Abstract
An enhanced series-parallel (S-II) model of one-dimensional conductive heat flow through a unit cell was developed to estimate the time-dependent thermal conductivity of Class C fly ash stabilized soils. The unit cell is composed of three separate heat flow paths: a continuous path through solid contacts (soil contacts, fly ash contacts, and soil fly ash contacts) in parallel arrangement, a series-parallel path of solids in a series arrangement with a parallel arranged path of solid-miniscule pores (miniscule portion of solid water and miniscule portion of solid air), and a continuous path through water and air in parallel arrangement. The solid-miniscule pores volume fraction and the fluid/air volume fraction changes during pozzolanic reaction were modeled by estimating the interparticle pore water consumption rate. In addition, the time-dependent thermal conductivity characteristics of the fly ash soil mixtures were investigated by conducting experimental tests. Based on the test observations and parametric analysis, interparticle voids, fly ash percentage and degree of cementation, volume change of the interparticle liquids, and curing time were all found to play critical roles on the effective thermal conductivity of fly ash soil mixtures. The predicted thermal conductivity using the enhanced S-II model was compared with the experimental test data with good agreement, suggesting that the enhanced S-II model is a robust tool for estimating the global effective thermal conductivity of Class C fly ash stabilized soils.
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Abbreviations
- \(\lambda _s\) :
-
Thermal conductivity of dry solid
- \(\lambda _w\) :
-
Thermal conductivity of water
- \(\lambda _a\) :
-
Thermal conductivity of air
- \(\lambda _f\) :
-
Thermal conductivity of fluid
- \(\Theta _{\mathrm{sb}}\) :
-
A continuous path through solid contacts
- \(\Theta _w\) :
-
A continuous path through water
- \(\Theta _\mathrm{f}\) :
-
A continuous path through fluid
- \(\Theta _\mathrm{a}\) :
-
A continuous path through air
- \(\hbox {n}_{\mathrm{wm}}\) :
-
A series-parallel path of solids in a series arrangement with a parallel arranged path of solid particles-miniscule pores filled with air/water
- n :
-
Soil porosity
- \(\varepsilon \) :
-
Interparticle air–water interfacial coefficient
- R :
-
Universal gas constant (8.3144 J/mol K)
- \(\omega _0\) :
-
Initial water content
- \(\omega _f\) :
-
Final water content
- T :
-
Temperature of the fly ash/fly ash soil mixture
- \(T_0\) :
-
The peak temperature of fly ash/fly ash soil mixture
- t :
-
Time
- \(t_0\) :
-
Time corresponding to the peak temperature of fly ash/fly ash soil mixture
- a :
-
The slope of the temperature drop
- b :
-
The temperature difference between the final temperature and the peak temperature at a given time
- k :
-
The pozzolanic reaction rate
- A:
-
Gas constant \((t^{-1})\)
- \(E_a\) :
-
Apparent activation energy (J/mol), the \(E_a\) of fly ash in this study is 12.5 J/mol
- \(T_{set}, T_{set}=\ln \left( {\frac{t}{t_0}} \right) \) :
-
The natural logarithmic of time over the time \(t_0 \)
- \(S\left( {T_{set}} \right) \) :
-
The summary of the speed from time 0 to infinity (28 days of curing)
- \(\gamma \) :
-
The Euler gamma constant (\(\gamma \approx 0.577\))
- \(G_s\) :
-
Specific gravity of soil
- \(e_0\) :
-
Initial void ratio
- Q:
-
The power per unit length (W m\(^{-1}\))
- \(\lambda \) :
-
The thermal conductivity of the sample (W m\(^{-1}\,\mathrm{K}^{-1}\))
- \(a^{\prime }\) :
-
The thermal diffusivity (m\(^{2}\,\mathrm{s}^{-1}\))
- r :
-
Radius of the measured temperature range
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Kang, X., Ge, L. Enhanced series-parallel model for estimating the time-dependent thermal conductivity of fly ash soil mixtures. Granular Matter 17, 579–592 (2015). https://doi.org/10.1007/s10035-015-0577-x
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DOI: https://doi.org/10.1007/s10035-015-0577-x