Résumé
Cellulose ethers (CE) are widely used in mortars as water retaining agents; however the cause of retention remains unknown. This paper attempts to clarify the involved mechanisms using several macroscopic experiments (water retention WR standard tests, imbibition and filtration tests). We highlight that WR is not specific to cement but occurs for every porous media. Then, using model porous media and different fluids we point out a critical mechanism of WR with CE solutions: a jamming effect during water transport through the porous medium. This effect may be explained by the presence of polydisperse aggregates which result from native cellulose or hydrophobic interactions. Finally we present a statistical model for filtration which predicts all the qualitative trends observed experimentally. 2012 Elsevier Ltd. All rights reserved.