious material formulation.”

When it comes to getting the robots to move during 3D printing, Pham explained that it will require “even higher precision in the localization of the base…to ensure that the layers are appropriately positioned one above the other.”

The team will also be working to add on-board obstacle (and human) detection to improve the autonomy of the robots, in addition to putting the robot arms on scissor lifts to increase their reach.

Co-authors of the paper are Xu Zhang, Mingyang Li, Jian Hui Lim, Yiwei Weng, Yi Wei Daniel Tay, Hung Pham, and Pham, all of whom are with NTU’s Singapore Centre for 3D Printing at the university’s School of Mechanical & Aerospace Engineering.

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[Images: Nanyang Technological University]

Live Demonstration of ACES Concrete 3D Printing Technology at CERL to 3D Print Barracks: Part 3

As part of a three-year program called Automated Construction of Expeditionary Structures (ACES), last year the US Army 3D printed a complete barracks, also known as a B-Hut, out of a patented concrete mixture. The program is researching 3D printing as a way to build semi-permanent structures out of concrete, made from locally available materials – the goal is to reduce the amount of building materials that need to be shipped out by half, and decrease construction manpower requirements by 62%, when compared to expedient plywood construction.

Last week I was invited out to the Engineer Research and Development Center’s Construction Engineering Research Laboratory (CERL) in Champaign, Illinois for a live demonstration of the ACES technology…an invitation I was happy to accept. Last year’s B-hut took 21.5 hours to print, but that’s the total number of print hours, and wasn’t continuous. This time, the ACES team, with assistance from its project partner – Chicago-based architectural and engineering firm Skidmore, Owings, and Merrill (SOM) – and Marines from the 1st Marine Expeditionary Force, was going to attempt something new.

The ambitious plan was to complete the two halves of another barracks structure, completely out in the open and not covered by a tent, in 24 hours of continuous 3D printing. What moves the demonstration from ambitious to brave was the team’s decision to invite journalists to see the live print, and I’m not just talking about myself – I saw cameramen and reporters onsite from at least two different local TV stations.

The Marines were briefed on the specifics of the technology ahead of time, and ran the equipment themselves this week, as they will be the ones actually 3D printing the structures in the future if the program is successful. However, the ACES team and SOM were onsite in case they needed to offer any assistance, and that assistance was needed a time or two during the live demonstration.

Program manager Michael Case, PhD, told me that an issue with concrete is evaporation drying, so when the forecast showed rain, the start time was moved up a few hours, only to halt again pretty quickly once the team realized that they needed a new pump – the interior of the original one had been torn up by the sharper materials used during a live demonstration at Fort Leonard Wood a few months ago. Then the kinks needed to be worked out of the hose, and when the material didn’t extrude properly after the print began, the team removed the nozzle and discovered that a rock was inside messing up the flow.

The material mixture had to be adjusted after the first layer because it was too sloppy, at one point the nozzle was accidentally sent over to the side that wasn’t being worked on yet, and when steel dowels were added for initial reinforcement to the first several layers of 3D printed concrete, work began on the wrong side. But in spite of these minor setbacks, work continued through the night and Public Affairs Specialist Mike Jazdyk told me that there were very few clogs.

[Image: Mike Jazdyk]

On the morning of the second day of printing, Jazdyk told me that the ACES team would not make its original goal of a continuous, 24 hour 3D printed concrete barracks. A lot of this was due to concrete curing inside of the pump, which caused the equipment to shut down and cause some overnight delays. By the time I had to head for home, the team had nearly completed the first half of the structure and was planning to take several hours of much-needed rest before starting in on the second half. Jazdyk informed me that work would begin again around midnight.

I received a call from Jazdyk on Friday afternoon, and he told me that the ACES team had to stop the print due to equipment failure, but that they had managed to complete roughly 80% of the structure before this happened – this is easy to see in the image below.

[Image: Mike Jazdyk]

“What you see is 40 hours of printing,” Jazdyk told me about these four photos he sent, noting that this number does not denote a continuous job, but rather is the total number of print hours.

Jazdyk explained that had the equipment not failed, the ACES team at CERL would have finished the structure in less than 48 hours, which is still an extremely impressive feat. As previously mentioned, the fact that the team was willing to have the press onsite for the live demonstration, without knowing for certain if they would make their goal, was valiant.

