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Knowing Our Food: Storage

by Posted in Concrete

Though food nourishes us every day, there is still much that we can learn about it. At Critical Concrete, we aim to consume as much local, seasonal food as possible and we have recently started growing it ourselves in our food forest. Unfortunately, it is quite common that we as a society eat food without paying attention to its seasonal availability; it is easy to be influenced by a globalized system that makes practically any food available at any time in the year regardless of climate and the environmental impact. The production of food outside of its peak season can have 3-10 times the emissions as food imported from better climates, so it is important to not only support local farmers, but also to mind the seasonality of fruits and vegetables.[1] While some imported foods, such as almonds and avocados, are imported by boat and have a lower footprint than locally produced options, other more perishable foods are freighted by air, which creates 50 times the carbon emissions as boat transportation.[2] Aside from environmental friendliness, seasonal, local food can be more nutritious and flavorful as it has more time to ripen before harvest, and supports small farms and sustainable farming practices.

That being said, choosing local and seasonal produce means nothing if our food goes bad before we have the chance to eat it. That means that storing food to extend its lifespan is highly important. This research grew out of our curiosity to know more about alternative ways of storing food that are not energy consuming. However, as we encountered more information, the research evolved to focus more on food knowledge, with the aim of informing ourselves and our readers about the needs of our fruits and vegetables and how we can store and consume them. Our upcoming articles from this research will delve into the topics long-term storage, food production, and the use of food scraps, and in this article, we will discuss how to make use of conventional kitchen storage to keep food fresh. 

Food Waste and the Fridge

Food waste is an immense problem that worsens each year. In fact, fighting food waste has been determined to be one of the most urgent solutions to fighting climate change.[3] The production and disposal of wasted food results in water waste, land waste and deforestation, and greenhouse gas emissions. Although a tremendous amount of food waste is the result of industrial food practices, in Europe 42% of food is thrown out by the consumer, and only one third of that food wasted consists of inedible residuals (skin, shells, peels).[4] Regardless of whether climate change can be tackled through individual actions, consumers can still reduce the amount of food lost to spoilage in their own homes. Even if it does not solve environmental issues in and of itself, when we learn about proper food storage and reduce our waste, we save money and take the first steps toward better societal food practices.

At first we were inclined to look for alternatives to our usual house appliances like the fridges, as refrigerants like chlorofluorocarbons (CFCs) are the main cause of the depletion of the ozone layer.[5] This led us to a few methods of long-term storage, which we built as prototypes to evaluate their efficacy in the climate our research lab is located in. Keep an eye out for our next article, detailing these methods and their benefits for different foods and environments.

However, it can’t be ignored that storing food in the fridge and freezer is such common practice, so this article will describe the ways to reduce food waste in the context of conventional storage practices. Thus we first have to analyse the way the fridge is used, to know its strong and weak points and the way it works. Additionally, it is crucial to understand the process of food decay and the science behind it. Once it is understood how food decays, the same principles can be applied everywhere. In order to reach a balance in the system, minimizing waste and prolonging the life of food, we must first know the needs of fruits and vegetables and demystify their storage environments, both artificial and natural.


Where to store different fruits and vegetables

Food Decay

Knowledge about everyday storage of fruits and vegetables is essential. In order to better understand the proper storage of fresh vegetables and fruits, the first step is to clarify the biochemical characteristics and processes which occur after harvesting. This knowledge can help reveal why certain foods become rotten very fast whereas other foods last for a long time. This phenomenon is influenced by two factors: the speed of natural metabolism depending on the specific plant and the way it is stored. 

Enzymes are proteins which serve as catalysts to chemical changes in living organisms and there are thousands of different enzymes with varying functions. Enzymes in our food cause changes to fruit and vegetables which cause them to spoil. In cool temperatures, these enzymes slow their activity, and they can die when cooked above 60 degrees.[6] 

Aside from enzymes, three other rotting agents can reduce the life of food. These are mold, which is visible, yeasts, which convert sugars into alcohol through fermentation, and bacteria, some of which can poison food.[7] Using this information, we can determine how to avoid mold and bacteria, and slow down the process of decay.

Conditions for storage

The best storage method for a given food depends primarily on three parameters: temperature, humidity and ripening.

