Women in South Asia have long been doing intense physical labor in building sites and brick industries for relatively low pay. And, yet it is discouraging to be a part of a heavily male-dominated construction industry. Whenever I passed by a construction site, I felt powerless and afraid of the tools that men carried effortlessly, as if to prove that gender disparity in the labor market exists for a reason. In other words, the construction world felt unattainable in all its toughness.

Image Source: Women at work © The Record Nepal

As an aspiring architect, the dichotomy between architecture and construction seems nonsensical, particularly in the ever-evolving realm of sustainable architecture, where prototyping and experimenting are at the core of design processes. There is also an assumption that architects are above construction workers – a dynamic that sustains social and class imbalance. While there are many structures to criticize about, luckily, there are also associations like Critical Concrete who facilitate three-weeks of intense, hands-on workshops to understand the material, building techniques, and teamwork as part of the post-graduation course in sustainable architecture. The workshop positively shifted my perspective of the construction industry and further expanded my own personal boundaries.

“Let’s get our hands dirty!” architect Hanno Burtscher, instructed a team of ten women who came from different professional backgrounds, race, and geographical locations. Hanno introduced himself as an earthman, with an Austrian sense of humor, quick wit, and great teaching style, he grouped students in pairs to use all four senses except for sight to identify the local materials used for raw earth construction. This is how the welcome ceremony to the workshop began and it had already set a higher bar for the rest of the workshop. The joy of sharing stories moved the conversation from endless banter about cheese and food to serious topics like what sustainable construction means and how the uncertainty during the time of pandemic has affected our lives. In short, the day exuded a sense of togetherness. 

*Sketch by Charlotte Schneider, Alumni, Post Graduation 2020-2021

WEEK 1 | RAW EARTH CONSTRUCTION | HANNO BURTSCHER

The first week of the workshop was a battle – a battle to make proper earth mix to build a heated earthen bench and flooring for the kitchen at Critical Concrete. From the start, we learned that the key components of earth mix are clay, small gravel (0-5 mm), big gravel (5-15 mm), sand (0-4 mm), and water.

Most of us were already aware of the composition elements through our Raw Earth online course, but what made the difference in the practical workshop was the experimentation and improvisation in the mixing process since the excavation materials were available in limited amounts. The question constantly surfaced during the workshop – how do we make the most use of what is available around us? And this was a revelation in itself because theoretically, we learn the ratio – 40% of excavation, 20% of small gravel, 20% of big gravel, 20% of clay, and water – to achieve the desired mix. 

In practice, however, there had to be adjustments in the ratio based on the materials that were available to us. The way we integrated the composite materials together also made a big difference in the quality of the earth mix. So, at times we had to find creative ways of using what was available to us.

“While nearing the end of the earth mix for the floor, we ran out of the large size rocks. My typical mindset is to say, “Let’s just go buy more.” However, with the mindset of Critical Concrete to use what we already have, we were not going to buy more. To finish the mix, we scrounged throughout the construction yard looking for proper sized rocks and were able to get the right volume,” Mary shared her experience. And this was the general experience during the workshop – how to find sustainable solutions when we hit a roadblock.

In our earliest days of the workshop, we dropped a fist-sized earth mix balls from 1 meter height to see whether they stuck together or crumbled. We concluded that the ball should drop in larger pieces rather than completely shattering or sticking together. If it’s too sticky, either the clay or water content is too high which will result in a mixture that won’t be suitable to create a form. The same logic applies for the dry mixture as well. After a process of trial and error, we realized that there was no concrete recipe to achieve the perfect mix. But there were a number of factors that determined the quality of the mix. One of them is the clay content, which is normally 20 percent in total but depending on the situation, it could range from 5 – 30 percent. The purpose of the clay is to bind the materials but the more surface area we have in the mix, the more clay we require, from which we can derive that the smaller the surface area of excavation, the higher clay content would be required to bind it. Simple physics!

