Capillary water absorption into alkali-activated slag materials: Experimental and numerical investigation

Abstract

This study conducted both experimental and numerical investigations on the capillary water absorption into AAS materials with varying mix proportions. The results demonstrate that the capillary water absorption of AAS mortars adheres to the square root of time (SRT) law until wetting front reaches the top surface of specimen. The isopropanol (IPA) absorption of AAS mortars also follows the SRT law, and the measured intrinsic capillary sorptivity $S_{\text{int}}$ for IPA and water are quite close. Through theoretical modeling and numerical simulation, the capillary absorption kinetics of different AAS mortars can all be accurately quantified using the Richards equation, regardless of the water retention curve model employed. These results suggest that the microstructure of AAS materials studied herein is stable during capillary water absorption. This may be attributed to the viscous characteristics of AAS materials, arising from the irreversible collapse and rearrangement of the nanostructure of C-A-S-H gels during drying.