Surface Chloride Research Articles

Groundwater Recharge Assessment Using Multi Component Analysis: Case Study at the NW Edge of the Varaždin Alluvial Aquifer, Croatia

Exploring the interaction between precipitation, surface water, and groundwater has been a key subject of many studies dealing with water quality management. The Varaždin aquifer is an example of an area where high nitrate content in groundwater raised public concern, so it is important to understand the aquifer recharge for proper management and preservation of groundwater quality. The NW part of the Varaždin aquifer has been selected for study area, as precipitation, Drava River, accumulation lake, and groundwater interact in this area. In this study, groundwater and surface water levels, water temperature, water isotopes (2H and 18O), and chloride (Cl−) were monitored in precipitation, surface water, and groundwater during the four-year period to estimate groundwater recharge. Head contour maps were constructed based on the groundwater and surface water levels. The results show that aquifer is recharged from both Drava River and accumulation lake for all hydrological conditions–low, mean, and high groundwater levels. The monitoring results of water temperature, chloride content, and stable water isotopes were used as tracers, i.e. as an input to the mixing model for estimation of the contribution ratio from each recharge source. The calculation of mixing proportions showed that surface water is a key mechanism of groundwater recharge in the study area, with a contribution ratio ranging from 55% to 100% depending on the proximity of the observation well to surface water.

Synthesis of antibacterial Janus sheets containing dual-active centers by quaternization fracture

The prevention of bacterial adhesion and proliferation on substrate surfaces have been recently growing interest of scientists. Herein, hollow Janus copolymer microspheres (PSV JMs) containing hydrophilic sodium sulfonate groups (-SO 3 Na) on its outer surface and hydrophobic benzyl chloride groups (-C 6 H 5 -CH 2 Cl) on its inner surface, were first synthesized through interfacial polymerization. Furthermore, the antibacterial Janus copolymer sheets (PSVNN JSs) with contact/release-based dual-active centers were successfully synthesized by using the obtained PSV JMs for two-step quaternization with hexadecyl trimethyl ammonium bromide (CTAB) and hexadecyldimethylamine (HDMA). Notably, PSVNN JSs could be effectively obtained through reasonable control of several factors, including the ratio of hydrophilic and hydrophobic monomers, the amount of crosslinker and pore-forming agent. Moreover, the resultant PSVNN JSs exhibited higher antibacterial activity due to the quaternary ammonium salts (QASs) groups connected by ionic bond and covalent bonds, which has bright prospects in application in biomedical and environmental science. • The interfacial polymerization was employed to prepare the hollow Janus copolymer microspheres (PSV JMs). • The antibacterial Janus copolymer sheets (PSVNN JSs) with dual-active centers could be realized by quaternization fracture of PSV JMs. • The PSVNN JSs exhibited higher antibacterial activity because of the synergistic antibacterial effect. • The PSVNN JSs would be of considerable significance for the construction of highly efficient antibacterial materials.

Numerical model of the effect of water vapor environment on the chloride transport in concrete

Chloride ions are known as one of the most crucial factors for rebar corrosion in reinforced concrete (RC) structures exposed to marine environments under drying-wetting cycles. In this condition, the chloride ion content in unsaturated concrete will change under the coupled effect of diffusion and capillary suction. This study simulates the atmosphere zone of the marine environment to explore the law of the chloride transmission behavior under the context of constant temperature and humidity. To analyze the effect of different drying-wetting ratios on the chloride ion profile in the concrete by conducting the dry-wet cycle tests. It is found that the most unfavorable drying-wetting ratios for RC structures in this study is 1:5.5. A finite element numerical model of chloride ion transmission based on Fick’s Ⅱ law was established by COMSOL Multiphysics. It can be used to predict the range of concrete surface chloride ion concentration, and dynamic change of the distribution of chloride ion concentration inside the RC structures under different drying-wetting cycles over time. The comparison of experiment data and simulation results verify that the chloride diffusion prediction model has a good correlation.

