Total Chloride Content Research Articles

The Effect of Palm Oil Fuel Ash as a Supplementary Cementitious Material on Chloride Penetration and Microstructure of Blended Cement Paste

This article presents the effect of palm oil fuel ash as a supplementary cementitious material on chloride penetration and microstructure of blended cement paste. Palm oil fuel ash (POFA) was ground to obtain two finenesses: one was the same size as the cement and the other was smaller than the cement. Type I ordinary Portland cement (OPC) was replaced by POFA at 0, 10, 20, 30, and 40% by weight of binder. All paste specimens were prepared using the same water to binder ratio as 0.35. The compressive strength, pore size distribution, total chloride content, free chloride content, and X-ray diffraction analysis of chloride penetration into blended cement pastes were investigated. The results indicated that, at 60 and 90 days, the blended cement pastes containing 30% of POFA with high fineness had 1.6 and 4.9% higher compressive strength than that of the OPC paste, respectively. POFA pastes had a lower chloride diffusion coefficient and shallower concentration profile of free chloride than that of the OPC paste. The specimens containing coarse fineness and small particle size POFA had lower chloride diffusion coefficient than OPC paste ranging between 13.2 and 61.0%. In addition, the chloride diffusion coefficient is linearly correlated with the critical pore diameters. Replacement of OPC by the fine-grained POFA resulted in the decrease in free chloride and in the chloride diffusion coefficient.

Effect of carbonation on release of bound chlorides in chloride-contaminated concrete

In this paper an experimental study is presented on the interaction between concrete carbonation and chloride attack. The experiments are carried out on chloride-contaminated cement pastes that have been exposed to a carbon dioxide environment. Free and total chloride contents at different carbonation times are measured in the tested specimens using traditional leaching and acid-soluble methods. Bound chloride contents are calculated from the measured total and free chlorides. The experimental data show that the carbonation of cement paste results in a release of bound chlorides, which is related to not only the decomposition of Friedel's salt, but also the decomposition of calcium-silicate-hydrate (C-S-H) gel. Based on the obtained experimental results, a numerical model is also developed for simulating the carbonation process of the chloride-contaminated cement paste. The model can be used to explain how the bound chlorides are released in a chloride-contaminated cement paste under the influence of carbonation reactions.

Comparison of existing chloride ingress models within concretes exposed to seawater

Numerous models to predict chloride ingress within concretes for different environmental conditions (immersed in seawater, located in the tidal zone or exposed to sea spray) have already been developed. Thanks to a benchmark, the objective of this paper is to contribute to the choice of a reliable engineering model for predicting chloride ingress in the case of saturated conditions. This study focus on a comparison between various physico-chemical models which rely on different approaches to account for transport phenomena and binding of chloride ions onto the cementitious matrix. The authors draw special attention to models using a limited number of input data (3 or 4): accessible-to-water porosity ( $$\phi _{\text{w}}$$ ), effective chloride diffusion coefficient ( $$D_{\text{Cl}^-}$$ ) and one or two parameter(s) characterizing the physical binding of ions Cl−. They are determined through the analysis of two simple and repeatable experimental tests: $$\phi _{\text{w}}$$ is measured directly by hydrostatic weighing and the other parameters are fitted by inverse analysis performed of a total chloride content (tcc) profile at a given exposure time. An application of the method and a comprehensive comparison between predicted chloride profiles and experimental data (tcc profiles at other ages than the one used for the fitting and free chloride concentration profiles) have been carried out for two mortars and seven concretes exposed to laboratory or in-situ conditions. The performance of the studied models is assessed thanks to statistical tools and recommendations are pointed out for the development of new numerical models.

Photochemical fate and photocatalysis of 3,5,6-trichloro-2-pyridinol, degradation product of chlorpyrifos.