Temperature: Cooling down slows down the metabolic process and thus has an immense effect on preservation. Nevertheless, there are certain plants, such as bananas, tomatoes, eggplants or cucumber which are very sensitive to the cold and also others which lose vitamins and taste.[8] Moreover you should take into consideration where in the refrigerator to put things. The middle and the back are usually colder than the other areas of the fridge.[9] As there is no cooling on the bottom cold air coming from the middle can warm up and rise up which leads to the different temperatures levels.[10] 


Zones of the fridge and their temperatures

Humidity: Many fruits and vegetables, such as cucumbers, leafy greens, carrots and roots, are susceptible to humidity loss and shriveling.[11] For these, it is important to ensure a high level of atmospheric humidity. Many refrigerators have a crisper drawer for vegetables in order to keep a higher level of humidity. Some vegetables that should definitely be stored in the crisper drawer are spring onions, celery root, spinach, and leeks.[12] Otherwise, vegetables that are susceptible to moisture loss can be wrapped in damp towels and stored in other areas of the fridge.

Ripening: In basic terms, ripening can divide produce into two groups: the kind that continues the process of ripening after the harvest and the kind which abruptly stop ripening when harvested. This fact depends on the natural plant hormone ethylene. Ethylene is a gaseous hydrocarbon (C₂H₄) which speeds up the ripening process.[13] Some fruits and vegetables release ethylene gas in the process of becoming ripe.[14] Others, by contrast, are sensitive to ethylene and absorb it.[15] If you do not want to speed up the ripening and  spoiling effect, try to store ethylene-sensitive vegetables apart from those which release a lot of ethylene. 


Ethylene production and sensitivity in fruits and vegetables

According to their ethylene production, apples, tomatoes, peaches, apricots, avocados, kiwi, mango and bananas should be stored apart from other fruits and vegetables.[16] But you can also make use of this property when you want something to ripen faster. In that case, you purposefully store high ethylene producers together with ethylene sensitive ones.[17] When you have green tomatoes you can store them together with apples in order to get them to ripen faster.      

Referring to proper storage, there are some rules of thumb about food that should never be stored in the refrigerator. Fruits sensitive to cold are pineapples, avocados, bananas, mandarins, mango and melons.[18] Vegetables sensitive to cold are artichokes, tomatoes, potatoes, eggplants, garlic and onions.[19] Nevertheless, there are some real divas who cannot really decide whether they want to be stored in the fridge or in the room. Cucumbers and zucchinis for example are sensitive to cold but if too warm they lose humidity and start to shrivel fast.[19] Therefore, they should be stored in the crisper drawer or in the top part of the refrigerator, wrapped in a damp towel to avoid cold damage and humidity loss.[20]        

Additional Specific Storage Strategies 

With this knowledge of general food storage, we can delve into more specific ways to increase the lifespan of our fruits and vegetables. Berries and cherries are susceptible to mold, so they should not be washed until just before they are eaten.[21] Also, berries are often quite fragile and should be stored in a single layer, if possible.[22] Figs are sensitive to humidity, which makes paper bags good storage containers to absorb their excess moisture, but they can also be stored on plates in the fridge.[23]

As for vegetables, removing rubber bands from the stems is always the first step.[24] Radishes, beets, carrots, and turnips, should be separated from their greens to avoid losing moisture in the roots.[25] Then, the roots can be stored in an open container with a wet towel placed on top.[26] Greens are best in closed containers alongside a damp cloth to keep them from drying.[27] However, you can save room in the fridge by storing kale, chard, and collard greens upright in glasses of water on the counter.[28] Celery and fennel can be stored this way as well.[29] Asparagus is best stored upright in a water inside the fridge.[30] It should be noted that using paper bags, reusable containers, glasses, or damp cloths should make it easy to eliminate the need for any single-use plastic inside the fridge.

Conclusion      

Hopefully, being more cognisant of the needs of fruits and vegetables can limit food ending up in the trash or compost. Now that we understand how the chemical processes happening inside fruits and vegetables cause them to react to different conditions, we can store it in the right way. We can take advantage of the different areas inside your fridge, and organize our fridges to maximize the lifespan of our food. To help adjust to all this new information, we produced a chart to help understand fruits and vegetables and store them in the best way possible. Download it, print it, and put it on the wall in your kitchen! 

In our next article about food we will discuss different ways to store food for longer periods of time and the benefits of each method. Stay tuned to learn how fruits and vegetables can be enjoyed past the periods when they are in season, without forfeiting the nutritional value and flavor of eating seasonal food.

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Bibliography:

[1] https://ourworldindata.org/food-choice-vs-eating-local, opened 8.12.2020.

[2] Ibid.

[3] Hawken, Paul. Drawdown: The Most Comprehensive Plan Ever Proposed to Reverse Global Warming. New York, New York: Penguin Books, 2017.

[4] Principato, Ludovica. Food Waste at Consumer Level a Comprehensive Literature Review. Springer International Publishing, 2018. p. 5.

[5] https://www.conserve-energy-future.com/causes-and-effects-of-ozone-hole.php, opened 8th of December, 2020.

