Article

Recurrent studies of chloride ingress in uncracked marine concrete at various exposure times and elevations

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Abstract

Uncracked reinforced concrete slabs were field exposed mounted on a floating pontoon and partly submerged for 5 years at the Swedish west coast. The total chloride ingress was analysed at various exposure times at 3 elevations representing a submerged, a splash, and an atmospheric exposure zone. The concrete mixtures varied in w/c ratio, type of cement, and amount and type of pozzolan used in the binder. The data is unique as it represents recurrently measured total chloride penetration profiles at various exposure ages, providing a foundation for the prediction of chloride ingress in concrete in a given environment. The results after 5 years of exposure confirmed the expected inverse relationship between water-to-binder ratio and chloride ingress. The use of 5–10% silica fume in the binder had a very positive effect on reducing the chloride ingress, but little or no benefit at all was found for concrete with fly ash in the binder as compared to the use of 5% silica fume. The chloride penetration rate as expressed by a calculated effective chloride diffusivity has a tendency to decrease over time. High- performance concrete with w/c ≤ 0.4 and a minimum of 5% silica fume added as a well dispersed slurry exhibited an effective chloride diffusivity in the range of 1 × 10−13 to 5 × 10−13 m2/s after 5 years exposure in the splash zone.

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... were arranged in three tiers that define their exposure zone: submerged zone, splash zone, and atmospheric zone. A report of chloride ingress after an exposure of five years was re ported by Sandberg, Tang, and Andersen [6]. Samples were extracted from the exposure site and milled, starting from the exposure surface, in 1 mm increments. ...
... In the report of Sandberg et al. [6], the chloride ion diffusion coefficient was estimated from the chloride concentration profile within the concrete. These concentration profiles are shown as filled symbols in Fig. 2. It is common that chloride concentrations have a maximum within the concrete, so least squares regression between the solution to Ficks law and the recorded values was applied to the data on the "falling" side of the curve. ...
... The curves in Fig. 2 are the 4SIGHT predictions for the chloride Table 1. The variation in the diffusion coefficients calculated by regression analysis [6] was less than expected. This is striking given the range in estimated paste porosities. ...
... where 4 CS and 4 D are the known probability density functions of the random variables C S and D respectively. No depassivation will occurs if C S < C cr (g is undefined in this case, according to (35)) and then the lower limit of integration variable C S must be chosen as C S ¼ C cr and not as C S ¼ 0. If D, C S , C cr , and c are assumed as random variables and C 0 as a deterministic one a four random variables model is obtained. Choosing C cr as the dependent variable the g function in given by equation (32), and equation (25) yields: ...
... A representative value [11,12,34] for the critical chloride concentration equal to 0.05% referred to concrete mass has been considered for SRT model. The location x (from the maximum inwards [35]) in the profile where this concentration is located is searched and then the k value is calculated as k ¼ x= ffiffi t p , where t is the age of the profile. For EF and CF models, the experimental profiles have been fitted to equations (31) and (38) respectively, obtaining the corresponding transport parameters. ...
... For EF and CF models, the experimental profiles have been fitted to equations (31) and (38) respectively, obtaining the corresponding transport parameters. Only the points from the maximum inwards have been used for the fitting, which is a common practice in profile treatment [35]. One of the profiles did not met the minimum requirements to be fitted [36] and was discarded. ...
Article
Full-text available
Estimation of depassivation time is a key issue in corrosion prevention. A method to get a probabilistic model from a deterministic one is presented and applied to three simple models: square root of time (SRT), error function (EF) and constant flux (CF) models. Probability distributions of the involved random variables are needed as input parameters. Experimental data have been obtained from a concrete structure exposed to the atmospheric marine environment. These data are analysed to obtain the probability distributions of chloride transport parameters: penetration velocity k (SRT model), diffusion coefficient D (EF and CF models), surface chloride concentration (EF model), and chloride ingress flux J (CF model). These distributions are used to calculate the depassivation time probability distributions according to the three models and the orientation of the samples respect to the sea. This allows to estimate depassivation time for a given depassivation probability.
... blocks in a beach site (Huelva) before 1990 to study the main characteristics related to the chloride penetration [10]. Sweden established the Träslövsläge site in 1990 to study the chloride diffusion in concretes and its influencing factors [11], helping the calibration of ClinCon model [12] and the service life prediction of concrete structures. A French exposure study was initiated in 1996 including the tidal zone of one marine site (La Rochelle), and the observations helped to quantify the long-term performance of concretes with different binders [13]. ...
... The w/b ratio has also notable effect on chloride ingress: lowering w/b effectively reduced the apparent chloride diffusion coefficient, and the diffusion coefficients all decayed with the exposure age [44]. The supplementary cementitious materials (SCM) enhanced the chloride ingress resistance by incorporating 5-10%SF [11] or 15-35%FA [45], and using SCM increased both the long-term strength and the corrosion resistance of reinforced concrete [46]. For aggregates, concretes using lightweight and conventional aggregates have basically the same resistance to chloride penetration [47]. ...
Article
This paper reviews the technical aspects related to the long-term field exposure practice in marine environments, based on the return of experiences of major marine exposure sites in world-wide scope. The long-term exposure practice helps both the research on durability mechanisms of structural concretes under real environments and the calibration of durability models to support the life-cycle management of concrete structures. The presentation of the field exposure data can be categorized into the information relevant to exposure sites, the data related to the exposed materials and specimens, the information of environmental actions, and the data related to the performance of materials. A standardized presentation of these data can help the efficiency of data sharing and exploitation. The exploitation of exposure data employs various models to represent the chloride ingress and the induced corrosion risk of the embedded steel bars. There are needs for models addressing the strong environment-material interactions, and simple yet reliable durability indicators for engineering use. The design and operation of exposure stations need the careful choice of exposure sites and specimens, the appropriate scheme for monitoring and inspection of exposed specimens, the systematic recording and management of exposure data, and the regular maintenance of exposure facilities. The support of exposure data for life-cycle management is demonstrated through the durability planning of a real project case. The good practice of long-term field exposure is summarized in the end.
... The maximum chloride concentration in Table 2 hasn't obvious law owing to exposure time, complicated environments, such as high temperature [75], high salt [33], the distance from seashore [87] and binder [80]. The C max tends to increase with increasing w/b and t in same environment [33,46,80]. ...
... Schematic of the skin effect of concrete based on a random chloride profile[32,46]. ...
... However, in general, laboratory conditions did not accurately represent real conditions, where influencing parameters act simultaneously. There are few works developed under real conditions and many of them consider either the underwater structures or structures in tidal zones [11][12][13]. The interaction of chlorides from marine aerosol with real structures built inland has been studied even less [14][15][16]. ...
... Chloride profiles show a typical influence of concrete characteristics on chloride transport into concrete [11][12][13][14], as a consequence of the materials porosity and the chloride binding capacity of the mixtures, which have different cements and cement contents per volume of concrete. Typical chloride profiles for representing these situations are shown in Fig. 4. ...