In this study we have focused on 3,5,6-trichloro-2-pyridinol (TCP), degradation product of chlorpyrifos. Photolysis experiments were conducted in order to elucidate its degradation mechanism. Identification of products was performed using the LC-MS technique. To evaluate the mineralization efficiency, TiO2 photocatalytic study was performed. Under photolytic experimental conditions, the concentration of TCP after 120 min of irradiation reached 5.9 ± 1.5% of the initial concentration, while chloride concentration reached approximately 73% of total chloride concentration. The TOC measurements after 120 min of photocatalytic degradation experiment revealed high mineralization rate, i.e. 53.6 ± 1.9%, while chloride concentration reached 26.6 mg L(-1) what means almost quantitative transformation of organic chlorine into chloride. TIC chromatogram (ESI, negative ion mode) of the reaction mixture after 30 min of irradiation revealed the presence of several peaks. One of them has already been reported previously. Two other products have been identified in this study for the first time. They have been formed by radical attack of the reactive OH(•) species on the carbonyl group followed by the corresponding N-C or C-C bond cleavages and recyclization with formation of the pyrrol structures substituted with carboxylic groups. Both deprotonated molecules easily lose CO2 in ESI conditions.

염해 실태조사를 통한 철근 콘크리트 교각의 내구수명 평가 - 결정론적 및 확률론적 해석방법

Abstract: RC (Reinforced Concrete) structures are considered as cost-benefit and durable however performances of structural safety and du rability are degraded due to steel corrosion. Service life in RC structure is differently evaluated due to different local environmental conditions even if it is exposed to the same chloride attack. In the paper, 25 concrete cores from field investigation are obtained from 4 RC columns with durat ion of 3.5 ∼4.5 years exposed to sea water. Through total chloride content measurement, surface chloride contents and apparent diffusion coefficients are evaluated. Service life of the target structure is estimated through deterministic method based on Fick's 2 nd Law and probabilistic method based on durability failure probability, respectively. Probability method is evaluated to be more conservative and relatively decreased service life is eva luated in tidal zone and splash zone over 40.0 m. Chloride penetration behavior with coring location from sea level and the present limitations of durab ility design method are investigated in the paper.Keywords: Durability design, Deterministic method, Probability method, Apparent diffusion coefficient, Field investigation

Determination of the chloride diffusion coefficient in blended cement mortars

The rapid chloride migration test (RCM) is a commonly used accelerated test for the determination of the chloride diffusion coefficient in concrete. Nevertheless, the initial development and further experience with the RCM test concern mainly the ordinary Portland cement system. Therefore, the objective of this work is to analyse the application of this test method for other types of binders, by performing and analysing the RCM test results for mortars prepared with additions of supplementary cementitious materials. A comparison is given between the total chloride concentration profiles measured in concrete after the RCM test and the colourimetric test results. The presented results show that the accuracy of the silver nitrate colourimetric technique is sufficient for the determination of the chloride penetration front and that the RCM test is a suitable method also for the determination of chloride diffusion coefficient in mortars with blended cements.

Evaluation of chloride-penetration resistance of metakaolin concrete by means of a diffusion – Binding model and of the k-value concept

In this paper, the effect of the addition of metakaolin on chloride-penetration resistance of concrete is investigated. Greek kaolin thermally treated at defined conditions and a commercial metakaolin were used. Eight mixture proportions were used to produce high performance concrete, where metakaolin replaced either cement or sand in percentages 10% or 20% by weight of the control cement content. The specimens were placed in a NaCl solution for 90 days and the concentration of total and free (unbound) chloride was determined. The chloride penetration was studied by means of a fundamental model taking into account diffusion and binding (adsorption & desorption) processes. The efficiency factors (k-values) for the studied metakaolins were determined. Both metakaolins present a considerable chloride-penetration resistance, depending on active silica and alumina contents, and their addition significantly decreases chloride penetration leading to improved concrete durability.

Analysis of total chloride content in concrete

This research paper presents an analysis of total chloride contents in concrete. The concrete mixtures that were approved by the municipality of Riyadh city in Saudi Arabia for a main ready mix concrete plant were considered in this study. The analysis was based on an experimental investigation of chloride levels in mixing water, aggregates, and concrete. The analysis also used the maximal total chloride limits of British Standards for the concrete in conjunction with other ingredients required for the mix.The results obtained suggest that the effect of chloride content in mixing water has minimal to moderate influence upon the chloride content of concrete up to w/c equal to 0.4. It also shows that aggregate is the critical ingredient in terms of determining the presence of chloride in concrete. Critically, the limits of chloride content in any concrete mix could be violated even though the limits of chloride content still meet some standards for their content within concrete ingredients. The proportions of any mix design are also an important factor to be considered when attempting to specify the limits of chloride content of the ingredients of concrete mixtures for any type of concrete. It is vital to investigate empirically the relationship between total chloride and chloride contents in ingredients in order to precisely define the limits of chloride content in concrete mix ingredients. Mix design that has the lowest w/c ratio is preferable as far as the chloride content is concerned. Finally, water chloride content could be higher than ASTM specified limits with mix designs that have low water cement ratios and should be lower than the ASTM limits with high water cement ratios.

