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The self-healing concrete that can fix its own cracks


Of all the carbon emitters that surround us every day it’s easy to overlook one of the most ubiquitous: concrete.

The material that builds our buildings, paves our roads and spans our bridges is the most widely produced and consumed material on earth apart from water, according to a WBCSD report. By 2030, urban growth in China and India will place global cement output at 5bn metric tons per year, with current output already responsible for 8% of the global emissions total, according to a WWF report.

Although its environmental impact is far from benign, concrete – defined as the mixture of aggregates, water and the hydraulic powder material known as cement – is incredibly useful and widely applicable. Thanks to its durability, easily-sourced raw materials and thermal resistance, it is unlikely that an alternative building material will replace it on a large scale any time soon.

Hendrik Jonkers, a microbiologist at Delft University and a finalist at the recent 10th annual European Inventor Awards, has a plan to increase the lifespan of concrete. His innovation, which embeds self-activating limestone-producing bacteria into building material, is designed to decrease the amount of new concrete produced and lower maintenance and repair costs for city officials, building owners and homeowners.

Jonkers’ self-healing concrete marries two fields: civil engineering and marine biology.

“One of my colleagues, a civil engineer with no knowledge of microbiology, read about applying limestone-producing bacteria to monuments [to preserve them],” Jonkers said. “He asked me: ‘Is it possible for buildings?’ Then my task was to find the right bacteria that could not only survive being mixed into concrete, but also actively start a self healing process.”

When it comes to Jonkers’ concrete, water is both the problem and the catalyst that activates the solution. Bacteria (Bacillus pseudofirmus or Sporosarcina pasteurii) are mixed and distributed evenly throughout the concrete, but can lie dormant for up to 200 years as long as there is food in the form of particles. It is only with the arrival of concrete’s nemesis itself – rainwater or atmospheric moisture seeping into cracks – that the bacteria starts to produce the limestone that eventually repairs the cracks. It’s a similar process to that carried out by osteoplast cells in our body which make bones.

Healing these cracks the old-fashioned way is no small expense. According to HealCON, the project working on the self-healing concrete, annual maintenance cost for bridges, tunnels and other essential infrastructure in the EU reaches €6bn (£4.2bn) a year.

The invention comes in three forms: a spray that can be applied to existing construction for small cracks that need repairing, a repair mortar for structural repair of large damage and self-healing concrete itself, which can be mixed in quantities as needed. While the spray is commercially available, the latter two are currently in field tests. One application that Jonkers predicts will be widely useful for urban planners is highway infrastructure, where the use of de-icing salts is notoriously detrimental to concrete-paved roads.

Encouraging as it sounds, Jonkers’ self-healing concrete can’t cure very wide cracks or potholes on roads just yet; the technology is currently able to mend cracks up to 0.8mm wide. And while making better concrete is a more feasible approach to sustainable building than shifting to an entirely new building material, that doesn’t mean the innovation is a sure bet. The current cost would be prohibitive for many. A standard-priced cubic meter of concrete is €70, according to Jonkers, while the self-healing variety would cost €100.

John Alker, director of policy at the UK Green Building Council, says the success of any new green infrastructure technology relies on innovators like Jonkers being able to demonstrate the particular benefit of a product, whether that’s around cost or enabling a client to meet environmental targets.

“We’ve seen a lot of innovation around concrete as it is a highly impactful product in terms of the energy that goes into producing it and it’s simultaneously a very important construction product globally,” Alker said. But persuading the construction industry to change its behaviour will be tough, he says. “It comes down to innovative clients and developers being willing to experiment with their building and try and test these materials and prove a track record before others will follow.”

Though Jonkers is aware of the challenges of reaching wide adoption of the material, he points out that in particularly vulnerable environments – such as coastal communities or tropical regions that are increasingly experiencing extreme rainfall – some are already seeing the cost-benefit analysis of using this technology from the outset.

“We did a project in Ecuador where we made a concrete canal and irrigation system with self-healing concrete,” Jonkers said. “We are doing tests all over the world in developing countries where they realise that though this is more expensive than current tech, they see the profit because they will have to avoid repair down the line.”

Modix are known for their cost-effective, sturdy, large format filament extruding 3D printers. They range in size from the BIG-60 (60cm x 60 cm build plate) all the way up to 1.8 meters (x-axis) for the BIG-180X machine. They certainly offer a lot of bang for your buck.

And to add even more bang to that aforementioned buck, the company has just announced major updates and a fresh new look for its 3D printer range.

The new “Generation 4” variants will expand the core performance and capabilities of its line of 3D printers. And thanks to an aesthetic upgrade, they look nice too!

Generation 4 Updates
1 – IDEX Dual Printing

IDEX stands for Independent Dual EXtruder. With this feature, each extruder can ‘park’ outside of the bed when inactive, while the other one carries on printing with a different filament. You can see an object that has been printed with the IDEX mode on the BIG-METER printer in the image below. Note the two filament reels on the side.

IDEX drastically reduces the manual labor involved in removing supports by efficiently using a special type of breakaway support filament. This is especially critical for printing advanced models with internal geometries using water-soluble filament. The IDEX add-on is a significant upgrade in Modix’s offering.

2 – Faster Printing

The new machines can reach speeds of up to 350 mm/s, with high quality printing being achievable at 100 mm/s, and higher speeds being used for draft printing.

Such remarkable speeds are made possible by the strong Nema-23 motors on the X -axis, which replace the current Nema-17 motors.

Also, since the IDEX configuration uses two Y-axis motors (one per extruder), the motor
weight-load on the Y-axis is reduced, and thus, the speed is increased.

3 – Fully Automated Calibration

Modix is now offering a full set of automated calibrations routines to all our models including automated bed tilt, bed leveling, gantry alignment, and Z offset calibration.

Multiple other improvements including optical end-stops that improve job recovery accuracy, stronger Nema-23 Motors on the z-axis as well, improved enclosure design, and emergency stop button as standard.

And it all comes in a fresh new aesthetic. You can see the revamped BIG-120Z machine in the image below.

The “Z” suffix means that the largest print dimension of 120cm is in the z-axis, just as a reminder.

The product will continue to evolve in future also, with a near term add-on road map including a closed-loop motion system, heated chamber (wow!), and a XXL-flow extruder.

“Modix continues its journey to becoming the market leader by integrating top of the line technologies while maintaining its printers outstanding price-to-performance ratio,” said Shachar Gafni, Modix CEO.

“Our unique modular self-assembly kits approach allows us to move fast and improve our platforms gradually over time, instead of waiting for a major release”.

The company has seen several key improvements to their range over the past year, including a new print head, clog detector and a magnetic bed. Modix sees this as a perfect time to refresh the platform with the new design.

As always, backward compatibility is an important value for Modix, so all owners of previous models will be able to upgrade their machines with these new technologies. Everything is interchangeable!

“The new IDEX technology allows Modix to expand its offering by answering to more types of customer’s needs,” said John van El, CCO at Modix.

“As a result, Modix reselling partners will be able to close more deals with more types of customers.”


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