A comparative study of OPC, WPC, and LC3 cements by low-field 1H TD NMR
Anastasiia Nagmutdinova, Leonardo Brizi, Claudia Testa, Villiam Bortolotti, Lucia Ferrari
Abstract
Limestone Calcined Clay Cement (LC3) is a promising alternative to Ordinary Portland Cement (OPC); however, its characterization using Time-Domain Nuclear Magnetic Resonance ( 1 H 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 T 1 (longitudinal or spin-lattice) relaxation time and T 2 (transverse or spin-spin) relaxation time. The T 1 / T 2 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 T 1 - T 2 correlation 2D maps, we followed two spin populations present in the samples, assigned to interlayer water and gel pores, which exhibited distinct T 1 / T 2 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 1 H TD NMR investigation of LC3 hydration, analyzing T 1 , T 2 , and T 1 / T 2 in comparison with WPC and OPC. It reveals the evolution of relaxation times with hydration and iron content and complements previous T 2 -focused studies by incorporating T 1 to offer deeper insight into hydration mechanisms.