Scientists have created construction material from peat - decaying organic matter - and oil shale ash, that could reduce costs of building a house nearly tenfold.
Scientists from the University of Tartu and the Estonian University of Life Sciences wanted to create a self-supporting construction material based on local natural resources and waste that could be used to 3D print houses up to two-storeys high directly at the construction site.
Wetlands cover about 22 per cent of Estonia's area, but the peat growing there is not widely used. Only the drier top part of the peat layer has been deemed usable. The unused part is left to decay.
This peat could also be used in an economically beneficial way. Many fractions can be separated from peat, for example humic substances and waxes, and the final residue can even be used for producing cellulose.
The most popular method for mining peat is milling. During milling, 10 to 20-mm layers are cut loose from the peat deposit and left to dry. For this method to pay off, most milling fields are larger than 100 hectares.
"So far, no one has produced peat composite as a construction material because peat prevents many materials from hardening. In our project, we managed to overcome this issue," said Juri Liiv, from University of Tartu.
Instead of the usual cement, scientists from Tartu use oil shale ash as the binder in their mix.
More From This Section
In Estonia, it is estimated that about 7 million tonnes of oil shale ash are created in a year, only five per cent of which is reused. The rest is deposited in ash hills and this creates considerable environmental pollution.
Oil shale ash is classified as a hazardous waste because it becomes very basic when in contact with water (pH almost 13). However, ash with such a pH is the best fit for construction materials. The developed material is completely harmless and safe for the environment.
Furthermore, during testing, the scientists found a solution for reducing the setting time from about 30 days to one day. If the pH of a pore solution is below nine, it won't harden.
This issue is solved by a very high pH by binding the potassium oxide and alkali metals found in oil shale ash to insoluble compounds.
Inside the peat, oil shale ash reacts with humic acids and absorbs carbon dioxide. Due to chemical reactions, the binder becomes regular concrete and limestone.
According to Toomas Tenno, a professor at the University of Tartu nanosised additives, such as nanosilica or silicon smoke, are added to peat and oil shale ash to improve their properties.
"As the particles are very small, they dissolve well and distribute throughout the material evenly. Silicon smoke improves the quality of this material significantly," said Tenno.
It took about a year before the right mixture was found for the material that is strong and has high thermal conductivity. After final hardening, the material is strong and very light, has low heat transfer and is durable.
Even though peat is also used as fuel, the material developed by scientists is incombustible. The peat material achieves its initial hardness in 24 hours but remains elastic for a considerably longer time.
Thus, there is no need for insulation or fillers and the entire structure becomes airtight without adding any wind protection. Furthermore, it is a good noise blocker.