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Portland-limestone cement

Portland-limestone cement is a more sustainable, lower carbon cement that reduces CO2 emissions by up to 10% while still producing concrete of equivalent performance, including strength and durability, to concrete produced with portland cement.

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What is portland-limestone cement?

Portland-limestone cement’s 10% reduction in CO2 emissions occurs during the cement manufacturing process. While portland cement may contain up to 5% ground limestone, portland-limestone cement is made by intergrinding up to 15% limestone, reducing the amount of clinker required. By reducing the amount of clinker used in the manufacturing process, the associated energy demand and process emissions per tonne of PLC are reduced. As a result, the CO2 emissions associated with PLC are less than those of traditional PC, while equivalent performance is maintained. Overall, the transition to PLC has the potential to save Canada approximately one megatonne of CO2 emissions annually.

Why should my project consider portland-limestone cement?

Concrete is the most widely used construction material on earth and increasing quantities are being produced to meet the needs of increased global population and urbanization. Portland cement, the main binder used in the production of concrete, is responsible for up to 90% of the embodied energy and carbon of concrete, and up to 8% of global anthropogenic CO2 emissions. Over the last 30 years, the cement industry, especially in Canada, has invested in new production facilities that have substantially reduced its energy use and CO2 emissions. In addition, the cement and concrete industry has widely adopted the use of supplementary cementing materials (SCMs) and chemical admixtures to improve performance and further reduce the cement clinker content of concrete, but global demand for concrete continues to increase.

In the last ten years, portland-limestone cements have been introduced and adopted in standards to meet the challenge of further reducing its CO2 emissions by reducing the clinker content of cement without impacting on the performance of concrete.

How is portland-limestone cement made?

Portland-limestone cement’s manufacturing process involves modifying the clinker, calcium sulphate and limestone proportions before the final grinding takes place. The limestone, being a softer material, is ground finer than the clinker. Along with selection of component proportions, this process of achieving the proper size and distribution of particles in PLC is commonly referred to as “optimizing” the cement.
A comparison between traditional portland cement and portland-limestone cement. The portland cement uses up to 5% limestone, while the portland-limestone cement uses up to 15%
In addition, portland-limestone cement performs well when used together with supplementary cementitious materials (SCMs). Using portland-limestone cement together with SCMs provides further clinker reduction of the cementitious materials component of concrete, and thus allows further reduction of Global Warming Potential (GWP).

History of portland-limestone cement use

Portland-limestone cement has been used in Europe for over 35 years and has a long-established record of field performance in a variety of exposure conditions and applications. In Europe, portland cement is considered a premium product, as low clinker cements (i.e. cements with a low clinker-to-cement ratio) are more prevalent than in North America. European cement standards allow up to 35% limestone content in PLC, which can restrict the use of such concrete mixes to select applications as limestone content increases. Canadian standards, meanwhile, have limited the inclusion of limestone in PLC to 15% in order to maintain comparable performance when compared to traditional portland cement concretes.

Research on PLC with Canadian source materials began in 2006 before PLC was first introduced to the Canadian Standards Association cementitious materials standard in 2008 and concrete materials standard in 2009.

technical introduction to portland-limestone cement for municipal and provincial construction specifications. August 2023. V2.0

Read the Technical introduction to portland-limestone cement

technical introduction to portland-limestone cement for municipal and provincial construction specifications. August 2023. V2.0

Read the Technical introduction to portland-limestone cement

Concrete Zero: Canada’s cement and concrete industry action plan to net-zero