scholarly journals Chloride Transport Behaviour and Service Performance of Cracked Concrete Linings in Coastal Subway Tunnels

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6663
Author(s):  
Sulei Zhang ◽  
Qing Xu ◽  
Rui Ren ◽  
Jiahao Sui ◽  
Chang Liu ◽  
...  
Keyword(s):  
Service Life ◽  
Numerical Simulations ◽  
Chloride Transport ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Service Performance ◽  
Concrete Lining ◽  
Cracked Concrete ◽  
Transport Behaviour ◽  
Subway Tunnels

The concrete lining in subway tunnels often undergoes cracking damage in coastal cities. The combination of cracked tunnel lining structures and high concentrations of corrosive ions in the groundwater (e.g., chlorine) can accelerate concrete erosion, reduce the mechanical performance of the lining structures and shorten the tunnel service life. This paper investigates the chloride ion concentration in the groundwater of several subway tunnels in the coastal city of Qingdao, China. Indoor experiments and numerical simulations are conducted to investigate the chloride ion transport behaviour and service performance of cracked concrete linings. The results are applied to predict the service life of lining structures. The crack depth in concrete linings is found to have the most significant effect on the transport rate of chloride ions, followed by the crack width. The numerical simulations are carried out using COMSOL software to study the chloride transport behaviour in cracked specimens and predict the service lifetimes of lining structures of different thicknesses, and the results correspond well with the experimental data. The durability of a concrete lining can be enhanced by increasing the thickness of the protective concrete layer. Additional measures are proposed for treating cracked concrete linings to resist chloride ion attack in subway tunnels.

scholarly journals Analysis of changes in sodium and chloride ion transport in the skin

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Iga Hołyńska-Iwan ◽  
Karolina Szewczyk-Golec
Keyword(s):  
Ion Transport ◽  
Electrical Resistance ◽  
Chloride Transport ◽  
Electrical Potential ◽  
Chloride Ion ◽  
Skin Condition ◽  
Chloride Ions ◽  
Chemical Stimulus ◽  
Experimental Conditions ◽  
Chloride Ion Transport

Abstract The measurement of electric potential and resistance reflect the transport of sodium and chloride ions which take place in keratinocytes and is associated with skin response to stimuli arising from external and internal environment. The aim of the study was to assess changes in electrical resistance and the transport of chloride and sodium ions, under iso-osmotic conditions and following the use of inhibitors affecting these ions’ transport, namely amiloride (A) and bumetanide (B). The experiment was performed on 104 fragments of rabbit skin, divided into three groups: control (n = 35), A—inhibited sodium transport (n = 33) and B—inhibited chloride transport (n = 36). Measurement of electrical resistance (R) and electrical potential (PD) confirmed tissue viability during the experiment, no statistically significant differences in relation to control conditions were noted. The minimal and maximal PD measured during stimulation confirmed the repeatability of the recorded reactions to the mechanical and mechanical–chemical stimulus for all examined groups. Measurement of PD during stimulation showed differences in the transport of sodium and chloride ions in each of the analyzed groups relative to the control. The statistical analysis of the PD measured in stationary conditions and during mechanical and/or mechanical–chemical stimulation proved that changes in sodium and chloride ion transport constitute the physiological response of keratinocytes to changes in environmental conditions for all applied experimental conditions. Assessment of transdermal ion transport changes may be a useful tool for assessing the skin condition with tendency to pain hyperactivity and hypersensitivity to xenobiotics.

Test Research of Chloride Ion Penetration in Concrete Tunnel Lining Structure

2012 ◽  
Vol 446-449 ◽  
pp. 3155-3159
Author(s):  
Zhong Li ◽  
Yan Peng Zhu ◽  
Xiao Yan Cui
Keyword(s):  
Service Life ◽  
Penetration Depth ◽  
Chloride Ion ◽  
Chloride Content ◽  
Chloride Ions ◽  
Tunnel Lining ◽  
Chloride Ion Penetration ◽  
Lining Structure ◽  
Erosion Environment ◽  
Ion Penetration

Chloride ion diffusion coefficient is an important indicator reflected the concrete durability in chloride erosion environment, and affects the service life of concrete structure directly. By the indoor test of chloride acceleration permeability, the chloride ions diffusivity is studied in the tunnel lining structure, and the variation law of the chloride content is tested with the change of penetration depth of different age specimen. Tests shows, with the increases of the penetration depth, the chloride content decrease gradually and finally tend to the initial chloride content of the specimen. Penetration time has a strong cumulative effect on the internal concentration of chloride ions in concrete, the high or low level of chloride ion concentration have a role of promotion or reduction for the chloride ion penetration in the concrete inside. The results provide an important basis for the predictions of service life of tunnel lining in chloride erosion environment.