Chloride ion penetration into fly ash modified concrete during wetting–drying cycles

The subject of this paper is the extent to which, during wetting–drying cycles, chloride ions penetrate into fly ash modified concrete. Detailed chloride profiles were recorded which show how the total and water-soluble chloride contents vary with the depth of penetration of these ions into the concrete. In order to study the effect of exposure time, fly ash content, and fly ash composition on such penetration, two different types of fly ash were used as a partial replacement of Portland cement, their proportions amounting to 0%, 20% and 50% by weight of the binder.The results of the investigation showed that the chloride penetration depths were smaller in the case of the fly ash modified concretes than in the case of the unmodified concrete (i.e. concrete which did not contain fly ash), so that thinner layers of concrete cover could in this case be used to protect the steel reinforcement from the effects of corrosion. This indicates the potential beneficial effect of the use of fly ash on the service life of reinforced concrete structures. It is not just the porosity of the fly ash which plays a key role in the case of chloride penetration into concrete, but also the composition of the fly ash, and especially its calcium content.

Use of a multi-species reactive transport model to simulate chloride ingress in mortar exposed to NaCl solution or sea-water

Simulations of ion ingress in Portland cement mortar using a multi-species reactive mass transport model are compared with experimental test results. The model is an extended version of the Poisson–Nernst–Planck equations, accounting for chemical equilibrium. Saturated mortar samples were exposed after 8days of hydration to a NaCl-solution or natural sea-water in a laboratory controlled environment for the experimental part. The samples were analyzed for the total chloride content after 21, 90 and 180days of exposure, at varying depths from the exposed surface. The applicability of the reactive mass transport model is shown by comparing the simulation and experimental results. The tortuosity factor used in the simulations is adjusted to obtain the best reproduction of the experimental results. The model predicts the total chloride content satisfactorily, despite assumptions in the simulation like fixed hydration degree over time. Improvements and suggestions for further development of the model are discussed, e.g. extended hydration description, improved overall chemical description and a more strict use of the tortuosity factor.

Hematologic and biochemical reference intervals for Wild Boar (Sus scrofa) captured by cage trap

Establishing reference intervals (RI) for hematologic and biochemical variables in wild animals presents great challenges because capture stress or anesthesia during sampling can affect blood variables. The aims of this study were to establish RI for hematologic and blood biochemistry variables for Wild Boar (Sus scrofa) caught using cage traps, and provide information on the studied variables for different age groups. Blood samples were obtained from 89 Wild Boars captured by cage trap between 2005 and 2013 in northeastern Spain. Piglets were handled without anesthesia, while juvenile and adult animals were anesthetized using a combination of tiletamine and zolazepam. Blood samples were collected from the anterior vena cava and were placed into plain and EDTA tubes. Thirteen hematologic and 21 biochemical variables were determined. Reference intervals for piglets and juvenile and adult groups were determined, and differences between these groups were statistically analyzed. Adults had higher HGB, PCV, MCH, MCHC, neutrophil count, and total protein, albumin, creatinine, and chloride concentrations than juveniles; in contrast, juveniles had higher values for lymphocyte count, cholesterol concentration, and ALP activity. Reference intervals determined in this study provide a baseline for interpreting hematologic and biochemical results in Wild Boar at different age stages, and contribute to optimization of the management of this species.

Investigation of long term coupled effect of high temperature and constant high humidity on corrosion rehabilitated patches of reinforced concrete structures

This paper aims at finding the long term coupled effect of high temperature and constant high relative humidity on the corrosion rehabilitated patches of chloride contaminated steel reinforced concrete. This paper is an extension of previous research in which the authors experimentally corroborated re-corrosion in the repaired reinforced concrete (RC) patches in the form of macro-cells. In previous research, the coupled effect was investigated by laboratory controlled experimentation at varying temperature of 30, 40 and 50°C and a high ambient relative humidity of 85% in environmental control chambers for duration of one year. The specimens were prepared having total chloride concentration in mixing water 3% and 5 % by mass of binder. In this present research paper, the two year results of the same specimens are presented to get a deep insight of the long term phenomenon of macro-cell corrosion under the coupled effect of high temperature and humidity on repaired RC patches.

