Bricks are part of the collective imagination when thinking about construction. These are elementary, ubiquitous, modular, light, and reliable materials for erecting buildings. However, traditional ceramic block manufacturing relies on burning clay in kilns at high temperatures, often powered by non-renewable fossil fuels such as coal or natural gas. Furthermore, the transportation process significantly increases its environmental footprint, as the materials are heavy and bulky. In light of this, there is a growing interest in alternative construction materials that offer a lower environmental impact and greater sustainability. Soil cement bricks –or Compressed Stabilized Earth Blocks– are a good example of an existing alternative, as they have a smaller environmental footprint due to their use of local raw materials and the elimination of the burning process, while maintaining many of the intrinsic qualities of traditional bricks.
But what are Compressed Stabilized Earth Blocks (CSEB)? Commonly called soil cement bricks, or ecological bricks, they are construction materials composed of dry inorganic subsoil, non-expansive clay, aggregates, and Portland cement. To properly manufacture the bricks, choosing the appropriate soil is essential: typically, sandy soil with a sand content greater than 50% and clay between 20 and 30% is the most suitable. Over the years, several techniques have been developed to optimize the production and use of these materials, including improved soil selections, binder percentages, compression methods, and curing techniques.
The manufacturing process is quite simple. It starts with preparing the soil and mixing it with a small proportion of cement, where water is gradually added until the desired consistency is reached. After this, the soil and cement mixture is compacted using a press, exerting pressure to form solid bricks, which may or may not have holes. Once compacted, the blocks are stacked and left to cure under a tarp or plastic covering to retain the moisture essential for proper curing.
Ecological Bricks offer a series of significant advantages. They are cheaper to produce compared to traditional ceramic bricks, but they have impressive strength and durability, guaranteeing long-lasting structures that are resistant to various climatic conditions. They can even work as self-supporting structures, allowing the passage of steel bars and hiding plumbing and electrical conduits. Despite its many advantages, CSEB also has some challenges. The need for specialized equipment, such as manual or hydraulic presses, can present an initial investment challenge for some builders. Furthermore, quality control is essential to ensure the structural integrity of the blocks, requiring careful soil selection, precise cement proportions, and appropriate curing methods.
But because it is a material that does not require much technology or knowledge to manufacture, it can be made on the construction site itself, with local labor and using the land's soil. This is the case of community projects in Africa, such as AWF Primary Schools in Karamoja, or Gando Teachers' Housing, by Kéré Architecture, where the community itself was involved in manufacturing the blocks, which naturally adapt well to the local climate.
These blocks can take on functions that go beyond walls. This is the case, for example, of the Secondary School and Auxiliary Buildings of Bangre Veenem School Complex, designed by Albert Faus, in which the blocks are used in the walls and create domes over the rooms. Through a precise curvature that forms an air cushion next to the metal tiles above, the bricks help improve thermal comfort in the hot climate.
The material can also be industrialized, maintaining its natural characteristics but adding a better finish and more precise dimensions, which can work well for larger-scale projects or those seeking a less raw aesthetic. This is the case, for example, of the Symbiosis University Hospital and Research Centre, where the ecological block walls rest on concrete slabs and are worked to form façade elements. Another example comes from Brazil, in the Vargem Grande House, by Ayako e Zebulun arquitetura, in which parallel gables of industrialized CSEB shape the spatiality of the house on a slope, keeping the material visible both inside and outside.
For more examples of architectural projects that use CSEB ingeniously, visit this folder on MyArchDaily.
