Summary/Summary Reader Response Draft #Final : Concrete that grows

 

The concept of living concrete and environmental benefits has been elaborated by Corless. (2020) in the article “Scientists create living concrete from bacteria and sand”. Conventional concrete is known to contribute a great amount of carbon dioxide (CO2) emission to the environment, while living concrete containing bacteria aids in the reduction of CO2 emission. Researchers from University of Colorado Boulder mixed components such as sand, hydrogel, and bacteria to create a living substance with the strength of cement-based mortar and the prospect to perform photosynthesis. In the process of designing living concrete, researchers used a 3D sand–hydrogel scaffold containing cyanobacteria. Cyanobacteria are able to adapt in extreme environmental conditions. Furthermore, carbon dioxide is converted to sugars during the process of photosynthesis. Regeneration of cyanobacteria can be obtained from a source, while achieving the original properties as the source with the extension of hydrogel scaffold. The development of living concrete will give rise to advantages to the environment. However, certain trade-offs should be recognized such as this type of concrete is only able to obtain its maximum strength when it is dried completely, it is more costly than conventional concrete, and it is not suitable to grow in any atmosphere and media. 

Firstly, Trimmer (2020) mentioned that living concrete has lower compressive strength than conventional concrete. This leads to the presence of bacteria being compromised during the drying process as it requires humidity to function. In order to maintain the structure of the concrete, mixing the bacteria with gelatine is required . In addition, Timmer (2020) discussed that an ambient humidity of 50% and above is necessary to demonstrate moisture for the gelatine to absorb adequate water to support the bacterial life for at least a week. Therefore, maximum strength is not achievable where bacteria exist in the concrete.

Secondly, an additional factor to consider would be the cost of living concrete as it is more expensive in comparison to conventional concrete. With a combination of biological and chemical properties, living concrete is ahead in technology advancement as compared to conventional concrete. This leads to more case studies behind the project. It can be beneficial to the environment, but on the other hand,  high cost of production would be a major consideration. With a cost factor in mind, small medium enterprise and private companies would make careful considerations when choosing such concrete. Hence, there might be more supply than demand within the industry.

Lastly, Shantilal Vekariya and Pitroda (2013) pointed out that the growth of bacteria is not well supported in the atmosphere. Different types of nutrients and metabolic products are used to grow calcifying micro-organisms as they can influence survival, biofilm and crystal formation . Additional work should be done in the retention and metabolic product of the building material. As countries have different ambient temperatures, researchers need to conduct various case studies for individual countries and customise a suitable living concrete accordingly. 

However, a main advantage of living concrete is being able to heal by itself. All concrete is known to crack eventually, which is mainly caused by wear and tear. Typically, if the cracks are not fixed immediately, at times, it will lead to high permeability where water is able to flow through those cracks. In such cases, steel reinforcements are stored in the concrete. After a period of time, steel will corrode,  and eventually result in structure collapse. With the invention of living concrete, it can heal by itself with the use of bacteria as it is more active in moist conditions. Hence, in the scenario where water flows into the concrete, bacteria are able to mend the cracks.  Stewart (2016) mentioned that bacteria and calcium lactate will be mixed into capsules where the capsule will be added into the wet concrete mix. In the event where cracks occur, water will flow through it, and the capsules will be open when it gets in contact with water which will eventually close up the cracks.

In conclusion, further research in living concrete needs to be done to achieve similar properties as conventional concrete. Additionally, because profits are maximized with high sales and low material cost, it would be ideal to weigh a balance between cost and the properties to ensure maximum profits and benefits. In addition, due to the varying ambient temperatures in different countries, further studies also need to be done to ensure uniformity between temperature and the growth of bacteria to produce a suitable living concrete.

Reference

 

Corless, V. (2020, January 16). Scientists create living concrete from bacteria and sand. Advanced Science News. https://www.advancedsciencenews.com/scientists-create-living-concrete-from-bacteria-and-sand/

 

Shantilal Vekariya, M & Pitroda, J. (2013, September 9). International Journal of Engineering Trends and Technology, 4(9).

http://www.ijettjournal.org/volume-4/issue-9/IJETT-V4I9P181.pdf

Stewart, A (2016, March 7). The “living concrete” that can heal itself. CNN. ‌https://edition.cnn.com/2015/05/14/tech/bioconcrete-delft-jonkers/index.html

Timmer, J. (2020, January 18). "Living concrete" is an interesting first step. Ars Technica. https://arstechnica.com/science/2020/01/living-concrete-is-an-interesting-first-step/