IMX Talks - Breaking through the concrete decarbonisation paradigm with fundamental cement science and calcined clays

Concrete stands as the predominant construction material, serving as a cornerstone in modern society. However, the production of portland cement, the integral binder in concrete, contributes significantly to the global carbon footprint, constituting approximately 8% of annual manmade CO2 emissions. To address this pressing environmental concern, the adoption of cement substitution materials like fly ash, blast furnace slag, ground limestone, and natural pozzolans has been recognized as an effective strategy. Despite their efficacy, the dwindling availability of some of these materials poses a challenge.

Limestone calcined clay cements (LC3) emerge as a promising solution, representing a family of blended cements that incorporate limestone and calcined kaolinitic clays, replacing 50%+ of the carbon-intensive clinker. Understanding the intricate mechanisms governing LC3 reactivity is pivotal for optimizing and facilitating the global deployment of this technology. Within LC3, a series of coupled chemical reactions involving metakaolin and calcium hydroxide lead to the formation of C-A-S-H and carboaluminates, effectively reducing porosity while enhancing strength and durability. Pioneering studies utilizing solid-state NMR and time resolved mineralogical characterization shed light on the nascent reactivity of metakaolin in cementitious systems. n conjunction with emerging insights into the surface reactivity of these materials, the foundational science of cement will persist in influencing the trajectory of the industry's decarbonization efforts over the next five decades. This will be achieved through the utilization of innovative, sophisticated characterization techniques and the comprehensive elucidation of the fundamental hydration mechanisms at play.

Leveraging concrete mixture design optimization serves as an additional tool to diminish the overall portland cement consumption. The synergy between cement chemistry and concrete mixture design engineering presents complementary avenues that can significantly contribute to mitigating the overall environmental impact of the construction industry. This multifaceted approach underscores the importance of advancing our understanding of the fundamental processes driving sustainable innovations in the realm of concrete technology.