Shadowing Practice: Introduction 1, Context - Learn English Speaking with Video
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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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Vocabulario y notas de pronunciación para esta lección
Esta lección de conversación de nivel C1 se basa en el vídeo “Introduction 1, Context”. Las palabras que más se repiten: cement, material, emissions, concrete, amount. Este vídeo tiene 115 frases y 1706 palabras para practicar shadowing. La parte hablada dura 11:57. El hablante mantiene un ritmo constante de unas 143 palabras por minuto, cómodo para el shadowing. El 86 % de las palabras está entre las 3.000 más comunes del inglés; conviene repasar el resto antes de empezar.
Vocabulario clave de este vídeo
Las 15 palabras más avanzadas del vídeo, con su pronunciación y significado:
| Palabra | Pronunciación | Significado |
|---|---|---|
| cement sustantivo | /səˈmɛnt/ | cemento |
| emission sustantivo | /ɪˈmɪʃ.ən/ | emisión |
| module sustantivo | /ˈmɑd͡ʒul/ | módulo |
| kilogram sustantivo | /ˈkɪləɡɹæm/ | kilogramo, quilogramo |
| footprint sustantivo | /ˈfʊtpɹɪnt/ | pisada, huella |
| calcium sustantivo | /ˈkælsi.əm/ | calcio |
| carbonate sustantivo | /ˈkɑɹbəneɪt/ | carbonato |
| fossil sustantivo | /ˈfɑsl̩/ | fósil |
| kiln sustantivo | /kɪln/ | horno |
| overwhelm verbo | /ˌoʊ.vɚˈwɛlm/ | apabullar, arrollar |
| trajectory sustantivo | /tɹəˈd͡ʒɛktəɹi/ | trayectoria |
| aluminium sustantivo | /ˌæl.(j)uˈmɪn.i.əm/ | aluminio |
| limestone sustantivo | /ˈlaɪmˌstoʊn/ | caliza |
| sustainability sustantivo | /səˌsteɪnəˈbɪlɪti/ | sostenibilidad, sustentabilidad |
| vegetarian sustantivo | /vɛ.d͡ʒɪˈtɛ.ɹi.ən/ | vegetariano, vegetariana |
Phrasal verbs que vas a escuchar
| Palabra | Pronunciación | Significado |
|---|---|---|
| make up verbo | /ˌmeɪk ˈʌp/ | reponer, suplir |
| come out verbo | /ˌkʌm ˈaʊt/ | revelarse, salir a la luz |
| cut down verbo | talar | |
| find out verbo | averiguar, anoticiarse | |
| look forward to verbo | no ver la hora de, quedar a la espera de | |
| slow down verbo | desacelerar, decelerar |
Gramática en este vídeo
Las estructuras que más usa el hablante, con las palabras exactas del vídeo:
| Estructura | En el vídeo |
|---|---|
| “Used to” used to + verbo — un hábito o estado pasado que ya no es cierto | used to be · used to make |
| Present perfect have/has + participio pasado — una acción pasada que sigue importando ahora | I've normalized · has increased · has really been driven |
| Oraciones de relativo who / which + oración — información extra sobre una persona o cosa | people who need · highest, which is · fuels, which will |
| Voz pasiva be + participio pasado — importa lo que ocurre, no quién lo hace | be housed · been driven · has been estimated |
Pronunciación a tener en cuenta
El hablante usa 29 contracciones y formas reducidas, como we're, we've, you're. Dilas en su forma corta, tal como las oyes.
- Los sonidos de “th”: thermodynamic /ˌθɝmoʊdaɪˈnæmɪk/, thermodynamics /ˌθɜː(ɹ)moʊdaɪˈnæmɪks/
- Los sonidos de “sh” y “zh”: emission /ɪˈmɪʃ.ən/, cementitious /ˌsɛmɛnˈtɪʃəs/, implication /ˌɪmpləˈkeɪʃən/, equation /ɪˈkweɪ.ʒən/
- Palabras largas — cuida el acento: cementitious /ˌsɛmɛnˈtɪʃəs/, implication /ˌɪmpləˈkeɪʃən/, trajectory /tɹəˈd͡ʒɛktəɹi/, aluminium /ˌæl.(j)uˈmɪn.i.əm/, sustainability /səˌsteɪnəˈbɪlɪti/
Sonidos difíciles para hispanohablantes:
- /v/ — no es /b/: los dientes tocan el labio inferior: overwhelm /ˌoʊ.vɚˈwɛlm/, vegetarian /vɛ.d͡ʒɪˈtɛ.ɹi.ən/, valorize /ˈvæləˌraɪz/, vividly /ˈvɪvɪdli/, inevitably /ɪˈnɛvɪtəbli/
- /z/ — sonora, no /s/: normalize /ˈnɔː.mə.laɪz/, optimize /ˈɑptɪmaɪz/, valorize /ˈvæləˌraɪz/
- /dʒ/ — no es la “y” ni la “ch”: module /ˈmɑd͡ʒul/, trajectory /tɹəˈd͡ʒɛktəɹi/, vegetarian /vɛ.d͡ʒɪˈtɛ.ɹi.ən/, imaginary /ɪˈmæd͡ʒɪˌn(ɛ)ɹi/
Cómo practicar con este vídeo
- Escucha el vídeo entero una vez sin hablar y anota las palabras que no conoces.
- Haz shadowing frase por frase a velocidad normal, repitiendo cada una hasta que tu ritmo coincida con el del hablante.
- Grábate y compara con el original, prestando atención a palabras como cement, emission, module.
¿Qué es la Técnica de Shadowing?
Shadowing es una técnica de aprendizaje de idiomas respaldada por la ciencia, desarrollada originalmente para la formación de intérpretes profesionales y popularizada por el políglota Dr. Alexander Arguelles. El método es simple pero poderoso: escuchas audio en inglés nativo y lo repites en voz alta de inmediato, como una sombra que sigue al hablante con solo 1-2 segundos de retraso. A diferencia de la escucha pasiva o los ejercicios de gramática, el shadowing obliga a tu cerebro y músculos de la boca a procesar y reproducir simultáneamente patrones de habla reales. Las investigaciones muestran que mejora significativamente la precisión de la pronunciación, la entonación, el ritmo, el habla conectada, la comprensión auditiva y la fluidez al hablar, convirtiéndola en una de las metodologías más efectivas para la preparación del IELTS Speaking y la comunicación en inglés en el mundo real.