Article
The relationship between chlorides from marine aerosol and chlorides accumulated into concrete is discussed in this paper. The experimental programme comprised an environmental characterisation, with climatic and chloride deposition data, and a study of chloride penetration into concrete based on natural exposure of specimens in a marine atmosphere zone. Results show that salt concentration in marine aerosol strongly decreases in the first meters from the sea. Chlorides present in the atmosphere can be studied using the wet candle method and correlated with chlorides accumulated into concrete. This relationship can be represented by the equation Ctot=C0+kd·Dac, where kd is a coefficient which depends on concrete and environmental characteristics, Ctot is the average total amount of chlorides accumulated into concrete, C0 is the chloride content in concrete before exposure and Dac is the accumulated dry deposition of chlorides.
... However, the impact of CSH on the increasing/ decreasing trend of Cl − binding in the HCP samples could not be decoupled from potenital binding of Cl − by AFm. Sandberg and Larson [20] mixed cement paste with a synthetic CPS and found a reduction in the binding capacity at increasing pH levels. Tritthart [21] also found a similar trend when the cement paste samples were exposed to Cl − solutions with different pH levels. ...
... The increase in the Ca 2+ concentration in CPS may also have increased the Ca/ Si ratio of CSH, which may have caused the higher Cl − binding capacity as observed in [60]. The higher Cl − binding capacity in CPS/12.6 at C f > 1.7 M (i.e., log(C f ) > 0.23 log(M)) is probably due to the higher solubility of CH [20], which may have caused the formation of CaCl 2 and thus an increase in the formation of FS as observed by other researchers [11,62,63]. The lower binding capacity of HCP in CPS/12.6 at C f < 0.1 M (i.e., log(C f ) < − 1 log(M)) may be due to the presence of SO 4 2− in the solution because SO 4 2− competes with Cl − that causes a reduction in the formation of FS [17]. ...
Article
In this paper, chloride (Cl −) binding isotherms are developed for cement hydration compounds, specifically, calcium-silicate-hydrates (CSH) and AFm phases including mono-sulfate aluminate, hydroxy-AFm, mono-carbonate-AFm, and hemicarbonate-AFm, in simulated concrete pore solutions to account for the effect of pH and the presence of other ions. pH and the presence of other ions have a strong influence on the Cl − binding capacity of cement compounds, which have not been taken into consideration in previous research. A novel experimental technique is developed to characterize the binding capacity from very low (1 mM) to very high concentrations (5 M). To overcome the existing challenges of measuring both low and high Cl − concentrations without significant dilution and in the presence of SO 4 2− and OH − ions, a potentiometric method was used. The amorphous CSH in the hydrated cement paste; thus, the heterogeneity of the hydrated components of the cement paste was also quantified and accounted for in this study.
... SCMs such as fly ash (PFA), metakaolin, GGBS, when used as additives also reduce the rate of chloride ingress [164,186,[214][215][216]. Dhir et al. [217] found that substituting PC with PFA up to 50% greatly increased the chloride binding capacity, and reduced the chloride permeability of concrete. ...
Thesis
Full-text available
The use of GGBS as supplement for cements has been shown to improve the long-term strength and durability properties of concrete. In practice, while the chemical composition of GGBS from a single plant may be constant, due to the varying sources from which GGBS is obtained the chemical composition from plant to plant may vary. The wide variability in the use of GGBS as a SCM in different climates, coupled with differences in chemical composition, is bound to have impact on the performance of slag blends. This study investigated the combined influence of difference in slag composition and temperature on the performance of slag blends. Performance was evaluated in terms of strength and transport properties. Paste samples were characterised by calorimetry, TGA, XRD and SEM to follow hydration and microstructural development. Mortar samples were used to follow strength development and transport properties. All tests were carried out at temperatures of 20 and 38°C. Curing at 38°C accelerated the early hydration, but not the later hydration. This led to higher early strengths and lower later strengths, and was attributed to the coarsening of the pore structure caused by the high temperature curing. Except at the early ages at 20°C, both slag blends showed better strength performance than the reference cement. The slag blends also showed better transport properties than the reference cement, especially at 38°C, and this was attributed to their finer pore structure and higher chloride binding capacity. Of the two slags studied, the more reactive slag (slag 1) had better performance, especially at 38°C. Performance of the slag blends at 20°C was influenced mainly by the length of curing, and by the difference in chemical composition at 38°C.
... In addition, the rate of the pozzolanic reaction of MK is higher than that of SF early in the life of the concrete [21,24]. Reducing the w/c ratio by 10% and adding 5% SF may reduce the chloride diffusion by a factor of up to 10, as indicated by Sandberg et al. [25]. ...
... Then, the effects of the convective and wick actions are shown in a peak of chloride content in the ingress profile, with the maximum chloride content at a certain depth. Two zones are therefore differentiated [16][17][18] : an inner zone (diffusive) where diffusion dominates the ingress process, and an external zone (convective) where absorption, desorption, and washing by rainwater take place. The thickness of the external zone may be linked to concrete porosity (and therefore to the w/c and the hydration degree) and to the environmental aggressiveness. ...
Article
Blended cement concrete is currently a necessity to reduce the environmental impact of the construction industry. The lower clinker content may affect some durable characteristics of concrete, such as the resistance to chloride ingress. On the other hand, mineral admixtures may present pozzolanic activity that improves concrete performance over time. This paper presents the results of chloride ingress in concrete specimens made with slag and limestone filler blended portland cement (BPC) when located in the marine environment. Parameters including two watercement ratios (w/c), three curing treatments, and two maximum aggregate sizes were analyzed. Water-soluble and total chloride ingress profiles were determined during an exposure period of 3 years. The results allowed the time evolution of both the surface chloride content and diffusivity of BPC concrete to be assessed by natural mechanisms.
... The instrumented concrete blocks were designed in a co-operation between Femern A/S and Danish Technological Institute. Based on experience from former field exposure tests in Sweden [1] and Denmark [2] it was agreed that instrumented concrete blocks with rebars and anode ladders should be produced with dimensions of 2x1x0,2 m (HxWxD). This size should allow long-term exposure before interaction from the opposite exposed face needs to be taken into consideration. ...
Conference Paper
Three concrete blocks instrumented with rebars, anode ladders and other sensors have been produced and exposed to sea water in Fehmam Belt field exposure site in Roedbyhavn in Denmark. The corrosion activity on the anode ladders is continuously monitored by measurements of half-cell potentials and linear polarisation resistance. The design of the instrumented concrete blocks is presented together with the first results after 2 years marine exposure. Corrosion initiation on anodes with small concrete cover has been identified from the electrochemical measurements and verified by visual inspection. Chloride profiles have been measured for three different binders.