[6] Seymour, John. The Self-Sufficient Gardener: A Complete Guide to Growing and Preserving All Your Own Food. Dolphin Books, 1980. 

[7] Ibid.

[8] https://www.rollende-gemuesekiste.de/wp-content/uploads/Lagertipps.pdf, opened 24.11.2020.

[9] Ibid.

[10] Ibid.

[11] 

[12]https://myplasticfreelife.com/wp-content/uploads/images/Berkeley%20Farmers%20Market%20Tips%20for%20Storing%20Produce.pdf, opened 27.11.2020.

[13] https://www.theproducenerd.com/2018/02/what-is-ethylene-how-is-it-used/, opened 10.12.2020 December

[14] Ibid.

[15] Ibid.

[16] Sächsische Landesanstalt für Landwirtschaft. Verbraucherinformationen Obst Und Gemüse Richtig Lagern, 2003.

[17] https://www.rollende-gemuesekiste.de/wp-content/uploads/Lagertipps.pdf 

[18]https://myplasticfreelife.com/wp-content/uploads/images/Berkeley%20Farmers%20Market%20Tips%20for%20Storing%20Produce.pdf, opened 27.11.2020.

[19] Ibid.

[20] Ibid.

[21] Ibid.

[22] Ibid.

[23] Ibid.

[24] Ibid.

[25] Ibid.

[26] Ibid.

[27] Ibid.

[29] Ibid.

[30] Ibid.

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The reality of concrete

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Concrete, as the most used building material worldwide has a huge impact on our cities, societies and environment. Much of our research is based on the idea to create an alternative solution for conventional methods of building, such as building with concrete. In this article, we will tackle basic and relevant knowledge and information about concrete, to understand why it is important to think about alternative solutions for the future of our building habits. This write-up will be part of a series of small papers related to meaningful knowledge, to understand why it’s urgent to rethink our conventional building approaches.

Concrete, cement & mortar – definitions

To give a brief overview of what we are talking about in specific, we will first define the most important terminologies that we will need to understand the whole topic around concrete.
Four important terms you should know about and understand their exact definitions: 

Diagram showing the composition of concrete
Typical composition of concrete

cement  // səˈment

Cement is the key ingredient to mix concrete. This product is mainly made out of crushed limestone mixed with shales and slates, shredded to a fine powder and heated up to approximately 1450°C. The heat causes a chemical reaction, also known as calcination.[1] That reaction along with the heating process causes a high amount of carbon-dioxide emissions, which makes cement production a big driver of greenhouse gas emissions. The entire process happens in a giant mixer, called a cement kiln. [2] The most popular kind of cement is portland cement, developed in England in the early 19th century. [3]

concrete // ˈkänˌkrēt

Concrete is an artificial building material, which consists of a binding agent like cement or lime, in addition to water and aggregates (sand and gravel) as well as potential  additives (like fly ash or plasticizers). The cementitious part gets liquified with water. By adding water to the cement a chemical reaction is caused and the process of crystallization begins. In the next step some additives such as gravel and sand are added. These aggregates are held together by the liquified cement. Once the whole mixture is cured, this process will finish with a solidified product, called concrete.

mortar // ˈmôrdər

Mortar is a workable paste, used to bind bricks, stones or to fill gaps and holes. The basis is made out of a binding agent (such as slaked lime, ash or, most commonly nowadays, cement) added with water and a fine aggregate, mainly sand. 

Mortar is one of the oldest building materials, used for many thousand years. For a long time, slaked lime, volcanic ashes or clay worked as a binding agent. During the nineteenth century portland cement was invented. From that time cementitious mortar rose in popularity and replaced the old binding products.

These two kinds of mortar differ in two ways. On the one hand cementitious mortars usually are more workable due to faster curing, higher water resistance and less cracking, on the other hand non-cementitious mortars significantly cut greenhouse emissions while processing. It even can absorb CO2, which appears to happen when lime mortar cracks, so that air (especially CO2) can be absorbed. By absorbing CO2, lime mortar is even molding and gets even stronger.[4] To put it plainly:  it’s an environmentally friendly and more sustainable alternative.

reinforced concrete // ˈˌrēinˈfôrst ˈkänˌkrēt

In most cases concrete is combined with steel rebars, to compensate for the low tensile strength. The capability of concrete to react on compressive load is ten times bigger than the capability to bear tension loads.[5]

A more advanced and further developed version of conventionally reinforced concrete is prestressed concrete. To make concrete structures more durable against tensile forces, tendons, a high performing kind of rebar gets tensioned. Mainly these tendons are wires or threaded rebars. When applying in the casted concrete, the concrete part gets compressed, which gives the structure a higher performance, while being in service. [6]

Why is cement concrete so popular?