Experimental Study on Improvement Mechanism of Silane Emulsion on Acid Rain Corrosion of Green Ecological Concrete

2020 ◽  
Vol 12 (6) ◽  
pp. 873-883
Author(s):  
Wei Xun Hu ◽  
Yao Zhuang Li ◽  
Hua Peng
Keyword(s):  
Compressive Strength ◽  
Service Life ◽  
Acid Rain ◽  
Concrete Structure ◽  
Test Group ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Test Time ◽  
Ratio Test ◽  
Mixing Ratio

Concrete structure is vulnerable to acid rain corrosion, which affects the service life of the material, in the corrosive environment, and concrete structure will deteriorate because of the erosion of water/chloride ions. Therefore, waterproof treatment of concrete structure is needed to improve the durability of the structure. In this study, the green ecological concrete is taken as the research object. The concrete is mixed with a certain amount of silane emulsion to reduce the probability of corrosion of concrete due to moisture and chloride ions, thereby prolonging the service life of this kind of concrete. During the experiment, in order to further test the corrosion resistance of silane emulsion to this kind of concrete, different kinds of concrete were taken as test objects and divided into 3 test groups, namely, the original test group (ITE), the non silane emulsion test group (TWSE) and the optimal ratio test group (OT-SE). It is proved by experiments that the best proportion of concrete mixed with silane emulsion is 0.32 of water binder ratio, 18% of coal powder mixing ratio, 37% of gravel mixing ratio and 0.23% of proportion of silane emulsion. The above factors are applied to compressive strength test, and 30 days as test time, the compressive strength of concrete with fly ash is measured. In the experiment of anticorrosion, compared with the traditional concrete samples, the electrical flux of concrete mixed with silane emulsion decreased by 28.7% in 8 h, that is, chloride ion permeability decreased significantly.

scholarly journals Durability of Subsea Tunnels under the Coupled Action of Stress and Chloride Ions

2019 ◽  
Vol 9 (10) ◽  
pp. 1984
Author(s):  
Qingli Zhao ◽  
Limin Lu
Keyword(s):  
Differential Equation ◽  
Partial Differential Equation ◽  
Service Life ◽  
Reliability Index ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Ion Concentration ◽  
Influence Coefficient ◽  
Partial Differential ◽  
Convection Diffusion

The durability of subsea tunnels under the coupled action of stress and chloride ions was analyzed to estimate the service life and provide a theoretical foundation for durability design. The influence coefficient of the stress on chloride ion transmission at lower stress levels was discussed according to the material mechanics, and was verified by experimental data. A stress calculation model of a subsea tunnel’s lining section is proposed based on the plane-section assumption. Considering the space-time effect of the convection velocity, a partial differential equation was constructed to calculate the chloride ion transfer condition under the coupled action of stress-convection-diffusion. The numerical solution of the partial differential equation was solved and the sensitivity of the parameters was analyzed. The subsea tunnel’s time-varying reliability index was calculated following the Monte Carlo method, and was used to predict the service life. The results show that the chloride ion concentration calculated by considering the coupled action is larger and the reliability index is lower than calculated only considering diffusion. Our findings contribute to the conclusion that durability designs of subsea tunnels should consider the coupled action of stress-convection-diffusion. An effective method to improve the service life of a subsea tunnel is to reduce the water–binder ratio or increase the thickness of protective cover.