Many construction sites are not inviting spaces for women. Women’s work is often considered too frivolous to the degree that they are rendered valueless in the number-driven capitalist economic system. During the workshop, this dynamic was challenged. A team of mostly women and Hanno prepared the foundation for raw earth flooring and built the formwork for the bench. As I was lifting heavy stones and using power tools, I occupied a space that was not ‘normalized’ for women. I quickly realized that the problem wasn’t these too feminine, delicate hands but rather it was the devaluation of women’s work that put women in confinement of patriarchal ideas.

“We either put 100 percent into this or we don’t do it at all,” Hanno remarked while we were putting earth mix into the form work. The workshop was fueled by this exact mindset but was also filled with laughter and leisure in between our hard work. Overall, during the first week with Hanno, he guided us by observing the way we were interpreting the materials. We were able to experiment with the materials and make decisions based on our judgement.

Week 2 | Esposende Building Site | Hugo Dourado, Pietro

Degli Esposti, Martina Eandi

Esposende was roughly a forty-minute drive away from the city of Porto. And when the drive is long, conversations of past, present, and future start bouncing around.

“How do you say it?” Bara from Czech Republic asked.

“Vastu Shastra,” I repeated.

“And that means harmony of energy through design? That is how I would like to design the interior of my place one day,” remarked Charly from Germany. 

The conversation moved in such a way during the Esposende trip. The practical workshop as a part of the post graduation course merged people with similar ideologies, dreams, and passion of bringing social and political change through architecture and urban planning. The workshop also meant more than fulfilling a part of the course. Some of us had flown miles away leaving their usual life to come to Portugal to venture in a new journey.

*Sketch by Charlotte Schneider, Alumni, Post Graduation 2020-2021

The building site was under construction, so there were different tasks that the students could choose from such as fixing the board and batten cladding system, wood charring station, tiling the roof, or constructing a rocket stove.

The name rocket stove in itself made me curious. On top of that, I had also done some research on rocket stoves in one of the Participatory Design courses. I started my second week with Pietro, our Raw Earth course instructor and Martina, Mycelium course instructor, to complete the stove that could be used for both cooking and heating the entire house.

The making of the rocket stove involved lots of earth mix, it didn’t involve knowing rocket science at all. First, a stone wall had to be built to lay an exhaust pipe with an inclination of 30 degrees. The purpose of this was to carry the smoke from the rocket stove out of the house. For the stone wall, we prepared Argamassa (mortar) to attach stones of many sizes together and this alone took days to finish. As soon as the wall was completed, we started to make the exterior of the rocket stove with earth mix. The earth mix was ¼ part lime, 2 ½ part excavation, and ½ part straw. Since we were working with materials that were locally available, the excavation we were using included large stones. We wanted the mix to be a combination of lime, earth, and straw, so we sieved the stones out.

At times building with raw earth felt like cooking, in a sense that there is a process to achieve the result. You cannot skip a part to make the process faster, there is a procedure that you must follow otherwise the mix will not be suitable for construction. Therefore, while making the earth mix, it is important to completely let lime and excavation combine before putting any water. Once lime and excavation are completely mixed, giving off a grey-brown color, you slowly add water and straw to make a mixture. We used the cob technique to compress and compact fist sized balls, smashing it to attach them onto the pre-existing walls.

Slap slap slap!! We were hitting the earth mix on the side with a board to pack it down together. Another important thing that Pietro shared with us was that the cob technique allows us to build 30 cm per day. Since the earth mix is massive and wet, it needs time to dry and be compacted to build another layer on top of it. To keep the layers of earth mix interconnected, we created a vertebra-like structure at the end.

​​The rocket stove workshop made me realize how earth as a material is flexible. I could mold it in any shape I wanted and working on it with hands felt therapeutic. With the rocket stove, we were trying to achieve a dome shaped exterior to give it a character of its own. We molded the earth mix into long tiny sausages to create a curve on the upper part of the stove. It was interesting to see how earth could be shaped into any form with the right formwork which is also one of the big advantages of working with this natural material.