Time-dependent chloride transport models for predicting service life of bridge decks under chloride attack

This study aims to propose a set of time-dependent chloride transport models based on the measured data of 16 locations of monolithic concrete bridge decks under the attack of chloride ions in form of de-icing salts. This is carried out due to the shortcomings in the previous study which developed time-independent models containing two regression parameters. In this study, there are four regression parameters to be determined. They are simultaneously calculated using the finite difference formulation embedded with regression analysis. From the study, it is observed that the developed chloride transport model can predict the chloride content in most bridge decks. Although the prediction in some cases falls outside 50% margin of difference, they are on the conservative side. The regression parameters in the surface chloride function calculated here is higher than those in the previous study by two times. Seemingly, the diffusion coefficient in this study is comparable with that in Life-365 program. On the measurement or field survey date, if using the critical chloride value of 0.6 and 1.2 kg/m3, most and 5 of 16 bridge decks, respectively, would have rebar corrosion. However, there would be no concrete cracking if using the critical chloride value of 2.0 kg/m3.

A sensitivity analysis of predictive modelling for chloride diffusion in reinforced concrete structures

The corrosion of steel due to chloride ingress is one of the major causes of deterioration of reinforced concrete structures. In order to ensure a structure achieves the design life specified, predictive modelling is employed. To undertake this modelling, details are required on a number of variables; however, each of these variables has a level of uncertainty which can affect the reliability of the model. To address these issues, this paper reports the analysis of data taken from four distinct elements on a port structure, in Australia, constructed in three phases between 1926 and 1985, using both pre-cast and cast in situ techniques. The cover depth, surface chloride concentration and chloride diffusion coefficient were determined for different elements on the structure, with a total of 244 data points obtained. The data was analysed to identify the statistical distributions and probability density functions produced. A novel analytical model was developed based on the solutions to Fick's equation. The results showed that both surface chloride and the diffusion coefficient were positively skewed with no significant variation in the sensitivity. It was also found that controlling the diffusion coefficient has a more influential effect than increasing the cover.

Experimental and numerical analysis of chloride transport in finite concrete under reverse water pressure

This paper investigates chloride ion convection–diffusion transport in the finite RC structure under reverse water pressures. The chloride ion penetration in concrete is examined experimentally and theoretically. One-dimensional experiments are designed to reveal the characters of the time-varied behaviors of surface chloride ion concentration and the chloride ion penetration under different reverse water pressure in the concrete. A numerical solution of the chloride ion convection–diffusion penetration is also established by finite element method (i.e., FEM) via software entitled COMSOL Multiphysics. The K-C model is attempted to be used for the assess of the permeability of concrete. The results suggest that the reverse water pressure can weaken the accumulation of chloride ion on the concrete surface and effectively prevent the chloride ions from invading into the concrete. The results of this paper offer much-needed insights into this growing discussion in the field of assess of durability of finite marine RC structure.

Time-varying behavior and its coupling effects with environmental conditions and cementitious material types on surface chloride concentration of marine concrete

A time-varying multi-factor model for surface chloride concentration (Cs) of marine concrete was developed by adopting reciprocal function and taking into consideration the coupling effects of exposure duration with cementitious material types and environmental conditions. Firstly, a total of 1385 sets of field test data for Cs of marine concrete under different environmental conditions (i.e., tidal, splash, submerged and atmosphere zones) were collected from 17 countries. Then the reciprocal function was adopted to describe the time-varying behavior of Cs based on detailed comparison with different types of time-varying function. Furthermore, two coefficients were introduced to account for the coupling effects of exposure duration with cementitious material types and environmental conditions on Cs of marine concrete. Subsequently, a time-varying multi-factor model in terms of reciprocal function was developed for Cs of marine concrete under different environmental conditions. Finally, comparison with several different models for Cs was conducted to validate the proposed model. Results show that the proposed time-varying model for Cs accounts for the coupling effects of exposure duration with cementitious material types and environmental conditions, and has high accuracy and general validity.

