Accuracy and applicability improvement of detecting SAPs water absorption and desorption behavior in cement paste via low-field NMR

1 H Low-field nuclear magnetic resonance (LF NMR) has emerged as a promising technique for tracking water migration of superabsorbent polymers (SAPs) incorporated cementitious materials. Critical challenges persist in signal identification and pore size estimation, particularly dependent on echo time ( T E ) selection. This study aimed to establish optimal T E settings for monitoring SAPs water evolution considering various types of SAPs materials. Experimental results revealed that T E variations govern the detectability of water signals and systematically altered the measured transverse relaxation times ( T 2 ) of identical water signals, as T 2 was inversely proportional to the square of T E . The effect of SAPs’ characteristics on water absorption and desorption was determined by its physical structure and chemical composition. An optimized T E protocol was developed through the research purposes and SAPs characteristics. The approach enables quantifying the SAPs absorption and desorption behaviors accurately. This work provides practical guidelines for parameter selection in NMR-based SAPs studies, advancing standardized characterization of water migration and microstructural evolution of SAPs blended concrete. • The effect of various T E settings on monitoring SAP water evolution were determined. • T E = 1.0ms was identified as the optimal setting for SAP water absorption/desorption monitoring. • A rapid absorption period of SAP was correlated to the depletion of Ca 2+ during acceleration period. • An order-of-magnitude discrepancies in measured T2 was induced when T E changed.