Life on Site

The Esposende building site was located between the ocean and mountains. In the early morning, you could see the tip of the mountains covered in fog and in the late afternoon during those early hot, summer days, you could see the blue ocean in the distance. With our cup of coffee that the Critical Concrete team prepared for us every morning, the day started with division of tasks and the students always got to pick first which task they wanted to be involved in.

After our coffee we all got into the groove and the site came to life again. Some of us were carrying heavy stones, using power tools, hanging on the roof putting tiles while others were listening carefully to what Hugo, our Vernacular Architecture course instructor, with immense knowledge and a sense of perfection, had to teach about board and batten cladding systems. It was fascinating to observe how everybody worked individually and in teams and clearly I wasn’t the only one who thought this. The neighbors in Esposende would walk by observing, commenting on our work, with their hands clasped behind their backs!

“It’s called umarell in Italian,” Linda shared jokingly.

Apparently, in Italian slang, umarell is when elderly people gather to observe construction sites and comment on how to do the work, often with holding their hands behind their back.

I became a umarell when it came to food. The Critical Concrete team prepared big batches of healthy, colorful vegan food during lunch time and we would all observe in awe. The variety of food made from simple ingredients that Critical Concrete provided us inspired me to be creative with food that we eat on a day-to-day basis. How many times do we actually think about eating in a sustainable manner? How do we creatively use leftover food in our diet? These questions among many others helped me unlearn and learn new ways of looking at sustainability.

Week 3 | Furniture Workshop | Samuel Kalika

I noticed how different building materials can be. Whereas with raw earth, exactness is not so important, with wood each millimeter is important. Building beautiful furniture requires many steps, patience, and exactness,” Viviana shared. After working with flexible material like earth, wood seemed like unlocking a whole different dimension. Samuel, our Participatory Design course instructor, understood this well and he made our work easier by giving us instructions on every powerful tool we were using.

Precision was the key. While cutting wood, if it’s 1 cm off, what could we do? We could not undo a cut once it was made neither could we adjust it, so a big part of the furniture workshop was to find a solution on the spot. We used many different tools to achieve the desired finish and construction: a universal machine to obtain desired thickness, sizes, flatness, and straight surfaces; the meter saw; the sander. Gradually the counters for the kitchen in Esposende house began to take shape. “As soon as I started approaching the work, I understood the importance of being precise in all the small details. Once we developed a good flow in the process, the work became easier and faster,” commented participant Linda Tonin.

*Sketch by Charlotte Schneider, Alumni, Post Graduation 2020-2021

While trying to achieve precision, mistakes are bound to occur but this is part of the learning process and that made the experience lighter and took away the fear of judgment. 

“To assemble the pieces, in particular for the bigger elements, we set up a strategy, naming the pieces of wood and measuring the different thicknesses needed for the joining beams. Since different people worked on the cutting process, sometimes the joints’ holes had different sizes. We took these mistakes as an occasion to add different colors of wood to fill the spaces: the mistakes, at the end, added aesthetic value to the furniture pieces,” Linda reflected.

REFLECTION

During the whole workshop, each one of us were sharing our experience of working in different environments. We were trying to understand what our preferences are, what materials, tools we like to use, and which instructors’ teaching style catered to our learning approach.

“Beyond the excitement, time passing and the verge to finish, it was necessary to maintain a safe working space, making sure you and everyone around is comfortable and don’t cause any danger. Having this in mind, I learned how to remain calm and careful with all the tasks, machines and my colleagues. This atmosphere brought a lot of awareness and future-thinking into my habits,” Agnieszka described her experience.

“Starting with the fact that the workshop took me out of all my comfort zones, I can say that the first learning was that the “unknown” can be very good. And the learnings went beyond practical. Being in contact with such an international and so human team certainly awakened in me my best version, my confidence in a more correct and viable future and made me reflect and work on my limiting standards. It was definitely a great achievement to be in a healthy work environment,” shared Júlia.