... Observa-se que a adição de sílica ativa no concreto minimiza a penetração de cloretos se comparada com outras adições, como os resultados apresentados por SANDBERG et al. (1998), mostrarando que o uso de um teor de sílica ativa entre 5 e 10% sobre a massa de cimento exerce um melhor efeito do que os mesmos teores de cinza volante na penetração de cloretos. ...
... Concrete is an inexpensive artificial building material that has been extensively used for marine concrete reinforcement protection (Sandberg et al., 1998;Wei et al., 2021;Ashish and Verma, 2021). For reinforced concrete (RC) structures constructed in a marine environment, the actual service life of RC is shorter than the designed service life, primarily due to chloride induce corrosion (Nguyen et al., 2021;Shi et al., 2021). ...
Article
Chloride induce corrosion destroys the structure of marine concrete, thereby shortening its actual service life. In this study, Fe-based layered double hydroxides (LDHs), including CaFe-NO3 and CaFeAl-NO3 LDHs, and polyvinylpyrrolidone (PVP), were added to increase the anti-corrosion property of mortar. Electrochemical tests and chloride penetration resistances of the samples were conducted, and the corresponding micro-mechanisms were investigated. The samples that were immersed short-term (5 d) exhibited similar electrochemical characteristics and corrosion tendencies compared to the 7 d samples. With increasing immersion time, all the samples were corroded, whereas the LDHs-PVP composites still exhibited higher resistances and impedance, larger arc radius, and a lower corrosion current density and corrosion rate than the other samples due to the synergistic effect via the formation of a passive film by PVP, the increased compactness and adaptability by Fe-based LDHs, and promotion of uniform dispersion of LDHs in slurry by PVP. Further, the work function of the LDHs-PVP composites was lower than that of the control, indicating that the addition of LDHs and PVP decelerated the corrosion reaction of steel. Thus, the LDHs-PVP composites exhibited high anti-corrosion property; the rapid chloride migration coefficient and total charge passed decreased by 17.5% and 4.9% compared to those of the control, respectively, highlighting the potential of this composite as effective inhibitors for marine concrete corrosion.
... The w/c ratios of the concretes were ranging between 0.25 and 0.75 (in the following, results are presented only for w/c ratios up to 0.5 since there were not enough data for the concretes with higher w/c ratios to estimate all the model parameters). Details on the slab arrangement and the concrete mixes used can be found in [17]. According to the results values of the achieved diffusion coefficient for almost all the considered concretes decrease with time. ...
... SF is an artificial pozzolan that increases the compressive strength of concrete by strengthening the transition zone and increasing the rate of hydration early in the life of the concrete (Shekarchi & al. 2009). Reducing the w/c ratio by 10% and adding 5% SF may reduce the chloride diffusion by a factor of up to 10, as indicated by Sandberg et al. (1998). ...
... According to the observation of concrete structures, however, it is our understanding that corrosion is not a serious problem for many structures with cracks longer than the concrete cover. This has been confirmed by a few studies which have shown that rebar corrosion is not an immediate threat to the structure in such conditions [22,23]. It has also been found that the chloride ions' concentration to cause corrosion is lower than the case of uncracked concrete, and that for the splash zone, the initiation time could be very short, and that the active corrosion rate becomes so small after only few months that it could be considered harmless. ...
Article
The ingress of chloride ions into concrete plays a crucial role in reinforcing bar corrosion and, hence, for the durability and life of a structure. The problem is more acute once cracking has occurred. This paper presents mathematical models and numerical simulations for water movement and chloride ions ingress by diffusion and advection in cracked and uncracked concrete under saturated or unsaturated conditions. It has been shown that water movement at a crack is very sensitive to its saturation level and chloride ions ingress is also significantly affected by the presence of cracks. Empirical equations for the determination of chloride ions diffusion coefficients have also been proposed for a wide range of w/c ratios based on a comprehensive database and sample design nomographs for concrete cover shown.
... rebar). Considerable work has been done to examine chloride ingress through the concrete pore network (Sandberg et al., 1998;Dhir & Jones et al., 1996;Jensen et al., 1999;Gjorv & Vennesland, 1979) and its effect on the corrosion of rebar (Mohammed et al., 2004;Hope & Ip, 1987;Beaudoin et al., 2000). It is clear that the quality and depth of the concrete cover is of major importance to determine the durability of the structure (Jaegermann, 1990). ...
Article
Full-text available
Reinforced concrete structures are exposed to harsh environments, yet they are often expected to last with little or no repair or maintenance for long periods of time (often 100 years or more). For this reason, a durable structure needs to be produced. In addition, bridge reinforced concrete suffering from attacks of chloride penetration that cause corrosion of the steel in the reinforcement concrete that leads to reduction in strength and serviceability cracking, which cause further repair and rehabilitation for the structure and greater maintenance and repair costs. This research focuses on self-compacting concrete with Jordanian Phosphate (JORPHOS) as a filler. The permeability for different percentages of JORPHOS were tested by using Rapid Chloride Permeability Test (RCPT). It was concluded that the addition of different percentages of JORPHOS minimizes chloride penetration in concrete.
... Over previous decades, a significant amount of research has been performed on the chloride ingress into the concrete both experimentally and numerically, to predict the corrosion initiation time of the reinforcement. Castro et al. [5] and Sandberg et al. [6] obtained chloride profiles in RC structures experimentally in the marine environment. Castro et al. [7] and Oh et al. [8] investigated chloride threshold values for the reinforcement to initiate the corrosion regime. ...
Article
Full-text available
Corrosion of the reinforced concrete (RC) structures has been affecting the major infrastructures in U.S. and in other continents, causing the recent several bridge collapses and incidents. While the theoretical understanding is well-established, the reliable prediction of the corrosion process in the RC structural systems has hardly been successful due to the inherent uncertainties existed in the electrochemical corrosion process and the associated material and environmental conditions. The paper proposes a computational framework to develop evidence-based probabilistic corrosion initiation models for the reinforcing steels in the RC structures, which predicts the corrosion initiation time and quantifies the inherent variances considering various acting parameters. The framework includes: probabilistic modeling with Bayesian updating based on the sets of previously generated experimental data; Bayesian model/parameter selection considering various parameters, such as material properties and environmental conditions; corrosion reliability analyses to predict the probabilities of the corrosion initiation at given time t, structural configurations, and environmental conditions; and sensitivity analyses to measure and to rank the influences of each acting parameter and its uncertainty to the probabilities of the corrosion initiation. Total of 284 sets of experimental data exposed to the coastal atmospheric environments are used for the modeling. The goal of the Bayesian model selection presented in this paper is to obtain the most accurate and unbiased model using the simplest form of expression. The developed example corrosion model is currently limited to the initiation of diffusion-induced corrosion. The model can be updated, improved, or modified upon future available sets of data. The research contributes to the decision making to improve the corrosion reliability, corrosion control, and further the structural reliability of corroding structures.