There are many reasons for its popularity: its liquid stone characteristics were revolutionary and created the possibility to make nearly every form out of concrete.

Cement concrete structures can be segmented and precast, making it suitable for big construction projects; and once solidified, it is a very strong material with the ability to bear high amounts of load. Designers adopted the versatile material, and nowadays we find furniture and accessories made of this material, in every kind of shape.

The use of concrete can be dated back to the ancient times. Romans mastered the use of hydraulic lime as a binding agent, called “opus caementicium”. After the fall of the Roman empire, the use of concrete faded, till it got resurrected in the early 19th century. Instead of using hydraulic lime, portland cement, a further development of the ancient version, was invented and led to a big rise in popularity of concrete in building industries. The first buildings during this time were bridges, foundations and harbours, facilitated by the compressive strength and workability of the new material.[7] 

In the late 19th century iron rods, and later steel rebars, were added to poured concrete to increase tensile strength. It was mainly developed by the French Joseph Monier [8]  – an invention which is ubiquitous in building industries nowadays. This invention led to a big rise in popularity in the residential and social housing sector. In comparison to conventional houses in those days, new concrete based housing projects were more durable, termite and fire resistant. The workability of concrete made it fast and easy to use on site. Pre-castable and serial development of construction elements cut costs significantly. In the 50s of the last century, concrete played a major role in evolving the architectural style of Brutalism, a socio-aesthetically driven architecture movement of showing raw, honest constructions often used for big scale civic and public projects. This architectural style was a dominating force during the next two decades. [9]

In addition, the raw materials of concrete are available in large quantities around the globe, which makes concrete cheap to produce. Limestone, sand and gravel are quite cheap. The main processing costs are caused by the cement production. 

What quantity of resources are needed to produce cement concrete?

Image showing 3.8t of concrete per person globally

There are four main components of cement concrete (cement, water, sand and gravel). For reinforced concrete, there is an additional component – steel. Besides these materials, there are more raw resources needed to produce the main ingredients. To produce one tonne of cement, approximately two tonnes of raw limestone are necessary. [10] The production of cement is a high energy consuming process. One ton of cement takes about 120 kWh of energy in process heating. This energy is mainly obtained from fossil fuels and burning waste. [11]

The cement concrete recipe

There are several different recipes for making concrete. The recipes mainly differ in the ratio of cement and the added aggregates. Concrete can be mixed with different ratios to get a higher load bearing capacity or to get a higher ability to withstand different exposures, such as seawater, moisture or frost.

The following recipes just give you a basic overview about how a classic mixture of concrete could look like:
A standard concrete mix consists of 1 part water (7,7%), 2 parts cement (15,4%) , 4 parts sand (30,7%) and 6 parts gravel (46,1%). [12] 

The higher the load the more cement you’ll need (f.e. a concrete column, foundation needs 1 part water (11,1%), 2 parts cement (22,2%), 2 parts sand (22,2%) and 4 parts gravel (44,4%) ).
Around 70% of the built concrete constructions are reinforced with steel, so you would usually have to add a certain percentage of steel rebars to the produced concrete (60-80 kg/m3 of concrete).[13]

That means a ton of average concrete consists of:

77 kg of water (7,7%)154 kg of cement (15,4%)307 kg of sand (30,7%)461 kg of gravel (46,1%)
Components of concrete
Components of 1 tonne of concrete

Where is concrete used?

The use of cement concrete has various fields of application in construction and design. Since it was developed in the early XIXth century as a powerful structural material, it can be found in several constructive elements. The constructive elements made out of concrete can be summed up in three main categories:

massive built horizontal and vertical load bearing elements such as foundations and walls, used for small to middle scale buildings, such as residential housing.filigree skeleton construction elements, such as pillars and beams, mainly found in high rise buildings and large scale commercial buildingsspecial construction elements for infrastructural and exceptional building typologies, such as bridges, tunnels, dams or bunkers.

Where is concrete useful?

Nowadays concrete is used in many different ways. All constructive elements can be made in concrete and in most cases they are realized with this material.
But is it really necessary to replace other common construction methods with concrete?
It makes sense to use concrete in constructions, where load bearing elements have to bear big compressive strengths. A high rise a few hundred meters high? A tunnel? A dam? For sure! – There are fields of application, where no other material performs as well as concrete but in many cases concrete is used in small scale projects, where it is unnecessary and over proportioned.

How sustainable is cement concrete?

Concrete is certainly one of the building materials which gives a nearly unlimited range of use. As mentioned before, there are many upsides to using concrete. But there are always two sides of the coin.

A general definition for sustainability is meeting the needs of the present without compromising the ability of future generations to meet their needs. Sustainability is often discussed in environmental terms. It can also be related to two other important topics: society and economy.

