Problem

Concrete Background

Deena's concrete lecture provides some basic knowledge on concrete as well as answers to questions asked after our presentation at the 2010 iGEM UK Get Together.

Reasons cracks are bad

1. Cracks allow water to reach and corrode steel reinforcements;
2. They weaken concrete structures;
3. They are difficult to repair.

Work in this area has already been started: [http://www.youtube.com/watch?v=PyBR3PDPa-c Bio-concrete] and a non-biological method [http://ace-mrl.engin.umich.edu/ self healing concrete].

The projects mentioned above are different from our project because they only use bacteria to repair cracks that form in specialised concrete in new buildings, whereas our BacillaFilla can repair cracks that were formed in existing structures. This makes a big difference to the construction industry because it can protect against the process of corrosion in steel reinforcements in existing structures.

How our project is helpful

Our project aims to:

1. Reduce the rate of corrosion of the steel reinforcements
2. Reduce the need to demolish and replace existing concrete structures
3. Reduce the need for cement production
4. Reduce carbon dioxide emission from cement production
5. Reduce the consumption of energy resources

How our project is novel

1. Our project focuses not only on newly set concrete structures, but also existing ones.
2. All the cells will produce calcium carbonate which has similar properties as that of concrete.
3. Filamentous Bacillus subtilis cells have similar properties to the synthetic fibres used in fibre-reinforced concrete, and thereby act as reinforcements within the cracks.
4. Getting BacillaFilla to produce levans glue that is able to hold the calcium carbonate and filamentous cells together. It will then fill up the crack.
5. Environmental kill switch which allows BacillaFilla to kill itself in the absence of sucrose, which we will add to the cracks in the concrete.
6. We are working with a well known strain: Bacillus subtilis 168 (previous work required specific strains).

Visit to the Structures Lab

Concrete Splitting Test

On the 5th of August, the whole team went down to the Structures Lab of Cassie Building that houses the School of Civil Engineering and Geosciences, to do tensile splitting test on a concrete cylinder. We tried to understand the problems of crack formation on the concrete structures and how our project BacillaFilla can help.

More photos

Dr. Colin Davie showing steel reinforcements of concrete	How cracks form in bridges	Concrete in tensile strength testing machine	Concrete cylinder cracked into two
Teaching properties of concrete	Tensile strength testing machine	Dr. Colin Davie carrying cracked concrete	Concrete in tensile strength testing machine
Structures lab assistant, Billie explaining how concrete cracked

Materials used to mix concrete

Coarse aggregates

Fine aggregates

Cement

References

1. Neville A. (2008) Properties of Concrete. 4th Edition, London, Pearson Education Limited.