Bio-based repair method for concrete

1. A process for the bio-based reparation of a concrete element having an element surface with cavities, the process comprising applying a first liquid with a first composition and a second liquid with a second composition to the element surface of the concrete element to provide a combined product to the cavities, wherein the first composition and the second composition are selected to provide gel formation in the cavities after application of one or more of the first liquid and the second liquid to the element surface, wherein the first composition and the second composition are also selected to provide bacterial material, a calcium source, and a nutrient for bacteria in the cavities after application of the first liquid and the second liquid to the element surface, wherein the first liquid at least comprises sodium silicate in an amount of 0.5-20 wt. %, wherein the second liquid at least comprises the calcium source, wherein the nutrient comprises (i) a nitrate compound, (ii) a yeast extract, and (iii) one or more of a lactate and a gluconate, and wherein both the first liquid and the second liquid comprise water.

2. The process according to claim 1 , wherein the molar ratio between silicate and calcium is in the range of 0.05-5.

3. The process according to claim 1 , wherein the first liquid comprises sodium silicate in an amount of 0.5-20 wt. %, wherein the first liquid has a pH of at least 11, and wherein the second liquid comprises calcium nitrate in an amount of 10-75 wt. %.

4. The process according to claim 1 , wherein the second liquid comprises calcium nitrate.

5. The process according to claim 1 , wherein first the first liquid comprising the sodium silicate is applied to the element surface and subsequently the second liquid comprising the calcium source is applied to the element surface.

6. The process according to claim 1 , wherein the bacterial material is selected from the group consisting of a bacterium, a lyophilized bacterium and a bacterial spore of a bacterium.

7. The process to claim 6 , wherein the bacterium is selected from the group consisting of aerobic bacteria and anaerobic bacteria.

8. The process according to claim 6 , wherein the bacterium is selected from the group consisting of bacteria that can form a phosphate or a carbonate precipitate in an alkaline medium.

9. The process according to claim 6 , wherein the bacterium is selected from the group of genera consisting of Planococcus, Bacillus and Sporosarcina.

10. The process according to claim 6 , wherein the bacterium is a denitrifying bacterium.

11. The process according to claim 1 , wherein the second liquid is applied to the element surface within 0.5 h after applying the first liquid to the element surface, or wherein the first liquid is applied to the element surface within 0.5 h after applying the second liquid to the element surface.

12. The process according to claim 1 , wherein the first liquid and the second liquid are applied to the element surface by spraying the liquids on the element surface.

13. The process according to claim 1 , wherein the element is comprised by a building or a civil engineering structure.

14. The process according to claim 3 , wherein the second liquid comprises calcium nitrate in an amount of 25-55 wt. %.