Segui questo link per vedere altri tipi di pubblicazioni sul tema: Chlorure. carbonation.
Articoli di riviste sul tema "Chlorure. carbonation"
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Vedi i top-50 articoli di riviste per l'attività di ricerca sul tema "Chlorure. carbonation".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Vedi gli articoli di riviste di molte aree scientifiche e compila una bibliografia corretta.
1
Xu, Lina, Yan Zhang, Shuyuan Zhang, Shuyuan Fan e Honglei Chang. "Effect of Carbonation on Chloride Maximum Phenomena of Concrete Subjected to Cyclic Wetting–Drying Conditions: A Numerical and Experimental Study". Materials 15, n. 8 (14 aprile 2022): 2874. http://dx.doi.org/10.3390/ma15082874.
Testo completoAbstract (sommario):
The combined action of chloride and carbonation generally accelerates chloride penetration in concrete. Plenty of studies have revealed a chloride maximum phenomenon in the chloride profiles of concrete under wetting and drying cycles, which affects the accuracy of the service life prediction of concrete structures. Carbonation is probably one of crucial factors inducing chloride maximum phenomena. To investigate the influence of carbonation on chloride distribution of concrete subjected to cyclic wetting–drying conditions, this study established a numerical model coupling carbonation effect, simulated chloride distribution at different carbonation degrees, and verified the simulation results with experimental results. The results show that a chloride peak appears in all predicted chloride profiles when carbonation effect is taken into account, and the higher the carbonation degree is, the more significant the chloride peak is. This demonstrates that carbonation can enhance the forming of chloride maximum phenomenon under cyclic wetting and drying. Moreover, the calculated results are highly consistent with the experimental results under different carbonation conditions, especially in terms of the peak chloride concentration and the corresponding depth. Furthermore, the significance degree of the chloride maximum phenomenon is closely related to some key parameters, such as CO2 concentration, environmental humidity, and temperature.
2
Yuan, Yezhen, Kaimin Niu, Bo Tian, Lijuan Kong e Lihui Li. "Effect of Metakaolin on the Diffusion Properties of Chloride Ions in Cement Mortar under the Coupling Effect of Multiple Factors in Marine Environment". Advances in Civil Engineering 2023 (25 maggio 2023): 1–15. http://dx.doi.org/10.1155/2023/6961234.
Testo completoAbstract (sommario):
To address the problem of chloride ion transport in cement concrete in marine environment, this study investigates the effect of metakaolin dosage on the chloride ion diffusion resistance of mortar and its mechanism by testing the chloride ion binding capacity and microstructure of mortar under the coupling effect of chlorine salt-sulfate-carbonation multiple factors. The results show that the coupling of sulfate or carbonation reduces chloride ion transport to some extent compared with single chlorine salt attack, while the three-factor coupled environment promotes free chloride ion diffusion. This is because the products of calcium alumina, gypsum, and calcium carbonate grow together and compete with each other to form more large capillaries; thus, accelerating the diffusion of chloride ions in cement mortar. Metakaolin, due to its higher pozzolanic activity, increases the monocarbon aluminate content in the erosion products, promotes F-salt generation, and increases the Al/Si ratio, which strengthens the binding ability of C-S-H gel to chloride ions, so the free chloride ion concentration inside the specimens doped with metakaolin is lower. In particular, the three-factor coupled environment has less 0.05–10 μm capillary pore content and higher F-salt stability in the specimens, which has the strongest effect on chloride ion curing, and the free chloride ion concentration integral in M-SCCl is reduced by nearly 30% compared with MF-SCCl and F-SCCl.
3
Nakamura, Eisuke, Yuki Kurihara e Hirohisa Koga. "Outdoor Exposure Test of Concrete Containing Supplementary Cementitious Materials". Key Engineering Materials 711 (settembre 2016): 1076–83. http://dx.doi.org/10.4028/www.scientific.net/kem.711.1076.