Analysis of Poultice-Based Desalination of a Nineteenth Century Brick and Stone Cathedral after the Event; A Longitudinal Study of Surface Chloride Readings

St George’s Cathedral in Perth was consecrated in 1888 and constructed using hand-made bricks and limestone. After 120 years of exposure to salt-laden winds, rising salty water and leaky roofs significant deterioration due to salt efflorescence and water penetration necessitated an $18 million AUD restoration program in 2002. Before accepting the heritage architect’s proposal to replace all the worst damaged brick and stone elements, surface chloride activity mapping of the affected areas was conducted. The survey found that the worst decay was associated with high chloride ion concentrations, with a maximum value of 10,000 ppm on a brick buttress and 7,600 ppm on a stone colonnade on the west front. After four months of treatment, the Westox Cocoon papier-mâché pulp poultice had lowered the surface chloride readings to 10 ± 5 ppm on the bricks and stone. Ten years after the work, a series of tests were conducted on salt-damaged reference stone and bricks to find formulae for converting surface chloride readings into weight percent extractable chloride concentrations. This data was then retrospectively applied to the treated cathedral fabric to estimate how much chloride had been removed. Without the poultice treatment, large sections of the original fabric would have been lost.

Influence of some added electrolytes on the surface and thermodynamic propertiesof cetylpyridinium chloride in aqueous medium

The effect of some added electrolytes, viz. NaCl, CaCl2 and AlCl3, on the critical micelle concentration (CMC),maximum surface excess concentration (Γmax) and minimum area per molecule (Amin) at air-liquid interface of a cationicsurfactant cetylpyridinium chloride (CPC) in aqueous solutions have been studied at 288.15, 293.15 and 298.15 K usingtensiometric method. The effect of an added electrolyte on decreasing CMC of CPC is found to be in the order (AlCl3) >(CaCl2) > (NaCl), which falls in the same order as of the moles chloride ions furnished by each mole of the addedelectrolyte. The Γmax decreases with increasing temperature and electrolyte concentration leading to an enhanced availablearea per molecule at the air-liquid interface. The process of micellization and adsorption of CPC at air-liquid interface areboth favoured by exothermic enthalpy change as well as entropy gain. The observed features such as lowering of CMC,higher thermodynamic micellar stability, more relaxed surfactant molecules at the interface, due to an added electrolyte,may be exploited for improving the efficiency of the surfactant as a detergent, solubilizing agent, froth floatation process forconcentrating ores, petroleum oil recovery and oil spill management.

Permeation Characteristics and Surface Accumulation of Chloride in Different Zones of Concrete along Altitude in Marine Environments

The accumulation characteristics of surface chloride in concrete in different zones are different in the marine environment. A series of laboratory experiments were conducted to investigate the surface chloride and permeation characteristics of concrete in a simulated marine environment. The experimental results indicated that the surface chloride and chloride profiles of concrete in different zones of marine environment decreased in the following order: tidal zone > splash zone > submerged zone > atmospheric zone. The width of the ascent zone of Cl− concentration at tidal and splash zones was far less than that of the influential depth of moisture transport (IDMT), and the range of convection zone was dependent on the IDMT. Cl− at splash and tidal zones penetrated into concrete as a bulk liquid by non-saturated permeation driven by a humidity gradient. The change of chloride profiles in concrete along the altitudinal gradient was consistent with that of the cyclic water absorption amount (CWAA). The transport rate of chloride was the highest at the highest point of the tide.

Time-varying behavior of corrosion-damaged piles under cyclic lateral loading in marine environments

In this study, degradation models for pile and soil stiffnesses under cyclic lateral loading in marine environments are established. Based on the proposed models, the time-varying behavior of corrosion-damaged piles under cyclic lateral loading in marine environments is analyzed. The influences of the surface chloride concentration, number of cycles and cyclic load amplitude on the behavior of corrosion-damaged piles under cyclic lateral loading are investigated. The results show that the degradation rate of the pile stiffness speeds up with the increase in surface chloride concentration and that the attenuation coefficient of the soil stiffness gradually decreases with the increase in the number of cyclic lateral loads. The lateral displacement of the pile at the same depth increases with increasing exposure time and the number of cycles. The bending moment of the pile decreases with the deepening of the corrosion degree of the pile at the same pile depth. The position of the rotation center gradually moves down with the increase in the cyclic load amplitude. For the same exposure time, the lateral displacement of the pile top increases with increasing cyclic load amplitude, and the maximum bending moment of the pile increases with increasing cyclic load amplitude.

