Concrete as Sustainable Material

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How Concrete can be considered a Sustainable Building Material It is pretty much recognized that the production of 1 ton of cement released 1 ton of CO2 (Hostettler, 2014). Knowing this, it is reasonable to ask how concrete can be considered as a sustainable material. This essay will analyze this question considering the life-cycle of different construction materials and the increased use of recycled and substitution materials in concrete. Life-cycle One of the best way to compare the sustainability of different materials is through a life-cycle analysis. As cement usually represent only 10-15 % of a concrete mix (PCA, 2014), energy required to produce concrete isn’t so important. Actually, cement production energy is around 5 GJ/t, but reinforced concrete one is only 2.5 GJ/t (Penttala, 1997). In comparison, steel requires 30 GJ/t, and aluminium 270 GJ/t (Penttala, 1997). But, life-cycle doesn’t take in consideration only the production energy. It should consider energy consumption on all the life duration of the material. At this point, concrete energy is still only of 6.3 GJ/m3 compared to the 236 GJ/m3 of the steel (Penttala, 1997). Also, it is important to consider that steel strength is much higher than concrete one’s. In that case, energy consumption of reinforced concrete is of 0.47 GJ/m3 MPa and steel one’s is of 0.96 GJ/m3 MPa (Penttala, 1997). As sustainability of a material doesn’t depend only of its energy consumption, but also of the emissions released, concrete produces around 147 CO2 kg/t, and metals 3,000 CO2 kg/t (Penttala, 1997). Those difference are due to the method of production of each materials and the fact that steel is usually produce far from where it is use. Concrete has this advantage that most of its components (water and aggregates) can be found locally (CAC, 2012). Recycled and substitution materials Another reason why

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