Proton Time-Domain Nuclear Magnetic Resonance (1H TD-NMR) was applied to investigate the role of water in low-carbon cements containing calcined clay, both in the fresh and hardened state. Water distribution in cement pastes was studied using transverse, T2, relaxation times acquired with Carr–Purcell–Meiboom–Gill (CPMG) sequences. It is shown that the intraparticle pores of calcined clay particles absorb a significant fraction of the mixing water, reducing the amount of free water available in the system. This phenomenon affects the rheological behavior of fresh binders and may explain the loss of workability commonly observed in calcined clay-based cements.

Furthermore, Logarithmic Aperiodic Pulse Saturation Recovery (LAPSR) experiments and two-dimensional T1–T2 relaxation maps were used to follow the evolution of water environments during hydration. The NMR signals were processed through quasi-continuous linear 1D and 2D inversion using the software packages UPENWin and MUPEN2D, respectively, allowing the reconstruction of one- and two-dimensional relaxation time distributions. The analysis provided information on water mobility, pore structure refinement and the progressive development of hydration products.

In particular, white Portland cement, ordinary Portland cement and limestone calcined clay cement were investigated, and they showed distinct relaxation behavior, with T1/T2 ratios of approximately 2.5, 2.0 and 1.5, respectively. Relaxation behavior revealed differences in water–surface interactions and pore structure evolution during hydration, with iron-bearing phases affecting microstructural development but not significantly altering interlayer water relaxation.

The combined use of TD-NMR relaxation time distributions and T1–T2 correlation maps enabled the characterization of water dynamics and pore structure evolution during hydration of low-carbon cementitious systems.

 

References:

A. Nagmutdinova, L. Brizi, C. Testa, V. Bortolotti, and L. Ferrari, “A comparative study of OPC, WPC, and LC3 cements by low-field 1H TD NMR,” Constr. Build. Mater., vol. 506, Jan. 2026, doi: 10.1016/j.conbuildmat.2025.144785. 

Lucia Ferrari, Anastasiia Nagmutdinova, Arnaud Müller, Nikola Mikanovic, Mohsen BenHaha, Villiam Bortolotti, Elisa Franzoni. “Disclosing the mechanism behind rheological challenges in calcined clay-based cements,” Constr. Build. Mater., vol. 492, p. 142837, Sep. 2025, doi: 10.1016/j.conbuildmat.2025.142837 

V. Bortolotti, L. Brizi, A. Nagmutdinova, F. Zama, G. Landi. MUPen2DTool: A new Matlab Tool for 2D Nuclear Magnetic Resonance relaxation data inversion. SoftwareX, Vol. 20, 2022. https://doi.org/10.1016/j.softx.2022.101240