Unleashing the Potential of Limestone Calcined Clay Cement (LC3)

Why India’s new LC3 code is a game-changer for decarbonizing concrete.

With a consumption rate of 30 billion tons annually, concrete is the world’s second most consumed substance. Cement, a major ingredient, is responsible for about 90 percent of the emissions in concrete and accounts for 8 percent of global anthropogenic CO2 emissions.

In India, the annual per capita cement consumption is almost equal to food consumption, emphasizing the importance of reducing CO₂ emissions from the cement industry as demand for cement grows in the country. India is committed to the path of sustainable development and meeting its Intended Nationally Determined Contribution (INDC) toward achieving the Paris Climate Agreement and doing so will mean lowering its cement sector emissions footprint. LC3 (limestone calcined clay cement) is emerging as a climate-friendly innovative cement solution: a cement blend made with clinker, calcined clay, limestone, and gypsum that can typically achieve emissions reductions of up to 40 percent as compared with Ordinary Portland Cement (OPC).

In a significant development, the Bureau of Indian Standards (BIS) just recently released an exclusive Indian Standard (IS) code (IS 18189: 2023) for LC3 in India. The code provides comprehensive guidelines and specifications for the production, testing, and usage of LC3 in concrete.

With the introduction of this code, LC3 is poised to gain wider acceptance and adoption in the construction industry within India, paving the way for scaling low-carbon cement blends. In this blog post, we delve into the details of LC3, its environmental advantages, and the implications of the new IS code, all of which signal a transformative shift towards greener infrastructure and decarbonizing the cement industry.

LC3 as a replacement for conventional cement

LC3, a brainchild of the École Polytechnique Fédérale de Lausanne (EPFL) and the Swiss Agency for Development and Cooperation (SDC), was developed as a low-carbon alternative to ordinary Portland cement (OPC). A typical LC3-50 cement blend mixture consists of 30 percent calcined clay, 15 percent limestone, 5 percent gypsum, and 50 percent clinker, which together result in roughly 40 percent carbon emissions reduction over traditional OPC and an up to 25 percent reduction in overall cost. An important concern with LC3 production and performance includes the availability of clays and the associated kaolinitic content.

Almost a decade of research in India at the Society for Technology and Action for Rural Advancement (TARA), Indian Institute of Technology Delhi, and Indian Institute of Technology Madras found that LC3 exhibits improved durability characteristics, making this cement blend suitable for various construction applications. Its increased resistance to chloride ingress and sulfate attack makes it an excellent choice for structures located in coastal areas. Additionally, LC3 has a lower alkali content, minimizing the risk of alkali-silica reactions and enhancing the longevity of concrete structures.

A growing awareness of climate change and the demand for sustainable construction practices prompted researchers and industry professionals to take the next step and develop a national standard for LC3.

Dr. Shashank Bishnoi, a professor at IIT Delhi extensively involved in drafting the IS 18189, said this code represents years of collaborative effort by academia and the cement industry and hopes to see its implications in India and other countries: “Quality and performance of cement is crucial to the development of a safe infrastructure, so this standard went through detailed scrutiny from various stakeholders, which only helped in making the standard stronger. IS 18189:2023 offers the industry an opportunity to produce cement that is not only more sustainable, but also has a higher performance.”

LC3 deployment around the globe

LC3 innovation is not new. After it was first conceptualized in 2005 by Prof Karen Scrivener at EPFL, it was then formalized as a project and has been supported by the Swiss Agency of Development and Corporation since 2014.

Today, LC3 is no longer a project. We’re seeing large-scale deployment across the globe as climate concerns about concrete’s emissions footprint begin to rise and as the availability of other supplementary cementitious materials (SCMs) like fly ash and slag continue to drop globally, owing to the decrease in dependency on coal-powered electricity plants (a drastic 83 percent decrease by 2030 in the EU). Here are just a few examples:

In Cuba, an LC3 pilot production plant was installed in 2020. Cuba is in the process of constructing over 20 smaller plants which will produce a clay mixture that can be blended with regular cement directly at construction sites (with an estimated cost reduction of 20 percent).