Testo completoAbstract (sommario):
An outdoor exposure test was conducted to investigate the resistances of concrete containing supplementary cementitious materials (SCMs) to carbonation and chloride ingress at three outdoor exposure testing sites in Japan. The test results indicated that concrete specimens containing larger amounts of SCMs exhibited larger carbonation depths but the carbonation rates decreased as the testing period was extended. Additionally, the resistance to chloride ingress was improved by the use of SCMs in cases where the carbonation depths were negligible. Concrete specimens containing high-volume SCMs, however, showed inverse chloride profiles due to large carbonation depths; chloride contents were low in zones of carbonation but large beyond these zones. The resistance to carbonation was found crucial for preventing reinforcement corrosion induced by not only carbonation but also incidental chloride ingress in concrete containing high-volume SCMs.
4
Chang, Wang, Jin, Li, Feng, Ye e Liu. "Durability and Aesthetics of Architectural Concrete under Chloride Attack or Carbonation". Materials 13, n. 4 (12 febbraio 2020): 839. http://dx.doi.org/10.3390/ma13040839.
Testo completoAbstract (sommario):
Architectural concrete has been wildly used nowadays, and those served in an offshore environment often suffer from chloride penetration and carbonation. To assess the protection and decoration performances of architectural concrete, this study exposed architectural concrete to actual marine environments and accelerated carbonation conditions. The chloride and carbonation resistance of architectural concrete was determined to evaluate the protection performance, and the corresponding surface-color-consistency was adopted to characterize its decoration performance. The results show that the total and free chloride of concrete in the marine atmosphere zone and the tidal zone generally decreases with depth; chloride content arguments significantly with exposure time, with a chloride maximum peak near the surface. Moreover, the chloride diffusion coefficient is small throughout the measurements, indicating the superior chloride resistance of architectural concrete. Furthermore, architectural concrete also possesses excellent carbonation resistance based on the carbonation depth data obtained from the carbonation experiment. Therefore, architecture concrete served as protection covers can withstand both the chloride attack and carbonation tested in this paper. In addition, carbonation was found to have a profound influence on the aesthetics of architectural concrete. Therefore, carbonation should be carefully handled for better maintaining the aesthetic appearance of architectural concrete in long-term service.
5
Chen, Chunhong, Ronggui Liu, Pinghua Zhu, Hui Liu e Xinjie Wang. "Carbonization Durability of Two Generations of Recycled Coarse Aggregate Concrete with Effect of Chloride Ion Corrosion". Sustainability 12, n. 24 (16 dicembre 2020): 10544. http://dx.doi.org/10.3390/su122410544.
Testo completoAbstract (sommario):
Carbonation durability is an important subject for recycled coarse aggregate concrete (RAC) applied to structural concrete. Extensive studies were carried out on the carbonation resistance of RAC under general environmental conditions, but limited researches investigated carbonation resistance when exposed to chloride ion corrosion, which is an essential aspect for reinforced concrete materials to be adopted in real-world applications. This paper presents a study on the carbonation durability of two generations of 100% RAC with the effect of chloride ion corrosion. The quality evolution of recycled concrete coarse aggregate (RCA) with the increasing recycling cycles was analyzed, and carbonation depth, compressive strength and the porosity of RAC were measured before and after chloride ion corrosion. The results show that the effect of chloride ion corrosion negatively affected the carbonation resistance of RAC, and the negative effect was more severe with the increasing recycling cycles of RCA. Chloride ion corrosion led to a decrease in compressive strength, while an increase in carbonation depth and the porosity of RAC. The equation of concrete total porosity and carbonation depth was established, which could effectively judge the deterioration of carbonation resistance of RAC.
6
Yoon, In Seok. "Deterioration of Concrete Due to Combined Reaction of Carbonation and Chloride Penetration: Experimental Study". Key Engineering Materials 348-349 (settembre 2007): 729–32. http://dx.doi.org/10.4028/www.scientific.net/kem.348-349.729.
Testo completoAbstract (sommario):
In most studies, deterioration of concrete due to carbonation or chloride penetration is investigated separately. However, the deterioration of concrete is normally caused by the combination. The purpose of this study is to investigate the interaction between carbonation and chloride penetration and their effects on concrete. This was examined experimentally under various boundary conditions. For concrete under the double condition, the risk of deterioration due to carbonation was not severe. However, it was found that the carbonation of concrete could significantly accelerate chloride penetration. As a result, chloride penetration in combination with carbonation can cause harmful deterioration of concrete.
7
Li, Zhen, Zhen He e Xiaorun Chen. "The Performance of Carbonation-Cured Concrete". Materials 12, n. 22 (12 novembre 2019): 3729. http://dx.doi.org/10.3390/ma12223729.