Diffusivity Resistance of Concrete Systems in Chloride Rich Environment for Corrosion Protection of Embedded Steel Bars

2013 ◽  
Vol 831 ◽  
pp. 3-8
Author(s):  
Suad Khalid Al-Bahar ◽  
Safaa M. Abdul Salam ◽  
Adel M. Husain
Keyword(s):  
Service Life ◽  
Concrete Structures ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Steel Reinforcement ◽  
Mineral Admixtures ◽  
Chloride Ingress ◽  
Corrosion Initiation ◽  
Chloride Ion Penetration ◽  
Ion Penetration

Improving concrete performance and minimizing corrosion-induced deterioration of reinforced concrete structures are mandated Building Codes Practices and Specifications in arid regions such as the Arabian Gulf. Concrete structures resist corrosion due to the passivating properties of the hydrated cement around the steel reinforcement created by the high alkaline environment within the composite structure (pH > 12). However, the presence of chloride ions in the pore structure of the concrete destroys this passivating layer, which makes the steel reinforcement vulnerable to chloride-induced corrosion attack that accelerates degradation and deterioration of concrete structures. Corrosion activities-related tests such as Time-to-Corrosion Initiation (Modified ASTM G-109)6, and Corrosion Rate Test (Lollipop Test), can be effectively used to monitor the behavior of corrosion development, while chloride ingress characteristics tests such as Electrical Indication of Concretes Ability to Resist Chloride Ion Penetration ASTM C-1202-91)7, and the Resistance of Concrete to Chloride Ion Penetration (AASHTO T 259-80)8, are applied to evaluate the rate at which chloride ions can diffuse through concrete to onset the time-to-corrosion initiation, which will impact the structure service life and compromise its sustainability. Efforts have been made by scientists to develop mathematical simulation models that predict the service life of the structure based on Ficks Second Law for semi-finite diffusion of chloride ions, concentrated at different concrete depths. The study concluded that mineral admixtures have contributed to the enhancement of concrete performance and its resistance to chloride diffusivity, as well when in combination with corrosion-inhibiting admixture such as calcium nitrite.

The effect of hydrophobic impregnation on chloride ingress into cracked concrete

2019 ◽  
Author(s):  
Haris Sohawon ◽  
Hans Beushausen
Keyword(s):  
Service Life ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
Water Repellent ◽  
Chloride Ingress ◽  
Chloride Diffusion Coefficient ◽  
Product Lines ◽  
Cracked Concrete ◽  
Cover Depth ◽  
Hydrophobic Silane

<p>Premature concrete degradation due to rebar corrosion has many financial and social implications on a large scale. Direct costs relate to the repair and rehabilitation of existing structures to maintain serviceability while indirect costs include loss in productivity and reduced economic growth. Hydrophobic (silane) impregnation represents a cost-effective way to increase the durability of concrete structures in cases where insufficient design cover quality and depth have been achieved. The water repellent product lines the internal capillary pore structure and provides a water-repellent concrete surface. Thus, the risk of reinforcement corrosion initiation and subsequent deterioration can be reduced as the ingress of water-dissolved aggressive species (chlorides) is minimised or prevented. The purpose of this study was to investigate and quantify the influence of silane impregnation as a remedial measure for poor quality or insufficient cover depth in newly constructed structures and ultimately predict the service life extension possible for specific cover depths. The effectiveness of silane impregnation in cracked concrete was also studied. The results indicate that silane impregnation reduces capillary absorption and conductivity of chloride ions for all the mixes. Chloride ingress in the treated concrete mixes was suppressed and lower chloride surface concentration (C<sub>s</sub> and apparent chloride diffusion coefficient (D<sub>a</sub>) were recorded. A slight decrease in carbonation depth was observed in the w/b 0.60 concrete mixes. The results also suggest that silane impregnation reduces chloride ingress in cracked concrete (up to a crack width of 0.6 mm). A lower rate of chloride ingress was predicted in the silane treated concrete and consequently to achieve the same service life, smaller cover depths are required. The overall results indicate that the service life of concrete with inadequate cover depth and quality, regardless of the binder type, can be effectively extended using hydrophobic (silane) impregnation, assuming proper surface preparation and application methods.</p>

Concentration Distribution of Chloride Ion in Cracked Concrete

2013 ◽  
Vol 351-352 ◽  
pp. 1581-1584
Author(s):  
Bo Yu ◽  
Zhong Hui Huang ◽  
Ming Wu ◽  
Hui Liang Sun ◽  
Lu Feng Yang ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Concentration Distribution ◽  
Chloride Ion ◽  
Diffusion Path ◽  
Chloride Ions ◽  
Time Dependent ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Cracked Concrete ◽  
Ions Transport

