Monitoring Short-Term Moisture Progression in Superabsorbent Polymer-Modified Mortar Using Hygro-Electrical Measurements

This study evaluates whether electrical resistance (ER) measurements can track short-term moisture-front progression in uncracked mortar modified with superabsorbent polymers (SAPs) under sustained hydrostatic pressure through comparison with internal relative humidity (IRH) measurements. The novelty lies in simultaneous, continuous monitoring at multiple depths using two independent sensing principles. Prism specimens (75 × 75 × 275 mm) containing control and 0.25 wt% acrylic acid-based SAP were monitored for 144 h under a hydrostatic pressure of approximately 0.01 MPa generated by a constant 1000-mm water head. One instrumented specimen was monitored for each mixture. At the 85% IRH threshold, the front reached 51 mm in the control and 43 mm in the SAP-modified mortar. The ER measurements were consistent with the moisture-front progression indicated by IRH measurements within each specimen. The measurements document specimen-specific IRH and electrical-resistance responses and motivate further investigation of depth-resolved moisture distributions in SAP-modified cement-based materials.