추출방법에 따른 톳 추출물의 품질특성

The physiological properties of water extracts from Hizikia fusiformis extracted using different extraction methods (water extraction, WE; autoclave extraction, AE; high pressure extraction, HPE) were investigated. The freeze-dried powder yields from HPE, AE and WE were 29.33, 27.84 and 23.63%, respectively. The L* and b* color values were higher in WE, while the a* color values were higher in WE and AE. The total sugar content of AE (60.14%) was higher than those of WE (47.10%), HPE (40.97%). The reducing sugar content (7.88%) and protein content (42.83%) of AE was higher than those of WE, and HPE. The uronic acid (5.04%), total free amino acid (785.19 mg/g), taurine (19.16 mg/g), aspartic acid (66.63 mg/g), asparagine (204.84 mg/g), alanine (188.87 mg/g) and ammonium chloride (243.91 mg/g) contents, however, were the highest in HPE. Additionally, the crude polysaccharide yield was higher in HPE (4.75%) than in AE and WE, and the crude saccharide (fucose, galactose, glucose, xylose and fucose) yields were higher in AE. It can be concluded that optimum conditions for the efficient extraction of Hizikia fusiformis depending on components are high pressure and a lower temperature than in the typical process.

Effect of Sulfonated Acetone Formaldehyde (SAF) on the Firing Resistance and Aggressive Attach of SRC-SF Composite Cement Pastes

This work aimed to study the effect of the dosage of laboratory synthesized Sulfonated Acetone Formaldehyde (SAF) on the physic-mechanical characteristics and durability of SF-SRC cement pastes immersed in 4% MgCl2 or 4% MgSO4 solutions or at elevated temperatures up to 800°C. The compressive strength of thermally treatment cement pastes with 1.5% SAF increases up to 600°C, then decreases up to 800°C. Presence of 2.0% SAF works to produce a compact cementing structure, which decreases the accessibility of the penetration of chloride as well as sulphate ion penetration and enhances the durability, hence the total chloride and sulphate contents diminished.

THE INFLUENCE OF INFILTRATION OF LEACHATE FROM LANDFILLS ON THE CHANGES OF CHEMICAL PARAMETERS OF THE SOIL

The article presented the results of geochemical research of clean soil and soil contaminated with the leachate from the landfill. Two types of soil were studied – brown with a stony foundation and loamy. The aim of the research was to compare the impact of leachate infiltration on the changes of chemical parameters of soils and to determine their buffer properties and susceptibility to contamination on this basis. The obtained results showed that the total acidity, mineral alkalinity and chloride content in the studied soils reduced after the contamination with the landfill leachate. While the chloride content, general hardness and general alkalinity increased. It has been found that the effect of infiltration of the landfill leachate was the significant reduction of mineral substances due to their washout of the soil profile. It has also been shown that the studied landfill leachate contained substantial quantities of substances favourable to the plant growth.

Long term changes in nutrients, chloride, and phytoplankton density in the nearshore waters of Lake Erie

Monitoring at five municipal water treatment plant intakes revealed several significant trends in Lake Erie's nearshore water quality since the 1960s and 1970s. Phytoplankton densities, in particular the abundance of diatoms, decreased following early phosphorus loading controls and the establishment of dreissenid mussels, while silica concentrations increased. There were notable reductions and breakpoints in the trends in phytoplankton cell densities in consecutive years from the west to the east of the lake (western basin in 1987, central in 1988, and eastern in 1989) coinciding with the reported timing of dreissenid mussel invasion and establishment. There have also been shifts in phytoplankton species composition that were related to variations in total phosphorus, chloride, silica, and nitrate concentrations. Annual mean phosphorus concentrations have decreased significantly and remained low since the early 1990s in the eastern basin, showed no consistent trend in the central basin, and decreased in the western basin. Concentrations have increased in the western basin since the mid-1990s, although not to the levels seen during the early 1980s. Recently, chlorophyll a concentrations have also increased in the western and eastern basins of the lake.