I resonate with both Agnieszka and Júlia. My experience with working in a group was liberating. It taught me how everybody in a team works differently — how each individual works, thinks, coordinates and cooperates while working on a project. On top of that, our group was very diverse, so learning from each one of them and getting to interact with everybody in-person felt special during this uncertain pandemic time. We were able to transfer our expertise and learn from each other’s skills. At the same time, we were a group of women doing construction work, realizing our own potential and that was empowerment in itself.

On a personal note, the workshop also altered my relationship with the construction industry and my perception of emancipated women. Historically, women have existed within the confinement of domestic space therefore women who occupy space outside of the predictable situations are labeled ‘modern’. And if the working conditions are healthy and their work is comparable to the status of a male, they are given recognition and visibility. But are all women able to get the same visibility and prestige as the emancipated, educated women? Women from lower class and caste in South Asia have been working in extreme conditions in construction sites and brick factories out of economic necessity. They have to go through daily work toxicity in a largely male-dominated workplace. While reflecting back on the practical workshop, I realize the utter importance of an equal workplace environment in the labor industry and greater recognition of those women who have paved the way.

The post An SSA student’s perspective on working in construction and practical workshops appeared first on Critical Concrete.

Did you miss our previous article…
https://www.thevisualconcretegroup.com/?p=341

While you’re in the planning stages of your latest project, have you considered the benefits of onsite mixed concrete? If not, let us explain!

Budget

One of the great benefits is the amount of control that you have if you opt to use on-site mixed concrete. You see with this method you will receive the exact amount and mix of concrete that you require. As a result, you are controlling your budget by only paying for the amount you use. It avoids having loads of unused concrete hanging about!

Consistency of Concrete

Using mixed on-site concrete supply allows you more control over the consistency of the concrete. This is because, with the volumetric mixers that will be used, the materials that go into the concrete are kept separate until the batching process. This will mean you would be able to pick an exact consistency that would suit your needs.

 

Say, for some reason the consistency required changed halfway through the project, have no fear, as it’s on-site, this can still be altered! The great thing is the logistical advantage-you have when the concrete is delivered directly to your site. You will find that many companies offer next or even same-day delivery.

Fresh Concrete

That points us to another mixed concrete benefit. If you have the supply on-site, you’re providing your team with access to constant fresh concrete. When it comes to the pouring, it is always fresh. There are times when a delay may hit your project but that cannot be helped, and the fact you can keep the concrete fresh is a massive bonus.

 

Do note that if traditional drum mixers are being used, these can be impacted by delays because of their need to transport pre-mixed concrete in a drum from the yard to a site, meaning there is a chance it could go off. But with a mixed onsite service, there will be the option to change or extend the order on the spot, because the concrete providers will be able to produce the exact type of concrete needed-fresh!

Reduced Waste 

Keeping with the notion of how much more control you have with this concrete set up when it comes to on-site mixed concrete it is easier to scale your needs in relation to project size. Working on a very large site? You would benefit from volumetric mixers as these can hold up to twice the amount of the traditional drum mixers. Or perhaps it’s more of a smaller project? Likewise, on a small site, the mixers can produce smaller volumes with ease. This helps you to have the amounts you need and cut down on waste in the process.

Regarding quality, all the best onsite mixed concrete services will make sure to be providing you with concrete that is made from only the finest materials. Also, keep in mind you will be able to have the mix tailored to suit your needs, so if you require a tougher mix that can be made up or something more workable can also easily be fixed up, no issues.

 

If you agree that onsite mixed concrete is the way to go for your project, Base Concrete can help. Thank you for reading this blog post. If you are looking for anything to do with concrete, Base Concrete has you covered. Call today on 01442 389105 or visit our contact page for more details.

The post Benefits of Onsite Mixed Concrete first appeared on Base Concrete.

Depurating Landscape: an introduction to plants as a water treatment alternative

This article is a collaboration between Degré47 and Critical Concrete, aiming to be an introduction to phyto purification’s general concepts for self-constructors. It also aims to shed light on these systems as low-cost, low-tech and self-constructible wastewater treatment solutions. 