So often with 3D printed construction projects, we are assaulted with people and companies saying, “Look, I’m the first!” or “I did it the fastest!” or “I built the biggest thing in the world!” At CERL this week, everyone I spoke to was very candid with the issues the project was running into, and no one tried to pull the wool over my eyes or move me away if something went awry. People answered every question I asked openly and honestly, even if it was a question relating to something that was currently going wrong – this is admirable.

“No one shows you under the skirts of large-scale concrete 3D printing – all you see are the videos that are posted online of just what people want you to see, and nothing else,” project manager Megan Kreiger told me. “You don’t see all the problems that you have to overcome. They make it look like they’re doing it super fast, super easy, and that they’re doing it under 24 hours, but none of it’s true.”

Team members also shared their hopes for the program with me, like ultimately lowering the cost of materials and the amount of manpower needed, and the potential applications the ACES technology could eventually be used for other than 3D printing buildings, such as culverts, barriers, and bridges, and more humanitarian efforts, like schools.

“There’s a tremendous number of uses,” Dr. Case told me.

Jazdyk told me today that they will attempt to complete the 3D printed concrete structure next week at CERL. I am confident that they will succeed, but, knocking on wood and knowing that sometimes things just go wrong, I am also confident that should more problems arise, the ACES team will handle them with grace, learn from them, and keep on trucking.

Stay tuned to 3DPrint.com for more news about my recent visit to CERL, including plenty of information that I did not previously know about concrete and the importance of the shape of these 3D printed walls.

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[Images: Sarah Saunders for 3DPrint.com, unless otherwise noted]

Live Demonstration of ACES Concrete 3D Printing Technology at CERL to 3D Print Barracks: Part 2

One half of the 3D Printed Strcture.

I was recently invited to the US Army’s Engineer Research and Development Center’s (ERDC) Construction Engineering Research Laboratory (CERL) in Illinois to see a live demonstration of its Automated Construction of Expeditionary Structures (ACES) technology. Last year, the US Army used ACES to 3D print a complete barracks, or B-Hut, in 21.5 hours with the Army’s patented concrete mixture.

Having only seen still images and video of this unique technology, I knew I couldn’t pass up the opportunity to see a 512 square foot barracks 3D printed live in front of my very eyes within 24 hours. So yesterday afternoon, I hopped in my car for the roughly four-hour drive out west to Champaign.

A closer look at a completed section.

The goal for this ACES demonstration is to successfully 3D print the exterior concrete walls of a 8 foot building in 24 hours. While the ACES team and its project partner, Chicago-based architectural and engineering firm Skidmore, Owings, and Merrill (SOM), are both onsite, Marines from the 1st Marine Expeditionary Force are running the equipment; obviously, if the project is successful and this technology is able to be deployed overseas to our troops in the future, they will be the ones actually 3D printing the structures.

Benton Johnson, PE, SE, the Associate Director at SOM, told me yesterday that the Marines were briefed on the ACES technology and equipment via conference call and email. From the looks of things, they seemed to have gotten the hang of everything – preparing and mixing the materials, running the computer, cleaning up the printed layers by hand and clearing away material from the bolts, etc. Johnson pointed out that the main coder of the project was onsite, but only to offer assistance if needed.

A close up of the nozzle 3D printing the barracks. Image Sarah Saunders.

“I think part of this is a learning curve, because all the Marines that were out there operating the machinery had never seen this or touched it before,” Captain Matt Friedell told me.

“But they took to it, and once they learned it, they started to get in their groove and really pick up the pace. And we knew when we were going to attempt this that it was going to be a challenge.”

Obviously, there were a few glitches, as people rarely get the hang of new technology perfectly the first time out. The barracks is being 3D printed in two halves, and at one point the Marine running the computer accidentally sent the nozzle over to the side that wasn’t being worked on yet; later, when steel dowels were being added for initial reinforcement to the first 18″ or so of 3D printed concrete, work began on the wrong side. But none of this seemed to slow the process down.

However, as I mentioned yesterday, things did not start off swimmingly. Program manager Michael Case, PhD, told me that one of the issues with concrete is evaporation drying. So when the forecast showed rain today, the start time of the demonstration was moved up a few hours, only to halt again pretty quickly. Dr. Case explained that the material used at the Fort Leonard Wood demonstration a few months ago was sharper and more angular than it is here at CERL, and tore up the inside of the pump.