Obvious and hidden impacts on our environment

Graph showing global concrete emission percentages
Pie chart comparison between countries CO2 emissions and cement production

The impact on our environment caused by the cement industry and by building with concrete is enormous. The production of cement is a high energy consuming process. This energy is mainly obtained from fossil fuels or burning waste [14] In addition the chemical process of producing cement releases one molecule of carbon-dioxide per each molecule of calcium silicate hydrate. For each ton of produced cement, one ton of CO2 is emitted just by chemically processing it [15] Besides the vast amount of carbon dioxide emitted, many other hazardous air pollutants such as NOX or PM10 are emitted during the process. [16]

Cement is just one part of concrete. The added aggregates, such as gravel and sand, are mined in humongous amounts to cover the demand of concrete industries. Many environmental systems are suffering from negative effects such as land loss by erosion, destruction of natural habitats, sealing and contamination of soil. Some of these aggregates, especially sand, have to be shipped around the world to service demands. [17] Just to give a short glimpse of one of the biggest cruxes in world of the concrete industries – new developing middle-east states, such as the United Arab Emirates or Qatar have to import big amounts of sand to service their huge demand in building industries, despite the fact that cities like Dubai or Qatar are located in the middle of sandy deserts. [18] However, not all of the sand we can find on the globe is suitable for concrete production; desert sand is too fine and round to be used as an aggregate. [19]
Furthermore, concrete production is a thirsty industry. It needs almost 10% of annual industrial water withdrawal, and 75% of the concrete production takes place in regions which are already facing water stress and drought. [20]

Beside this, the impact on society has to be emphasized. The internationalization of architecture and modern building technologies have a negative influence on vernacular building technologies and local architecture. New buildings tend to be built in a modern way with modern materials, such as concrete. Cost efficiency, the establishment of new building technologies and the time aspect are reasons for a significant decrease of traditionally built projects. 

Impact of globalization and industrialisation on building traditions.

Diagram showing concrete accounts for 66% of building materials
Comparison between the use of concrete and other building materials

One of the main issues caused by that situation is the loss of building knowledge and traditions. Traditional building techniques are being replaced by modern approaches. Around the world, houses and cities have been built according to local tradition for centuries. Now, knowledge that was gained in a long and enduring process is about to get lost in a few decades. 

Main drivers for the loss of vernacular architecture are caused by the growing globalization and industrialization of the world. Innovations in building technologies can be spread easily around a fully connected world. Rare materials not locally available can be easily shipped from anywhere – and they get transferred in humongous amounts around the planet. 

Downcycling cement concrete

The economic sustainability of concrete is always mentioned as a big pro. Nonetheless there are a few facts which are not properly taken into consideration. The production of concrete is cheap in comparison to other materials. A main reason for this, is that the aggregates you need to mix concrete are available in large quantities almost everywhere around the planet. But in recent times the local availability of certain components, such as sand are diminishing. [21] Our resources on the planet are finite, so using and monetizing resources as if they are infinite is unsustainable. To address this, the concrete industry tries to emphasize their product as recyclable, but to make it clear – concrete is not recyclableRecycling means, returning a material into a previous stage of a cyclic process. In case of the mentioned material, this is not completely possible. During calcination, the processing of the raw resource of limestone comes to a point of no return. Once cement is made, the process is irreversible. There is no commercially viable process to recycle it.[22] Recent reusing methods of concrete consist of shredding it and mainly using it as gritting material for infrastructural projects. In some cases this crushed concrete can be used as an aggregate to partly substitute gravel in concrete. Nevertheless these substitutes are small in numbers and in the end new concrete still requires additional water, cement, sand and gravel [23] Technically, the recent approaches to recycling concrete can be better named downcycling processes or a kind of mitigation. Many experts criticize the bigger potential of reusing shredded concrete for new concrete projects, [24] an effort which should be broadened in the future. 

Contradictive durability of concrete structures

Many proponents often mention concretes’ durability as a big pro. The use of concrete without adding any other materials (such as rebars, made out of metal) technically creates a very durable building material. Despite, most of the applied concrete is reinforced to be able to react on tensile stress. But the application of reinforced concrete in terms of durability is a contradiction in terms. Here nature inevitably can shorten the life span of buildings built out of reinforced concrete. Due to different thermal expansions and the inevitable inheritation of oxidation of the used steel rebars, concrete constructions suffer fast deterioration during their lifespan. Recent studies have shown that there is a 50% chance of reinforced concrete structures to not fulfill their service in terms of load bearing after just 35 years of use. [25]

What can be used instead of cement based concrete?

