Early-Age Hydration of Low Carbon Cements, Part 1 of 2

Tuesday, November 5, 2024  11:00 AM - 1:00 PM, Grand BR Salon D

To fulfill the decarbonization roadmap established for the concrete industry, the average substitution levels of clinker by SCMs need to increase from about 25% currently to above 50%. This poses practical challenges in terms of early-age strength development and flowability properties of fresh concrete. This session will cover aspects of the early age reactivity, rheology, hydration and development of strength. It is aimed for professionalsand scientists working with different types od low-carbon cements. At the end of the sessions, the attendees will be able to identify strategies to tackle the outstanding challenges related to early age performance of these systems.

Improving Early Strength of Low Clinker Cements and Concretes

Presented By: Karen Scrivener
Affiliation: Ecole Polytechnique Federale de Lausanne
Description: Lowering the clinker content of cement and concrete is critical to lowing their carbon footprint. The main technical limitation is the early strength at 1 or 2 days needed to keep existing construction schedules. In this presentation we will look at strategies to improve early strength development, including optimised grinding and particle packing, seeding and accelerators.

Packing Properties of Particles at Various Length Scales: A High Potential Path for More Sustainable Construction Materials

Presented By: Nicolas ROUSSEL
Affiliation: Gustave Eiffel University / RILEM
Description: We discuss in this lecture the various existing theories behind the packing and jamming of non-spherical interacting rigid particles. We moreover retrace the history of the integration of such physics in the mix design tools available for the civil engineers. We then discuss the potential gains and practical limits in terms of clinker saving at various length scales (or particle sizes) made variable for such controlled and engineered changes to the particle size distribution. We finally extrapolate the packing and jamming concepts at the level of the hydrates with a specific focus on ettringite in blended cements.

Early Age Strength Enhancement via Nucleation Seeding

Presented By: Nishant Garg
Affiliation: University of Illinois at Urbana-Champaign
Description: For low-carbon concrete mixtures, where high SCM contents (>40%) are employed, one of the primary challenges that need to be addressed is the low early-age strength. Without sufficient early-age strength, the construction schedule can be jeopardized. One approach to improve and potentially enhance early-age strength is that of nucleation seeding. Introduced in the late 2000s, C-S-H seeds have been known to accelerate and enhance hydration kinetics. Today, several commercial admixtures based on these C-S-H seeds are available in the market. In this talk, I will share our latest results with some of these commercially available C-S-H seeds – both from the lens of lab testing as well as field implementation. Finally, in addition, I will briefly touch upon newer lab-based, synthetic versions that can be potentially used as strength enhancers in the future.

Chemical Admixtures for Blended Cements: More Problems or More Solutions?

Presented By: Robert Flatt
Affiliation: ETH Zurich
Description: This presentation will begin by reviewing basic principles about the working mechanism and mutual interactions between chemical admixtures. It will then examine how such principles may be applied to blended cements, discussing implications on dispersion efficiency and flow retention in particular. A particular emphasis will then be placed on examining the issue of flow retention in LC3 when PCE superplasticizers are used. Issues and possible solutions will be both illustrated and discussed.

Optimization of Sulfate Balance in LC3 by Machine Learning

Presented By: Newell Washburn
Affiliation: Carnegie Mellon University
Description: This study assesses the influence and quantifies the relative significance of compositional predictors on the sulfate balance and cumulative heat evolved by 24 h for LC3 through a stepwise regression model based on calorimetry and X-ray diffraction data. Sulfate balance was defined as the time difference between the sulfate depletion point and the time of maximum of alite peak obtained from a time derivative of data obtained through isothermal calorimetry. A methodology based on Kernel smoothing was used to precisely identify these events and allowed the optimization of sulfate to regulate ettringite formation and C3A dissolution. The results suggest that the metakaolin fraction influences the sulfate balance of LC3 both directly and through its interactions with other constituent materials.