... Such results need to be considered with caution, since the observed trends in Dnss and Mnss at early ages may not be representative for longterm behaviour. Sandberg et al [1998] and Lindvall and Nilsson [2001] studied various types of concretes with Portland cement, fly ash and silica fume. These showed that after 5 years of salt exposure in sea water or road environments, 5% of silica fume addition reduced the diffusion coefficient by a factor 2 with respect to plain PC-concrete having the same w/c-ratio. ...
Technical Report
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ASTRA research report 676. Print on demand via: www.astra.admin.ch/dienstleistungen/04844/06083/index.html?lang=de Abstract: In this report, an empirical prediction model for the corrosion onset of reinforced concrete exposed to deicing salts (chlorides) is proposed. Concrete corrosion due to chloride ingress remains to be a problem in Switzerland. With the proposed model the remaining corrosion-free service life of existing concrete structures can be estimated. For new concrete structures, the model helps with determining the reinforced concrete properties that are required for achieving a specific service life. The model is based on the error-function solution of Fick’s second law of diffusion and is very similar to the well-known DuraCrete model. It can be easily implemented in an Excel spreadsheet. The input parameters of the proposed model were tuned by using the data of the Naxberg and other field experiments. In these experiments, different concrete types with Portland or blended cements were exposed to road spray water containing deicing salts. The state of chloride ingress was measured after intervals up to a concrete age of 10 to 18 years. The model input parameters that were found to simulate the measured chloride profiles best, were used to make various general predictions. These predictions show how concrete type, cover thickness, and environmental conditions affect the corrosion-free service life of reinforced concrete. The model was also used in combination with standard prescriptions in order to evaluate if current Swiss standards guarantee enough durability for the XD3 exposure class. The results show that in the case of a (very) high chloride supply the current standard specifications for concrete density (i.e., the migration coefficient M28d) and cover thickness may not provide enough corrosion-free service life in some cases. Relative small changes, e.g., M28d = 8 instead of 10·10-12 m2/s, or a cover thickness of 50 instead of 45 mm, could increase service life by 25 years under XD3 exposure. Corrosion inhibitors, resistant rebar type, and application of a hydrophobic agent are alternative solutions for improving the corrosion-free service life of concrete structures in XD3 conditions. The positive effects of hydrophobic treatment and alternative rebar types have been clearly shown in the Naxberg field experiment. The report concludes with step-by-step guidelines that explain how to make actual lifetime predictions for existing or new concrete structures. The report also describes a new method for measuring the critical chloride content of concrete.
... Another aspect to be considered in this analysis is the aggressiveness of the environment to which concrete structure is subjected. At locations with a greater availability of chlorides in the atmosphere, there is a stronger increase in Cs in the initial years, with a subsequent attenuation with time [3,14]. However, it can be expected that Cs may present some fluctuation over the years, which may be related to the movement of ions towards bulk concrete or to direct environmental interaction, which can promote several removal effects, such as surface chloride removal due to rainfall [12]. ...
Article
Full-text available
Surface chloride concentration (Cs) is a key parameter used to feed models adopted to simulate chloride penetration into concrete and evaluate the initial period of corrosion. Although there are several models that have been proposed for the representation of Cs behaviour in the marine atmosphere zone, such models are still scarce. In this context, we analysed the behaviour of surface chloride concentration in concrete specimens exposed over 12.5 years in a marine atmosphere zone in the northeast of Brazil. The experimental work was carried out in two steps: environmental characterization, which was undertaken for temperature, relative humidity, rainfall, wind characteristics and sea-salt data; and chloride concentration measurements for the concrete surface considering three different concrete mixtures with w/b ratios of 0.65, 0.57 and 0.50. The results showed that the Cs increase over time followed three stages: a first short stage characterised by an initial dispersion, followed by an increase period and then a final period of stabilisation, which was not fully reached in the present study. This behaviour can be represented by a power function or a sigmoidal function, with a better fit with the latter. Chloride concentration in the atmosphere plays an important role in Cs behaviour. Higher availability of chlorides means higher Cs values. The relationship between Cs and the rate of chloride deposition on a wet candle was analysed and the function Cs=C0+kcs·(Dac)n was the one that best fit the experimental data.
... Experience from earlier work (e.g. Träslövläge field exposure site in Sweden [2]) shows that the amount of cement paste in the extracted concrete cores can vary substantially from core to core, even when the cores are extracted from the same concrete block. Furthermore, the paste content will increase towards the exposed surface from a depth of approx. ...
Conference Paper
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Femern A/S, the Owner of the coming Fehmarnbelt Fixed Link, has built a marine field exposure site in the harbour of Roedbyhavn as a part of the preparations for the coming 17.6 km long immersed tunnel between Denmark and Germany, which will be the longest combined rail and road tunnel to date. A total of 15 large concrete blocks (2 x 1 x 0.2 m) with different concrete mix designs and 15 small concrete blocks (1 x 1 x 0.2 m) with concrete mix designs matching the large blocks were produced in 2010 by the Danish Technological Institute (DTI is external concrete laboratory for Femern A/S). The large blocks were placed partly submerged in seawater in Roedbyhavn field exposure site and the small blocks were placed outside the laboratory. The 15 mix designs include concrete with three different cement types (two Portland cements and one blast furnace cement) and three different pozzolans (silica fume, fly ash and blast furnace slag). The field exposed concrete blocks will be monitored at least until the end of the construction period (2021). Chloride penetration profiles have already been measured after ½ years and 2 years field exposure in immersed zone and in splash zone. The results are presented and compared to results from accelerated laboratory testing of samples from the small blocks by the chloride migration test according to NT BUILD 492 at the maturity age of 1 month and 6 months.
... Generally, the rate of chloride ingress into concrete depends on the chloride diffusion coefficient (D c ), which varies with the time of exposure [3]. Therefore, studies on the long-term performance of chloride ingress into concrete should consider the variation of chloride diffusion coefficient during the exposure period [4]. Many studies have investigated the chloride profile in concrete over long-term [5]. ...
Conference Paper
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Harsh marine exposure conditions provide an aggressive condition for reinforced concrete structures, mainly due to its hot, humid and saline environment. In this study, variations in diffusion coefficient value over time is investigated and compared in five different exposure conditions for silica fume concrete with different water to binder ratios under long-term exposure in a marine environment. Samples were taken at the ages of 3, 9 and 36 months and analyzed to determine the chloride diffusion coefficient and surface chloride content. Regression analysis of the surface chloride content data is carried out by applying two empirical models that were in the literature and compared to each other to suggest the best fitted model in order to make a logical trend about surface chloride content for long term exposure conditions.