Testo completoAbstract (sommario):
The research shows that carbonation-cured concrete has several mechanical and durability properties that are better than those of moisture-cured concrete. However, many properties of carbonation-cured concrete have not yet been studied. In this research, carbonation-cured concrete was prepared by pre-curing, carbonation curing, and then moisture curing. The compressive strength, CO2 uptake, pH value, chloride ion permeability and abrasion resistance of the carbonation-cured concrete were investigated. Results showed that the compressive strength of carbonation-cured concrete was more than 10% higher than that of moisture-cured concrete at the same age; a steel bar is stable in carbonation-cured concrete; and carbonation-cured concrete exhibited better abrasion resistance and chloride ion permeability than that of moisture-cured concrete. The optimization of pore structure and improvement in the micro-hardness are the reasons for the improved chloride ion permeability and abrasion resistance of carbonation-cured concrete.
8
Chen, Xiangsheng, e Jun Shen. "Experimental Investigation on Deterioration Mechanisms of Concrete under Tensile Stress-Chloride Ion-Carbon Dioxide Multiple Corrosion Environment". Journal of Marine Science and Engineering 10, n. 1 (8 gennaio 2022): 80. http://dx.doi.org/10.3390/jmse10010080.
Testo completoAbstract (sommario):
The adverse effects of a hostile marine environment on concrete structures inevitably result in great economic loss and may contribute to catastrophic failure. There is limited information on the durability of concrete in a tensile stress-chloride ion-carbon dioxide (TCC) multiple-corrosion environment. The objective of this study is to explore the impact of a TCC multiple-corrosion environment on concrete considering three coupled factors of compressive strength, Cl− penetration, and carbonation. Dry–wet cycle tests were conducted to determine the strength degradation and Cl− penetration concentration of concrete in a hostile multiple-corrosion marine environment. The results show that the effects of water-soluble chloride ions (Cl−), carbon dioxide (CO2), and tensile stress on concrete are not a simple superposition, but involve obvious interaction. The compressive strength of a concrete specimen first increases and then decreases in chlorine salt-carbon tests. The Cl− concentration and tensile stress affect the carbonation depth of concrete, which increases with an increase in Cl− concentration, and with the application of tensile stress. The Cl− concentration has an obvious effect on the carbonation depth. In addition to experimental observations, a stepwise regression equation was established based on the multiple linear regression theory. A correlation analysis considering different factors was conducted to reflect the corrosion results more directly.
9
Zhou, Xiangong, Xiaoyu Zhang, Gang Li e Jialu Li. "Carbonation Characteristics and Bearing Capacity Attenuation of Loaded RC Beam Coupled with Chloride Erosion". Advances in Civil Engineering 2022 (15 luglio 2022): 1–15. http://dx.doi.org/10.1155/2022/5365789.
Testo completoAbstract (sommario):
The durability of a concrete bridge structure is a systematic problem composed of material, structure, natural environment, and service environment. Various factors are coupled, which affect each other, and single-factor research cannot fundamentally solve this problem. In this paper, the carbonation characteristics of RC beams with different loading states under the coupling action of carbonation and chloride erosion are studied. Through the experiment, the author tries to find the influence of stress state and chloride ion erosion on the carbonation of concrete and analyze the failure mode and the attenuation rules of the flexural and shearing capacity of the corroded RC beams under the coupling action. For this purpose, five groups of experiments under different working conditions were designed, including chloride ion erosion and carbonation experiments without external load of the cubic blocks, and chloride erosion and carbonation coupling experiments of RC beams under different stress states and stress levels. The carbonation rate of concrete can be reduced by 56%∼60% under the coupling action of chloride salt. Different loading states and stress levels have an obvious influence on carbonation and chloride ion corrosion, which further affects the corrosion rate of steel bars. Under a low corrosion rate, the bending and shear failure modes of the corroded beams are similar to those of the noncorroded beams, and the section strain distribution still approximately conforms to the plane section assumption. The relationship between the relative ultimate shear strength or the relative ultimate flexural strength and the average section-corrosion rate of the reinforcement is approximately linear.
