Our bridges, motor­ways, tun­nels, and dams, and all the build­ings that make up our infra­struc­ture are vital to our soci­ety and eco­nom­ic growth yet we take them for grant­ed. The shock­ing truth is that our infra­struc­ture is crum­bling beneath our feet. And this is cost­ing us dear­ly, both in terms of mon­ey and car­bon.

Now, most of our infra­struc­ture is actu­al­ly made up of a remark­able con­struc­tion mate­r­i­al, con­crete. But con­crete dete­ri­o­rates, and for decades we have been neglect­ing its upkeep. It is now reach­ing a state of cri­sis. It will require huge amounts of mon­ey to upgrade it.

And we use so much con­crete, around three tons for every per­son on the plan­et, per year. It is the second-most used sub­stance on earth after water. It con­sumes huge quan­ti­ties of nat­ur­al resources, and the pro­duc­tion of its cement com­po­nent alone emits about 8% of all man-made CO2, rough­ly one ton per ton.

The sta­tus quo does not make any eco­nom­ic or envi­ron­men­tal sense. Which begs the ques­tion, can we design our con­crete struc­tures to look after them­selves? This way, they could last so much longer, we would use far less con­crete, slash­ing expen­di­ture, car­bon emis­sions, and envi­ron­men­tal dam­age.

Looking to nat­ur­al sys­tems for inspi­ra­tion, the con­cept of self-healing mate­ri­als emerged. So, can we turn the non-living con­crete all around us into liv­ing sys­tems? Wee see advances in oth­er sec­tors. Self-healing paints for our cars, and self-healing asphalt for our roads are becom­ing a real­i­ty.

But con­crete is a far more com­plex mate­r­i­al. It is a multi-component, multi-layered sys­tem, and dam­age occurs at dif­fer­ent length and tem­po­ral scales. As pat of a nation­al team, our inspi­ra­tion came from the sim­i­lar­ly com­plex way in which our skin deals with dam­age at dif­fer­ent lev­els.

So for small-scale dam­age, my team at Cambridge has been devel­op­ing tiny cap­sules which we felt with a heal­ing agent and we mixed with­in the con­crete. They then remain dor­mant until the con­crete is attacked. A crack would them rup­ture the cap­sules, releas­ing the heal­ing agent, which fills the crack, seal­ing it.

Similar to the for­ma­tion of a blood clot, the whole of the self-healing process has to be com­pat­i­ble with a con­crete matrix and to restore func­tion­al­i­ty, and we have been able to deliv­er a sim­i­lar func­tion using min­er­al com­pounds. Some strains of bac­te­ria that pro­duced lime­stone, which is a nat­ur­al cement, is anoth­er good con­tender.

For large-scale dam­age, we are employ­ing shape-memory poly­mers, the same mate­ri­als used in med­ical sutures or shrink-wrap. These are plas­tic rods placed strate­gi­cal­ly with­in the con­crete, and they shrink when large cracks form, there­by clos­ing them, and the cap­sules can actu­al­ly fin­ish their seal­ing process.

Now dam­age is some­times recur­rent. And like our cir­cu­la­to­ry blood sys­tem, we are devel­op­ing flow net­works using small inter­con­nect­ed tubes. Through these, we can con­tin­u­ous­ly cir­cu­late a heal­ing agent with­in the con­crete so that it’s avail­able when it’s need­ed again and again. So, we have made sig­nif­i­cant advances on the per­for­mance of indi­vid­ual self-healing com­po­nents, and are col­lec­tive­ly work­ing on the more chal­leng­ing inte­grat­ed con­fig­u­ra­tions.

There is also the chal­lenge of longevi­ty and resilience, as well as of course min­i­miz­ing any addi­tion­al cap­i­tal cost of the con­crete. Together with our indus­tri­al part­ners, we have con­duct­ed full-scale field tri­als through which we’re demon­strat­ing some of the devel­oped self-healing sys­tems, and we are mon­i­tor­ing those in the real world. We are test­ing both con­crete repair appli­ca­tions as well as new con­crete con­struc­tion.

We are also impact­ing on oth­er sec­tors where con­crete and oth­er sim­i­lar mate­ri­als like grouts and mor­tars play a key role. Our focus is on extreme and inac­ces­si­ble envi­ron­ments, for exam­ple under­ground nuclear repos­i­to­ries, or in oil well cement­ing appli­ca­tions, where safe­ty is para­mount.

Self-healing con­crete can deliv­er a low-carbon infra­struc­ture by poten­tial­ly elim­i­nat­ing inspec­tion, repair, main­te­nance, and replace­ment, and build­ing the future with a much low­er whole-life cost. We can trans­form our land­scapes and our every­day lives.

We are con­fi­dent we can pro­duce self-healing con­crete, but it’s going to take a lot more than that to make it into a com­mer­cial real­i­ty. We are also explor­ing self-sensing, self-reporting, and self-immunity in con­crete.

So my ques­tion to you is, how can we all work togeth­er to trans­form this remark­able con­struc­tion mate­r­i­al all around us into a far more remark­able liv­ing sys­tem? Thank you.

Further Reference

The con­crete that heals its own cracks ” by Abir Al-Tabbaa, at the World Economic Forum site.

Faculty page at the University of Cambridge.

Help Support Open Transcripts

If you found this useful or interesting, please consider supporting the project monthly at Patreon or once via Cash App, or even just sharing the link. Thanks.