Test and prediction of chloride diffusion in recycled aggregate concrete

Recycled aggregate concrete (RAC) specimens with different recycled coarse aggregate replacement ratios by mass (R) are fully immersed in a 10% chloride solution for 235 days. Both free chloride concentration (C f ) and total chloride concentration (C t ) are then measured employing a rapid chloride test (RCT) system. The Fick’s second diffusion law is verified by the test data and used to predict chloride concentration distribution at different immersion periods. Additionally, pore structures of the new and old mortar in RAC are tested by mercury intrusion porosimetry (MIP). It is found that binding chloride concentration (C b ) linearly increases with C f . In natural aggregate concrete (NAC), C f is obviously smaller than that in the RAC in the same testing environment and this is different from the test results of C t and C b . Furthermore, the effects of R on the chloride concentration of RAC become severe for specimens subjected to long immersion periods, which can be explained in terms of the pore structures of the new mortar and old adhesive mortar in RAC.

Physico-chemical, mechanical, microstructure and durability characteristics of alkali activated Egyptian slag

The aim of the present work is to study the characteristics of alkali activated Egyptian slag (GBFS) mixed with different contents of Na2O and SiO2. The rate of the kinetic of activation of GBFS has been studied by electrical conductivity, FTIR, DTA/TGA, XRD and SEM techniques. Electrical conductivity of alkali activated slag systems depends mainly on the binder composition, the activator type and its concentration. The increase in alkali activator contents affected the location and intensities of the conductivity maximum. As the hydration time increases the amount of hydration products increase, hence the chemically combined water and combined slag contents increase. SEM images showed the presence of (N,C)ASH gel with low porosity. With the increase of the content of Na2O leads to form a denser closed microstructure, leading to higher compressive strength values. The activated GBFS showed good durability in 5% MgSO4 or 5% MgCl2 solution, i.e., the compressive strength increased gradually with immersing time up to 180days. The total chloride and total sulphate contents decrease with alkali activated GBFS due to the forming hydrated products that fill some available open pores, thereby inhibiting Cl− or SO42− ions penetration; this effect leads to a decreased accessibility of Cl− or SO42− ions towards the more dense with low capillary pore structure. It can be concluded that alkali activated GBFS are more durable in 5% MgSO4 or 5% MgCl2 than OPC pastes.

The effect of chloride binding on the predicted service life of RC pipe piles exposed to marine environments

Chloride binding capacity has a significant effect on the service life of reinforced concrete (RC) pipe piles exposed to marine environments. Four typical chloride binding isotherms (i.e., null, linear, Langmuir and Freundlich binding isotherms) were reviewed in this paper. The effect of chloride binding on service life predictions of RC pipe piles, in terms of these different binding isotherms, was investigated. An experimental program was conducted to verify the theoretical predictions developed in the present study. The free and total chloride concentration profiles were presented for RC pipe piles exposed to submerged and splash zones for 5, 10 and 30 years. Furthermore, the predicted service life of RC pipe piles exposed to submerged and splash zones, using different binding isotherms, was also presented in this paper. The results of the present study indicated that the chloride binding has a more significant effect on the service life of RC pipe piles in submerged zone than in splash zone, and RC pipe piles in submerged zone display longer service life than those in splash zone.

무기질 혼화재가 해양콘크리트의 염화물 고정화에 미치는 영향

The use of industrial by-products is extending steadily in concrete admixtures. However, the effects of these mineral admixtures on the chloride binding in concrete have been insufficiently studied. In this study, the chloride binding effect of various mineral admixtures is evaluated and the results can be drawn as follows. The resistance to chloride penetration was greatly improved when ground granulated blast-furnace slag (GGBS) and silica fume (SF) was used in concrete. The chloride penetration resistance of concrete used fly ash (FA) was improved after 91 days. The chloride penetration depth of concrete used GGBS was lowest and concrete used SF showed second-lowest penetration depth. Concrete used FA having the effect of long-term strength development by pozzolanic reaction showed the lowest resistance to chloride penetration. In case of concrete used only ordinary portland cement, chloride migration coefficient reduced approximately 40.3% when compressive strength increased 10%. Chloride migration coefficients of concrete used FA, SF and GGBS was reduced 24.9%, 23.0% and 14.1%, respectively. Soluble chloride content was various with types and replacements of mineral admixtures in range of 41% to 77% of total chloride content. The chloride binding effect of concrete used FA was highest because concrete used FA was not denser than concrete used GGBS or SF and chloride ion penetrated inside more. However, concrete used GGBS or SF was dense and chloride ion concentrated inner surface portion of specimen. It caused lower chloride binding effect of concrete used GGBS or SF.