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hello and welcome to technically speaking a podcast where scientists and engineers come together to chat about common interests share knowledge and satisfy some curiosity i'm anika and in this episode i'm joined by ruether laura and cara to talk about concrete and offer our points of view on its use as a building material so to start off with laura why do you care about concrete well it's it's actually quite a complicated material that's got lots of different things going on in it
um so you've got all these really kind of slow chemical processes that over time add up to some really big changes which i find quite interesting definitely is interesting what about you cara what are your thoughts on concrete well i guess i studied civil engineering and i find concrete incredibly boring i have to be honest at the time that i was studying civil engineering it was the part of engineering i just didn't find interest in at all from the engineering perspective of trying to
figure out how it works and why but actually the more i kind of learned about building materials and why we use them and what the reasons are behind them and kind of like the kind of personal stories that really go into stuff that's when i started to find actually concrete quite a bit interesting i like that i've never heard of someone talking about the personal stories that related to concrete and i think that's such a nice thing to think about because we don't often
think there is personality behind these buildings someone's put all the effort making them yeah you don't i think there's like a lot of it around the world but i'm irish my background what we did was we emigrated around the world and built stuff so there's probably a lot of irish stories within concrete well within the lane of concrete not in the engineering behind it definitely and there's a lot of irish pubs in any country in the world yeah maybe they were built by by
concrete uh as well yeah exactly um what about you rueda what are your thoughts i started dealing with concrete in my underregretted civil engineer i didn't like it much then um it was like a reinforced concrete design was really good to me it was kind of complicated for an undergrad at the time um then i ended up doing a phd in concrete and fire where i found concrete really interesting um it's also like it's the way that concrete could form into any shape
which make the building really look nice if you want it to be and that's why i really find the concrete to be a fascinating material did you say your phd was setting concrete on fire yeah so it's basically concrete have a good reputation for being a good resistant in in for uh for a fire scenario however after 500 degrees centigrade it will start to degrade and have all this weird behavior because the moisture will go out of the concrete and that's when it becomes a bit dangerous
and not as stable as we think it would be and any kind of deformation to the concrete would be irreversible in case of a fire so that's why i was starting to find it more interesting definitely super super interesting there's so much for us to all learn um so as you probably guessed we do have a concrete expert with us um rueda so now we've got some kind of idea of why concrete is interesting to all of us um rueda can you tell us a bit about how you make it so basically concrete is not a one
material it's a mixture of a few stuff so is aggregate um which is gravel and sand and cement and water and cement do act like the glue in the concrete so it's the glue that bring everything together um an interesting fact about the cement itself it was made in the uk and leads by someone called joseph aston and it called portland cement and also there's another funny story about the name portland cement anyone want want to say why it's called like portland it's from a place what land maybe i
don't know roughly so there's like the sharp and it's portland huge rock in there and it's gray and cement is gray and when they were promoting something they said is as strong as the portland rocks also like because you mix few materials to make the concrete and that make it kind of an inhomogeneous and making the cement itself is basically you need to get some rocks that contain silica and calcium burn these rocks and then you'll get the cement it's interesting when you
make the concrete you'll add the water back to your cement to make it harden again quite interesting isn't it very interesting i've always used cement and concrete interchangeably as two words i don't know if that's maybe because i'm not from a civil engineering background but i always do that but so that's incorrect so basically cement is the powder if you mix the cement only with water that would be a grout okay or a cement based if you add sand to it and that's when you use it to glue
masonry units together bricks uh that called mortar and concrete is actually when you add in the aggregate which i didn't know that i'm glad to be nice to you yeah it's interesting how many civil engineers graduate without knowing that because no one indicated to them um and i keep saying that all the times like there's two three different types of things in concrete which brings me to another point there is reinforced concrete and there is normal concrete so normal concrete is
not really really good in intention so basically when you try to bend it snap so we add steel in the tension bit and that will become reinforced concrete so there is concrete there's reinforced concrete as well which is a different animal i think that's really interesting as well because actually living in the uk anyway we see with grout mortar and concrete all the time and there are the buildings all around us and people probably refer them as different names so like in your everyday life
it's quite interesting just to know that there have correct names for those things [Laughter] then the differences between them and like because yeah we just think they're either all the same but they have quite a few differences so that's really interesting so we've talked a bit about how concrete is made can you discuss a bit about the impact on the on the environment like this manufacturing process of concrete how does that impact the climate there's two things would impact