... Among these factors the most important are those that determine the material resistance to chloride ingress: porosity of the matrix (Collepardi et al. 1970;Monosi et al. 1989) (determined by the w/b ratio, compaction degree, curing), content and type of cement (Collepardi et al., 1970;Glass and Buenfeld, 2000), porosity of the interfacial transition zone (Delagrave et al., 1997a), and porosity of aggregate (Fernández Luco, 2001). The aggressiveness of the environment defines external factors (Sandberg et al., 1998;Traversa, 2001;Andrade et al., 2002;Traversa and Di Maio, 2002;Di Maio et al. 2004), characterized by the average temperature and relative humidity, incidence of winds, rain, distance and height with respect to sea level. Finally, the presence of protective surface layers on the structure (paint or finishing) must be considered as these reduce the exposure level (Di Maio et al., 2000). ...
Article
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This paper presents an analysis of experimental data from conventional concrete regarding sorptivity and penetrability under pressure comparing these parameters to chloride diffusion rate determined in the laboratory and in actual marine environment. Prescriptions for durability assurance of reinforced concrete structures is based on the qualitative characterization of transport properties. For the specific case of the marine environment, it is required to assess the resistance of concrete to chloride ingress. The results show the limitations of both parameters as prescriptive indexes, with capillary absorption rate showing some advantages over water penetration under pressure.
... Researches and applications on marine concrete have attracted attentions all around the world for many decades [1][2][3][4][5][6]. Cementbased materials severely suffer from multiple rigorous corrosion in marine environment, among which ions erosion plays a nonnegligible part [7][8][9][10]. ...
Article
In this study, the hydration mechanism of cement-based materials served in marine environment during early-age magnesium precipitation is discussed. The classical precipitation theory is used to analyze the suitable condition for significant precipitation of Mg2+. Thermogravimetric analysis and SEM-EDS are employed to characterize the formation and transformation of hydration products with and without Mg2+ incorporation. Mechanical property is adopted to demonstrate the corresponding mechanical reduction. Most importantly, the relationship between specific surface area and hydration processes of cement is also discussed. The obtained results show that inhibition degree of Mg2+ on cement hydration is closely related to pH development in pore solutions. In conventional cementitious system, inhibition of Mg2+ on cement hydration can be further equivalent to decrease on specific area of cement.
... An interesting observation was the peak of chloride concentration occurring not at the surface but a few millimeters inside the mortar. This has been observed many times [65][66][67] and explained by a difference in composition of the concrete skin (the region closest to the surface) due to the contact with mold walls, segregation of aggregates, and environmental actions, inducing a gradient of moisture along the cover depth [65]. It has also been proposed that surface chemical reactions with the environment change the composition of the outer layer (concrete skin) of the concrete [67]. ...
Article
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This work investigated the use of ZnAl-layered double hydroxide (LDH) intercalated with nitrate or nitrite ions for controlling the corrosion of steel in reinforced concrete. The work started by analyzing the stability of the powder in the 1–14 pH range and the capacity for capturing chloride ions in aqueous solutions of different pH. The effect of the ZnAl-LDH on the corrosion of steel was studied in aqueous 0.05 M NaCl solution and in mortars immersed in 3.5% NaCl. It was found that the LDH powders dissolved partially at pH > 12. The LDH was able to capture chloride ions from the external solution, but the process was pH-dependent and stopped at high pH due to the partial dissolution of LDH and the preferential exchange of OH– ions. These results seemed to imply that ZnAl-LDH would not work in the alkaline environment inside the concrete. Nonetheless, preliminary results with mortars containing ZnAl-LDH showed lower penetration of chloride ions and higher corrosion resistance of the steel rebars.
... Another aspect to be considered in this analysis is the aggressiveness of the environment to which concrete structure is subjected. At places with a higher availability of chlorides there is a stronger increase of Cs in the first years with a subsequent attenuation with time (Sandberg et al., 1998;Costa and Appleton, 1999). However, along the years, Cs may present some fluctuation, which can be related to the ions movement towards bulk concrete or to effects like surface chloride removal due to rainfall. ...
... Therefore, this study considered concrete performances exposed to seawater, this approach could consent more realistic evaluation of concrete containing CBA as cementitious material under aggressive environment. Since long, concrete under seawater exposure is a subject of interest and most of previous research was carried out on the concrete structures underwater, structures in tidal zone or in environments closer to the sea [8][9][10]. According to the reported of Suprenant [11] concrete structures exposed to seawater could deteriorate much faster because of combined actions of physical and chemical processes, i.e. ...
Article
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Concrete structures are seriously deteriorated under marine environment because marine water is aggressive in nature; it contains salts of sulphate and chloride and others. These salts deteriorate the plain and reinforced concrete structures. However, most of previous research was investigated on concrete performances exposed to single solution, such as sulphate or chloride attack, even though the actual conditions are the combination of both. Therefore, the object of this study is to evaluate the performances of concrete containing coal bottom ash (CBA) with different fineness as a supplementary cementitious material (SCM) exposed to seawater. This study considered 10% ground CBA as a SCM in concrete. The original CBA was ground in a ball mill for 20 and 30 h, to get different particle fineness. Initially all specimens were cured in normal water for 28 days as to achieve targeted strength and then half of the specimens were shifted into seawater for further 28, 56, 90 and 180 days and other specimens were kept in normal water. The particle fineness of CBA influence on the concrete performances was assessed in terms weight variations, compressive strength and chloride permeability. Experimental results demonstrated that concrete strength with CBA of fineness 3836 cm2/g (type-A) delivers around 11.9% and 8.5% higher than control mix in water and seawater respectively at 180 days. Subsequently, concrete strength with CBA fineness of 3895 cm2/g (type-B) brings about 12.7% and 5.8% greater than control mix in water and seawater respectively at 180 days. However, it was also detected that concrete with CBA-type-A and CBA-type-B exhibits around 45.4% and 42.4% reduction in chloride penetration as compared to control mix at 180 days. Hence, it was concluded the strength performances of CBA-type-B is superior than the control mix at 28 days. However, CBA-type-A gives the better performances at later ages of 90 and 180 days. Hence, CBA-type-A is suggested for the future studies, based on strength performances and resistance to chloride penetration. This study encourages the use of ground CBA in concrete as SCM in normal as well as in marine environment
... Finally, the longer initiation period of corrosion for mixtures with GCBW also contributes to decrease the apparent diffusion coefficient values. Although Fick's second law considers surface chloride concentration and diffusion coefficient constants over time, it is well known that these parameters are time dependent and, in the case of diffusion coefficient, it decreases over time as a consequence of material microstructure changes [41,42]. In the case of the tests carried out in this work, there was a significant increase in the initiation period of corrosion for mixtures with GCBW, which means an increase between 3.3 and 4.4 times when comparing GCBW concretes with reference concrete. ...
