Micro-cap­sules and bac­teria to be used in self-heal­ing concrete

The life of con­crete struc­tures is reduced when the mater­i­al cracks and water is able to get at the steel rein­force­ment, caus­ing rust and degrad­a­tion. The research team at Bath will work to devel­op meth­ods to keep bac­teria alive in con­crete. The team at Bath aims to devel­op a con­crete mix that con­tains bac­teria with­in micro­cap­sules, which will ger­min­ate when water enters a crack in the con­crete to pro­duce lime­stone (cal­cite), plug­ging the crack before water and oxy­gen has a chance to cor­rode the steel rein­force­ment. Self-heal­ing con­crete could vastly increase the life of con­crete struc­tures, and would remove the need for repairs, redu­cing the life­time cost of a struc­ture by up to 50 per cent. Over sev­en per cent of the world’s CO₂ emis­sions are caused by cement pro­duc­tion, so redu­cing the amount required by extend­ing the life­time of struc­tures and remov­ing the need for repairs will have a sig­ni­fic­ant envir­on­ment­al impact. Dr Richard Cooper, from the Depart­ment of Bio­logy & Bio­chem­istry, said: ​“Cement is highly alkaline, mak­ing it a hos­tile envir­on­ment for bac­teria. We’ll be assess­ing dif­fer­ent spe­cies of bac­teria to find one that is able to form abund­ant spores and which will sur­vive and ger­min­ate in this envir­on­ment. The work will involve find­ing alkaline-tol­er­ant isol­ates and test­ing their bio­logy and physiology.” Dr Kev­in Paine, from the Depart­ment of Archi­tec­ture & Civil Engin­eer­ing, said: ​“Con­crete dens­i­fies as it hardens, so the pore size decreases to a level where bac­teria may be crushed. We’re look­ing at enclos­ing the bac­teria in micro-cap­sules, along with nutri­ents and cal­ci­um lact­ate which the bac­teria will con­vert when water becomes present and use to fill cracks in the con­crete.” Dr Andrew Heath, also from the Depart­ment of Archi­tec­ture & Civil Engin­eer­ing, said: ​“Self-heal­ing mater­i­als are par­tic­u­larly suited to situ­ations where safe access for main­ten­ance is costly, so the out­puts of this exten­ded research pro­gramme could reduce the life-cycle costs of infra­struc­ture.” Dr Cooper added: ​“Includ­ing bac­teria in con­crete offers a double lay­er of pro­tec­tion in pre­vent­ing steel cor­ro­sion. Not only do the bac­teria work to plug cracks in the con­crete, the pro­cess of doing so uses oxy­gen present which would oth­er­wise be involved in the cor­ro­sion pro­cess of the steel bars.” The research team will assess the sur­viv­al of dif­fer­ent spe­cies of bac­teria in the con­crete over time. They’ll allow the con­crete to mature over cer­tain time peri­ods and then grind it down to cre­ate a sus­pen­sion which can be assessed by bio­lo­gists for sur­viv­ing bac­teria. The pro­ject is fun­ded by a £2m EPSRC grant, matched by an addi­tion­al indus­tri­al con­tri­bu­tion of just over £1 mil­lion, and will involve Bath research­ers in col­lab­or­a­tion with part­ners Cardiff Uni­ver­sity (the lead part­ner) and the Uni­ver­sity of Cam­bridge. Source: Uni­ver­sity of Bath