Biocement: the future of sustainable construction

Biocement, and bioreceptive concrete in particular, represents a crucial breakthrough toward more environmentally friendly construction in harmony with the environment. This innovative technology offers concrete solutions to mitigate the environmental impact of construction by integrating nature directly into structures.

What is Bioreceptive Concrete?

Unlike traditional concrete, which creates a hostile environment for plant life, bioreceptive concrete is specifically designed to accommodate the growth of mosses, lichens and other microphytes. This is achieved through a combination of factors acting on the microstructure and chemical composition of the material.

Fundamental Principles of Bioreceptive Concrete:

• Controlled Porosity: Porosity is critical for water retention, which is vital for plant survival. In bioreceptive concrete, porosity is not only higher than in conventional concrete, but also carefully controlled in terms of pore size and interconnection. This ensures better capillarity and even distribution of water within the material, creating a moist and stable microclimate. To achieve the desired porosity, aerating agents or specific mixing techniques are often used.

• Optimized Composition: The basic concrete mixture is modified by adding specific components that perform different functions:
  • Pozzolanic materials (fly ash, blast furnace slag): These materials react with the calcium hydroxide produced during cement hydration, reducing the pH and increasing the durability of the material. They also improve water retention and provide micronutrients to plants.
  • Fibers (natural or synthetic): Fibers increase the tensile and flexural strength of concrete, preventing the formation of cracks that could compromise plant growth. Natural fibers, such as hemp or flax, can also contribute to water retention.
  • Superabsorbent Pol ymers (SAP): These polymers can absorb large amounts of water and release it gradually, providing constant hydration for plants even in times of drought.

• Surface Roughness: A rough, irregular surface provides greater anchorage for moss rhizoids and lichen hyphae, the structures they use to adhere to the substrate. This roughness can be achieved by using aggregates of different grain sizes or by applying specific surface treatments.

How Different Realities Operate:

• Academic Research: Universities and research centers, such as the Delft University of Technology in the Netherlands, play a key role in the study of interactions between concrete and plant organisms. Their research focuses on:
  • Optimization of mixtures to maximize plant growth and material durability.
  • Study of the influence of environmental conditions (temperature, humidity, sun exposure) on plant growth.
  • Development of protocols for monitoring and maintenance of vegetated surfaces.
  • Analysis of the impact of biorective concrete on the urban environment (heat island mitigation, CO2 absorption, increased biodiversity).

• Specialized Companies: Several companies have specialized in developing and marketing products and solutions based on bioreceptive concrete:
  • Respyre (Netherlands): This company is known for its approach that combines a special concrete with a “biogel” that acts as a nutrient substrate for moss. They offer complete solutions for facade coatings, with a focus on the use of mosses.
  • Other companies, while not exclusively focused on biocement, produce additives and materials that can be used to make it, such as suppliers of pozzolanic materials, natural fibers, or superabsorbent polymers. It is difficult to provide an exhaustive list, as the market is constantly evolving, but it is possible to find specialized suppliers by consulting catalogs of environmentally friendly building materials.

• Practical Applications: Architects, engineers and landscape architects integrate bioreceptive concrete into their projects to create:
  • Vertical green walls, which improve the aesthetics of buildings and contribute to thermal and acoustic insulation.
  • Permeable pavements, which promote rainwater drainage and reduce the risk of flooding.
  • Elements of street furniture (benches, planters, retaining walls) that integrate vegetation into the urban environment.

Specific Examples and Operational Details:

Respyre: As mentioned above, Respyre uses a biogel that provides the necessary nutrients and moisture for the initial growth phase of the moss. Once the moss is established, the system becomes relatively self-contained, requiring minimal maintenance.

Research at Delft: Research conducted at Delft University of Technology investigated the influence of different additives (fly ash, blast furnace slag, fuming silica) on the porosity, water retention, pH and mechanical strength of the material, with a focus on the growth of Bryum argenteum moss.