Print Email Facebook Twitter How methylhydroxyethylcellulose (MHEC) influences drying in porous media Title How methylhydroxyethylcellulose (MHEC) influences drying in porous media Author Faiyas, A.P.A. Erich, S.J.F. van Soestbergen, M. Huinink, H.P. Adan, O.C.G. Nijland, T.G. Publication year 2015 Abstract This article presents both an experimental as well as a theoretical study on the effect of MethylHy droxyEthylCellulose (MHEC) on drying in porous materials using Nuclear Magnetic Resonance Imaging (NMR). MHEC, a water soluble polymer, is normally added to glue mortars as a water retention agent in order to improve the drying by increasing Accepted the open time. However, the exact processes that determine the drying rate of a glue mortar are unknown. In this study, we therefore focus on investigating the drying of a Fired day Brick (FCB) saturated with an aqueous MHEC solution. By using a FCB as a model system, the influence of hydration and changing of pore sizes due to hydration can be removed. The performed NMR experiments show a transition from homogeneous drying for a water saturated FCB toward an inhomogeneous (front receding) drying behavior for FCB saturated with increasing MHEC concentration. The capillary number (Ca) indicates a homogeneous drying for water saturated brick (Ca«i) and an inhomogeneous drying (Ca»1) in case of saturated brick with more than 1.5 wt% MHEC. Analysis of capillary number shows that the main parameter determining the capillary numbers are viscosity, surface tension, contact angle and evaporation rate. Among this viscosity change match with change in capillary number and therefore viscosity has a major influence on the drying behavior and rate. Based on the measured profiles, the moisture diffusivity is calculated. Using an empirical equation, the moisture diffusivity and NMR profiles were fitted to obtain the key parameters. From these analyses we conclude that 1) the moismre diffusivity scales with viscosity, which is the main parameter in shift in drying behavior. 2) Surprisingly, the presence of MHEC reduced the evaporation, which is unexpected since evaporation of MHEC solutions, for instance present in capillaries do not exhibit this behavior. 3) A minimum moisture diffusivity is found which shows to correlate to the evaporation process, which indicates that this might be the result of a vapor dominated diffusion flux. Subject Fluid & Solid MechanicsSR - Structural ReliabilityTS - Technical SciencesBuildings and InfrastructuresMaterials2015 UrbanisationViscous fluidPorous mediaTransport prcoessesDiffusionDryingNMR To reference this document use: http://resolver.tudelft.nl/uuid:df6b9217-45b2-45a9-a316-4685fcaa9867 TNO identifier 523956 Source Chemical Engineering Science, 123, 620-628 Document type article Files To receive the publication files, please send an e-mail request to TNO Library.