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This work analyses the influence of cement replacement by ground clay bricks waste (GCBW) on paste and concrete properties and on reinforcement corrosion triggered by chlorides. TGA/DTG of pastes show the GCBW pozzolanic effect. Porosity decrease in GCBW concretes contributes to their compressive strength increase. XRD tests show more Friedel's salt formation in GCBW paste. GCBW concretes revealed a decrease in chloride threshold due to their alkalinity decay and in chloride transport rate, what is explained by porosity reduction caused by pozzolanic and filler effects and binding ability improvement. Broadly, concretes with 20–30% of cement replacement presented the best performances.
... Uncracked concrete covering rebar provides a high pH value and physical barrier [1] in concrete to protect the rebars from the ingress of aggressive substances, such as chloride or sulfate, in a marine environment. Usually, improving the cover quality (such as reducing the water-to-binder ratio or using supplementary cementitious materials) raises the mechanical performance and durability of concrete. ...
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When subjected to loading or thermal shrinkage, reinforced concrete structures usually behave in a cracking state, which raises the risk of bar corrosion from the working environment. The influence of cover cracking on chloride-induced corrosion was experimentally investigated through a 654-day laboratory test on cracked reinforced concrete specimens exposed to chloride solution. The concrete specimens have a dimension of 100 mm × 100 mm × 400 mm and a single prefabricated crack at the midspan. When the percentage concentration of chloride ion (0.6%, 1.2%, 2.1%, 3.0%, and 6.0%) and crack width (uncracked, 0.2, 0.3, 0.4, and 0.5 mm) are taken as variables, the experimental results showed that the corrosion rates for cracked specimens increased with increasing percentage concentration of chloride and increasing crack width. This study also showed the interrelationship between crack width and percentage concentration of chloride on the corrosion rate. In addition, an empirical model, incorporating the influence of the cover cracking and chloride concentration, was developed to predict the corrosion rate. This model allows the prediction of the maximum allowable wcr based on the given percentage concentration of chloride in the exposure condition.
... The instrumented concrete blocks were designed in a co-operation between Femern A/S and Danish Technological Institute. Based on experience from former field exposure tests in Sweden (Sandberg, 1998) and Denmark (Bager, 2008) it was decided that instrumented concrete blocks with rebars and anode ladders should be produced with dimensions of 2x1x0.2 m (HxWxD). ...
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The threshold value for chloride initiated reinforcement corrosion is of major importance for the outcome of estimates from service life models. Unfortunately, a generally accepted standard test method for determination of this parameter does not exist. The durability of the coming Fehmarnbelt link between Denmark and Germany is highly depending on the choice of a correct design values for chloride penetration parameters and chloride threshold values. This resulted in start-up of a Danish marine field exposure site in Rødbyhavn harbour in 2010. This paper presents details on the concrete composition, the layout of concrete blocks, the test setup, and the marine exposure for the ongoing reinforcement corrosion tests in Rødbyhavn marine field exposure site. Chloride profiles and data from corrosion measurements during the first 5 years exposure are presented, and chloride threshold values are estimated.
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Steel corrosion owing to chloride ion penetration is one of the most common problems related to the durability of concrete structures. Although previous studies of this phenomenon have produced useful results, they primarily focused on unstressed concrete. To study the effect of stress on the resistance of concrete to chloride ion penetration, tests of stressed specimens exposed to salt solution immersion and salt spray were performed. The chloride contents in uncracked concrete specimens with different water-cement ratios, states and levels of stress, and environmental conditions are analyzed in this article. The results show that the resistance of concrete to chloride ion penetration can be improved by reducing the water-cement ratio. The content of chloride ions is higher in concrete stressed in tension than in unstressed concrete. For concrete stressed in compression, chloride content depends on stress level. Salt solution immersion is more severe than salt spray. DOI: 10.1061/(ASCE)MT.1943-5533.0000281. (C) 2011 American Society of Civil Engineers.
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Recently, the durability of concrete structures has received great attention as the number of sea-side structures, such as new airport, bridges, and nuclear power plants, increases continuously. In this regards, many studies have been done on the chloride attack in concrete structures. However, those studies were confined mostly to the single deterioration due to chloride only, although actual environment is rather of combined type. The purpose of the present study is, therefore, to explore the effects of combined deterioration due to chlorides and sulfates in concrete structures. To this end, comprehensive experimental program has been set up to observe the chloride penetration behavior for various test series. The test results indicate that the chloride penetration is more pronounced for the case of combined attack than the case of single chloride attack. The surface chloride content is found to increase with time and the diffusion coefficient for chloride is found to decrease with time. The prediction equations for surface chloride content and diffusion coefficient were proposed according to test results. The equations for chloride penetration considering the time-dependent diffusion coefficients and surface chlorides were also suggested. The present study allows more realistic assessment of durability for such concrete structures which are subjected to combined attacks of chlorides and high concentration sulfates but the future studies for combined environment will assure the precise assessment.
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This paper aims to study the long-term durability of reinforced concrete in Persian Gulf region, as one of the most aggressive marine environments. Ten mixtures with Type II, and V cement and Portland Pozzolanic cements including IS(20), IPnp(15) and IPsf(10) with three cover thicknesses (35, 50 and 70 mm) utilized. In the preliminary laboratory stage, the compressive strength and depth of water penetration measured up to 365 days. Then, in the field stage, specimens exposed in atmospheric condition, tidal zone and totally submerged in seawater to evaluate the 18 years-corrosion performances. In tidal zone, Type V mixtures experienced a high degree of corrosion in the field study and IPsf(10) and IPnp(15) exhibited the best performance up to 18 years exposure. Moreover, in this condition, the corrosion potential of Type V concrete with 35 mm cover thickness had increased after 6 years and its reinforcements experienced pitting corrosion. Generally a minimum 50 mm concrete cover thickness might be proposed as a criterion for long-term durability in tidal zone.
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Porosity evolution caused by electrochemical chloride removal (ECR) process can affect the transport behaviour of concrete and vice versa. The main task in this investigation is to quantitatively understand the porosity evolution effect on ECR process, and find a more accurate model that gives good correlation with the experimental results concerning the ionic transport in concrete during the ECR. The porosity of the concrete near the cathode and anode were measured, before and after ECR treatment (mainly 7 days, 15 days and 30 days). A method to analyse and calculate the porosity profiles was proposed according to the ECR experimental data. The penetration and leaching of ionic species in concrete are studied by using a finite element procedure based on the Nernst–Planck equations. The proposed method is capable of reducing the numerical modelling error of the chloride profile in concrete during the ECR.
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Slow strain rate testing showed that stress corrosion cracking (SCC) of A537 steels could occur in both simulated seawater and alternating wet–dry environments. The SCC mechanism was anodic dissolution (AD) under anode polarization and open circuit potential, and hydrogen induced cracking (HIC) under cathode polarization with high potential difference. The additive stress σp, induced by the corrosion process controlled susceptibility to SCC, regardless of the AD mechanism or HIC under either anodic or cathodic polarization conditions. SCC initiated at the interface between matrix and MnS inclusions, which was as anodic phases to promote the AD process.
