Scientists at Nanyang Technological University, Singapore (NTU Singapore), have found a way to create biocement from waste, making the alternative to regular cement even greener and more sustainable.
the biocement is a renewable form of cement that often uses bacteria to form a hardening reaction that binds the earth into a solid block.
NTU scientists have now succeeded in using two common wastes, industrial carbide sludge and urea, which comes from mammalian urine, to create biocement.
They developed a process in which the reaction of urea with calcium ions in industrial carbide slurries forms a hard solid, or precipitate. When this reaction takes place in the soil, the precipitate binds the soil particles together and fills the spaces between them, creating a compact mass of soil. The result is a solid, resistant and less permeable block of biocement..
The research team, led by Professor Chu Jian, President of the School of Civil and Environmental Engineering, showed that your biocement could become a sustainable and cost-effective method of soil improvementas the refuerzo del terreno para su uso en la construcción or la excavation, el control de la erosion de las playas, la reducción del polvo o la erosion delviento en el desert, o la construcción de depósitos de agua dulce en las playas o dans the desert.
It can also be used as a biocement to seal cracks in rock to control seepage and even to touch up and repair monuments such as rock carvings and statues.
Biocement is a sustainable and renewable alternative to traditional cement and has great potential for use in construction projects that require soil treatment. Our research makes biocement even more sustainable by using two types of waste as raw material. In the long term, not only will this make biocement cheaper to manufacture, but it will also reduce the cost of waste disposal.
Chu Jian
Contents
Urine, bacteria and calcium: A simple recipe for biocement.
The biocement manufacturing process requires less energy and generates fewer carbon emissions compared to traditional cement production methods.
The NTU team’s biocement is created from two types of waste: industrial carbide sludge, acetylene gas production waste from factories in Singapore, and urea found in urine.
The team first treats the carbide sludge with an acid to produce soluble calcium. The urea is then added to the soluble calcium to form a cementation solution. The team then adds a bacterial culture to this fining solution. The bacteria in the culture break down the urea in the solution to form carbonate ions.
These ions react with soluble calcium ions in a process called microbe-induced calcite precipitation (MICP). This reaction forms calcium carbonate, a hard, solid material found naturally in chalk, limestone and marble.
When this reaction occurs in soil or sand, the resulting calcium carbonate binds the soil or sand particles together to increase their strength and fills the pores between them to reduce water seepage through the material. The same process can also be used on rock joints, making it possible to repair rock carvings and statues.
Biocement-reinforced soil has an unconfined compressive strength of up to 1.7 megapascals (MPa), greater than that of the same soil treated with an equivalent amount of cement.
This makes the biocement kit suitable for use in soil improvement projects such as soil reinforcement or reducing water seepage for use in construction or excavation or beach erosion control along the coasts.
A sustainable alternative to cement.
Biocement production is more environmentally friendly and sustainable than the methods used to produce traditional cement.
Part of the cement manufacturing process involves burning raw materials at very high temperatures, above 1000ºC, to form clinker, the binder in cement. This process produces a large amount of carbon dioxide. However, this biocement is produced at room temperature without burning anything, making it a more environmentally friendly, less energy-intensive and carbon-neutral process.
In Singapore, carbide sludge is considered waste. However, it is a good raw material for the production of biocement. By extracting calcium from carbide slurries, we make production more sustainable because they don’t need to use materials like limestone, which has to be mined from a mountain.
Limestone is a finite resource: once it’s gone, it’s gone. Limestone mining also affects our natural environment and ecosystem.
The research team points out that if the production of biocement could reach the manufacturing levels of traditional cement, the overall cost of its production compared to that of conventional cement would be lower, which would make biocement a greener and cheaper alternative. in cement.
Restore monuments and strengthen the coasts.
Another advantage of the NTU team’s biocement formulation method is that the bacterial culture and the cementing solution are colorless. When applied to dirt, sand or rock, they retain their original color.
This makes it useful for restoring ancient rock monuments and artifacts. For example, Dr. Yang Yang used biocement to repair ancient Buddha monuments in China. Biocement can be used to seal gaps in cracked monuments and has been used to restore broken pieces, such as a Buddha’s fingers. As the solution is colorless, the monuments retain their original color, thus keeping the restoration work true to history.
In collaboration with the relevant national authorities in Singapore, the team is currently testing its new biocement in the East Coast Park, where it is used to reinforce beach sand. By spraying biocement solutions on the sand, a hard crust is formed which prevents the sand from being washed out to sea.
The team is also investigating other large-scale applications of its biocement in Singapore, such as repairing roads by sealing cracks in roads, sealing holes in underground tunnels to prevent water seepage, or even as potting soil for coral reefsbecause carol larvae like to grow in calcium carbonate.
More information: www.sciencedirect.com (English text).
Going through www.ntu.edu.sg