When we think of the Netherlands, we think of tulips and windmills. In fact, its scenic spots are not unique, such as the former Royal Dutch Summer Palace. The Palace in Apeldoorn, built between 1684 and 1686, is a Baroque courtyard surrounded by forests. Originally built for King William III and Mary II of England, the Palace has since been the summer palace of the Dutch royal family.
In 1984, the Palace became a national museum. In order to maximize the charm of the Palace in the 17th century, the government paid great attention to the renovation of the building.
A recent report in Nature Biotechnology described a technique involved in the restoration of The Palace that links construction to biology- to eco-friendly bioconcrete.
Bacteria repair cracks in buildings.
Green Basilisk, a biotech start-up based in Delft, the Netherlands, is involved in the renovation of the Palace.
Green Basilisk, which has a patent for self-healing concrete, specializes in repairing cracks in walls with microbially generated limestone. The company is said to have been able to repair the 0.8 mm crack.
As can be seen, It is through this special technique that Green Basilisk has realized the renovation of the Luo Palace building.
First of all, we need to understand the importance of repairing the walls of buildings.
One of the key indicators for the construction industry to judge the quality of concrete is the pressure strength of concrete, which in turn is limited by the strength of cement and the ratio of water ash.
In general, concrete is a relatively high pressure-resistant material, but tiny cracks in concrete are not completely avoidable.
Cracks can cause water seepage, corrosion of steel bars buried in concrete, and weaken the entire structure. Therefore, the solution to the cracks this project can not be underestimated, once the cracks can not be repaired, the structure can only be abandoned, a large amount of garbage will also be produced.
So how do microbes repair walls?
According to Nature-Biotech, Green Basilisk added bacterial spores and calcium lactate to the concrete.
Among them, bacterial spores can remain “sleeping” for several years, and when the walls start to crack and seep, they will be “awakened” – starting to digest lactic acid and releasing carbon dioxide.
So far, most people have forgotten the same chemical principle to come in handy: inside the concrete, carbon dioxide (CO2) and calcium ions (Ca2) combine to form solid calcium carbonate (CaCO₃).
After this change, the cracks in the wall were repaired within a month.
Henk Jonkers, co-founder of Green Basilisk and from Delft University of Technology, one of the world’s leading polytechnics, said it took the team years to find a natural bacterium that could thrive in such a harsh environment. The reason for looking for natural bacteria is:
Given the limitations of the law, it can be very difficult to study bacteria from genetic engineering.
Eventually, the team found three strains of Bacillus bacteria in an alkaline lake in the desert region of northern Spain and Russia, and confirmed that they could produce fresh calcium carbonate in concrete.
However, the company now has a new goal of developing another substance that could replace lactic acid bacteria and reduce costs.
The reason is that the price of plain concrete is $68-91 per cubic meter, while the company’s eco-friendly bioconcrete is $46 per cubic meter, which may deter some consumers.
However, Henk Jonkers believes that bioconcrete is more cost-effective, given the cost of other repairs to ordinary concrete.
A new trend in environmentally friendly buildings.
In fact, in addition to the self-healing concrete of Green Basilisk, several companies around the world are now exploring how to combine biology and construction to pursue a new wave of environmentally friendly buildings.
As shown in the table below, there are two main ideas for the design of environmentally friendly building materials:
Bacterial technology: can be manufactured concrete repairers, biocement, etc.
Fungal Technologies: Can make indoor tiles, decorative panels, foams, etc.
The reason for the development of eco-friendly buildings is the enormous pressure on the environment caused by the current construction industry, where cement production exceeds 4 billion tons per year, bringing in about 8% of the world’s total CO2 emissions. In contrast, bio-based building materials can isolate carbon dioxide from the atmosphere.
In addition, there is a difference between traditional building materials and environmentally friendly building materials – carbon-absorbing capacity.
Just to take wood, compared with a group of traditional building structures, wood structure can be completely degradable, recycled, has shown great advantages in environmental protection. However, compared with the use of bacteria, fungi developed materials, its carbon absorption capacity is very weak.
For these reasons, more and more construction companies are also beginning to pay attention to and experiment with bio-building materials.
In 2015, Costain, a British construction company, experimented with four self-healing concrete technologies in a road improvement project, one of which was a bacterial spore concrete technology similar to Green Basilisk.
However, Costain selected four suppliers for the same project to conduct the experiment, and naturally not just to transform the road.
Costain is involved in a $6 million Bioelastic Materials (RM4L) research project in the UK to develop self-healing building materials and embedded sensors that can identify damage.
Susanne Gebhard, RM4L project leader and microbiologist at the University of Bath, has said:
We’re trying to transform concrete into a biological system that automatically detects damage and then repairs itself.
It has been reported that much of the WORK on the RM4L project is focused on chemistry and materials science, but Susanne Gebhard and her team are also exploring the interactions between bacteria, nutrients and concrete in order to find a combination that goes beyond existing systems.
For example, the team has encapsulated the spores of a B. cohnii bacteria in an inflatable concrete particle and covered it in a waterproof polyethylene alcohol shell.
It should be noted here that the package is designed to avoid “activating” bacteria until cracks appear in the housing and water comes into contact with spores.
On this basis, the researchers added growth media containing yeast extract and calcium nitrate to the concrete particles, and found that the healing effect of bacterial cracks increased.
For now, designing biobuilding materials is a small matter, but as Will Srubar III, a civil engineer at the University of Colorado at Boulder, says:
This field is just beginning, but it is also growing rapidly.