Prática de Shadowing: Introduction 1, Context - Aprenda a falar inglês com vídeo
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Cement Chemistry for Sustainable Cementia Materials Hello and welcome to this series on Cement Chemistry for Sustainable Cementia Materials.
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In this series of modules, we're going to look at the cement chemistry and how this helps us to understand the sustainability of these very important materials.
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Most of the modules should be really understandable to anybody with a fairly basic knowledge of high school chemistry.
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So in this first module, we're going to look at the overall context.
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We're going to look at the role of cementitious material in the world today
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and what are the origins of their CO2 footprint.
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Now, in this first slide, we can see the overwhelming dominance of cementitious materials.
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They make up between 30 to 50 percent of everything we produce,
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probably about 50 percent of solid materials and 30 percent if we include things like fossil fuels.
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And in the light of that, the fact that they're responsible for CO2 emissions of around 5 to 10 percent is a very good ratio.
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But more importantly, we can really see
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that it would in no way be possible to replace semantitious materials with alternatives at any meaningful level.
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For example, if we look at the amount of wood produced worldwide, this is between 10 and 15% the amount of cementitious materials.
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And already it's estimated that this amount of wood is beyond the limits of sustainability.
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That's to say we're cutting down more trees than we're planting.
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So while this may be a nice option in Europe and North America, it's really not practical for the many people who need to be housed in countries like China,
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India, Africa, South America.
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This slide here really shows how the environmental footprint of concrete is very low.
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And we should talk about concrete because concrete is the final material we really use.
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Cement is the precursor and there's roughly about 10% of cement in concrete.
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On the right here, I've normalized these figures compared to the highest, which is aluminium.
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You can see very vividly just how much energy and CO2 you can save by recycling aluminium.
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And I hope after seeing this, you don't throw your Coke can in the bin anymore.
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But concrete is really extremely low, lower than almost all other materials.
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Of course, this is just on a weight basis.
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When you put this into a structure, it becomes more complicated.
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We're not going to go into that here, but generally, even in that situation,
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concrete still comes out very strongly as an environmentally friendly material.
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The amount of cement we're using has increased very, very dramatically in the past few decades.
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Since 1950, the population has increased about threefold, and in the same period,
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the amount of cement we use has increased by about 34 times.
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In recent decades, this has really been driven by the development in China.
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And we should not view this negatively because this development has lifted a lot of people out of poverty.
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It's provided them with decent homes, with roads, railways to get around and everything like that.
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But we certainly cannot imagine that this growth in demand for cement is going to slow down because there are many,
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many other parts of the world where people still haven't had decent housing or transportation systems.
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Finally, what we do with our lives and the CO2 produced is a question of choices.
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And here again, you know, if we decide to build a house, we make maybe a house for a family of three people,
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this will typically take about 10 to 20 tons of cement and last for about 50 years.
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So we can calculate from that
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that the CO2 to do with your materials in your house is about 12 kilograms a month.
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Now, if you're driving a car, which you almost certainly are,
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that same family of three will probably drive at least 10,000 kilometers a year.
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And then they'll be consuming fossil fuels, which will be producing about 90 kilograms of CO2 per year,
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seven or eight times more than the materials in their house.
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But we should also reflect on our other choices in life, for example, the food we eat.
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Here you can see for a very meat intensive diet,
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the associated CO2 production would be around five to seven kilograms of CO2 per day.
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whereas a vegetarian diet is much lower at around 3 to 4 kilograms of CO2 per day.
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And so if we calculate for the same imaginary family of three that they went from eating meat to being vegetarian
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maybe for just two
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or three days a month this would be equivalent to saving all the CO2 that they needed to build their house.
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So rather than just blaming the producers of these materials we have to think about what we're doing in our lives
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and what we choose to do that produces CO2.
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Okay, there's no reason for complacency because if we did nothing about the CO2 footprint of cementitious materials,
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we could end up in a situation like this.
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Here we see the blue line is the trajectory
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that has been estimated we should try to meet if we're to restrict global warming to this two degrees temperature rise.
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Whether we're going to do that or not is another question, but that's the trajectory of overall global emissions if we're going to do that.
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If we achieve that blue line and we did nothing about cement,
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then the emissions from the production of cement and cementitious materials would follow the red line.
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And we see
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that by 2050 we would end up in a situation where
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cementitious materials would be responsible for something like 30% of world CO2 emissions, which is clearly unacceptable.
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So where is the consumption of cement taking place?