the environment is the manufacturing bit when you try to produce concrete as i said you get rock you burn them burn them co2 and the other bit is the reaction is cell for the cement to be going back to its hardened status when it's used as the glue and that would release co2 as well so it's like two things contribute to that the carbon photograph coming from the concrete is about 200 gram per kilo however it is much less than the footprint for steel so that steel will have five times higher
footprint that concrete yeah definitely something we have to consider a lot more these days you know when we're talking about climate change and all of these issues but nevertheless concrete definitely has its uses as we've mentioned we see it all over the place um all around the world so i'd like to ask two of our non-concrete specialists laura and cara if you were to build your dream house what would you want to know about concrete so my dream house um so i
i live near lake district national park in the uk which is very pretty it's also very wet um so i'd want something that would be sort of protective from the damp um and probably quite warm which i think from what i can tell seems like it would have to be kind of like these partially underground to retain the heat um so how would i go about creating sort of like almost like i want to say concrete bunker but that sounds really grim to live in um laura do you know what i mean sounds
reasonable having having a concrete bunker i'd say but anyway yeah it would have like carved out into the hillside so you could have some views across the mountains um but how else would you have a bunker unless it was carved out bunker with a view yeah well interesting though because you could use the concrete in your frame um so the frame of your of the building um and you could shave that in any way because you could cast the concrete because we always try to make the concrete
workable so it would be easily poured into a different shape so you could use the concrete as the frame of your house um which also you could if you're very if you're worried of the on the environment you could use some of the ad mixture like fly ash to reduce how much cement you'll have in it um and pouring your frame of your bunker from concrete would uh be very good um also you could use the masonry breaks in for the isolating stuff or you can um because like you you wouldn't want to
cast your walls out of concrete you're not building a nuclear reactor there um so you would use masonry brakes which have some concrete with where the motors come in as well and it's also like shapes like that it could be shaped in any way you would like however like having um the structure the main structure from casted uh concrete would be fine so that would be my idea of this one okay so if i wanted to keep it like really insulating is there anything particular i'd have to
do to it to make it like sort of retain the heat in the winter it would retain the heat anyway in the winter so because concrete thermal conductivity is really low um and that is uh one of the advantages of having uh building with concrete is this thermal conductivity is really low so let's say if you cast the the slab which is the roof or the flooring between your floors from concrete the heat won't travel in between the two stories uh as much as from another material
let's say like timber or something else because it's have a very low thermal conductivity so it will help your insulation however i would not recommend casting walls of concrete because twit black hideous so if i had like a concrete floor on a concrete ceiling and then like maybe some walls that were covered in something else like you know part of the magnet yeah okay yeah that's what i would i would assume like having the walls to be built with masonry bricks there is um
something i would not recommend using very much to reduce its impact on the environment but if you need there is concrete blocks and they could act like a masonry unit so they would cast them into a masonry shape and they built with them and they would really help with insulation because they cast in a way that they're from concrete and they have a garb in the middle that would reduce their uh well we'll increase the thermal insulation really not reduce it okay and i i know that there are some
quite slow chemical processes that go on in concrete that i i think does it normally have like a design life of about 50 years um yes and no so basically they assume the design life of the concrete span is 50 years because they would think it's not as durable however you need design it it depends on where you place your structure so if you're on a marine structure you would want to regularly maintain that because the concrete will be directly affected by salt water where
salt will attack the concrete and the degrade the bond between its material and that's where it would become kind of dandruff also like a bridge case could be another example for that so because uh concrete is very suspectable to the web to the weather however is very durable um so the strength could decrease i wouldn't worry if i'm building a house with concrete to have a span of 50 years it would definitely have a higher spun cool that's good to know so it'll outlast me probably
mm-hmm yeah it'll be fine bunker needs concrete seems like convincible material cara what about you what would you want uh you know in your dream house that maybe concrete could help fulfill uh i have to say every reader so yeah okay well i've got some questions for you first of all i you've done the job of convincing me that concrete is actually kind of interesting i actually have loads of questions for you know what you've just said um so i don't know i want to make a few points actually so
you're making me think about how you should build houses the one you've just said is a concrete is really good for building because it doesn't um transfer thermal doesn't transfer heat very easily this makes me wonder why are there so many countries building giant glass buildings if they should be using things like concrete instead that aren't transferring heat so easily right in turning houses into greenhouses whereas things like concrete might do a slightly better job
and then you said so that wasn't what i was thinking originally what i actually was going to ask was that my dream house was always going to be the opposite of whatever concrete could be because in ireland they have really weird planning rules for for generate for decades in the republic of ireland where there's something called i think it's called like development blight where you basically build a house wherever you wanted if you had land and everyone built it from