The wastewater issue 

It isn’t new to argue that the disorganized and centralized population growth in urban areas has brought challenges to the natural environment. In addition to CO₂ emissions, waste production and impermeabilization of soil, wastewater is one of the fundamental issues local governments need to address. At the very least, the wastewater from human activities of any sort needs to be treated to be assimilated by nature. 

There are many water treatment solutions, from the collective to the individual scale. One of the most common sanitation solutions in urban centres is a collective one: wastewater treatment plants. These centres manage the wastewater through physical, chemical and biological processes in a complex and highly specialized infrastructure. [1] 

After the physical filtration through decantation, flotation, filters and/or membranes, traditional treatments commonly make use of chemical products, notably coagulants (ferric chloride, aluminium sulphate, etc.), flocculants, and sometimes disinfectants such as chlorine or ozone. These processes, however, are arguably costly and energy-intensive, not to mention polluting. They also necessarily generate by-products such as coarse waste, sand and sludge that must be cleaned, decanted, stabilised and treated. [2] 

In addition, in the ever-growing urban centres, many areas aren’t able to access the public sewage system, bringing up the importance to think of alternatives for wastewater treatment, especially low-cost and low-maintenance ones, as the mismanagement of effluents can pose a serious issue to natural hydric resources. [3]

Individual or small-scale collective sanitation solutions might be a good way to tackle the situation. A solution that stands out is the phyto-purification system with its low energy and low maintenance (as there’s no need for emptying and transporting). It is already the main sanitation system in France for cities of less than 1,000 inhabitants. [4]

This system, which is based on the use of plants (phyto) to filter the wastewater has been proving to be a low-cost yet highly efficient way to treat domestic wastewater. Because it is energetically and logistically autonomous, phyto-purification can be considered an ecological sanitation solution. 

Purification with plants 

Phyto-purification consists of wastewater purification systems that make use of aquatic plants, reproducing water depuration processes typical of humid areas. There are two main methods of phyto purification: lagooning, which consists of ponds with microphytes, similar to natural wetlands, and the filters planted that make use of macrophytes and consist of ponds filled with aggregates in which the water circulates for treatment. [5]

In these systems, the plants are responsible for bringing oxygen through their roots whereas the aggregates act not only as a physical filter — as bigger particles can’t penetrate it — but also as a chemical filter as they absorb phosphorus and ammoniacal nitrogen. In these basins, an important biological process also occurs: the microfauna present in the system degrades organic matter, turning it into nutrients to be absorbed by the plants. [6]

The interesting aspect is that, although the name might indicate, the wastewater is not filtered by the plants. In reality, the plants are the key element to create the environment for bacterial activity, especially in the region around the plants’ roots. The plants greatly benefit from the system as it absorbs nutrients that are liberated in the process of depuration. It’s a symbiotic relationship.

The different methods

There are two groups of phyto purification systems that can be used according to different needs and types of wastewater: lagooning and filters planted. [7]

Lagooning 

This system makes use of microphytes (small aquatic plants), microorganisms and (sometimes) substrate to control water pollution. Its main characteristic is the resemblance with natural wetland areas in which the majority of elements are saturated, i.e submerged in water. [8] 

In this model, the main purification process occurs on the aquatic surface where the plants and the bacteria present in their roots are located.  In this solution, the effluent is continuously supplied and homogeneously distributed on the surface, flowing horizontally and superficially at low scooping velocity. The water is then collected by a drainage pipe located in the basin’s bottom. [9]

It is important to stress that in this solution, the substrate is not a requirement, and when not applied, fluctuant aquatic species should be used (see image 1). [10]

 

fig. 1: Different types of plants

 

Because there’s no emphasis on physical filtration with a substrate, this solution requires a previous treatment focused on the removal of organic matter and suspended solids as it mainly targets the removal of nutrients, especially phosphorus by the plants and bacteria. [11] The use of a substrate, however, can be beneficial if residual suspended solids end up in the basin. 

