What exactly is Self-Healing or Living Concrete?

Self Healing Concrete

Self-Healing Concrete or Living Concrete

Living Concrete is made by embedding bacteria in concrete in order to repair cracks. This is accomplished by mixing Bacillus Subtilis and Calcium Lactate into the concrete as it is being poured. Bacteria in concrete can remain latent for up to 200 years until the concrete splits and the bacteria is exposed to moisture. The bacteria are activated by the dampness. By replacing water in fresh concrete, bacteria solution is introduced. Calcium Lactate is added to the concrete at a rate of around 1% by weight.

The bacteria's spores germinate and begin feeding on the Calcium Lactate, consuming oxygen. Calcium Lactate, which is soluble, is transformed to Calcium Carbonate, which is insoluble (limestone). Without any external assistance, the insoluble limestone begins to solidify, filling the crack.

The self-healing process will continue until the bacteria have enough Calcium Lactate to feed on. When it is consumed, the self-healing process comes to a halt.

This concrete is often referred to as Bacterial Concrete or Self-Healing Concrete.

Other procedures that can make Self-Healing concrete include:

Mineral healing capsules

Using a shape memory polymer (SMP)

However, these do not produce Live Concrete in the strictest sense because they rely solely on chemical processes and do not involve any living organism.

Advantages:

Bacterial concrete is environmentally friendly. Even before cracking, the presence of bacteria has a favorable influence on the compressive strength and density of concrete. The increase in strength is due to the rapid and uniform hydration of cement and the filling of pores around the cement particles, which causes the porosity of hardened cement paste to decrease and its density to increase. This leads to less corrosion of steel reinforcement and lower maintenance costs. Another advantage of Self-Healing concrete is that it can mend itself in situations where physical repair is difficult. The self-healing process takes about a month to seal the fissures, limiting the detrimental effect.

Disadvantages:

Because the preparation of Calcium Lactate is an expensive procedure, the cost of Self-Healing concrete is double that of regular concrete.