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What we see here is the distribution of cement use around the world.
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And only about 10% of cement use is taking place in OECD countries.
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And in these countries, it's forecast that demand will really stay pretty much constant.
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More than 90% of consumption is taking part in the developing world,
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particularly in China, which has been very dominant over the past two decades.
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It's been estimated in the last three years, China produced more concrete than was produced in the whole of North America in the 20th century.
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and many other countries like India in particular are looking to follow this development path to provide decent houses for their people,
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decent rail systems, decent road systems and this will inevitably mean that the growth in use of cement is going to increase.
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So if we're going to meet this challenge of the growing demand for cement we need solutions
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which are first of all practical, They can be used by unskilled workers.
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And, you know, this shows you the kind of typical situation you can have for mixing concrete.
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The example is from India.
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And also economically.
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Now, you know, cement is an incredibly cheap material.
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In most of Europe, you can buy a ton of cement for less than 100 euros for a whole ton.
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In many developing countries, though, the prices are actually higher, even though the incomes are lower.
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So it's very important that we have solutions
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which are really economically viable for these countries where there's this huge need for building infrastructure and housing,
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etc. So let's look at where these CO2 emissions are coming from.
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Unlike most other industrial processes, only a minority of the CO2 emissions are coming from the energy consumption.
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Producing cement is a high temperature process.
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you're going up to temperatures of 1450 or so and this does take energy but it's still the minor amount.
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A cement kiln as we see here looks like a fairly unsophisticated type of instrument.
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But this is in fact not true
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because in the past few decades there's been very dramatic improvement in the amount of energy needed to produce cement.
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And in really state-of-the-art equipment now the production process is highly optimized up to nearly 80% of the thermodynamic limit
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which is those of you who or study thermodynamics will know, is very close to the maximum you can achieve.
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Another factor which is important is that rather than using fossil fuels, which used to be the dominant means in the past,
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nowadays we can use a wide variety of waste fuels.
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So for example, off cuts from producing furniture,
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old car tires, Many, many different kind of waste can be burnt in a cement kiln.
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And in many parts of Europe, plants are using more than 80% of waste fuels.
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So this is a very efficient tool for valorizing waste materials.
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So if we're going to make improvements, we need to turn to the other side, to the 60% of the equation.
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And this 60%, this comes from the breakdown of calcium carbonate into calcium oxide and CO2.
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Calcium carbonate, this is in fact limestone, which is 80% of the raw material used to make cement.
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Now, the fact we have this chemical CO2 means that if we're going to reduce this, then we're going to have,
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this has implications for the chemistry of the cement.
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And that means it has implications for the whole way it behaves, in use, etc., etc., which of course is a big challenge.
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So what have we seen in this lecture?
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Well, we've seen how important semantitious materials are, how they make up by far the overwhelming majority of all the materials we used
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and therefore cannot be replaced by other materials.
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We've seen that in fact the environmental footprint from these materials is in fact quite low
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and we've looked at where the CO2 emissions come from
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and we've seen that most of the CO2 emissions come from the chemical breakdown of limestone,
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that's calcium carbonate, and therefore we can't really imagine to do much about CO2 emissions by, for example, looking at alternative energies.
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So in the next lecture, we're going to go into more detail about why the chemistry of cement is as it is.
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So I look forward to seeing you next time and I hope you've enjoyed this first module.
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If you want to find out more, then this publication, Ecoefficient Cements, which we published in November 2016,
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gives you a very good background to all the aspects I will tackle in this first module.
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Vocabulário e dicas de fala para esta lição
Esta aula de conversação de nível C1 usa o vídeo “Introduction 1, Context”. As palavras que mais se repetem: cement, material, emissions, concrete, amount. Este vídeo tem 115 frases e 1706 palavras para praticar shadowing. A fala dura 11:57. O falante mantém um ritmo estável de cerca de 143 palavras por minuto, confortável para o shadowing. 86% das palavras estão entre as 3.000 mais comuns do inglês; vale a pena estudar o restante antes de começar.