Analysis of time-dependent chloride diffusion in surface-treated concrete based on a rapid numerical approach

Reinforcement corrosion induced by chloride penetration is a major threat to reinforced concrete structures in marine environments. The use of surface treatments to improve the durability of reinforced concrete structures has drawn increasing attention in recent decades due to their cost-effectiveness and convenience in construction. However, current knowledge of a practical, durable design to protect surface-treated concrete structures from chloride-induced steel corrosion remains insufficient. On this account, a rapid numerical approach was developed in this study to analyse the chloride diffusion in bilayer materials. In this approach, the time-dependency was considered for the chloride diffusion coefficients of both the surface-treated layer and the underlying concrete substrate and for the surface chloride content. The validity of this approach was verified with the finite element method and the computation time was only one hundred-thousandth that of the latter. This proposed approach makes it feasible in practice to estimate the probability of corrosion initiation in surface-treated concrete structures via Monte Carlo simulation.

(Invited) Atomic-Scale Investigations on the Wet Etching of Group IV Semiconductors in Acidic H2O2 Solution: The Case Ge Versus Si-Ge

Over the decades, Si-based complementary metal–oxide semiconductor (CMOS) technology has challenged the semiconductor industry in improving device performance while maintaining the scaling requirements. However, the use of the group IV semiconductor as a channel material is reaching its ultimate limit due to physical complications, such as gate leakage, parasitic resistance/capacitance and size channel effects [1]. Some workaround solutions have implemented trigate structures, while novel gate-all-around (GAA) nanowire or nanosheet devices are also explored.[2] One of the core challenges for these devices is the highly selective removal of sacrificial SiGe epitaxial layers to release active parts of the device.[3] This aspect is further complicated by the introduction of Ge as an alternative channel material of higher mobility.[4]Wet-chemical processing remains an essential step for new nanodevice fabrication. With channel widths of only a few tens of atomic layers, etching control up to the atomic-layer-scale is necessary. To achieve such a level of precision, basic insights in semiconductor/electrolyte interactions are indispensable. Unlike for Si, the surface chemistry of Ge in wet-chemical solutions has remained relatively unexplored. One of the factors impeding in-depth surface analysis is the high reactivity of Ge in air. For this reason, the use of an integrated surface preparation apparatus in a surface analytical tool is crucial to rule out controversial effects of atmospheric oxygen and water.In this work we discuss the wet-chemical etching of Ge (100) in acidic H2O2 solutions. Kinetic studies were performed using inductively coupled plasma mass spectrometry (ICP-MS). Under reaction limited conditions, we showed that surface chloride chemistry has a profound impact on the dissolution kinetics and the anisotropy of wet etching, while proton effects were found to be less important. These results served as a starting point for the comparison of Ge versus SiGe. We provide an atomic scale investigation on the influence of the Si bulk concentration versus the kinetics of etching. The results are complimented by synchrotron X-ray photoemission spectroscopy (SXPS) measurements. We highlight the use of an integrated surface preparation chamber directly connected to SXPS apparatus to obtain fundamental insights into the surface chemistry of these technologically relevant group IV semiconductors. The results suggest that, while the release of Ge atoms from surface sites is favorable, the Si oxide chemistry determines the etching kinetics of SiGe. Basic etching schemes help to explain the formation of a (quasi) self-limiting oxide on SiGe. Energy dependent surface composition analysis provided insight into the nature of the oxide layer that showed depletion of Ge components at the outer surface due to pull out effects.[6]In summary, this research provides a new outlook for various applications such as biomedicine [7], photodetectors [8] and for light absorbing and harvesting of solar energy [9]. In addition, it serves as an eye-opener for the potential of semiconductor surface chemical studies using an UHV-integrated chemical cell connected to XPS to study etching systems.[1] R. Pillarisetty, Nature 479 (2011), p. 324-328.[2] J. Ryckaert et al., IEDM San Francisco, CA, USA, pp. 29.4.1-29.4.4 (2019)[3] K. Wostyn, F. Sebaai, J. Rip, H. Mertens, L. Witters, R. Loo, A. Y. Hikavyy, A. Milenin, N. Horiguchi, N. Collaert, A. Thean, P. Mertens, S. De Gendt and F. Holsteyns, ECS Trans., 69, 147 (2015).[4] M. Kobayashi, G. Thareja, M. Ishibashi, Y. Sun, P. Griffin, J. McVittie, P. Pianetta, K. Saraswat, Y. Nishi: J. Appl. Phys. 106, p. 104117-7 (2009).[5] G. H. A. Abrenica, M. V. Lebedev, G. Okorn, D. H. van Dorp and M. Fingerle, Appl. Phys. Lett., 113, 062104 (2018)[6] Graniel Harne A. Abrenica, Mikhail V. Lebedev, Mathias Fingerle, Sophia Arnauts, Nazaninsadat Bazzazian, Wolfram Calvet, Clement Porret, Hugo Bender, Thomas Mayer, Stefan de Gendt and Dennis H. van Dorp, J. Mater. Chem. C, 2020, 8, 10060 (2020)[7] H. Geng, J. Dai, J. Li, Z. Di and X. Liu, Sci. Rep. 6, 37474 (2016)[8] J. Michel, J. Liu and L. C. Kimerling, Nat. Photonics 4, 527534 (2010)[9] S. L. Shinde, T. D. Dao, S. Ishii, L-W. Nien, K. K. Nanda and T. Nagao, ACS Photonics 4, 1722-1729 (2017)

