Interpretation of Full Sorption-Desorption Isotherms as a Tool for Understanding Concrete Pore Structure
Author(s)Pinson, Matthew B.; Jennings, Hamlin M.; Bazant, Martin Z.
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Sorption isotherms are frequently used to characterize the structure of porous materials such as cement. Their interpretation has been somewhat hindered by the large hysteresis observed between the adsorption and desorption processes. Here, we model the hysteresis due to pore blocking, whereby water condensed in small pores prevents propagation of a vapour interface into the pore structure, trapping water condensed in larger pores in a metastable state. The model identifies the adsorption isotherm as more useful in determining the pore size distribution. Additionally, and of particular interest, it provides a way of calculating an additional structural parameter, quantifying the exposure of mesopores (gel pores) to the surrounding atmosphere. This exposure is higher for samples with higher water-to-cement ratio, suggesting that it is mediated by capillary pores. The model also allows calculation of the connectivity of the pore structure, although the intertwined influences of exposure and connectivity make the latter difficult to interpret.
DepartmentMassachusetts Institute of Technology. Department of Chemical Engineering; Massachusetts Institute of Technology. Department of Civil and Environmental Engineering; Massachusetts Institute of Technology. Department of Mathematics; Massachusetts Institute of Technology. Department of Physics
Mechanics and Physics of Creep, Shrinkage, and Durability of Concrete
American Society of Civil Engineers (ASCE)
Pinson, Matthew B., Hamlin M. Jennings, and Martin Z. Bazant. “Interpretation of Full Sorption-Desorption Isotherms as a Tool for Understanding Concrete Pore Structure.” Mechanics and Physics of Creep, Shrinkage, and Durability of Concrete (September 23, 2013).
Author's final manuscript