Einfluss der elektrochemischen Doppelschicht auf die Sorption und den Transport von Chlorionen im Zementstein / Influence of the electrochemical double layer on sorption and transport of chlorides in hardened cement paste

2000 ◽  
Vol 6 (4) ◽  
pp. 415-428
Author(s):  
O. Wowra ◽  
M.J. Setzer
Keyword(s):  
Double Layer ◽  
Cement Paste ◽  
Building Materials ◽  
Pore Solution ◽  
Chloride Ions ◽  
Transport Processes ◽  
Cement Matrix ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Electrochemical Double Layer

Abstract Besides the formation of Friedel salt the transport and binding of chlorides in concrete is mainly defined by the electrochemical double layer at the interface between cement matrix and pore solution. Due to the alkaline pore solution the surface of hardened cement paste is negatively charged which may change to positive values by the potential regulating calcium ions. Inverting of the surface charge leads to an attraction of anions and therefore, to an adsorption of chloride ions in the diffuse part of the electrochemical double layer. Influence from outside like sulphates and carbon dioxide may lead to a decomposition of Friedel salt. Apart from these effect temperature, pH-value and certain environmental conditions affects the electrochemical double layer as well. The chloride equilibrium is mainly controlled by adsorbed ions in the electrochemical double layer. The model presented here is relevant for the assessment of ion transport processes in mineral building materials. Continuing investigations may lead to optimize transport models and a better evaluation of the critical chloride threshold value in reinforced concrete.

scholarly journals Thermal analysis of water confined in fully and partially saturated cement paste

2020 ◽  
Vol 172 ◽  
pp. 17008
Author(s):  
Dalia Bednarska ◽  
Marcin Koniorczyk
Keyword(s):  
Thermal Analysis ◽  
Cement Paste ◽  
Pore Solution ◽  
Cement Matrix ◽  
Complex Nature ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Scanning Calorimetry ◽  
Partially Saturated ◽  
Different Temperatures

The main object of the presented research is to apply thermal analysis in order to investigate microstructure of hardened cement paste. The test is conducted by means of differential scanning calorimetry on samples stored in various relative humidity levels as well as the fully saturated ones. The obtained results describe water solidification beginning at several different temperatures, which implies complex nature of cement paste microstructure. The recorded thermograms consist of two main peaks, which clearly indicate the division into capillary and gel pores. Additionally, the thermodynamic properties of actual pore solution confined in cement matrix are investigated. The obtained results indicate ions present in the liquid strongly affects its phase transition temperature as well as amount of ice formed during such the phase change.

Simple Approach for Computing Chloride Diffusivity of (Non)Carbonated Concrete

2008 ◽  
Vol 385-387 ◽  
pp. 281-284 ◽  
Author(s):  
In Seok Yoon
Keyword(s):  
Experimental Data ◽  
Structural Properties ◽  
Cement Paste ◽  
Scientific Knowledge ◽  
Pore Solution ◽  
Simple Approach ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Chloride Diffusivity ◽  
Concrete Materials

The purpose of this study is to establish a simple approach to compute the chloride diffusivity of (non)carbonated concrete. The chloride diffusivity of concrete should is defined, based on engineering and scientific knowledge of cement and concrete materials. In this paper, parameters affecting the chloride diffusivity, such as the diffusivity in pore solution, tortuosity, micro-structural properties of hardened cement paste, volumetric portion of aggregate, are taken into consideration in the calculation of the chloride diffusivity of noncarbonated concrete. For carbonated concrete, reduced porosity due to carbonation is calculated and used for calculating the chloride diffusivity. The results are compared with experimental data and previous research works.