Application of Novel Machine Learning Techniques for Predicting the Surface Chloride Concentration in Concrete Containing Waste Material.

Structures located on the coast are subjected to the long-term influence of chloride ions, which cause the corrosion of steel reinforcements in concrete elements. This corrosion severely affects the performance of the elements and may shorten the lifespan of an entire structure. Even though experimental activities in laboratories might be a solution, they may also be problematic due to time and costs. Thus, the application of individual machine learning (ML) techniques has been investigated to predict surface chloride concentrations (Cc) in marine structures. For this purpose, the values of Cc in tidal, splash, and submerged zones were collected from an extensive literature survey and incorporated into the article. Gene expression programming (GEP), the decision tree (DT), and an artificial neural network (ANN) were used to predict the surface chloride concentrations, and the most accurate algorithm was then selected. The GEP model was the most accurate when compared to ANN and DT, which was confirmed by the high accuracy level of the K-fold cross-validation and linear correlation coefficient (R2), mean absolute error (MAE), mean square error (MSE), and root mean square error (RMSE) parameters. As is shown in the article, the proposed method is an effective and accurate way to predict the surface chloride concentration without the inconveniences of laboratory tests.

A time-dependent chloride diffusion model for predicting initial corrosion time of reinforced concrete with slag addition

The effect of granulated blast furnace slag (GBFS) addition on the threshold chloride concentration (TCC) for rebar corrosion was investigated. A modified diffusion model, coupled with a time-dependent effective diffusion coefficient and surface chloride concentration, was proposed to predict the chloride profile. The corrosion initiation time was estimated based on the model predictions and the measured TCC. The results indicate that adding GBFS decreases the TCC by lowering the pH value of the pore solution. The evolution of corrosion potential and current density is found to obey a 3-parameter Weibull distribution. MIP tests show that adding GBFS contributes to refinement of pore structure by decreasing the fraction of large capillary pores. The time-dependent model exhibits good predictive strength and helps understand how GBFS addition delays the corrosion initiation by retarding the chloride diffusion, though a lower TCC is obtained.

Engineering the Bandgap and Surface Structure of CsPbCl3 Nanocrystals to Achieve Efficient Ultraviolet Luminescence.

