Biological Concrete

So far we are well acquainted with various green construction practices with regards to vegetated roof gardens and walls which help in stabilization of the indoor environmental quality as well as absorbing carbon dioxide in the atmosphere. Various buildings have been developed with living walls, such as the mossy office buildings in Amiens, France and Sao Paulo furniture showroom. However, some of these measures can put various structural stresses on the building facades and are also difficult to maintain to quite an extent.

Therefore, the researchers from the Barcelona’s Universitat Politècnica de Catalunya (UPC) have developed a concept of merging the vegetation with structural support through production of biological concrete i.e. constructing a living façade with lichens, mosses and other living organisms. According to the researchers, this concrete captures rainwater which will create a favorable environment for the growth of organisms on the surface.

(Above: Simulation of a vegetated facade at the Aeronautical Cultural Centre in El Prat de Llobregat)

Often, the vegetated walls and the rooftop gardens require complex support systems, which are attached to the buildings or adjacent to the structures. However, the biological concrete provides a supporting system itself and also supports the growth of flora like moss and lichen. The biological concrete has more vegetation friendly ph than normal concrete and it is textured with greater porosity.

The biological concrete is composed of three layers. The innermost layer separates the organisms from the inner structural part of the concrete and it stays dry and free of vegetation. The second layer is designed to capture rainwater and support colonization. Since, this layer has the ability to store rainwater; it facilitates the biological growth. The final layer permits the entry of rainwater and prevents it from escaping. This helps in redirecting the outflow of water to the biological growth.

In studying this concrete, the researchers at UPC have focused on two cement-based materials. The first of these is conventional carbonated concrete (based on Portland cement), with which they can obtain a material with a pH of around 8. The second material is manufactured with magnesium phosphate cement (MPC), a hydraulic conglomerate that does not require any treatment to reduce its pH, since it is slightly acidic. Because of its quick setting properties, MPC has been used as a repair material in the past. Also, it has been used in the field of medicine and dentistry which proves that it does not have an adverse impact on the environment.

The biological concrete offers environmental, thermal and aesthetic advantages. Due to its biological coating, the concrete absorbs and reduces atmospheric carbon dioxide. It also has the capacity to capture solar radiation which helps in regulating the thermal conductivity inside the building. The biological concrete acts as an ornamental alternative as it can be used to decorate the façade of buildings. It has been designed for the colonization of certain areas with a variety of colors. It can be used in rooftop garden areas as a decorative element and as a sustainable means of blending buildings and constructions into the landscape. The idea is to create a patina in the form of a biological covering or a “living” painting.

 

The research team at UPC is currently investigating the best way to promote the accelerated growth of these types of organisms on the concrete. The goal of the research is to succeed in accelerating the natural colonization process so that the surface acquires an attractive appearance in less than a year. A further aim is that the appearance of the façades constructed with the new material should evolve over time, showing changes of color according to the time of year and the predominant families of organisms. On these kinds of buildings, other types of vegetation are prevented from appearing, lest their roots damage construction elements. At present, a patent is in the process of being obtained for this innovative product, and the Catalan company ESCOFET 1886 S.A., a manufacturer of concrete panels for architectural and urban furniture purposes, has already shown an interest in commercializing the material.