The Thermal Deformation of Cement-Based Material at Low Temperatures

2014 ◽  
Vol 1081 ◽  
pp. 279-283 ◽  
Author(s):  
Nan Zhang ◽  
Juan Liao ◽  
Tao Zhang ◽  
Wen Zhan Ji
Keyword(s):  
Low Temperature ◽  
Cement Paste ◽  
Low Temperatures ◽  
Thermal Deformation ◽  
Pore Solution ◽  
Freezing Point ◽  
Bulk Solution ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Cement Based Materials

Thermal deformation of concrete at low temperature expands from-20°C to-50°C and contracts from-30°C to-10°C. Based on previous studies, the paper tries to explain the deformaion trend by analyzing freezing point of bulk solution and pore solution in saturated hardened cement paste. The result shows that it is critical to thermal deformation of cement-based materials at low temperature that pore solution in the pores smaller than 8 nm freezes.

scholarly journals Effects of chloride ions on carbonation rate of hardened cement paste by X-ray CT techniques

2016 ◽  
Vol 122 ◽  
pp. 619-627 ◽  
Author(s):  
Jun-zhe Liu ◽  
Ming-fang Ba ◽  
Yin-gang Du ◽  
Zhi-min He ◽  
Jian-bin Chen
Keyword(s):  
Cement Paste ◽  
Chloride Ions ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
X Ray

scholarly journals Application of Crumb Rubber in Cement-Matrix Composite

Materials ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 529 ◽  
Author(s):  
Chi-Yao Chen ◽  
Maw-Tien Lee
Keyword(s):  
Cement Paste ◽  
Matrix Composite ◽  
Surface Modifications ◽  
Crumb Rubber ◽  
Cement Matrix ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Colloidal Probe ◽  
Atomic Force ◽  
Ft Ir

Many studies have used rubber as an additive to form a cement-matrix composite (rubcrete). However, rubcrete has a lower mechanical strength than standard concrete. To improve the properties of rubcrete, this study performed surface modifications on crumb rubber through a partial oxidization reaction. The optimal ratio of air to nitrogen was determined by experiments to be 1:4. Fourier transform infrared spectroscopy (FT-IR) was used to identify the functional groups on the surface of the crumb rubber. A colloidal probe of calcium silicate hydrate (C–S–H) was prepared, and the intermolecular interactions between the rubber and the C–S–H were measured using an atomic force microscope (AFM). The experimental results showed that the partially oxidized crumb rubber contained more hydrophilic S–O bonds. The intermolecular force between C–S–H and treated rubber increased by 23% compared to the force between the original rubber and C–S–H. The compressive strength of the hardened cement paste (56 days) with the treated crumb rubber increased 50% in comparison with that of the hardened cement paste with the as-received crumb rubber.

Electrical Resistivity and Dielectric Properties of Hardened Cement Paste and Mortar

1995 ◽  
Vol 411 ◽  
Author(s):  
D. Buerchler ◽  
B. Elsener ◽  
H. Boehni
Keyword(s):  
Electrical Resistivity ◽  
Dielectric Properties ◽  
Water Content ◽  
Cement Paste ◽  
Pore Solution ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Solution Composition ◽  
Cement Based Materials

ABSTRACTWater content, porosity, pore solution composition, resistivity and dielectric properties of hardened cement paste and mortar samples have been studied as a function of time and relative humidities. A model for the resistivity of cement based materials is presented and an interpretation of the dielectric properties is proposed.

Influence of an Anti-Chloride Corrosion Admixture on Density of Cement-Based Materials

2012 ◽  
Vol 430-432 ◽  
pp. 1315-1319
Author(s):  
Wei Zhang ◽  
Xiao Yao ◽  
Ru Mu
Keyword(s):  
Pore Structure ◽  
Cement Paste ◽  
Sem Analysis ◽  
Chloride Ions ◽  
Mineral Admixture ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Chloride Corrosion ◽  
Steel Bar ◽  
Cement Based Materials

A new admixture increasing the density of cement-base composites and hence preventing the penetration of chloride ions is developed and investigated. The new admixture is the combination of traditional mineral admixture and steel bar inhibitor. The composition of the admixture is optimized using water absorption tests. Then the effect of the new admixture on the workability of freshly mixed cement paste as well as the pore structure and SEM analysis of hardened cement paste is experimentally investigated. The results show that the new admixture is effective to increase the density of cement-based materials.

Sign in / Sign up

Export Citation Format

Share Document