1
Your book begins by taking the reader along with you, Alia, into the heart of the Algerian Sahara. Was it having your feet in the sand that led you to start questioning concrete?
I begin this global narrative with a personal experience. During a journey to the Algerian Sahara, specifically in the palm grove of Timimoun, a client approached me to design a guesthouse in the heart of the oasis. Upon discovering the site, I immediately felt uneasy about building there. Construction projects were proliferating, and concrete blocks were gradually replacing adobe bricks— earth used for centuries in the region and in the world. It seemed evident to me that, in this environment, adobe remained a far more suitable material.
I also became aware of my own limitations: I had never been trained to work with this material. During this stay, I discovered its qualities—its ability to be endlessly recycled, to regulate humidity and indoor temperature. It is surprisingly cool inside an adobe house.
I then tried to find a mason who still knew how to build with adobe. But the people I met tried to dissuade me: « Earth is for the poor, » they told me. They offered me concrete blocks instead, presented as more solid and modern.
It was then that I discovered that these blocks were made of cement imported from Algiers, and sand… also coming from the capital, over 1,200 kilometers away. Desert sand, being too fine, is unsuitable for concrete.
I found myself facing this contradiction: building with concrete in the desert, in the name of modernity, to produce buildings that would need to be air-conditioned… and sometimes even heated. It was from this experience that my initial doubts arose.
2
As an architect, you confront the immense prestige of concrete construction. You face this challenge doubly: first as an architecture student, and then, after your studies, with clients whom you must convince that other solutions exist?
Reinforced concrete shaped the 20th century. Composed of limestone, clay, and sand—materials available on every continent—it can be poured into molds, taking on any shape, and when combined with steel, it enables structural feats that have revolutionized architecture. Compared to stone, which is more restrictive in extraction and implementation, its success is understandable.
I do not reject the legacy of concrete nor that of modernity, but we have perhaps loved it too much: today, 80% of constructions are made of it. During my studies, this material was taken for granted, presented as the only solution to realize the open spaces, heavily influenced by the Corbusian thought of the 1920s, that we designed. Exposed concrete was even an ideal.
It was only after my studies that I began to question this dominance. I became aware of its environmental cost: the massive carbon footprint of cement production, the depletion of resources like sand, the obsolescence of the concrete-steel duo, and the difficulty of recycling these structures at the end of their life.
I then undertook to train myself in other practices, to explore alternatives to the dominant model. As an architect, and now as a teacher, I strive to raise awareness among my clients and students about the issues related to materials—their impact, both environmental and social, on territories. Given the strength of regulations, the inertia of habits, and the still prevalent industrial imagination, the path remains difficult. But it is necessary, and we must not give up.
3
Stone, straw, wood, raw earth… do you have a preferred solution?
I have no preference when it comes to materials: each response is highly local, dependent on the availability of resources and existing know-how. One cannot simply replace one material with another and think the problem is solved.
Globalization, as well as the supremacy of certain materials like concrete, or products derived from petrochemicals—glues, polystyrene insulation, plastic membranes—have profoundly altered our way of building. Our buildings today consist of a layering of materials from all over the world, often glued together, making any repair or substitution extremely difficult.
In response, I advocate for a more frugal architecture, a simplified construction attentive to the origin of materials, their integration into short supply chains, their socially responsible extraction methods, and their implementation. A construction that reintegrates the long term, allowing for repair, adaptation, and above all, extending the life of buildings.
In the 20th century, we decided to build for 50 years. This is obviously too short. Historically, cities have always been built upon the traces, ruins, and structures of their predecessors—without resorting to the landfill.
4
Concrete is not immune to mis-leading ecological marketing… you address « green concrete » in your book. Is it pure greenwashing?
Not exactly. Numerous studies are being conducted by university laboratories and certain R&D departments of major cement groups to reduce the carbon footprint of concrete. The most convincing example, in my opinion, is the development of LC3 (Limestone Calcined Clay Cement) by the École Polytechnique Fédérale de Lausanne, which offers promising prospects, with a potential reduction in CO₂ emissions of up to 40%. However, some initiatives, like Holcim’s ECOPact range, while claiming a significant reduction in carbon footprint, raise questions. It is essential to scrutinize these claims to distinguish genuine advancements from greenwashing strategies.
Indeed, critiques have been raised regarding the transparency and actual effectiveness of certain so-called « green » solutions. For instance, environmental organizations, such as the Carbon Disclosure Project, have assigned Holcim a « D » rating for its sustainability performance, highlighting a lack of sufficient investments to reduce direct emissions from its plants worldwide. Additionally, the use of blast furnace slag—a byproduct of the steel industry with a very low carbon footprint due to a European accounting decision—raises questions. Some companies also import clinker (the main component of cement) from countries outside the European Union, where the carbon footprint is not established, in order to present their cement as « low carbon » while circumventing European regulatory constraints. Currently, the green concrete sector resembles the « Wild West »: there is significant confusion, even among construction professionals. This situation is reminiscent of the use of hydrogen in aviation, where there is hope that zero-carbon concrete will allow business as usual to continue without changing practices, processes, or the cement supply chains that feed construction sites.