these concrete blocks you've just spoken about we call them breeze blocks and they leave them just looking like concrete squares and they're so unattractive they don't even paint them they just look so terrible and i always hated concrete because of that i was like it just looks outside but why would you want to build a house like that but so i thankfully kind of got over that a little bit and i've come to really appreciate things like brutalism you know we can
actually have some kind of like the rental building right is a great example of a concrete building which maybe was ugly for a while but we kind of can appreciate it again or the preston bus station which is like one of the best examples of like brutalism in the northwest people say um so i kind of come around it now so for me the things i would consider is if i'm weighing up what how to build a dream house it's between how does it look aesthetically what's
the environmental impact of it going to be but also what's the cost how easy is it to build with concrete and you kind of answered a lot of that already you kind of said concrete does a lot of the job of you can make it you can form it how you want so it looks quite nice it does things quite well with concrete we knew how to do it quite easily so maybe is the environmental impact the biggest thing here so what is it we really need to balance out when we're thinking about the environmental impact
of concrete um so first thing uh if you're worried about the environment there is few stuff that happening with concrete industry at the moment so some people will use their recycled aggregate so when they demolish the building they'll crash the concrete back to aggregate and reuse it so you could use a recycled conc aggregate for your concrete um or take some people will call that reclaimed aggregate the other thing that you would um also could use is using some of the
admixture because you're building your house uh you don't need a very high resistance you don't you're not building a high a skyscraper so um uh you could use what the admixture like fly ash or volcanic ash that would reduce the amount of cement in the concrete mix that you're using um the other possibility is lots of people using lightweight concrete now and they would use tire shredded tires in the concrete which make it light in weight and still have a good resistance so you could use
like lots of you could put in lots of stuff in your concrete that make it more environmentally friendly and reduce the impact of producing the concrete to the environment as well so there aren't that many volcanoes around we could but would that not then like push up the co2 emissions again because you're transferring stuff further than you necessarily have to well there's a fly ash coming from the steel industry i would argue there could be one thing we could use which would people say is
very environmentally friendly which is hemp and you can have hemp create right and so hemp is uh there's political arguments about why you should or shouldn't have hampered at different places and at the minute you can't farm hemp on a large scale i don't think that easily within the uk or the other than europe but apparently hemp is a great thing that you can't put into concrete and it's um a very sustainable source of plant material that could be used within concrete
i haven't had this there's wild all over the place as well right like yeah it does i know pakistan is like everywhere it's just yeah it's slightly different but like it just grows like yeah you can see it i have to say i don't know the actual science behind how comparable it is to volcanic ash or to fly ash but i know that it is uh an option at least for a different material it's quite like horsehair we read about crack and thinking horse hair is one of the first things that they used to put
in the concrete yeah they they put quite a lot of thing because basically that you you you add these to add the strength to extension because the long strand will give you more resistance in the tension so when you bend it it won't snap at you it would be a bit more detailed so it has to be longer you can't have like off cuts from the hairdressers used to reinforce that could be a good yeah there has to be long and there has to be a certain length to have some impact on the material
otherwise it's just something there and would not work fascinating um okay so i think we've discussed a lot about the dreams and potential things um for the future including hemp concrete um so why do we build with concrete i think we've covered a lot of this to be honest but if we could summarize why we still use concrete and why we build with it uh well first formable so you can form it into any shape durable and is very economic and have low thermal contactivity um
so that's why with i would build with concrete and basically civil engineers are here to make building safer and more affordable so concrete is a good choice awesome and i'd also like to ask our panelists what their favorite concrete buildings are i know cara's already mentioned brutalism and some of the buildings in manchester but yeah if everyone could say what their favorite concrete buildings are i don't have a favorite building as such but i know that when you polish it
and you bring out like all the shine like so you take off the surface layer and you reveal all the aggregate inside and you sort of shine that up it looks really really impressive um you can build like work tops out of it for kitchens and it looks so nice i never knew you could polish concrete this is oh my god you have to go it's so nice so this is blowing my mind right now that you can polish concrete i'm just like wow you can get polish concrete floors i totally agree laura aesthetically
spot on road about you you clearly love concrete a lot yes actually i have lots of favorite concrete structures um and i'll share two of them one of them is a bridge it's called decla uh clarkmanshire bridge which i found it very annoying to pronounce however it's a very fascinating bridge in scotland made from pre-stress concrete which is similar to reinforced concrete except for this time you will pre-stress your steel bar when you make your concrete to make it more resistant so
the spawn for the girder for this bridge is about 45 meter which is a huge span also the shape of the of the girder itself is shaped in a very nice way that would resist um the dynamic impact of the wind and so on and make it lightweight as well which could not be done without the concrete so that's the first structure the other structure is um the vna museum in dundee um and it's basically has the building made from concrete because the concrete is it's durable