Concrete as a kind of fluid stone has found use in all fields of construction. But is it always necessary to use concrete? There are new materials and also tried and trusted methods of building which have mostly been replaced by concrete solutions. The replacement of conventional portland cement based concrete can cut greenhouse gas emissions and other environmental impacts significantly. Basically there are two main ways to avoid a humongous use of classic portland cement based concrete. The first one is to substitute or avoid the most polluting ingredient of classic concrete, portland cement. In a second scenario different building approaches with alternating materials or other building techniques can be applied.

Cement substitutes

First of all, portland cement based concrete mostly can be substituted by pulverized fly ash (PFA), which is a side product of coal burning processes. Another substitute with a big potential is Ground Granulated Blast-furnace Slag (GGBS), which is able to replace portland cement up to 90%. GGBS substituted concrete sets more slowly than concrete made with ordinary portland cement. The higher the amount of GGBS in the cement mix the longer it takes to cure. Besides this, a positive side effect of using GGBS substituted concrete is that it continues to gain strength over a longer period leading to improved overall durability and life expectancy. [26] Nevertheless the mentioned substitutes are by-products of other industries, such as coal, steel or aluminium production, which also have an enormous negative impact on our environment.

Green concrete

During the last decade several scientists started working on green alternatives for concrete. The most advanced approaches use micro organisms such as algae, bacteria or fungi for biocement production (CaCO3) by using the metabolic activity of these microorganisms. [27,28] Some of these bioproducts achieve similar specifics as classic portland cement and present a feasible and viable alternative to conventional portland cement based concrete.

lternative construction methods

Besides an ingredient-related replacement of conventional concrete, there are many tried and trusted construction methods which were applied in vernacular building styles and local architecture traditions. There is no convincing evidence that justifies concrete as the ultimate building material for most building tasks.

This table aims to present a series of more ecologically friendly solutions for common uses of cement concrete:

construction elementclassic building material
to be replaced / substitutedeco friendly alternative (not exhaustive)foundationsreinforced concretetyre foundation (for point foundations) [29]
gabion foundations [30]pillarsreinforced concrete
steelwooden constructions (bamboo, pine, GLT – glue laminated timber)
cardboard tubeswalls(reinforced) concrete
bricks
steel sandwich panelswooden constructions (CLT – cross laminated timber, framework constructions)
rammed earth (clay)
hempcrete
bricksflooringcement based screedclay 
wooden planks roofsreinforced concrete (flat roofs)
steel sandwich panelswooden constructions
thatched roofs
green roofs
hempcretepathingcement based pavement
asphaltnatural stone :
cobblestone, granite plastergypsum based plaster
cement based plastercardboard + lime plaster [31]
hempcrete plaster
straw clay based plaster

Conclusion

Concrete plays a major role in building industries. The further development of newly industrializing economies with huge demands on concrete are driving the ongoing trend of a growing concrete industry. Beside its advantages and big popularity, concrete brings a lot of negative impacts on global warming, environmental systems, building culture and social city development. It is important to mention that concrete lacks recyclability. The present system around the concrete industry can be summed up as a cradle-to-grave system. Resources are extracted, used and then wasted and dumped or downcycled in the best case scenario. Due to the chemical process, cement, the most important ingredient of conventional concrete, will never be recyclable, which underlines the unsustainability of a whole industry. Its fast and wide availability and low costs in production make it popular for many large scale projects. 

Nevertheless there are recent approaches to develop more sustainable alternatives to the classic portland cement-based concrete by trying to avoid or minimize the use of cementitious components, aiming for a better reusability and recyclability of resources. 

In addition, investigating forgotten vernacular solutions reopens fields of research to move forward to a more environmentally respectful architecture. Stay tuned on our continuous research, on social media and if you can and feel like supporting the initiative, make a small donation on our Patreon! 

Sources

[1] https://www.sciencedirect.com/science/article/pii/B978008034720250023X , opened 12.08.2020

[2] https://www.britannica.com/technology/cement-building-material/Extraction-and-processing , opened 12.08.2020

[3] https://www.screedscientist.com/portland-cement-a-brief-history/ , opened 18.08.2020

[4]  Quantitative Analysis of CO2 Uptake and Mechanical … – MDPIwww.mdpi.com › pdf , opened 23.09.2020

[5] https://diglib.tugraz.at/download.php?id=576a7195cc9f9&location=browse , opened 11.08.2020

[6] 372R-13 Guide to Design and Construction of Circular Wire-and-Strand-Wrapped Prestressed Concrete Structures , 2013

[7] Historic Concrete in Scotland Part 1: history and Developmentpub-prod-sdk.azurewebsites.net › api , opened 13.08.2020

[8] https://www.britannica.com/biography/Joseph-Monier , opened 13.08.2020

[9] https://www.architectureanddesign.com.au/features/list/a-look-at-brutalist-architecture , opened 20.08.2020

