Scientists Create Cement Entirely Out of Waste Material

upstart writes:

Scientists Create Cement Entirely Out of Waste Material:

[Scientists] have discovered a method to produce biocement from waste, making the alternative to traditional cement greener and more sustainable. Biocement is a kind of renewable cement that uses bacteria to create a hardening reaction that binds soil into a solid block. The NTU scientists have now created biocement from two common waste materials: industrial carbide sludge and urea (from mammalian urine).

They devised a method for forming a hard solid, or precipitate, from the interaction of urea with calcium ions in industrial carbide sludge. When this reaction occurs in soil, the precipitate binds soil particles together and fills gaps between them, resulting in a compact mass of soil. This produces a biocement block that is strong, durable, and less permeable. [...] It can also be used as biogrout to seal cracks in rock for seepage control and even to touch up and repair monuments like rock carvings and statues.

[...] Firstly, the team treats carbide sludge with an acid to produce soluble calcium. Urea is then added to the soluble calcium to form a cementation solution. The team then adds a bacterial culture to this cementation solution. The bacteria from the culture then break down the urea in the solution to form carbonate ions.

These ions react with the soluble calcium ions in a process called microbially induced calcite precipitation (MICP). This reaction forms calcium carbonate - a hard, solid material that is naturally found in chalk, limestone, and marble.

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