and the building is just next to the tave bridge in dundee um and it's one of the very famous building as well and it have the main panel made of them of a structural glass as well and in the middle so it's it looks really nice um also like the facade of it made of these all all pre precast uh concrete beam i think when i read the report about it it was around 6 000 um being made to used in the facade they all had different dimension to make it look more modern so that's my two
favorite buildings i'm sharing with you some beautiful structures there i recommend everyone looks them up um so kara i know you mentioned the reynold building do you have any other fabulous concrete structures that stand out to you um i think as someone who doesn't know concrete as well i'm not a concrete expert i think it's difficult to do actually sometimes what buildings are made from concrete um because sometimes it's internally being used to hold things up but maybe
on the outside it's glass instead so you don't really know so yeah i have to say that i have struggled to pick just one building that i could really point at but i do really enjoy soviet architecture um i think generally it's it's after with a bit of distance now we kind of appreciate maybe the um concrete has kind of come back into fashion again a little bit or something i'm not sure but yeah i just really like aesthetically how the buildings look and how they manage to get artwork done
directly into the concrete on the facades yeah there's some awesome uh kind of this brutalist type architecture also like in berlin i remember similar types of architecture it's beautiful i think that's a really good point about not knowing whether a building has concrete inside like now i'm thinking does my house have concrete most likely it does but i never thought of that because it's just like i just see the bricks on the outside and it's really cool to think that yeah
there's all these buildings that have concrete and we wouldn't have even thought about it um okay so we've discussed about how concrete's been used in the past how it's used in the present do you guys think that concrete's still going to be used in the future or will we use something else um so from my perspective so first i want to comment on your house so your house probably have more time not concrete in it if it pulled with the brakes um so let's go back to remember this
from the beginning motor versus cement versus concrete i have learned something in this book i promise um yeah so back to the future yes we will still be building from concrete um however we're trying to make the concrete more you're more sustainable and more environmental friendly as well um the other material is which is of use now is timber um there's like lots of fascinating building build out of temper there is one one one one of them is the cube building in london is 33 meter high and the
new thing in civil engineering is called steel uh high body steel timber buildings which basically they mix the steel and timber in their building um and uh one example of that which is just approved is the southwark two tube station buildings so they will build a building with 17 story over that tube station in london um and i think it would be fascinating because both steel and timber could look really nice in a building there are some awesome awesome things to look forward to and an
unwitting reference to one of the best movies of all time back to the future at the beginning of that release segment and yeah love that movie so also watch back to the future guys um so we're coming towards the end now um so initially although concrete might seem kind of boring when you start talking to an expert and a group of interested people as we have done today it suddenly becomes really really interesting um it seems quite a complex material that's challenging to make
um but it's used in so many different applications because it's formable and it can make different shapes however it does have a bit of an impact on the climate so that's something we're going to have to think about moving forward um so just to end i want to ask our panel and our expert today if there's anything like any messages they want to reinforce do you get it funny and maybe not that funny um yeah you want to mention before we before we wrap up yeah we know we need some concrete
messages there aren't we oh yeah another great one love it yeah my response is definitely tipped for me to try not to use three terrible thoughts yeah i think that's fair i've been told that before so i will definitely take that moving forward although it does make the conversation more interesting well i don't know it's debatable isn't it we can ask our listeners please please contact us on our we have a twitter page now i should have mentioned this before uh what's our twitter handle laura
oh it's something like technically 11.
it's great isn't it but yeah you can find us if you just search potentially speaking in twitter and take a look for podcast artwork and let us know if you want more puns it can be arranged um but yeah no are there any any concrete things that people want to let people know before we finish um i would just say like all the material we're using to build will have an impact on the environment so we need to be reasonable when we build the stuff and we would need to think about the
impact of any material not only the concrete because it have two parts it has the production of it and the use of it and we need to be as environmental friendly when we're doing this so really being conscious of the life cycle of a whole project as you say going from the manufacturing to the usage and hopefully hopefully using stuff as long as possible and trying to extend the life of things that we already have rather than building new things um a lot of the time we hear people want
to demolish a lot of the buildings with this brutalist architecture but is there a way we can repurpose them for something that that's something definitely to think about um yeah thank you very much uh to laura carraway that was a fascinating conversation i hope everyone who's listening learnt about as much about concrete as i have today as a complete novice and yeah please get in touch with us on our twitter and hopefully we'll chat with you next time the views expressed in this podcast
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