[10] http://ecosmartconcrete.com/?page_id=208 , opened 12.08.2020

[11] https://global-recycling.info/pdf/GLOBAL-RECYCLING_2-2019 , opened 11.08.2020

[12] https://www.marshalls.co.uk/gardens-and-driveways/blog/how-to-mix-cement-to-make-mortar-or-concrete

[13] https://diglib.tugraz.at/download.php?id=576a7195cc9f9&location=browse , opened 26.07.2020

[14] https://global-recycling.info/pdf/GLOBAL-RECYCLING_2-2019 , opened 11.08.2020

[15] http://ecosmartconcrete.com/?page_id=208 , opened 12.08.2020

[16] http://ecosmartconcrete.com/?page_id=208 , opened 13.08.2020[1] http://ecosmartconcrete.com/?page_id=208 , opened 13.08.2020

[17] https://www.globalconstructionreview.com/news/shifting-sands-concrete-hungry-singapore-orders-mi/ , opened 28.07.2020

[18] https://www.bbc.com/worklife/article/20160502-even-desert-city-dubai-imports-its-sand-this-is-why , opened 19.08.2020

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[24] https://eu-recycling.com/Archive/22163 , opened 30.07.2020

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Charring Station

by Posted in Concrete Projects

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In the former articles was explained some of the advantages to be found within these ancient  common methods of charring wood. Historically and within many cultures, there are a myriad of charring modalities. In this article you will find adapted and illustrate one of those methods using a small wood burning flash oven that can effectively provide the charring levels needed without overtly case timber that has been dried too rapidly. This leads to reversed stresses; compression stresses on the shell and tension stresses in the core. This results in unrelieved stress called case hardening.[1]) the wood items placed through it. In this article we explain how our charring station is built and how it works. Charring systems like this one have been commonly found in many cultures and this is an adapted version of several of those [2]. It is adaptable, is easy to operate and runs without the use of gas or special tools. All that is needed are some (fire) bricks and scrap wood for fuel.

Counter-intuitively, charring wood has several astonishing advantages without involving any chemicals or additional energy consumption. The idea is to sear the surface of the wood without combusting the whole piece nor damaging the interstitial aspects of the wood so it will not warp over time. Besides giving the material an interesting and unique look, the process leads to a triple protection, all without the need of repeating the process after some time has past:

fire protection – charring the surface starts a superficial carbonation of the material and thus lowers the thermal conductivity. termite and mold protection – charring wood destroys the wood’s nutritional value to insects and fungi.water protection – the enhanced carbonation gives the charred layer a waterproof resistance, as water slips on burned wood like over an oily surface.

The easiest and most popular way to char wood commonly found today is probably with a blow torch. This can work, but regrettably too often performed without the attention to detail not to stress the wood from within. It’s easy and practical,  especially for small or irregular pieces but has to be performed with caution. But when searing many big wooden pieces it is slow and uses a lot of gas. These searing modalities are not to be confused with traditional Japanese, 焼杉 (Yakisugi) which is often misrepresented as 焼き杉 (aka shou-sugi-ban”) [3] – us included, in our previous articles!.

Yakisugi can only be achieved with a limited range of Cypress species found on the islands of Japan[4] and is a very unique process found within several methods of crafting guilds. The most commonly seen being where three planks of wood get bound together to form a long triangle and a fire is started in the resulting tube. There are several other methods, but they are for very specific formats and within context to only yakisugi and not the charing modalities found within other cultures.This technique works well only when you have similar boards, as it’s complicated to set up when boards have different widths and lengths.


Terunobu Fujimori, Tea House, Barbican. Photo Ben Tynegate

The birth of the charring station

This contemporary oven is based on some of the principles of a rocket stove. The main idea is to create a fire within a brick tube, which will become very concentrated and strong due to the tube-generated draft-effect (for more explanation on this and general information, check our articles on rocket stoves). Just over the burning material, where the fire is very strong, there will be small slots on the opposing sides of the tunnel. The wood, which needs to be seared, can be passed easily through the fire and thus be charred fast and safely.

After this oven was created with commonly available materials which enables us to char planks and boards of different sizes in an effective manner. This oven also allows the operator safety by lowering the risk of burning their hands, while also providing more control of searing the wood and less waste of fuels which is then more environmentally friendly.

How does the charring station work


Author: Melana Jäckels

1 – The main part is a L-shaped tunnel. On the bottom it has an opening on the side, where the air goes in and it flows all the way through the tunnel up to the upper opening. 

2 – Right after the curve, the fireplace is based on a second layer. Its bottom has two small gaps for the air to pass and to allow the finer ash to fall.

