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Concrete, a common building substance consisting of cement paste and aggregates, is one of the most destructive materials on our planet. Despite the fact that it is the second most used material after water and that it provides dwelling for more than 70% of the whole population, concrete - especially its main element cement - has an extensive negative impact on the environment. It generates between 4% and 8% of total CO2 emissions, absorbs considerable amounts of industrial water and heat from the sun. Moreover, concrete dust is a significant contributory factor in many respiratory diseases. Gradually man-made concrete structures are outgrowing the natural areas on Earth with little recent initiative to slow their spread.
To decrease the environmental footprint of concrete a number of options can be considered. Ashcrete, for instance, can replace around 20-40% of cement by using flyash - a by-product of coal-burning power plants combined with lime and water, which would have otherwise ended up in the landfill. It is a great substitute for traditional concrete as it is stronger and does not lead to as much bleeding and shrinkage of the material.
Another example is Timbercrete. This substance is primarily made of timber waste (e.g. sawdust, wood chips), cement, sand and binders. It is a remarkably sustainable alternative because it acts as a carbon trap and has lower embodied energy due to several factors, such as using a natural drying process. Other benefits include great workability (can be nailed and screwed), thermal efficiency, durability and being generally 2.5 times lighter weight than conventional concrete (which in turn lowers transportation emissions).
These are just a couple of examples of many new, modern and sustainable materials which can be used in construction. But it is vital to note that there is a different side to them as well: how sustainable is a building that burns down or is flooded after thirty years and has to be rebuilt? Experts advise that when considering to use a green material like wood, its longevity needs to be investigated to understand what risks can the material potentially introduce into the building - in this case, fire. Such a holistic approach can contribute to making construction more sustainable and prevent buildings from being frequently rebuilt.