PhD: Bacteria-Based Self-Healing For Renders and Mortars

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Detail information about job PhD: Bacteria-Based Self-Healing For Renders and Mortars. Terms and conditions vacancy

Supervisor nameDr Kevin Paine

Email contact[email protected]

Cement-based materials, such as renders and mortars, are used world-wide in buildings and infrastructure due to their compressive strength and versatility. However, the degradation of these materials is generally considered as inevitable and the cracking of renders and mortars can lead to long-term concerns due to the ingress of water-borne contaminants: requiring repair, renovation or replacement. 

However, researchers are now developing a range of ‘smart’ cement-based materials, with autogenous and autonomic self-healing and self-repairing capabilities. This development is likely to transform our building materials, enhance durability and serviceability, and reduce maintenance costs.

Whilst several approaches exist for self-healing, this research will focus on microbiologically-induced calcite-precipitation (MICP).

This form of self-healing utilises the metabolic activity of bacteria and biomineral organic precursors embedded within the material to form an inorganic material, usually calcium carbonate (CaCO3), in the form of calcite, as a healing compound. This healing compound develops within the crack and fills it providing sealing and healing. Water and carbon dioxide are also released which increases the formation of calcite, as an autogenous mechanism. Results of previous research at the University of Bath have shown that bacteria-based self-healing of concrete is sufficiently effective to return the permeability properties of cracked concrete back to that of uncracked concrete.

However, MICP is complex as it is necessary to encapsulate all the ingredients (bacteria, nutrients and organic precursors) within the material during the mixing stage and maintain them within an inert condition until such time that a crack appears and healing is required. Whilst it is necessary that any ingredient used does not affect the setting and hardening of the concrete, once a crack appears the ingredients must quickly become active and form calcite rapidly within the crack.

In previous work, the University of Bath have developed encapsulated systems that protect the self-healing agents during mixing and placement of concrete, and that keep the bacteria spores separate from the nutrient source so they will not develop healing compounds prior to any cracking.

This research will investigate the feasibility to incorporate this encapsulated system in renders and mortars. Whilst we anticipate that self-healing will be much more effective in these thin sections, there are a number of technological problems that need to be overcome.

Funding

The studentship is funded by the EPSRC and Saint-Gobain Construction Products UK Ltd (SGWUK), it lasts for 3.5 years and covers:

• tuition fees at the Home/EU rate 
• £1,000 TSF per year 
• annual stipend £14,553 (2017-8 rate) 

The funding this is only open to applicants with Home fee status, or EU nationals who have been residing in the UK for the past 3 years.