Using water vapour and N2 isotherms to unveil effects of SCMs on nanopores and evaluate hydration degree

Distribution and Dynamics of Water in the Blended Pastes Unraveled by Thermoporometry and Dielectric Properties

“…The CEM I paste has the lowest ice formation in all ranges of pores. These findings are somehow consistent with the measured moisture content by water vapour isotherms [9] and the pore size distribution in the same mixes with different curing conditions [2]. A further replacement of CEM I with limestone reduces the freezable water content compared with the binary slag paste.…”

“…This is probably due to the expelling of interlayer water into gel pores during the freezing. P045 and P245 have a higher C-S-H content than the other two samples in a well-hydrated condition [9]. Moreover, incorporation of Al in the C-S-H structure will stabilize the layer structure [46] to mitigate the effect of drying as well as freezing.…”

“…1b shows no indication on crystallization of water in P045 and P145 at RH of 33 %, but crystallization is detected in the slag blended pastes (P245 and P345) equilibrated at the same RH. This interesting result may be induced by the refined ink-bottle shape of pores with small necks [9]. During the drying process, it is difficult to dry the inner parts of these pores.…”

“…Drying of cement-based materials causes microstructural change of the main hydration products, such as contraction of layer and coarsening of capillary pores [9,55,56]. This dynamical change of the structure may induce an anomalous evolution of moisture redistribution, thereby increasing the portion of water in small pores while drying the large pores [57].…”

“…Incorporation of SCMs impacts the microstructure of hardened cement-based materials (hcp). Our previous investigation identified the effects of typical SCMs (fly ash, slag and limestone) on nanopore structure by water vapour desorption isotherms [9]. However, the sorption isotherm demonstrates the total moisture content in pores smaller than a critical value, and it cannot be used to characterize the detailed distribution of water in hcp at a specific relative humidity.…”