open access

https://hdl.handle.net/2115/61444

Effects of water-to-cement ratio and temperature on diffusion of water in hardened cement pastes

英語

hardened cement paste

2015-05

Taylor & Francis Ltd

Journal of nuclear science and technology

52(5)

728-738

Apparent diffusion coefficients (D-a) of water and activation energies (E-a) of diffusion in hardened cement pastes (HCPs) were determined as a function of water-to-cement (w/c) ratio (0.36-0.60) and temperature (293-323K) using HTO and (H2O)-O-18 as tracers. The values of D-a and E-a ranged from 1.1x10(-11) to 1.7x10(-10) m(2) s(-1) and from 21.5 to 31.3 kJ mol(-1), respectively. No significant difference between the D-a values of HTO and (H2O)-O-18 suggests that water predominantly diffuses as H2O molecule and dissociation of water is not significant even at high pH range in HCP. The values of E-a at low w/c ratio were higher than in bulk liquid water, suggesting a contribution of a different water regime, such as supercooled bulk water. Two simple models consisting of capillary and gel pores were considered to estimate the volume ratio of gel pores to total pores by optimizing the model to fit with the experimental data. The result suggests that HCP has a pore network mostly consisting of capillary pores with some very narrow pores plugged with hydrates, where HTO must diffuse through gel pores. This view of the HCP pore network was made available through analysis of E-a values.

学術雑誌論文

Accepted Manuscript

This is an Accepted Manuscript of an article published by Taylor & Francis in Journal of nuclear science and technology on May 2015, available online: http://wwww.tandfonline.com/10.1080/00223131.2014.979902

0022-3131