Cracks provide diffusion path for chloride ions transport from the external environment into the concrete, resulting in the durability degradation of concrete structures. In this paper, the boundary condition of cracked concrete and chloride diffusion coefficient in crack were analyzed. The time-dependent chloride diffusion model was established based on the time-dependent chloride diffusion coefficient and the Ficks second law of diffusion. The influence of crack on the concentration distribution of chloride ion in cracked concrete was quantificationally investigated.

scholarly journals Experimental Study and Simulation Calculation of the Chloride Resistance of Concrete under Multiple Factors

2021 ◽  
Vol 11 (12) ◽  
pp. 5322
Author(s):  
Yang Ding ◽  
Tong-Lin Yang ◽  
Hui Liu ◽  
Zhen Han ◽  
Shuang-Xi Zhou ◽  
...  
Keyword(s):  
Hydrostatic Pressure ◽  
Penetration Depth ◽  
Chloride Ion ◽  
Cementitious Materials ◽  
Chloride Ions ◽  
Finite Element Software ◽  
Chloride Resistance ◽  
Simulation Calculation ◽  
Marine Concrete ◽  
Resistance Performance

Cement is widely used in marine concrete, and its resistance to chloride ion corrosion has been widely considered. In this paper, based on a laboratory test, the influence of different hydrostatic pressures, coarse aggregate contents and w/c ratios on the chloride resistance performance is analyzed. Based on COMSOL finite element software, a two-dimensional cementitious materials model is established, and the simulation results are compared with the experimental results. The results show that the penetration depth of chloride ions in cement increases with the increase of the w/c ratio. Under the hydrostatic pressure of 0 MPa, when the w/c ratio is 0.35, the penetration depth of chloride ions is 7.4 mm, and the simulation result is 8.0 mm. When the w/c ratio is 0.45, the penetration depth of chloride ions is 9.3 mm, and the simulation result is 9.9 mm. When the w/c ratio is 0.55, the penetration depth of chloride ions is 12.9 mm, and the simulation result is 12.1 mm. Under different hydrostatic pressures, the penetration depth of chloride ions obviously changes, and with the increase in hydrostatic pressure, the penetration depth of chloride ions deepens. Under the w/c ratio of 0.35, when the hydrostatic pressure is 0.5 MPa, the penetration depth of chloride ions is 11.3 mm, and the simulation result is 12.1 mm. When the hydrostatic pressure is 1.0 MPa, the penetration depth of chloride ions is 16.2 mm, and the simulation result is 17.5 mm.

scholarly journals Broadband dielectric spectroscopy for monitoring temperature-dependent chloride ion motion in BiOCl plates

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Adrian Radoń ◽  
Dariusz Łukowiec ◽  
Patryk Włodarczyk
Keyword(s):  
Electrical Conductivity ◽  
Dielectric Spectroscopy ◽  
Low Frequency ◽  
Chloride Ion ◽  
Ion Source ◽  
Chloride Ions ◽  
Ion Concentration ◽  
Broadband Dielectric Spectroscopy ◽  
Free Chloride ◽  
Structure Rebuilding

AbstractThe dielectric properties and electrical conduction mechanism of bismuth oxychloride (BiOCl) plates synthesized using chloramine-T as the chloride ion source were investigated. Thermally-activated structure rebuilding was monitored using broadband dielectric spectroscopy, which showed that the onset temperature of this process was 283 K. This rebuilding was related to the introduction of free chloride ions into [Bi2O2]2+ layers and their growth, which increased the intensity of the (101) diffraction peak. The electrical conductivity and dielectric permittivity were related to the movement of chloride ions between plates (in the low-frequency region), the interplanar motion of Cl− ions at higher frequencies, vibrations of these ions, and charge carrier hopping at frequencies above 10 kHz. The influence of the free chloride ion concentration on the electrical conductivity was also described. Structure rebuilding was associated with a lower concentration of free chloride ions, which significantly decreased the conductivity. According to the analysis, the BiOCl plate conductivity was related to the movement of Cl− ions, not electrons.

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