This paper presents a generalized modified Poisson−Nernst−Planck (MPNP) model derived from first principles based on excess chemical potential and Langmuir activity coefficient to simulate electric double-layer dynamics in asymmetric electrolytes. The model accounts simultaneously for (1) asymmetric electrolytes with (2) multiple ion species, (3) finite ion sizes, and (4) Stern and diffuse layers along with Ohmic potential drop in the electrode. It was used to simulate cyclic voltammetry (CV) measurements for binary asymmetric electrolytes. The results demonstrated that the current density increased significantly with decreasing ion diameter and/or increasing valency |z i | of either ion species. By contrast, the ion diffusion coefficients affected the CV curves and capacitance only at large scan rates. Dimensional analysis was also performed, and 11 dimensionless numbers were identified to govern the CV measurements of the electric double layer in binary asymmetric electrolytes between two identical planar electrodes of finite thickness. A self-similar behavior was identified for the electric double-layer integral capacitance estimated from CV measurement simulations. Two regimes were identified by comparing the half cycle period τ CV and the "RC time scale" τ RC corresponding to the characteristic time of ions' electrodiffusion. For τ RC ≪ τ CV , quasi-equilibrium conditions prevailed and the capacitance was diffusion-independent while for τ RC ≫ τ CV , the capacitance was diffusion-limited. The effect of the electrode was captured by the dimensionless electrode electrical conductivity representing the ratio of characteristic times associated with charge transport in the electrolyte and that in the electrode. The model developed here will be useful for simulating and designing various practical electrochemical, colloidal, and biological systems for a wide range of applications.

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This study investigates the durability of cementitious composites containing microencapsulated phase change materials (PCMs). First, the stability of the PCM's enthalpy of phase change was examined. A reductionof around25% in the phase change enthalpy was observed, irrespective of PCM dosage and aging. Significantly, this reduction in enthalpy was not caused by mechanical damage that was induced during mixing, but rather by chemical interactions with dissolved SO 4 2ions. Second, the influence of PCM additions on water absorption and drying shrinkage of PCM-mortar composites were examined. PCM microcapsules reduced the rate and extent of water sorption; the former was due to their non-sorptive nature which induces hindrances in moisture movement, and the latter was due to dilution, i.e., a reduction in the volume of sorptive cement paste. On the other hand, PCM inclusions did not influence the drying shrinkage of cementitious composites, due to their inability to restrain the shrinkage of the cement paste. The results suggest that PCMs exert no detrimental influences on, and, in specific cases, may even slightly improve the durability behavior of cementitious composites.