A recent study published in Engineering titled “Technological Approaches to Improve Early-Age Strength of Limestone Calcined Clay Cements” by Franco Zunino, Xuerun Li, and Joachim Dengler, explores innovative methods to enhance the early-age strength of limestone calcined clay cements (LC³), a sustainable alternative to traditional Portland cement. The research critically examines various technological approaches, including physical, chemical, and hybrid methods, to address the slower early-age strength development of LC³ cements, which has limited their broader adoption.
Portland cement, the most widely used binder for concrete, contributes significantly to global CO₂ emissions. LC³ cements, which incorporate limestone powder and calcined clays, can replace up to 50% or more of clinker, thereby reducing CO₂ emissions by 30%–40%. However, the slower strength gain rate at early-age (< 2 d) compared to Portland cement poses a challenge for applications requiring rapid strength development.
The study investigates several strategies to boost the early-age strength of LC³ cements. One approach is increasing the fineness of clinker and supplementary cementitious materials (SCMs). The research found that finer cement particles, such as those in 52.5R cement (Blaine 5201 cm²·g⁻¹, d_v50 7.2 µm), exhibit greater compressive strength at 8 h and one day compared to coarser 42.5N cement (Blaine 3075 cm²·g⁻¹, d_v50 19.2 µm). However, this method is limited by industrial grinding setups and the different grindabilities of LC³ constituents.
Another effective method is reducing the water-to-cement (w/c) or water-to-binder (w/b) ratio. The study shows that decreasing the w/b ratio from 0.50 to 0.38 leads to a strength enhancement of over 100% at 8 h and over 60% at one day. However, this approach also reduces workability, requiring higher doses of dispersants to maintain flowability.
Chemical acceleration using calcium silicate hydrate (C-S-H) seeds is another strategy explored. C-S-H seeds, with a high surface area (100–200 m²·g⁻¹), act as nuclei for C-S-H growth, reducing the activation energy of the process. The study demonstrates that C-S-H seeding significantly boosts early-age strength, with an optimal dosage of about 1.5% for LC³-50 cements. However, this method is relatively costly.
The research also examines the use of chemical admixtures to promote the reaction of aluminate phases. The HyCon^® B additive, which enhances the ferrite and C₃A reaction, provides an instant early-age strength boost through ettringite precipitation. An LC³ cement with HyCon^® B and an 8% addition of anhydrite achieved a strength of 2.6 MPa at 5 h, compared to the reference LC³ which was still soft at this stage.
The study evaluates the environmental impact of these strategies, calculating the global warming potential (GWP) in relation to strength performance. While methods like C-S-H seeding and chemical admixtures effectively improve early-age strength, they may also increase late-age strength, necessitating a balanced approach to optimize both performance and sustainability. The research highlights the potential of combining these strategies to achieve better and greener cements, emphasizing the need for a comprehensive framework to advance LC³ adoption in high early-age demand applications.
The study provides valuable insights into enhancing the early-age strength of LC³ cements through various technological approaches, while also considering their environmental impact. These findings are crucial for the sustainable development of the cement and concrete industry, offering practical solutions to reduce CO₂ emissions without compromising on performance.

The paper “Technological Approaches to Improve Early-Age Strength of Limestone Calcined Clay Cements,” is authored by Franco Zunino, Xuerun Li, Joachim Dengler. Full text of the open access paper: https://doi.org/10.1016/j.eng.2025.03.029. For more information about Engineering, visit the website at https://www.sciencedirect.com/journal/engineering.