10
Haibier, Abuduhelili, e Yong Xin Wu. "Effects of Mineral Admixtures on Carbonation and Chloride Ingress of Concrete". Applied Mechanics and Materials 212-213 (ottobre 2012): 878–82. http://dx.doi.org/10.4028/www.scientific.net/amm.212-213.878.
Testo completoAbstract (sommario):
Reinforcement corrosion is one important factor affecting the durability and safety of reinforced concrete structures. Concrete carbonation and chloride ion penetration is the main cause leading to steel corrosion, also important indicators affecting the service life of concrete structures. An accelerated carbonation experiment and Chloride penetration experiment was carried out on ordinary Portland cement (OPC) concrete and admixture concrete in various conditions. Eight concrete specimens of different mixture properties were tested in experiment. Resistance of OPC concrete system with and without mineral admixture (fly ash, slag) and air-entraining agent against carbonation was investigated. Besides, the influence of mineral admixture on the chloride penetration was also studied. The carbonation process and the factors affecting concrete carbonation are discussed according to test results. The test results were presented and they were in good agreement with the results of previous research.
11
Li, Qiang, Hongfa Yu, Haiyan Ma, Shudong Chen e Shuguang Liu. "Test on Durability of Shield Tunnel Concrete Segment under Coupling Multi-Factors". Open Civil Engineering Journal 8, n. 1 (31 dicembre 2014): 451–57. http://dx.doi.org/10.2174/1874149501408010451.
Testo completoAbstract (sommario):
To study the durability of shield tunnel concrete segment under coupling multi-factors, the durability and degradation law of reinforced concrete segments under the joint action of carbonation, sulfate, chloride salt and stray current was studied by accelerated environmental and direct current (DC) power simulation test. The results show that the presence of the stray current not only accelerates the migration of chloride ions to the concrete, but also makes chlorine ion gradually converge to the steel surface. The steel corrosion near the corrosion solution on the up surface of segment is more serious than the steel corrosion near the carbon dioxide on the lower surface. The interaction of chlorine ions and stray current primarily controls the durability of the segment.
12
AL-Ameeri, Abbas S., M. Imran Rafiq e Ourania Tsioulou. "Influence of carbonation on the resistance of concrete structures to chloride penetration and corrosion". MATEC Web of Conferences 289 (2019): 08001. http://dx.doi.org/10.1051/matecconf/201928908001.
Testo completoAbstract (sommario):
Chloride-induced corrosion of steel rebar embedded in concrete is one of the major concerns influencing the durability of reinforced concrete structures. It is widely recognized that the carbonation in concrete affects the chloride diffusivity and accelerates the chloride-induced reinforcement corrosion. However, only very limited studies have dealt with this issue in the literature. The presence of service load related cracks also affects the reinforcement corrosion. This study aims to investigate the potential impact of concrete carbonation on the chloride penetration resistance, and degree of corrosion, in RC structures subjected to service related microcracks. The experimental programme involves casting of concrete prisms (100 x 100 x 500 mm) with different water-cement ratios (w/c) of 0.4, 0.5 and 0.6 and with four different crack widths (0, 0.05-0.15 mm, 0.15-0.25 mm and 0.25-0.35 mm). These samples were exposed initially to accelerated carbon dioxide (CO2) environment and then exposed to the accelerated chloride environment. Carbonation depth, chloride penetration, and the degree of corrosion (using half-cell) were experimentally measured. The results indicated that (i): The depth of carbonation increases with the increase in crack width and w/c ratio, (ii) chloride penetration depth in concrete structures increases significantly due to the influence of carbonation and (iii) half-cell corrosion potential increases significantly when carbonated concrete samples are exposed to the chloride environment relative to the uncarbonated concrete samples.
13
Nagao, Kenji, Takao Ueda, Masanobu Ashida e Toyoaki Miyagawa. "Application of Desalination to Concrete Admixing Fly Ash or Blast-Farnace Slag". International Journal of Modern Physics B 17, n. 08n09 (10 aprile 2003): 1452–57. http://dx.doi.org/10.1142/s0217979203019149.