This is a cheap and very low maintenance option, however, it generally requires a larger area than other methods. 

 

fig. 2: surface flow filter with substrate and emergent plants 

Filters planted 

In this model, the system works through percolation, meaning the wastewater infiltrates the substrate in the process of purification. Here the substrate can be saturated or not. [12] 

In this system, the water flows under the surface of the planted bed, through the pores of the substrate. There are two subsurface models: the horizontal flow filter and the vertical flow filter.

 In the horizontal model, the flow can be operated in a continuous input, intermittent or even in batch mode whereas the vertical flow model requires intermittent dumping of water in short periods, followed by long resting intervals. 

 

fig. 3: subsurface horizontal flow filter

The long periods between inflow in the vertical flow basin results in a high rate of oxygen transfer from the atmosphere to the system. In aerobic conditions the nitrification can occur, potentiating the nitrogen. In the horizontal flow basin, the poor levels of oxygen favor the occurrence of denitrification by anaerobic bacteria. [13]

 

fig. 4: subsurface vertical flow filter

In some cases, both flows can be combined to enhance the system’s performance. That’s the case of the double planted filter method applied by Kevin Quentric and documented and published as a tutorial by low-tech lab. [14]

It consists of two different units with a vertical and a horizontal water flow that perform complementary tasks in the process of depurating the wastewater. 

 

fig. 5: section of double filter planted 

The first phase of this system is a 60-80 cm² deep vertical filter (VF) which is divided into two parts and each part takes turns receiving the raw sewage (wastewater without previous treatment) from above (see fig. 6). The wastewater spreads on the surface of the first filter and has its solid particles such as hair, fat, faeces, etc, drying and decomposing on the surface whereas the water infiltrates downwards until it reaches the gravel layer. It might sound like the perfect recipe for a smelly garden but, as Kévin explained in emails to us, in a nutshell, bad smells occur in warm, low oxygen environments, when the water stagnates and fermentation takes place. In this double filter planted, however, the vertical filter is in open air, meaning it’s fairly oxygenated. The coarse material retained on the surface of the sand dries out and compost whereas the wastewater quickly infiltrates, without time to ferment. For this, the occurrence of smells is rather rare. 

After the percolation, the water then is collected by a drain in the bottom of the VF. This phase of the process is aerobic: the bacteria present in it require oxygen to mineralize the organic particles making the compounds absorbable by the plants. 

 

fig. 6: plan of double filter planted

The second part of the system, the horizontal filter (HF) is 60cm deep, filled with gravel and water 10 cm below the substrate. The second filter is then a poorly oxygenated environment, in which anaerobic bacteria live. These bacteria perform the important task of denitrifying the water by extracting the oxygen from the nitrate molecules, turning them into dinitrogen.

Another interesting aspect is that this system is energetically autonomous. For that, it relies on gravity: each stage into the water purification is lower than the previous one so the water can flow without the use of pumps. 

The step-by-step for this method can be found on the low-tech lab site. [15]

Pretreatment

In the double planted filter by Kevin Quentric there’s no need for primary treatment and the raw sewage can be discharged directly on the first filter. In some models, however, pretreatment is required before the wastewater discharge for removal of coarse particles and settleable solids in order to prolong the useful life of the systems, minimising the occurrence of clogging. 

The specific type of pretreatment depends on the type of sewage and on the chosen method of phyto purification. Some of the primary treatment methods are:

Screening: This is typically the first step, especially for surface flow filters. Screens are used to remove large debris. [16]Oil removal by decantation: The method is based on injecting fine air bubbles into the grease tank, allowing the grease to rise quickly to the surface (grease is hydrophobic). [17]Sedimentation: Water is typically retained in sedimentation basins for at least 4 hours, allowing particles to settle out. [18]

Domestic phyto-purification

The management of wastewater is of extreme responsibility but depending on which system is chosen and the knowledge of the builders, self-construction is an accessible and plausible option. In addition, professionals in the field can provide help for those seeking to build their own phyto-purification system at home.  