By the time the team finished replacing the pump and working the kinks out of the hose, it was almost the original start time of 5 pm. it looked like things were going to start moving, until the material didn’t extrude properly and some team members removed the nozzle to find that a rock inside was jamming things up. When the concrete finally started to print, the material mixture had to be adjusted after the first layer because it was too sloppy. But once this was fixed, things really took off, and work continued through the night, with very few clogs.

Spoiler alert: when I arrived back at CERL this morning, I learned that the team would not be able to make its original deadline of 24 hours. Dr. Case explained that “a big part of this is to figure out how long you can continuously use the equipment.”

“So we learned a lot about things…If you operate this type of concrete printing equipment long enough, you have to stop and service some of the equipment.”

Dr. Case said that if you don’t clean out the equipment, you can get concrete curing inside of the pump, and that it will eventually shut down, which caused some delays overnight. So by about 9 am this morning, the team had nearly completed the first half of the structure, and was planning on taking a few hours of much-needed rest before starting in on the second half.

While the ACES team won’t make the original goal of a continuous 24 hour print, the work they’ve completed and will continue throughout the rest of the day, is extremely impressive. Capt. Friedell told me as I was leaving CERL that he was certain this project is the tallest continuous 3D print in the US.

Stay tuned to 3DPrint.com for a more in-depth look at my visit to CERL this week! So far it has been very exciting to be able to have unfettered access to the site and to have been given access to all of the people involved. Issues with extrusion, rain and the weather that this team had actually made me question more the validity of some “3D printing a house in a day” claims. What this team ancountered were real-life challenges brought on by equipment and the weather that slowed them down. I think that CERL’s effort, undertaken with a journalist present, was much more transparent, open and honest than the commercial house printing initiatives who somehow always tell us after the fact the great feats that they’ve accomplished. I can now really see the value that house 3D printing could have for the Marine Corps, Army and for civilian use. Most of all I’m grateful that I got an up close and personal look at what it actually takes to 3D print a structure.

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[Images: Sarah Saunders for 3DPrint.com]

NOWLab Creates Smart Concrete Through 3D Printing

If you’ve ever been told you are as a dumb as a brick, you know (unless the accusation is true) that building materials aren’t renowned for their intelligence. However, while intelligence may be out of reach, it is true that they are increasingly becoming ‘smart‘, meaning they offer the capacity to interact with their users. That interaction goes beyond a simple on/off switching mechanism to include a connection to a network that allows for remote sharing and interaction. Today, there are a wide variety of things that we have come to rely upon for their smart enabled capabilities.

Beyond smartphones, the current gold standard in communications, there are smart home security systems and smart lighting systems that have introduced the idea of networked technology as an integral part of design and architecture. One company that has beenleading the way in this area is the German company BigRep, producers of the large-scale BigRep ONE 3D printer. Their innovation department, NOWLab, has been working on creating smart concrete with an adaptive surface enabled by embedded capacitive sensors. This translates to concrete with capabilities that are activated by the touch of a hand.

In the case of NOWLab’s efforts, this comes in the form of a wall panel with integrated lights that can be controlled by touching the surface of the concrete at any point. Concrete was one of the greatest innovations in the history of architecture; however, because of its ease of use, it has resulted in some of the least thoughtful building that has ever been undertaken. Its reputation has been tarnished by years of mindless application; a sort of dump and dash philosophy of building. The argument being made by the team at NOWLab is that through the utilization of advanced technologies such as 3D printing the forming of concrete can once again become a point of pride for the master builder, and the integration of sensorial capabilities can elevate the material beyond mere presence in a space to an active element in the formation of spatial experience.

The particular wall section they have created was designed using Arabic tiling logic put through a parametric design process, used to guide the tiles as they shift from closed on the bottom toward open on the top of the panel. Once the 3D model had been perfected, the concrete molds were then printed on the BigRep ONE, a machine capable of producing at an architectural scale. Within the openings, LED lights were placed, and a touch of the hand on the surface of the concrete is used to turn them on and off. The panel, reminiscent of Gaudi’s Sagrada Família, particularly the later portions, promise to show the way towards a reimagining of the possibilities for form once 3D printed molds are utilized.

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[Source/Images: Designboom]