Low-Carbon Concrete

Summary

Low-Carbon Concrete - is usually created by replacing traditional Portland cement with environmentally friendly cementitious material alternatives to create sustainable concrete with lower CO2 emissions.

Technical Information

Low-carbon concrete (LCC) is produced when supplementary cementitious materials (SCMs) such as fly ash, rice husk ash, ground granulated blast furnace slag (GGBS) or silica fume replace traditional Portland cement.

Alternatively, Portland/limestone cement blends can be used to create a lower carbon footprint.

While these replacements can significantly reduce carbon emissions compared to standard concrete, there are benefits and risks associated with LCC, especially for industrial flooring.

Several pros and cons of Low-Carbon Concrete are listed below:

Low-Carbon Concrete Pros

LCCs can reduce carbon emissions by up to 80% compared to standard concrete.
LCC can be made with locally sourced materials, reducing costs and emissions from transportation.
SCMs are mineral additions and more sustainable than Portland cement.
SCMs use less energy to produce and reduce the demand for finite resources like limestone and clay.

Low-Carbon Concrete Cons

Low-carbon concrete can be more expensive to make than traditional concrete.
As coal-burning power stations are replaced with greener energy sources, reports of fly ash and slag supply shortages will only increase.
Low-carbon concrete floors in warehouses and other industrial facilities have slower setting times and altered bleed water characteristics, meaning a higher risk of surface delamination. If finishing techniques aren’t adapted to the slower setting, the top layer of the concrete may dry out faster than the bottom layer creating surface crusting.
Altered bleed water characteristics from SCMs can increase the risk of plastic shrinkage cracking during the critical early hours of concrete setting. Anti-evaporative sprays are required to maintain the concrete’s structural integrity and surface aesthetics.
For high-performance industrial floors where wear resistance is critical, certain SCM mixes require specific curing practices to ensure effective abrasion resistance.

The Future of Low-Carbon Concrete

Advancements in low-carbon concrete are essential to help decarbonise the construction industry and promote sustainable building practices, with some of the latest developments listed below:

Traditional cement replacements such as geopolymers, and magnesium and sulphur-based cement are being developed to help reduce CO2 emissions during production.
Advancements in Carbon Sequestration by companies such as CarbonCure mean CO2 from industrial or atmospheric emissions is captured and injected into fresh concrete during mixing to help reduce the carbon footprint.
Self-healing or self-repairing concrete is currently in development. Self-healing elements are added to the concrete mix, including solutions such as dormant bacteria which react to water when triggered (https://www.rics.org/news-insights/building-a-sustainable-future-the-incredible-potential-of-self-healing-concrete) or carbonic anhydrase (CA) enzymes which interact with CO2 in the air to produce calcium carbonate crystals. These crystals mimic the characteristics of concrete and promptly fill in the crack. (https://newatlas.com/materials/self-healing-concrete-co2-blood-enzyme/)
Increases in recycling aggregates and reusing concrete from demolished structures help reduce the need for virgin materials and minimise waste.
If CO2 is injected into concrete during mixing, it mineralises becoming calcium carbonate and reduces the amount of energy required to cure the concrete.
Faster adoption of low-carbon practices and materials will be encouraged as governmental policies and regulations are introduced to lower carbon emissions in the construction industry. Programmes such as LEED and BREEAM will also promote greener construction, incentivising the use of low-carbon concrete for sustainable building certifications.
Future construction standards will emphasise concrete’s durability and adapt performance requirements to reflect the need for fewer repairs and rebuilds.
Low-carbon concrete mix designs will be critical for meeting performance requirements and industry standards whilst reducing CO2 emissions.