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To evaluate corrosion of reinforcing steel by the attack of chloride ion in concrete under high temperature, influence of temperature on diffusion coefficient of chloride ion in concrete was investigated. At first, two types of test equipments, immersion test type and diffusion cell method type, were manufactured. They were able to control condition of high temperature. Using these equipments, chloride ion diffusion tests were conducted. In the tests, temperature were controlled from 25 to 90°C. Water cement ratios of specimens were changed from 40 to 60%. The result of the tests showed that diffusion coefficient of chloride ion was affected significantly by temperature. The relationship between temperature and diffusion coefficient depended on Arrhenius' equation. The diffusion coefficient decreased as water cement ratio decreased. The tendency does not change even in high temperature. Based on the tests results, equations for evaluating diffusion coefficients of chloride ion in concrete as a function of temperature were proposed.
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Corrosion of steel due to chloride attack is a major concern in reinforced concrete structures which are located in the marine environments. In this case, Fick's 2nd law has been used for the prediction of chloride diffusion related with service life of concrete structures. However, those studies were confined mostly to the single deterioration due to chloride only, although actual environment is rather of combined type. The purpose of the present study is, therefore, to explore the influences of carbonation to chloride attack in concrete structures and to investigate the validity of Fick's law to chloride attack combined carbonation. The test results indicate that the chloride ion profiles from Fick's law using the diffusion coefficient of immersion tests is not reflected the effect of separation of chloride ions in carbonation region but valid in sound region in case of combined action. On the other hand, the chloride ion profiles from Fick's law using the diffusion coefficient of Tang and Nilsson's method coincide with test results under dry-wet condition but not under combined condition. The results of present study may Imply that the new method for the measurement of diffusion coefficient is required to predict the chloride ion profiles in case of combined action at early.
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An empirical model based on constant flux is presented for chloride transport through concrete in atmospherical exposure conditions. A continuous supply of chlorides is assumed as a constant mass flux at the exposed concrete surface. The model is applied to experimental chloride profiles obtained from a real marine structure, and results are compared with the classical error-function model. The proposed model shows some advantages. It yields a better predictive capacity than the classical error-function model. The previously observed chloride surface concentration increases are compatible with the proposed model. Nevertheless, the predictive capacity of the model can fail if the concrete microstructure changes with time. The model seems to be appropriate for well-maturated concretes exposed to a marine environment in atmospherical conditions.
Conference Paper
In order to better simulate the penetration process of chloride ions in the splash zone of concrete, this paper modified existing chloride ion transport model on the basis of capillarity-dependent model under unsaturated and non-pressure conditions to make it applicable to the calcualtion of choride flow flux. The artificial splash tests is firstly designed and conducted under varied conditions of water to cement ratio, splash time duratinoa and splash period. Then the original chloride constitutive model is improved by enhancement of convection term calculation. At last, the authors simulate the chloride ions penetration process under different conditions by reasonble design of equivalent chloride and moisture boundary to verify the effectiveness of capillarity-dependent model.
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Today, it remains unclear how ‘green’ concrete with high volumes of fly ash really is, especially when subject to chloride-induced corrosion. This paper presents chloride diffusion test results for high-volume fly ash and fly ash + silica fume concrete. Apparent diffusion coefficients and surface concentrations were compared with those for traditional concrete. Instantaneous chloride diffusion coefficients and ageing exponents were estimated and critical chloride contents for submerged exposure conditions were experimentally verified. The estimated time to chloride-induced steel depassivation for the two concrete types with fly ash (60 to more than 100 years) was much longer than for traditional concrete (24 to 32 years). As a consequence, global warming potentials (GWPs) calculated for the required concrete volume per unit of strength and service life indicate that an important reduction in greenhouse gas emissions is possible for both concrete types with high volumes of fly ash (GWP –50 to –82%).
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A several-year experimental program has been conducted on concrete samples stored in the laboratory as well as on reinforced concrete test specimens under field exposure, in order to characterize, in particular from a durability perspective, a fifteen concrete series ranging from B20 to B120. This program lies within the scope of the task group "Experimental study on exposure sites", as part of the working group "durability" of the National (French) Project "BMP 2000". It lies also within the scope of the research project directed by LCPC "Durability of reinforced concrete and of its constituents: control and performance-based approach". This paper is the fourth in the series "Ageing of concrete in natural environments: an experiment for the 21 st century". It presents the experimental program set up to monitor the precracked reinforced concrete test specimens located on the sites of Melun, La Rochelle, Maurienne and Canada. In addition, it includes the experimental results obtained during the first measurement sequence on the cores extracted from the various test specimens. In-situ data, as regards microstructure, moisture properties, mechanical strength, carbonation, chloride ingress, as well as frost and salt degradations (scaling), have been compared to the results from tests carried out on 28-day old water-cured laboratory samples. Gradients between core and surface zone have been observed in situ, which magnitude varied as a function of the mix and environment parameters. Generally speaking, an improved behavior has been observed with high-performance concretes. Moreover, a good agrement, as regards trends and ranking, has been recorded between the results obtained on field and those derived from laboratory samples.
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This paper presents the Location, the structural design as well as the anti-corrosion and the pilot programs of the marine exposure station of Zhoushan Archipelago seas sea-crossing bridges. Subjected to the marine environment, the concrete structures in serve with different mixing proportions, cover thickness, additional anti-corrosion measures such as rust-preventing agent, coating, penetration crystalline waterproof material, silicone and permeable fabric were studied. Those results obtained provide important information for the maintenance of marine concrete and the structural design of sea-crossing bridges in the above sea area.
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The concrete bridges in the infrastructure in the western world have reached an age where the costs of the maintenance activities have reached a level comparable to the cost of construction of new bridges. One of the main causes is chloride ingress and the resulting corrosion of reinforcement. The chloride concentration profiles are often determined from samples and used as a basis for assessment of the structure's current conditions and for the prediction of future performance. The author has collected in a European research project a large number of chloride profiles from structures (own inspections and literature) and test panels (literature) to establish an empirical model for the extrapolation of observed chloride profiles and to determine the variation in presumed homogeneous areas of the structure. The predictions from the model are compared to actual values and the variations are explained through the observed variation of the input.
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The exposure conditions for structures in marine ane road conditions exposed to chloride ions were studied. Field studies were made in both marine and road conditions, where the influence of the exposure conditions was measured as the environmental response of concrete and mortar. In marine conditions identical concrete specimens, exposed at different submerged locations, were investigated. In road conditions both existing structures and specimens were investigated. The resultant data were analyzed in detail.
