Insight into pore size distribution and moisture migration behavior in aerogel cementitious composites using N 2 physisorption/MIP and LF-NMR methods

Abstract

The service life of cement-based composites is significantly influenced by their internal pore structure and moisture migration behavior. This study employed low-field nuclear magnetic resonance (LF-NMR), nitrogen physisorption, and mercury intrusion porosimetry (MIP) to systematically investigate the effects of silica aerogel content (0%, 5%, 7%, and 10%) on pore size distribution, inter-pore water content, and internal moisture migration [NE1] [RC: Reviewer 1Point7] in aerogel-incorporated cementitious composites (AICs). The results show that increasing aerogel content creates extensive interfacial defects and microcracks between the hydrophobic aerogel and the hydrophilic cement matrix, forming an interconnected macropore network. Compared to the aerogel-free reference (AIC0), the porosity of AIC10 (10% aerogel) increases by 12%, accompanied by a higher proportion of macropores and enhanced pore connectivity. Despite the intrinsic hydrophobicity of aerogel, the percolating macropore network provides fast capillary pathways, leading to accelerated water transport. During water absorption, water preferentially wets the hydrophilic cement matrix and the connected macropores, whereas the aerogel particles and their surrounding hydrophobic interfacial regions remain poorly wetted. This mixed wettability results in a heterogeneous internal moisture distribution, with low-water-content areas appearing as cold tones in spatial images.