Cementos Argos announced the successful completion of a new calcined clay production line (at 450,000 tons per year capacity) at its Rio Claro plant in Colombia in early 2020.

LC3 can be a game changer for several geographies including Africa where the clinker needs to be imported owing to the scarcity of limestone reserves, making conventional cement expensive. CBI Ghana’s Accra plant is poised to become the largest production facility for LC3 globally by the second half of 2024. FLSmidth is set to install a new clay calciner system at the facility, which is expected to substitute clinker, reaching replacement levels of approximately 60–70 percent.

Additionally, in mid-March 2022, Lafarge Cement Malawi announced the launch of an LC3 project in Malawi, further highlighting the growing adoption of this innovative cement technology in the region.

In Europe, Holcim has introduced the inaugural calcined clay cement operation at its Saint-Pierre-la-Cour plant (production capacity of 500,000 tons per year) in France. This ground-breaking project enables the production of ECOPlanet green cement, which boasts a remarkable 50 percent lower CO₂ footprint compared to standard cement (CEM I).

Cementir Group’s FUTURECEM, a calcined clay cement product, debuted in Denmark in 2021. Through a pilot plant, the company successfully demonstrated the viability and potential of this innovative cement. Building upon its success, Cementir Group swiftly moved to introduce FUTURECEM to the cement markets in Benelux and France in 2022. In June 2021, Vicat awarded a contract for commissioning the Xeuilley integrated cement plant by 2023, where clay was proposed as a sustainable alternative owing to availability, EU regulations, and increased demand for a sustainable alternative to cement.

LC3 production and deployment in India

LC3 has been used in pilot projects across regions, implemented at different scales, and has already seen more than 25 applications since 2014. One notable project is the Jhansi model house in India, where 98 percent of the structure was constructed using LC3. In 2017, JK Lakshmi partnered with IIT Delhi to conduct the first-ever full-scale plant trial of LC3 at their Jhajjhar unit. This trial showed promising results, with potential CO₂ emission reductions of up to 30 percent and energy consumption reductions of 20 percent in cement production.

Additionally, the offices of the Swiss Agency for Development and Cooperation, located within the compound of the Swiss Embassy in Delhi, were constructed using LC3 prefab materials.

In 2022, JK Lakshmi Cement collaborated with TARA to incorporate calcined clay technology into its operations, enabling the production of LC3. There is momentum around other cement players in the country considering LC3 production as well.

Future outlook of LC3 and IS 18189: 2023

As India aims to reduce 45 percent of its emission intensity by 2030 as a part of its NDC under the Paris Agreement, LC3 presents a promising solution for low-carbon construction. A recent report by NIUA and RMI emphasizes the need to focus on low embodied carbon design and construction as well as low carbon material production and selection. While LC3 presents a promising solution for low-carbon construction, there remain barriers to its widespread deployment. They include raising awareness among construction professionals, ensuring consistent quality control, specialized training, availability of raw materials, integrating LC3 into existing supply chains, and acceptance by builders and regulatory bodies.

While this development may pose some quandaries for traditional cement manufacturers, it presents an opportunity and ushers in a new era of low-carbon cement production in the country. Aun Abdullah, ESG head, Lodha group, spoke to RMI India about their plans for LC3 deployment: “Lodha Net Zero Urban Accelerator, a partnership with RMI, is planning to deploy a pilot on LC3 with an objective to generate evidence and confidence about its benefit for the larger ecosystem of developers, contractors, industry supply chain and policymakers.”

With its reduced carbon footprint, improved durability, and economic benefits, LC3 has the potential to transform the way buildings and infrastructure are constructed in the country. With successful case studies already highlighting its effectiveness, the release of the IS code for LC3 marks a significant turning point in sustainable construction practices. The code’s publication is set to accelerate LC3 adoption across the country and sets a precedent for other countries who are evaluating the adoption of LC3 into their codes. As India strives for sustainable development, LC3 will undoubtedly shape the future construction landscape.

We’d like to acknowledge contributions from Tarun Garg, principal, RMI India Foundation, and Sai Sri Harsha Pallerlamudi, senior associate, RMI India Foundation towards this piece.