Herein, we report the design of novel ultraviolet luminescent CsPbCl3 nanocrystals (NCs) with the emission peak at 381 nm through doping of cadmium ions. Subsequently, a surface passivation strategy with CdCl2 is adopted to improve their photoluminescence quantum yield (PLQY) with the maximum value of 60.5 %, which is 67 times higher than that of the pristine counterparts. The PLQY of the surface passivated NCs remains over 50 % after one week while the pristine NCs show negligible emission. By virtue of density functional theory calculations, we reveal that the higher PLQY and better stability after surface passivation may result from the significant elimination of surface chloride vacancy (VCl ) defects. These findings provide fundamental insights into the optical manipulation of metal ion-doped CsPbCl3 NCs.

Engineering the Bandgap and Surface Structure of CsPbCl3 Nanocrystals to Achieve Efficient Ultraviolet Luminescence

AbstractHerein, we report the design of novel ultraviolet luminescent CsPbCl3 nanocrystals (NCs) with the emission peak at 381 nm through doping of cadmium ions. Subsequently, a surface passivation strategy with CdCl2 is adopted to improve their photoluminescence quantum yield (PLQY) with the maximum value of 60.5 %, which is 67 times higher than that of the pristine counterparts. The PLQY of the surface passivated NCs remains over 50 % after one week while the pristine NCs show negligible emission. By virtue of density functional theory calculations, we reveal that the higher PLQY and better stability after surface passivation may result from the significant elimination of surface chloride vacancy (VCl) defects. These findings provide fundamental insights into the optical manipulation of metal ion‐doped CsPbCl3 NCs.

Time-dependent concentration of chlorides at the concrete surface revisited

ABSTRACT Service-life modeling of concrete structures exposed to chlorides has received increasing attention in recent years. Despite developments in understanding the transport phenomenon, most models still have limitations, and their results should be interpreted cautiously. This paper presents a state-of-the-art review of recent advances in time-variant models of surface chloride concentration (Cs ) used as a boundary condition in service-life models, examining the role that boundary conditions can play in service-life estimates. Moreover, an overview of the root causes of variability in experimental results and a critical review of the strengths and limitations of time-variant Cs is provided. The results of numerical studies show that the time-variant boundary conditions considered in this work performed reasonably well with short-term empirical data and matched well with field observations. However, this review highlights the need for long-term field data to validate the performance and reliability of results obtained from service-life models using time-variant boundary conditions.

Influence of the rainfall intensity on the chloride ion distribution in concrete with different levels of initial water saturation

Reinforced concrete (RC) structures located in coastal salt spray areas are subjected to rainfall erosion and chloride ion corrosion throughout the year. Consequently, this study simulates a rainfall environment with artificial rainfall simulation devices and applies a potentiometer to determine the chloride ion concentration. The microstructures and chemical compositions of the concrete were revealed through microscopic experiments. The research results show that with a greater rainfall intensity, the surface chloride ion concentration decreases more obviously, the surface chloride ion loss is more serious, and the chloride ion binding capacity becomes weaker. As the saturation decreases, the binding capacity of chloride ions also decreases. This study can provide some theoretical ideas for the durability design of PC structures in rainy environments.

Prediction of chloride concentration with elevation in concrete exposed to cyclic drying-wetting conditions in marine environments

Chloride ions are generally considered one of the most significant factors in the corrosion of steel bars in reinforced concrete (RC) structures exposed to alternate drying-wetting marine environments. When RC structures are exposed to cyclic drying-wetting conditions, such as in the marine tidal zone, the chloride concentration distributions in RC structures along the elevation direction changes due to the influence of various drying-wetting ratios. In the study presented here, an indoor exposure experiment for chloride transport in concrete specimens under different conditions of drying-wetting ratios is employed to explore the chloride concentration distributions along the elevation of an RC structure. The elevation related to the peak value of the chloride concentration, which corresponds to the most unfavourable drying-wetting ratio for the RC structure, is determined. On the basis of the tested chloride concentration results, the variation of the time-dependent models of surface chloride concentration and apparent chloride diffusion coefficient with elevation are established for an RC structure. Furthermore, an empirical model of chloride diffusion based on Fick’s second law is developed and adopted to predict the chloride concentrations in concrete at an arbitrary elevation and exposure time. The accuracy of this prediction model of chloride diffusion is validated in terms of the experimental chloride measurements.