A comparative study of OPC, WPC, and LC3 cements by low-field 1H TD NMR

Limestone Calcined Clay Cement (LC3) is a promising alternative to Ordinary Portland Cement (OPC); however, its characterization using Time-Domain Nuclear Magnetic Resonance (1H TD NMR) remains underexplored, leaving important aspects insufficiently investigated. In this study, we analyzed OPC, White Portland Cement (WPC), and LC3 pastes at specific hydration times using a portable NMR MOUSE, which can be used in situ, and a wide-bore permanent magnet NMR for synchronized tests. Our results revealed a consistent decrease in the overall signal during hydration for both T1 (longitudinal or spin-lattice) relaxation time and T2 (transverse or spin-spin) relaxation time. The T1/T2 ratio, obtained assuming a monomodal relaxation time distribution, showed the LC3 > OPC > WPC trend for both NMR MOUSE and permanent magnet measurements, as well as dependence on the binder type and iron content. With T1-T2 correlation 2D maps, we followed two spin populations present in the samples, assigned to interlayer water and gel pores, which exhibited distinct T1/T2 ratios. We investigated the influence of iron content on relaxation times, and the component with short relaxation time (interlayer water) did not exhibit a dependence on iron content. This study provides the first detailed 1H TD NMR investigation of LC3 hydration, analyzing T1, T2, and T1/ T2 in comparison with WPC and OPC. It reveals the evolution of relaxation times with hydration and iron content and complements previous T2-focused studies by incorporating T1 to offer deeper insight into hydration mechanisms.