Vocabulário principal deste vídeo
As 15 palavras mais avançadas do vídeo, com pronúncia e significado:
| Palavra | Pronúncia | Significado |
|---|---|---|
| cement substantivo | /səˈmɛnt/ | cimento |
| emission substantivo | /ɪˈmɪʃ.ən/ | emissão |
| module substantivo | /ˈmɑd͡ʒul/ | módulo |
| kilogram substantivo | /ˈkɪləɡɹæm/ | quilograma, kilograma |
| footprint substantivo | /ˈfʊtpɹɪnt/ | pegada |
| calcium substantivo | /ˈkælsi.əm/ | cálcio |
| carbonate substantivo | /ˈkɑɹbəneɪt/ | carbonato |
| fossil substantivo | /ˈfɑsl̩/ | fóssil |
| kiln substantivo | /kɪln/ | fornaça |
| overwhelm verbo | /ˌoʊ.vɚˈwɛlm/ | engolir |
| trajectory substantivo | /tɹəˈd͡ʒɛktəɹi/ | trajetória, trajectória |
| aluminium substantivo | /ˌæl.(j)uˈmɪn.i.əm/ | alumínio |
| limestone substantivo | /ˈlaɪmˌstoʊn/ | calcário |
| sustainability substantivo | /səˌsteɪnəˈbɪlɪti/ | sustentabilidade |
| vegetarian substantivo | /vɛ.d͡ʒɪˈtɛ.ɹi.ən/ | vegetariano, vegetariana |
Phrasal verbs que você vai ouvir
| Palavra | Pronúncia | Significado |
|---|---|---|
| make up verbo | /ˌmeɪk ˈʌp/ | compensar |
| come out verbo | /ˌkʌm ˈaʊt/ | sair, partir |
| find out verbo | descobrir | |
| look forward to verbo | ansiar por, estar ansioso para | |
| slow down verbo | desacelerar |
Gramática neste vídeo
As estruturas que o falante mais usa, com as palavras exatas do vídeo:
| Estrutura | No vídeo |
|---|---|
| “Used to” used to + verbo — um hábito ou estado do passado que não é mais verdade | used to be · used to make |
| Present perfect have/has + particípio passado — uma ação passada que ainda importa agora | I've normalized · has increased · has really been driven |
| Orações relativas who / which + oração — informação extra sobre uma pessoa ou coisa | people who need · highest, which is · fuels, which will |
| Voz passiva be + particípio passado — o foco está no que acontece, não em quem faz | be housed · been driven · has been estimated |
Pronúncia para ficar de olho
O falante usa 29 contrações e formas reduzidas, como we're, we've, you're. Diga-as na forma curta, do jeito que você ouve.
- Os sons de “th”: thermodynamic /ˌθɝmoʊdaɪˈnæmɪk/, thermodynamics /ˌθɜː(ɹ)moʊdaɪˈnæmɪks/
- Os sons de “sh” e “zh”: emission /ɪˈmɪʃ.ən/, cementitious /ˌsɛmɛnˈtɪʃəs/, implication /ˌɪmpləˈkeɪʃən/, equation /ɪˈkweɪ.ʒən/
- Palavras longas — acerte a sílaba tônica: cementitious /ˌsɛmɛnˈtɪʃəs/, implication /ˌɪmpləˈkeɪʃən/, trajectory /tɹəˈd͡ʒɛktəɹi/, aluminium /ˌæl.(j)uˈmɪn.i.əm/, sustainability /səˌsteɪnəˈbɪlɪti/
Sons difíceis para falantes de português:
- Consoante final — sem acrescentar um “i” depois: cement /səˈmɛnt/, footprint /ˈfʊtpɹɪnt/, carbonate /ˈkɑɹbəneɪt/, calculate /ˈkælkjʊleɪt/, thermodynamic /ˌθɝmoʊdaɪˈnæmɪk/
- /l/ final — a língua toca o céu da boca, não vira “u”: module /ˈmɑd͡ʒul/, recycle /ɹəˈsaɪkəl/, viable /ˈvaɪəbəl/
Como praticar com este vídeo
- Ouça o vídeo inteiro uma vez sem falar e anote as palavras que você não conhece.
- Faça shadowing frase por frase na velocidade normal, repetindo cada uma até o seu ritmo ficar igual ao do falante.
- Grave a sua voz e compare com o original, prestando atenção a palavras como cement, emission, module.
O que é a Técnica de Shadowing?
Shadowing é uma técnica de aprendizado de idiomas com base científica, originalmente desenvolvida para o treinamento de intérpretes profissionais. O método é simples, mas poderoso: você ouve áudio em inglês nativo e repete imediatamente em voz alta — como uma sombra seguindo o falante com 1-2 segundos de atraso. Pesquisas mostram melhora significativa na precisão da pronúncia, entonação, ritmo, sons conectados, compreensão auditiva e fluência na fala.