It’s possible to make great concrete without the huge emissions from cement. Why isn’t this common?
Cement produces huge volumes of emissions – comparable to Russia or India. Why isn’t this alternative being used?
Concrete is the world's most utilized human-made material, with billions of tonnes produced annually. However, it contributes to 5-8% of global carbon dioxide emissions. This high emission rate stems primarily from cement production, a key component in concrete manufacturing.
Cement has been produced using the Portland cement method for two centuries. This process involves heating limestone to around 1400°C in kilns, which releases significant carbon dioxide. The energy source for these kilns, often coal or gas, exacerbates the emissions problem.
Yet, low-emission concrete is feasible. The key lies in replacing limestone cement with alternative binders. Geopolymer concrete, a promising alternative, often utilizes industrial byproducts, resulting in up to 80% fewer emissions than conventional Portland cement concrete.
Despite these advantages, geopolymer concrete hasn't seen widespread adoption over a decade since its first major project in Queensland. Several factors hinder its widespread use. Firstly, limited long-term performance data hampers the industry's ability to confidently guarantee or insure geopolymer structures.
Secondly, construction projects require evidence of long-term performance to accept new materials. Public infrastructure projects could aid in building this evidence base. Meanwhile, workability and handling of geopolymer concrete pose challenges. Workers accustomed to handling cement-based concrete need safety measures and additional training when dealing with geopolymer concrete, which has different setting and hardening properties.
Variation in product quality is another significant issue. Geopolymers are often produced from industrial by-products, leading to inconsistent feedstock quality. This inconsistency can affect strength, setting time, and durability.
Moreover, the production of feedstocks such as fly ash and chemical activators like caustic soda and sodium silicate can be location-dependent. As coal plants retire, fly ash availability may become an issue, creating a chicken-and-egg problem for the industry.
Overcoming these challenges requires a concerted effort. Government procurement policies and demonstration projects could create early demand and build industry confidence. With ongoing research, appropriate standards, targeted government support, and stronger industry engagement, geopolymer concrete could significantly contribute to Australia's emissions reduction efforts in the construction industry.
Written by urgent.news from The Conversation AU's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