Testo completoAbstract (sommario):
This paper mainly describes corrosion behavior of the steel bars in concrete specimens using fly ash or blast-furnace slag, deteriorated by chloride attack, carbonation of concrete, or complex of both mechanisms. Furthermore, chloride removal effect due to applying desalination to such deteriorated specimens is investigated. Results obtained from this study can be summarized as follows: (1) Carbonation depth of concrete using fly ash or blast-furnace slag was larger than that of normal concrete and the larger replacement rate of them became, the more carbonation depth of concrete increased. (2) As the result of measurement of Cl- content in concrete before desalination, in the case of carbonated specimens, soluble chloride percentage to total chloride near the exposed surface was increased with the influence of carbonation of concrete. (3) Chloride removal percentage due to applying desalination to non-carbonated specimens was 15-30% as a whole cover concrete. On the other hand, in the case of carbonated specimens, Cl- ion near the exposed surface was decreased by desalination and chloride removal percentage reached 50-80%.
14
Lü, Xiaoshu, Tao Lu e Tong Yang. "A Carbonation and Chloride Induced Corrosion Model for Hot-dip Galvanised Reinforcement Bar Material in Concrete". Journal of Building Material Science 3, n. 2 (17 settembre 2021): 13. http://dx.doi.org/10.30564/jbms.v3i2.3150.
Testo completoAbstract (sommario):
This paper focuses on methodological issues relevant to corrosion risk prediction models. A model was developed for the prediction of corrosion rates associated with hot-dip galvanised reinforcement bar material in concrete exposed to carbonation and chlorides in outdoor environment. One-year follow-up experiments, over five years, were conducted at various carbonation depths and chloride contents. The observed dependence of corrosion rate on the depth of carbonation and chloride content is complex indicating that the interaction between the carbonation and chloride influencing the corrosion. A non-linear corrosion model was proposed with statistical analysis to model the relationship between the corrosion rate and the test parameters. The main methodological contributions are (i) the proposed modeling approach able to take into account the uncertain measurement errors including unobserved systematic and random heterogeneity over different measured specimens and correlation for the same specimen across different measuring times, which best suits the measurement data; (ii) the developed model in which an interaction parameter is introduced especially to account for the contribution and the degree of the unobserved carbonation-chloride interaction. The proposed model offers greater flexibility for the modelling of measurement data than traditional models.
15
Wu, Yan, Sixiang Kang, Feng Zhang, Haisheng Huang, Haojie Liu, Jianbin Zhang, Hongze Li, Weihong Li, Zhou Zheng e Wenda Wu. "Study on the Effect of Water–Binder Ratio on the Carbonation Resistance of Raw Sea Sand Alkali-Activated Slag Concrete and the Distribution of Chloride Ions after Carbonation". Buildings 14, n. 7 (3 luglio 2024): 2027. http://dx.doi.org/10.3390/buildings14072027.
Testo completoAbstract (sommario):
The excessive extraction of river sand has led to significant ecological issues. Moreover, the environmental impact and resource demand of cement production have increasingly turned the spotlight on sea sand as a viable alternative due to its abundance and ease of extraction. Concurrently, alkali-activated binders, a novel type of low-carbon cementitious material, have gained attention for their low energy consumption, high durability, and effective chloride ion fixation capabilities. However, they are susceptible to carbonation. Introducing a controlled sea sand amount can raise the materials’ carbonation resistance, although carbonation may raise the concentration of free Cl− within the structure to levels that could risk the integrity of steel reinforcements by accelerating corrosion. In this context, the current study investigates sea sand alkali-activated slag (SSAS) concrete prepared with varying water–binder (W/B) ratios to evaluate its impact on flowability, mechanical strength, performances, and chloride ion distribution post-carbonation. The results demonstrate that the mechanical property of SSAS concrete diminishes as the water-to-binder ratio increases, with a more pronounced reduction observed. The depth of carbonation in mortar specimens also rises with the W/B ratio, whereas the compressive strength post-carbonation initially decreases before showing an increase as carbonation progresses. Furthermore, carbonation redistributes chloride ions in SSAS, leading to a peak Cl− concentration near the carbonation front. However, this peak amplitude does not show a clear correlation with changes in the W/B ratio. This study provides a theoretical foundation for employing sea sand and alkali-activated concrete.
16
Malheiro, Raphaele, Aires Camões, Gibson Meira, Maria Teresa Amorim e João Castro-Gomes. "Effect of coupled deterioration by chloride and carbonation on chloride ions transport in concrete". RILEM Technical Letters 5 (25 settembre 2020): 56–62. http://dx.doi.org/10.21809/rilemtechlett.2020.126.