When planning a phyto-purification system, some things must be taken into consideration, such as sizing, site and botanical species. 

Choosing a site

Ideally, the system should be located as close as possible to the sewage outlet. Remember to make sure the system works with gravity by building it on a slope or working with built and excavated basins. Earthwork is also an option but it might significantly increase the costs of the construction. In the elected site for construction, the soil should be sufficiently compacted to minimise groundwater infiltration and should be above the water table and floodplains.

Another aspect to have in mind is that phyto purification requires space. The site of construction should be of sufficient size to meet current and possible future expansions. Also, insects (especially on surface flow models) and, very rarely, odours can pose discomfort. Therefore, make sure the system is not too close to your and/or the neighbour’s house.

Lastly, the site should be very accessible to construction and maintenance machines and vehicles. [19]

Sizing

The dimensions of the system should be calculated by maximum capacity and a good way to do so is using the value of “inhabitant equivalent”, which relates to the house’s number of rooms and not to the number of inhabitants. In this model, each room of the house = inhabitant equivalent (2 to 4m²). [20]

Plants

To choose what species should be used, a few criteria need to be taken into consideration such as main pollutants to be removed; climatic conditions and local availability of species. They can be emergent, fluctuant or submerged species (see fig. 01). [21] 

In Europe, the common reed (Phragmites communis) is one of the main wetland plant species used for water treatment, especially on subsurface flow filters. Some examples are Caltha palustris,Veronica beccabunga and the Typha latifolia. 

fig. 7: Phragmites communis, Caltha palustris,Veronica beccabunga and Typha latifolia, respectively.

When the water goes through a pretreatment basin, the plants in the filter basin can be less resistant. Some examples are the Sparganium erectum, Alisma plantago and Iris pseudacorus. [22] Before mixing different species in the same basin, research about possible interactions between the species and if there is competition between them.

fig. 8: Sparganium erectum,Baldellia ranunculoides and Iris pseudacorus, respectively. 

It’s advisable to transplant seedlings of plants that have been removed from a nearby location, which are naturally more adapted to the local climate and to do so in the rainy season, in order to minimise conditions of hydric stress for the plants. Plant the botanical species between 20 to 30 days before starting the purification system so there’s time for biological adaptation of the plants to the new environment. 

Considering phyto purification

Phyto purification systems are economically efficient solutions. It is estimated that however the initial cost can be elevated (6.500 euros on the hybrid solution by Kevin Quendric, for example), these water treatment systems pay for themselves in about fifteen years time as they do not require electric energy nor maintenance by a qualified workforce. 

Unlike conventional purification systems, phyto purification can support insects, birds, amphibians, contributing to the local biodiversity. The lack of chemicals makes the system an environmentally-friendly option available for water treatment. 

In addition to environmental and economic upsides, planted filters can be a beautiful landscape project as it has an undeniable aesthetic value. A symbiotic relationship can emerge. The wastewater produced every day by humans is rich in nutrients valuable for certain plants of every shape and colour. 

[1] Dias, Richardsson Mendes. (2019) Eficiência da Fitodepuração como Alternativa de Tratamento de Águas Residuárias: Um Estudo de Caso. Teresina:  IFPI

[2]https://www.build-green.fr/phytoepuration-creer-un-filtre-plante/doing_wp_cron=1617567011.8170158863067626953125, accessed 4 April, 2021.

[3] Ibidem

[4] https://wiki.lowtechlab.org/wiki/Phyto%C3%A9puration_eaux_us%C3%A9es, accessed 5 April, 2021.

[5] https://www.lenntech.com/phytodepuration.htm, accessed 5 April, 2021.

[6] http://www.graia.eu/en/our-activities/phytodepuration-and-lagooning/, accessed 5 April, 2021.

