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On the whole, concrete is a fairly sustainable material. It has a number of environmentally-friendly benefits such as long-term durability, a high degree of reflectivity, high thermal mass, and high recyclability.
However, the production of concrete is associated with significant carbon dioxide emissions. In recent years, interest in more-sustainable "green" concrete has increased. A “greener” form of concrete is made using scientific production methods that are significantly less damaging to the environment than conventional methods.
Green concrete can also be made using waste materials instead of raw materials. The usage of recycled or waste materials is regarded as more sustainable as they reduce costs, raw material usage, and the need for landfill space. Crushed concrete can be reused as the particular matter, which is known as aggregate. Aluminum cans can also be used as it is processed easily into reinforcement fibers.
Currently, the development of new kinds of green concrete calls for designing new concrete mixes and a deep understanding of concrete qualities, including various production processes. Ideally, green concrete is environmentally-friendly and cost-effective. Moreover, green concrete can be a substantial upgrade in strength compared to normal concrete.
Consider the following types of green concrete that are currently in development and/or being used.
In May 2018, researchers in the UK announced the development of a type of green concrete that incorporated bits of graphene. The researchers behind the new material said it is more environmentally-friendly and stronger than standard forms of concrete.
Increased strength means less concrete is needed for walls and other building structures. That is significant because the manufacture of cement, the main ingredient in concrete, is responsible for 5 percent of global carbon dioxide emissions. More strength also means graphene concrete lasts longer, lowering the demand for new concrete.
This new kind of green concrete is also four times less susceptible to water infiltration than ordinary concrete, meaning buildings and structures made from it could last longer, particularly in flood zones. Furthermore, this new material is more flexible than regular concrete, meaning it could be a better option for construction projects in areas susceptible to earthquakes.
In addition to providing these physical properties, graphene also enables this kind of green concrete to become a good conductor of electricity. This could result in revolutionary new applications, such as electrified roads which can melt ice.
Fly Ash Concrete
Fly ash is a waste product from coal-based power production and is often discarded in landfills. While fly ash has been used in concrete for decades, recent studies have found that fly ash can almost entirely replace cement in concrete.
Incorporating more fly ash enhances fresh concrete by decreasing the mixing water requirement and increasing the flow behavior. A different benefit to using more fly ash is how it reacts with available lime and alkali in concrete, generating more adhesive compounds.
Geopolymer concrete is a growing subset of green concrete that makes use of fly ash in place of cement. Geopolymer concretes represent a significant new direction for fly ash cement. Geopolymer mixes use significantly more fly ash than conventional cement and have a totally different chemical make-up which produces far fewer carbon dioxide emissions.
Geopolymer cements don’t have to be fired in production, nor do they release carbon dioxide during curing. While they do have to be heated at low temperatures in order to cure, the energy needed to create geopolymer concrete is much less than that needed for conventional concrete.
When compared with ordinary cement, geopolymer concrete has more corrosion resistance, significantly greater fire resistance, higher compressive strength, higher tensile strengths, and lower shrinkage.
Geopolymer concrete's biggest plus may be its greenhouse gas reduction potential over the course of its entire life cycle, which is up to 90 percent less than ordinary cement.
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