Testo completoAbstract (sommario):
Carbonation is one of the factors that can influence the chlorides transport. Despite the combined action of chlorides and carbonation being a reality, there is no consensus on the effect of this coupled deterioration on chloride transport. Accelerated tests were used to simulate this environment. Concrete specimens were cast using 0.60 water/cement ratio and CEM I 42.5R. After curing, half of specimens was submitted to accelerated carbonation test (20ºC, 55% RH and 4% CO2) during 1 and 7 months. The other half was protected with plastic film during the same period. Then, the specimens were submitted to the accelerated chlorides attack using: migration test and immersion test. Finished the immersion test, powder samples were extracted from surface to bulk and analysed to obtain free and total chloride profiles and pH profile. According to migration test results, the carbonation increases chloride transport regardless the test period. According to the immersion test results, there is a decrease in chloride ions transport when the specimens are carbonated for 1 month and a noticeable increase when carbonation period increases to 7 months. The redistribution of pores in carbonated concrete and the difficulty of chlorides binding in carbonated concrete are related to these results.
17
Tan, Ke Feng, e Qing Cao. "Chloride Binding of Cementitious Pastes". Advanced Materials Research 152-153 (ottobre 2010): 363–67. http://dx.doi.org/10.4028/www.scientific.net/amr.152-153.363.
Testo completoAbstract (sommario):
An experiment was undertaken to investigate the effect of mineral admixtures, w/b, external chloride solution concentration, and carbonation on chloride binding capacity of cementitious paste. The test method was based on equilibrium method. Test results show that incorporating metakaolin, blastfurnace slag, steel slag, and flyash increases chloride binding capacities by 65.9%, 55.3%, 43.9%, and 26.8% respectively. Increasing external chloride concentration and w/c ratio can improve the chloride capacity of pure cement paste. Carbonation of cement paste will reduce the chloride capacity. Chloride binding do affect the durability of reinforced concrete in saline environment.
18
Paglia, Christian, e Samuel Antonietti. "The carbonation and chloride penetration along highway concrete structures in a South alpine space". MATEC Web of Conferences 361 (2022): 01003. http://dx.doi.org/10.1051/matecconf/202236101003.
Testo completoAbstract (sommario):
Reinforced concrete structures are subjected to atmospheric agents during time. The cyclic exposure to natural parameters such as temperature, wind, rain and snowfall may emphasize the detrimental effect on structures. The different types of infrastructure may also be exposed to artificial phenomena such as, salt spreading, splashing of salt containing water or leaching effects. These phenomena contribute to the degradation of cementitious material, and the main induced mechanisms are carbonation and chloride ingress into the structures. Many types of structure such as tunnels, underpasses, walls, bridges and manholes have been investigated along a 11 km long highway close to the Alps in their South part. The aim of the study was to clarify the extent of carbonation and chloride ingress, as well as their relationship over a 40 year period. The mean climatic parameters were also registered over the years. Generally, the structures exhibited a different behaviour. The carbonation was maximal in tunnels and underpasses. A generalyl high chloride content was found for all artefacts, well beyond the 0.025 % referred to the concrete mass up to 0.400 %. The tunnels exhibited both high mean carbonation and chloride content, while all other structures indicated a slight correlation between high chloride content and low carbonation. These latter parameters were also influenced by processes such as leaching, splashing and indirect exposure to the degrading agents
19
Murali Krishna, B., P. Sai Asrith e T. P. Tezeswi. "Creep, chloride, carbonation and sulphate attack on concrete". IOP Conference Series: Earth and Environmental Science 982, n. 1 (1 marzo 2022): 012002. http://dx.doi.org/10.1088/1755-1315/982/1/012002.
Testo completoAbstract (sommario):
Abstract Deterioration of concrete structures with age and environmental factors like creep, chloride, carbonation and sulphate attack in the presence of a corrosive environment leads to a decrease in their performance in terms of load-bearing capacity and serviceability. The present work attempts to develop a model for the impairment in the strength of RC beams because of the combined effects of creep and sulphate attack. It also aims at studying the individual effects of chloride carbonation attacks with the help of established deterioration models. The equations of instantaneous elastic modulus and long term creep described in Indian standard codes (IRC 112) enable modelling the deterioration of modulus of elasticity of concrete as a function of time. The influence of sulphate attack on concrete strength against time is obtained from an empirical research study. Standard numerical models are employed to understand the effects of chloride ingress and carbonation phenomena. The consequences of the aforementioned attacks on an M30 grade concrete girder beam are presented in this paper. The results showed that the creep and sulphate attacks tend to dwindle over the course of time, while the effect of the former is more dominant than that of the latter. In addition, the initiation times for carbonation and chloride attacks were estimated, and it was observed that for a pristine RC beam chloride attack is highly imminent than carbonation.