[7]https://www.build-green.fr/phytoepuration-creer-un-filtre-plante/?doing_wp_cron=161756 7011.8170158863067626953125, accessed 6 April, 2021.

[8] Ibidem

[9]https://www.researchgate.net/publication/326352770_Manual_de_sistemas_de_Wetlands_construidas_para_o_tratamento_de_esgotos_sanitario_implantacao_operacao_e_manutencao, accessed 6 April, 2021.

[10] Ibidem

[11] Ibidem

[12]https://www.build-green.fr/phytoepuration-creer-un-filtre-plante/?doing_wp_cron=1617567011.8170158863067626953125 , accessed 8 April, 2021.

[13]https://www.researchgate.net/publication/326352770_Manual_de_sistemas_de_Wetlands_construidas_para_o_tratamento_de_esgotos_sanitario_implantacao_operacao_e_manutencao, accessed 8 April, 2021.

[14] https://wiki.lowtechlab.org/wiki/Phyto%C3%A9puration_eaux_us%C3%A9es, accessed 8 April, 2021.

[15] Ibidem

[16]https://www.sciencedirect.com/topics/earth-and-planetary-sciences/water-purification-plant, accessed 9 April, 2021.

[17]https://www.build-green.fr/phytoepuration-creer-un-filtre-plante/?doing_wp_cron=1617567011.8170158863067626953125, accessed 9 April, 2021.

[18] https://www.sciencedirect.com/topics/earth-and-planetary-sciences/water-purification-plant, , accessed 11 April, 2021.

[19https://wiki.lowtechlab.org/wiki/Phyto%C3%A9puration_eaux_us%C3%A9es, accessed 11 April, 2021.

[20] Ibidem 

[21] https://www.researchgate.net/publication/326352770_Manual_de_sistemas_de_Wetlands_construidas_para_o_tratamento_de_esgotos_sanitario_implantacao_operacao_e_manutencao, accessed 11 April, 2021.

The post Phytodepuration with Degre.47 first appeared on Critical Concrete.
Did you miss our previous article…
https://www.thevisualconcretegroup.com/?p=296

Looking for an alternative, sustainable way of practicing architecture? Apply now for our Postgraduate!

jQuery(function() { _initLayerSlider( ‘#layerslider_20_1ugfk8lm0d267’, {createdWith: ‘6.11.2’, sliderVersion: ‘6.11.2’, skin: ‘v6’, navPrevNext: false, hoverPrevNext: false, navStartStop: false, navButtons: false, showCircleTimer: false, skinsPath: ‘https://criticalconcrete.com/wp-content/plugins/LayerSlider/assets/static/layerslider/skins/’}); });

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: 

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?

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 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

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.

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

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

[20] https://www.nature.com/articles/s41893-017-0009-5.epdf , opened 26.07.2020

[21] https://www.globalconstructionreview.com/news/shifting-sands-concrete-hungry-singapore-orders-mi/ , opened 29.07.2020

[22] CSI-RecyclingConcrete-FullReport.pdf , opened 29.07.2020

[23] https://www.archdaily.com/933616/is-it-possible-to-recycle-concrete, opened 30.07.2020

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

[25] https://www.structuremag.org/?p=9459 , opened 18.08.2020

[26] https://www.greenspec.co.uk/building-design/concrete-cement-substitutes/ , opened 25.08.2020

[27] https://www.mdpi.com/2071-1050/10/11/4079#abstract , opened 25.08.2020

[28] https://www.sciencedirect.com/science/article/pii/S2215017X18302923 , opened 25.08.2020

[29] https://criticalconcrete.com/tyre-foundations/ , opened 25.08.2020

[30] http://bristolgreenhouse.co.uk/site/foundations.html , opened 25.08.2020

[31] https://criticalconcrete.com/out-of-the-box-vol-3/ , opened 25.08.2020

The post The reality of concrete first appeared on Critical Concrete.
Did you miss our previous article…
https://www.thevisualconcretegroup.com/?p=265