Concrete as a construction material has become, alongside plastics, the basic material of a new geological epoch. Successive layers of homogeneous mixture of calcium oxide, sand, aggregate, and other materials have covered the surface of the Planet, intersecting contemporary landscapes with highways and railway lines, connecting various points of human activity. Before widespread industrialisation of construction processes, concrete was one of the options used in several regions of the world. Some architects, concerned about the environmental crisis, are seeking alternatives to the material. At the same time, material producers are seeking ways to reduce its environmental impact. However, attempts to improve processes to have less adverse environmental impact have focused on improving production efficiency while increasing profits. The industry related to concrete production has changed, and perhaps even shaped, contemporary architecture. The co-evolution of material and form has been ongoing since the beginning of the 20th century.
We have broken down concrete into its constituent parts throughout its lifecycle to better understand at which stage its negative environmental impact is greatest. We wanted to address the question: How to use concrete in a moment of planetary crisis? The lifecycle is a process consisting of many stages and considered from various aspects. It allows for a better understanding of the relationships that the studied object and its production process create with the surrounding environment. Described since the late 1980s using ISO 14040/14044 standards (Environmental Management – Life Cycle Assessment – Principles and Framework), it is, to the best of our knowledge, the most accurate research methodology. It combines inherent impact, use, and subsequent life of the studied object. This methodology will serve us in demonstrating the relationship and impact of concrete on the environment.
Life cycle assessment occurs in four main stages: Production and construction (A), Use (B), End-of-life (C), Second life (D). The stages are also grouped using broader concepts: from cradle to gate, as the name suggests, it considers processes from raw material extraction (e.g., sand excavation) to the production of the finished element in the factory (e.g., reinforced concrete beams). The next concept, cradle-to-grave, considers the end of the element’s use as the final boundary, such as the disposal of elements in a landfill. The last group, cradle-to-cradle, opens the material’s lifecycle to further possibilities, leaving the element or material in continuous circulation. An evaluation of Environmental Product Declarations of concrete products will demonstrate that manufacturers only specify the cradle-to-gate stage and do not investigate the impact of the material during its use or disposal.
Each of these stages can be measured using several indicators, including potential for photochemical ozone formation, eutrophication potential, and consumption of energy from renewable sources. Today, the best-studied aspect concerning architecture and construction is the potential for greenhouse gas emissions, also considered in environmental certifications for buildings. It also relates to planetary boundaries: climate change, which is discussed the most. This leads to the carbon tunnel effect described by Jan Konietzko, which, in 2021, through a single post on LinkedIn, finally became a topic of professional discussion. It reminds us that focusing only on one indicator and reducing it may increase the impact of others. This thought follows the systems theory, upon which planetary boundaries are based. It suggests that all elements operate on the principle of feedback. If one of them goes out of balance, the others do too. Concrete is also discussed by mainly analysing it from the perspective of carbon dioxide emissions. Probably all architects have heard that cement is responsible for 5%-7% of global greenhouse gas emissions. It is difficult for designers to make decisions based solely on this information. The only conclusion that can be drawn is to use less concrete. Despite this, production is increasing year by year.
To measure the impact in each life cycle stage using indicators, one must first determine the functional unit. Otherwise, we will examine a square meter of monolithic ceiling, which carries a load of 250-300 kg/m2, equally to one carrying a load of 500 kg/m2, or a self-levelling concrete screed with a thickness of 2 cm. Each of these functions requires a different amount of material with different properties. The functional unit also allows for the comparison of different construction methods, for example, ribbed and solid slabs from the perspective of their environmental impact. The unit can also be m3 of concrete mix, which can be used for various applications.
To conduct a material lifecycle analysis, besides defining the system boundaries (e.g., cradle-to-gate), indicators (e.g., Eutrophication Potential), and functional units (e.g., 1m2 of industrial ceiling), a temporal perspective for the study must be determined. Depending on the building elements, a different time horizon is assumed. The structure will remain until the very end of the building’s life. Columns, slabs, and staircases are elements that are retained even during deep renovations. Structural elements are measured over a 50 or 60-year perspective. This means that after this period, the element is environmentally amortised. If we reuse such a product, for example, a concrete column or a slab, its impact is practically non-existent, only related to transportation and installation in a new location.
Designing for durability leads to two solutions: designing flexible objects that can be subject to changes primarily in functional layouts and renovation possibilities, and second, designing for disassembly (DfD). Designing for disassembly is based on several principles that allow for easier dismantling of the building and develops the idea of circularity in the technical cycle described by Michael Braungart and William McDonough. It suggests designing components that are easy and intuitive to disassemble, connecting them using mechanical (e.g., screws) and modular elements. In the case of concrete, these are prefabricated elements designed with connectors. To not lose the value of concrete components, subsequent components like floors, windows, and insulations should also be designed and executed following the principles of DfD. Concrete and concrete elements are difficult to recycle and upcycle.
Concrete is produced from cement (binder), aggregates, water, and optional additives, admixtures, or fibres. With a few exceptions, it is used as reinforced concrete. Instead of cement, historically, in vernacular architecture, volcanic ash was used, among other materials.
In conclusion, concrete, like plastics, shapes our world. But its environmental impact requires scrutiny. Analysing its lifecycle through methodologies like ISO standards reveals challenges and opportunities for improvement, urging a holistic approach beyond focusing solely on greenhouse gas emissions. Designing for durability and embracing innovation offer sustainable solutions to mitigate concrete’s environmental footprint, emphasising collective efforts for responsible usage and preservation for a sustainable future. In the next part of the article we will look deeper into all phases of concrete production, to map the hotspots and propose ideas to minimise the negative environmental impact of concrete.
Dosta Tec 