Chloride Adsorption of Cement Hydrates Combined with Chemical Evolution of Pore Solution

Multi-factor sensitivity analysis of chloride ingression: A case study for Hangzhou Bay Bridge

Nitrite binding in cement

Modelling capillary effects on the reactive transport of chloride ions in cementitious materials

SA80INTERLEUKIN-8 (BUT NOT INTERLEUKIN-6) SHARES GENETIC OVERLAP WITH RISK FOR SUICIDE ATTEMPTS IN WOMEN (BUT NOT IN MEN)

Uptake of chloride and carbonate by Mg-Al and Ca-Al layered double hydroxides in simulated pore solutions of alkali-activated slag cement

Solidification of chloride ions in alkali-activated slag

Metakaolin concrete is a kind of porous material, which contains a variety of chemical ions in the pores. Solutions in these pores are exposed to the atmosphere and exist evaporation and condensation processes, therefore, the pore solution volume of concrete changes all the time. When the ion concentration in the pore solution changes, it has an important impact on the strength development and durability of concrete. However, the real-time monitoring of the concentration of pore solution was difficult. To study the chemical evolution of pore solution in concrete, the variation of saturated vapor pressure on the surface of metakaolin concrete was studied based on the Cisternas-Lam rule. The evaporation rate of solvent in the pore solution of concrete under the corresponding saturated vapor pressure in this paper was studied by the Stefan diffusion method. The dynamic equilibrium process equation of ions in pore solution was then established based on the thermodynamic equilibrium equation. Based on the above model, the change process of the pore solution of metakaolin concrete was studied, and it was verified by the results of the literature.

The theory of ionic diffusion in water-saturated concrete accompanying ion exchange with mobile or immobile adsorbed ions was constructed by using the general theory of diffusion and the condition of electrical neutrality. Analysis of the diffusion profile of chloride (Cl−) ions in concrete with the theory revealed that adsorbed Cl− ions in AFm and C-S-H are as mobile as free Cl− ions in the pore solution, so that the adsorption does not retard the ingress of Cl− ions. The existing test methods for determining the effective or apparent diffusion coefficient of Cl− ions were evaluated on the bases of the present theory and new experimental findings. It was revealed that steady-state electrochemical methods such as NTBUILD-355 and ASTM C1202 are not suitable for determining the diffusion coefficient, because the steady state methods expel preexisting diffusible ions which strongly affect the diffusion of Cl− ions. Moreover, the steady state methods overestimate the diffusion rate because the methods assume that adsorbed Cl− ions are immobile. The electrochemically-accelerated method NT BUILD 443 is also unsuitable for the diffusion test, because the acceleration is induced by the electro-osmotic flow of the external solution into concrete. The present diffusion theory necessitates the effective self-diffusion coefficient of not only Cl− ions but also all the other diffusible ions in concrete. A simple method of determining the effective self-diffusion coefficients of arbitrary ions in concrete from the diffusion profile of Cl− ions was presented.

Barite and gypsum precipitation in chalk: A numerical simulation approach revealing the coupled impact of physical and chemical heterogeneities in porous media

Kinetic, thermodynamic and equilibrium studies on chloride adsorption from simulated concrete pore solution by core@shell zeolite-LTA@Mg-Al layered double hydroxides

The effects of fly ash composition on the chemistry of pore solution in hydrated cement pastes

This work presents experimental evidence that confirms the potential for two specific zeolites, namely chabazite and faujasite (with a cage size ~2–13 Å), to adsorb small amounts of chloride from a synthetic alkali-activated cement (AAC) pore solution. Four synthetic zeolites were first exposed to a chlorinated AAC pore solution, two faujasite zeolites (i.e., FAU, X-13), chabazite (i.e., SSZ-13), and sodium-stabilized mordenite (i.e., Na-Mordenite). The mineralogy and chemical composition were subsequently investigated via X-ray diffraction (XRD) and both energy- and wavelength-dispersive X-ray spectroscopy (WDS), respectively. Upon exposure to a chlorinated AAC pore solution, FAU and SSZ-13 displayed changes to their diffraction patterns (i.e., peak shifting and broadening), characteristic of ion entrapment within zeolitic aluminosilicate frameworks. Elemental mapping with WDS confirmed the presence of small amounts of elemental chlorine. Results indicate that the chloride-bearing capacity of zeolites is likely dependent on both microstructural features (e.g., cage sizes) and chemical composition.

The hydration reaction of high alumina cement at a temperature of 20 ºC and water/cement ratio of 0.5 has been studied over a period of one month. The changes of the solid phase were followed by X-ray diffraction and thermal analysis. Besides, pore-solution was expressed by application of high mechanical pressure (500 MPa) during different periods of the reaction in order to study its Chemical composition evolution as a result of the hydration process.

Effect of MgO on chloride penetration resistance of alkali-activated binder

초록·키워드 목차 오류제보하기 등록된 정보가 없습니다. ABSTRACT1. 서론2. 임계 염소 이온량의 해석에 대한 이론적 기법3. 결과 및 분석4. 결론참고문헌요약