3 – It is important to have a tunnel that is at least 5 cm wider than the boards you plan to char. If a board fills the whole wide of the tunnel it stops the draft and decreases the fire.

4 – On the same level as the fire is also the stair-like firewood intake. The fire is started and fed from here. It’s important to have a brick to close the firewood intake so it does not disturb the air draft in the moments no wood is inserted.

5 – In the chimney, right above the fire, there are two vertical slots on opposing sides to insert the wood you want to char.

6 – Above the inserting slots the chimney narrows slowly. This is important to not happen in a sudden step, as it otherwise will decrease the draft and create a lot of smoke coming out of every small gap.

Building your own charring station

For our charring station we used 12 big bricks (ca. 29x18x9), around 70 medium-sized, red bricks (ca. 23x10x7) and 5 fireproof bricks (22x10x2). Depending on what is available, numbers and materials might be adjusted. Before starting the building process, it is important to choose a big outside space, which is not too windy and has a relatively leveled ground, with enough space on each side of the station to pass the board through.

Step by step:

First, we made a fire-resistant base which is leveled and flat. For this we used the big bricks

Afterwards we started to build a tunnel for the air intake with dimensions of 90 to 25cm. It is important that it is stable and possible to close with removable bricks on the sides

We covered the tunnel with the red bricks and left two gaps of about 1,5 cm each as seen in the picture. 

The fireplace gets covered with fireproof bricks and the next line of bricks is put on all sides

To protect the walls, we also placed fireproof bricks around the fireplace


The next step is to build the J-shaped intake with steps made of bricks, towards the fireplace. It is important to make sure its height will match up with the next row of bricks


Now it is time to create the slots where the to be charred boards will be inserted. For that we put two bricks flat across from each other. This  station works  well for boards with a maximum width of 16 cm. If you plan to use a roller stand, make sure the height of your slots measured from the ground is adapted to the height of the roller stand)


Above the slots we continued building the chimney in the original diameter for a few more rows, but then we start to become narrower by changing the order of the bricks

In this timelapse video you can see how we built up the station in 10 seconds!

How to use the Charring Station

Before starting, make sure to have the right equipment (fire resistant gloves, a mask, a bucket of water / sand, and a fire extinguisher) and enough material to burn! If you want to char a big quantity of wood it is also quite handy to have rolling stands.

Starting the fire works best when you build a little teepee out of dry kidlings and put some sawdust on it, light up the tip of a rolled paper (A4 is enough), and move it slowly into the directions of the teepee. Besides you can put another burning paper over the chimney, to facilitate the draft-effect. 

To avoid unnecessary interruptions, it is important to have a constant refilling of firewood. As soon as the fire burns strongly, the opening of the firewood intake can be closed and the boards can be inserted through the slots. Inside, the strong and concentrated fire will char the surface of the wood from below and the sides. The boards should be pushed through the fire in small steps to have a satisfying and regular result. After the first part of a board is charred, it can be taken out and pushed upturned through the fire again until both sides are completely charred. If the results are not satisfying, the pace should be adapted. Depending on the size, form and species of the wood it will take its respective time to finish one piece.

Once the board is charred it should be brushed with a metal brush and oiled. As the charring process dries the wood very rapidly, depending on its nature it might have a tendency to crack. The linseed oil will nurture the wood and compensate for this effect. For more information on this see our article on Natural Wood Protection.

Conclusion

We are using this method for a while now and we are super satisfied with the results. Not only we save time but also we are more independent of gas. The work with the charring station is safe and convenient. The station is easily adaptable and can be modified to different dimensions. We are looking forward to using the station in the future and improving it further. 

Check our YouTube video for a step-by-step tutorial how to build up your own station!

We would like to sincerely thank Jay C. White Cloud for his time, valuable input and collaboration on this research.

How to store food outside of the fridge

Sources

[1] Wikipedia “Wood drying”, [Online] available at https://en.wikipedia.org/wiki/Wood_drying (Last accessed in July 2020) 

[2] Jay C. White Cloud [Tosa Tomo Designs] https://about.me/tosatomo

[3] [4] Nakomoforestry “Yakisugi” Or “Shou Sugi Ban”? Learn What You Should Call It, And Why”, [Online] available at https://nakamotoforestry.com/yakisugi-or-shou-sugi-ban-learn-what-you-should-call-it-and-why (Last accessed in July 2020) 

Picture: Terunobu Fujimori, Tea House, Barbican. Photo Ben Tynegate [Online] available at https://www.ben-tynegate.com/tea-house (Last accessed in July 2020) 

The post Charring Station first appeared on Critical Concrete.
Did you miss our previous article…
https://www.thevisualconcretegroup.com/?p=261