Houses were built from cut peat blocks already thousands of years ago. Now, the scientists of Tartu have developed a material which would allow printing energy-efficient houses of milled peat and oil shale ash by using a 3D-printer.
A couple of years ago, doctor of chemistry, Jüri Liiv, created an organic humate bedding powder TURPS out of peat, poultry manure and wood ash, which makes the plants grow faster and increases soil fertility. While he was testing which pellets are of suitable hardness, he started thinking whether peat could be used to create self-sustaining building material.
Currently, Jüri Liiv can confirm that it is possible. Together with the scientists of University of Tartu and Estonian University of Life Sciences, he has created a building material, mainly of peat and oil shale ash which could reduce the building costs of a private house about ten times.
The goal was to create self-sustaining building material, based on local natural resources and waste, and which could be used to 3D printing up to two storey houses directly on the construction site. The Environmental Investment Centre financed the scientists’ project with approximately 200 000 euros.
Oil shale ash is recognised as hazardous because it transforms into an excessively alkaline material when in contact with water. The pH level of drinking water is 7, but that indicator for oil shale ash can be approximately 13, which makes it harmful to the environment. However, ash with such a pH level is most suitable as a building material.
Pore solution with a pH level under 9 does not harden at all. This problem can be solved at a very high level of pH, by using potassium oxides found in oil shale ash, and binding alkali metals into insoluble compounds. Inside peat, oil shale ash reacts with humic acids and absorbs carbon dioxide. This means that as a result of the chemical reaction, the binder will transform into plain concrete and limestone.
The scientists of Tartu carried out a number of analyses while developing the new building material, which revealed that the material is completely harmless to health and environment. While conducting the tests, they also discovered how to reduce the setting time from approximately 30 days to one day.
It is estimated that about 7 million tonnes of oil shale ash are created in Estonia per year, and of which 5% is recycled (for cement production and liming fields). The rest is stored in ash hills and this creates a significant environmental pollution. The usage of peat material would definitely help to reduce the storage of new ash.
According to the authority responsible for the project, Toomas Tenno, the professor of the Chair of Colloidal and Environmental Chemistry at the University of Tartu, additives are added to peat and oil shale ash in nanoscale to improve their qualities, for example, nano silicon dioxide i.e. silica fume.
“Since the particles are very small, they dissolve well and distribute evenly in the material. Silica fume significantly improves the quality of this material,” says Tenno.
At first, they also planned to use recycled plastic in the construction of peat houses in order to insert a reinforcing frame inside the whole material. However, the created material came out so good, that it stands up without the frame. The armature is only necessary for window apertures and doorways, arches and other more special architectural solutions.
The developed peat material achieves its initial solidness within 24 hours, but it remains supple for a long time. Therefore, no insulation nor fillings are needed, and the whole construction becomes air resistant without adding a wind deflector.
This building material has more great qualities. Country houses often have problems with rats, insects, and mould – this innovative composition is not suitable for any named pests. When using this composite, one does not have to be afraid of grass or trees growing on walls. The peat mixture used in crop production is completely different.
Since peat and oil shale ash does not cost much, the price of the material would make house builders especially happy. According to Liiv, the scientists calculated that the cost price of the construction expenses for a building shell with 100–150 square meter floor area could be about 5,000 euros (the construction of framework building shell of the same size would cost about ten times as much).
Therefore, peak material could be used to build a very cheap A-class energy house. The inner or exterior finishing could be printed to the material already when printing the building. The surface of the material is rustic and it can be filled to make it smoother and painted if desired.
Did you know?
Thanks to the 3D printing of peat material
- the local raw material peat would be transformed and additional value would be created
- hazardous production waste (oil shale ash) and recyclable raw material (plastic) would be used
- the emissions of carbon dioxide would be reduced
- the productivity would increase on those constructions which currently require a lot of manual work
- the speed of construction would increase significantly
- limitless export opportunities of this new technology would emerge
- ecological construction would develop
- cross-sectoral competence would develop remarkably