Influence of Nanostructure Change during Drying on Frost Resistance of HCP
By Yoshimichi Aono, Matsushita Fumiaki, Shibata Sumio and Yukio Hama

Concrete Research and Technology
Vol.19, No.2, May. 2008 (Issue 47)

Pore sturctural changes in hardened cemen patses, subjected to drying and wetting/drying cycles, were studied at micrometer and nanometer levels. Characterization techniques included NMR, nitrogen and water vapor adsorption, mercury intrusion porosimetry and under water weighing. Coarsening of pore structure and increase in the true density were observed. Decrease in specific surface area due to drying was observed with water vapor adsorption associated with Excess Surface Work (ESW) analysis suggested a development of cohesive and layered structure in C-S-H. The results of NMR confirmed polymerization of silicate anion chains. A model of change in nanostructure of C-S-H during drying was propsed. The deterioration of frost resistance is better examined by the coarsening of pore size distribution rather than cracking.
pore structures, mercury intrusion porosimetry, NMR, gas adsorption isotherms, CIF, frost resistance, hardened cement paste

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