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Aquaculture is among the oldest occupations of human being. Over the past quarter of century, the aquaculture industry has grown rapidly. The effect of water containing sodium sulfate on long term compressive strength of concrete of fishing ponds and channels is investigated in this paper. Aim of this paper was to analyze the strength of concrete channels and of aquaculture which are in direct contact with dissolved sodium sulfate. This is an ongoing laboratory investigation which consisted of 480 standard casting concrete cube mix designs and subjecting them to different curing condition environments. Analyzing laboratory results, it was found that for short period of time, the effect was negligible, but for longer periods up to seven months, EC (electrical conductivity) of water had a low negative effect on compressive strength of concrete, while specimens were placed in waters with different ECs. On the other hand, average compressive strength of concrete was almost 25 kg/cm(2) lower than estimated. However, loading the sample concretes up to failure resulted in strength loss of up to 10%. To solve this problem, designed compressive strength must be considered 10% higher than actual in order to have an acceptable concrete strength for water channels and ponds which are in direct contact with sodium sulfate ions in the water.
Article
Airborne chlorides are transported to inland by sea wind to be attached to seashore concrete structure surface then penetrated into concrete structure members. Since the surface attached chloride amount are dependent on the amount of airborne chlorides, the prediction of distribution of airborne chlorides is important information in preventing chloride corrosion problems in seashore concrete structures. The prediction of surface chloride amount from airborne chlorides environment is extremely difficult than concrete directly in contact with seawater. In addition, their penetrating tendency is different from that of concrete immersed in seawater. In this study, properties of surface and penetrated chlorides under airborne chlorides environment are investigated. Concrete specimens were manufactured and exposed to marine environment for 3 years. The specimens were analyzed at the time durations of 1, 2, and 3 years to check surface chloride amount to penetrated chloride depth. The results revealed that there were certain differences according to surface roughness of concrete and with and without washing effect due to rainfalls. The evaluation results showed that penetrated chlorides depend on amount of airborne chlorides and duration of exposure. In addition, a notable tendency of having deeper chloride penetration and higher chloride content in concrete members under long-term exposure was observed.
Article
Diffusion has been systematically described as the main mechanism of chloride transport in reinforced concrete (RC) structure, especially when the concrete is in a saturated state. However, the single mechanism of diffusion is not able to describe the actual chloride ingress in the nonsaturated concrete. Instead, it is dominated by the interaction of diffusion and convection. With the synergetic effects of various factors taken into account, this study aimed to modify and develop an analytical convection- diffusion coupling model for chloride transport in nonsaturated concrete. The model was verified by simulation of laboratory tests and field measurement. The results of comparison study demonstrate that the analytical model developed in this study is efficient and accurate in predicting the chloride profiles in the nonsaturated concrete.
Article
This paper presents a thoroughgoing research on chloride transport in damaged concrete. Effects of temperature and temperature gradient on chloride transport was investigated along with effects of relative humidity, humidity gradient, concrete damage and exposure time. The higher the temperature and the greater the humidity gradient were, the quicker chloride transport was. Moisture transport increased as concrete damage increased, while chloride transport decreased incrementally. Considering the effect of coupled heat and moisture on chloride transport in concrete, a chloride transport model was established and verified by experiments. Chloride profiles in damaged concrete were related to temperature, temperature gradient, relative humidity and humidity gradient. The chloride attack rate decreased with increasing concrete damage and exposure time. Hence, coupled heat and moisture as well as concrete damage had significant effects on chloride transport in damaged concrete, and effects of concrete damage on chloride transport should be considered when determining chloride profiles in damaged concrete.
Conference Paper
Full-text available
The most common form of deterioration is caused by chloride ingress through concrete, resulting in corrosion of the reinforcing steel. One of the factors affecting the penetration of chloride ions is the amount of surface chloride (Cs). In this paper, the amount of chloride on the surface of concrete specimens made with different pozzolan in tidal and splash zones is considered. The results show that the amount of surface chloride in the specimens of concrete sited in splash zone is more than tidal zone.
Article
In the European standardization organization CEN, a working group has developed a standard describing the procedures to be used when determin ing the thermal conductivity of masonry materials such as brick, aerated concrete, etc. It applies to measurements using a guarded hot plate or a heat flow meter appara tus. This paper deals with those clauses of the standard related to measurements on moist materials and describes the background and considerations needed for the drafting of these clauses. Preparation and conditioning of the test specimens are described. The paper analyses the effect of moisture redistribution during the measurements and reviews different options for dealing with these effects. It is possible, for the materials considered, to restrict the errors caused by effects of moisture in the materials to less than about 5%-that is to the same order of magni tude as the errors of the guarded hot plate or heat flow meter apparatus itself when testing dry masonry materials.
Chloride-Initiated Corrosion—Field Studies of Chloride Corrosion in Bridge Columns
  • Danish Directorate
Danish Road Directorate, Chloride-Initiated Corrosion—Field Studies of Chloride Corrosion in Bridge Columns. Copenhagen, 1991.
Building Research Institute, Chloride Durability of Concrete Coastal Bridges
  • Norwegian Directorate
Norwegian Road Directorate, Building Research Institute, Chloride Durability of Concrete Coastal Bridges. Oslo, 1993.
HETEK, A System for the Prediction of Chloride Ingress and Corrosion in Concrete
  • E Nilsson
  • P Poulsen
  • H E Sandberg
  • O Sørensen
  • Klinghoffer
Nilsson, E. Poulsen, P. Sandberg, H.E. Sørensen, and O. Klinghoffer, HETEK, A System for the Prediction of Chloride Ingress and Corrosion in Concrete. Report No. 83. The Danish Road Directorate, 1997.
P-96:6. 1996. FIG. 13. Measured maximum total chloride concentrations for concrete mixtures with pozzolan in the binder and w/c Յ 0
  • L Tang
L. Tang. Chalmers Univ. of Tech., Building Materials; Ph.D. Thesis. P-96:6. 1996. FIG. 13. Measured maximum total chloride concentrations for concrete mixtures with pozzolan in the binder and w/c Յ 0.40, exposed in the submerged zone (A) and in the splash zone (B).
Hardened: Accelerated Chloride Penetration
  • Nt Build
NT BUILD 443. In Concrete, Hardened: Accelerated Chloride Penetration, part 6.4.4 Profile grinding.
Reinforcement Corrosion (in Swedish), in Swedish Manual for High Performance Concrete
  • P Fidjestøl
  • O Jørgensen
  • K Pettersson
  • P Sandberg
  • K Tuutti
P. Fidjestøl, O. Jørgensen, K. Pettersson, P. Sandberg, and K. Tuutti, Reinforcement Corrosion (in Swedish), in Swedish Manual for High Performance Concrete. C. Ljungkrantz and N. Petersons (eds.), Stockholm, 1998. Vol. 28, No. 10
A System for the Prediction of Chloride Ingress and Corrosion in Concrete
  • L.-O Nilsson
  • E Poulsen
  • P Sandberg
  • H E Sørensen
  • O Klinghoffer
  • Hetek
Reinforcement Corrosion (in Swedish)
  • Fidjestøl
Durability of Building Materials and Components 7
  • Tang