6 Proven Materials Driving Down Cement’s Carbon Impact
Reducing the embodied carbon in cement greatly aids the industry in meeting sustainable construction goals. More recently cement products have incorporated alternative materials to replace or reduce clinker content, the most carbon-intensive component. These materials lower carbon emissions and also improve the durability and performance of concrete in various applications.
Below are six key materials contributing to low-carbon cement production.
Fly Ash
Fly ash is traditionally a by product of coal combustion in power plants and is widely used as a supplementary cementitious material (SCM). It replaces a portion of high-carbon Portland cement in concrete mixes, significantly reducing overall carbon emissions.
Fly ash also enhances concrete’s workability and long-term durability. Its pozzolanic properties improve strength by reacting with calcium hydroxide.
Overall, fly ash contributes to a circular economy by repurposing an industrial byproduct that would otherwise contribute to landfill waste.
Ground Granulated Blast-Furnace Slag (GGBFS)
Ground granulated blast-furnace slag, commonly referred to as slag, is another SCM that lowers the carbon footprint of cement. Derived from the steel manufacturing process, slag reduces clinker content and contributes to improved durability in concrete.
Its use decreases the heat of hydration in concrete, minimizing the risk of thermal cracking, particularly in large structures. Slag is also known for enhancing resistance to chemical attack, making it ideal for infrastructure projects.
Limestone
Limestone is a natural material that helps reduce the environmental impact of cement by decreasing the clinker content in cement. Finely ground limestone improves early strength development and the workability of concrete, particularly in mixes with a low water-to-cement ratio.
Its addition reduces the energy required during clinker production, leading to lower CO₂ emissions per tonne of cement. Limestone is an essential component of blended cements aiming to meet sustainability targets. For instance, OneCem® low-carbon Portland limestone cement utilizes quality limestone to reduce CO₂ emissions by 5-10% per ton, supporting sustainability goals without compromising on strength, durability, or performance.
Natural Pozzolans
Natural pozzolans, such as volcanic ash, are highly effective at lowering the carbon impact of cement. These reactive materials enhance concrete by forming additional calcium silicate hydrate (C-S-H) when they react with calcium hydroxide. This reaction increases concrete’s strength and durability while reducing permeability.
By replacing a portion of clinker, natural pozzolans help lower carbon emissions without compromising performance.
Recycled Aggregates
Recycled aggregates are sourced from crushed concrete and other construction demolition materials—an eco-friendly alternative to virgin aggregates in concrete mixes. Their use minimizes the need for additional cementitious materials, conserving resources while reducing landfill waste.
Incorporating recycled aggregates into concrete not only promotes circular construction practices but also reduces the overall carbon footprint of construction projects.
Silica Fume
Silica fume is a byproduct of producing silicon and ferrosilicon alloys and is a highly effective pozzolanic material. When added to cement, silica fume increases concrete strength and reduces permeability, enhancing resistance to chloride and sulphate attacks.
This material also densifies the cement paste matrix, improving durability in high-performance applications, such as marine structures and industrial facilities.
Partner with Lafarge for Low-Carbon Cement Solutions
Lafarge is leading the industry in low-carbon cement production with products like ECOPlanet, OneCem, Terraflow and TerraCem. These innovative cements incorporate fly ash, slag, limestone, and other materials to reduce embodied carbon while delivering exceptional performance.
Contact Lafarge today to explore how low-carbon cement solutions can support your projects.