20
Wang, Hui, Ailian Zhang, Linchun Zhang, Junzhe Liu, Yan Han e Jianmin Wang. "Research on the Influence of Carbonation on the Content and State of Chloride Ions and the Following Corrosion Resistance of Steel Bars in Cement Paste". Coatings 10, n. 11 (7 novembre 2020): 1071. http://dx.doi.org/10.3390/coatings10111071.
Testo completoAbstract (sommario):
In this paper, the changes of free chloride ion concentration and bound chloride concentration in cement paste with different total and proportion of mineral admixtures under carbonation were studied. Moreover, the following corrosion resistance of steel bars buried in cement paste under carbonation was researched by testing the electrical resistance and alternating current (AC) impedance spectroscopy of reinforced cement paste. Results indicated that fly ash and granulated blast furnace slag powder with the content less than 20% by mass ratio of total binder hindered the solidification of chloride ions in cement-based materials, and blast furnace slag powder with the content higher than 20% promoted the solidification of chloride ions in cement paste. The carbonation effect was able to decrease the amount of solidified chloride ion and increase the amount of free chloride ions leading to accelerating the corrosion of reinforcement. Meanwhile, the blast furnace slag powder with the content higher than 20% could effectively promote the corrosion resistance of steel bars.
21
Chen, Mengzhu, Fang Wu, Linwen Yu, Yuxin Cai, Hang Chen e Mingtao Zhang. "Chloride binding capacity of LDHs with various divalent cations and divalent to trivalent cation ratios in different solutions". CrystEngComm 21, n. 44 (2019): 6790–800. http://dx.doi.org/10.1039/c9ce01322a.
Testo completoAbstract (sommario):
Chlorides were bonded by LDHs due to ion exchange and surface adsorption. Carbonation resulted in the debonding of the chloride bond by ion exchange, however, surface adsorption was not affected by carbonation.
22
Liu, Yinglong, Pengzhen Lin e Junjun Ma. "Diffusion Behavior of Chloride Ions in Concrete Box Girder under the Influence of Load and Carbonation". Materials 13, n. 9 (2 maggio 2020): 2117. http://dx.doi.org/10.3390/ma13092117.
Testo completoAbstract (sommario):
In order to study the durability degradation characteristics of concrete box girder under load and carbonation and chloride ion erosion, a scale model of concrete box girder was made for experimental research. According to the test results, the diffusion characteristics of chloride ions in the concrete box girder under the coupling effect of load and carbon dioxide were analyzed. By revising the calculation formula of the existing chloride ion concentration considering multiple factors, a calculation model of chloride ion concentration considering the influence of carbonation was proposed, and the test results were verified. The results show that the chloride concentration of the box girder on the same cross section is non-uniformly distributed due to the shear lag effect and the spatial structure. After considering the effect of carbonation, the difference rate of the improved model proposed in this paper is generally within 10%. Compared with the original model, the difference rate is reduced by a maximum of 19%.
23
Ghahari, S. A., A. M. Ramezanianpour, A. A. Ramezanianpour e M. Esmaeili. "An Accelerated Test Method of Simultaneous Carbonation and Chloride Ion Ingress: Durability of Silica Fume Concrete in Severe Environments". Advances in Materials Science and Engineering 2016 (2016): 1–12. http://dx.doi.org/10.1155/2016/1650979.
Testo completoAbstract (sommario):
The effects of simultaneous carbonation and chloride ion attack on mechanical characteristics and durability of concrete containing silica fume have been investigated through an accelerated test method. Specimens containing different amounts of silica fume were maintained in an apparatus in which carbon dioxide pressure and concentration and relative humidity were kept constant, and wetting and drying cycles in saline water were applied. Surface resistivity, sorptivity, CO2consumption, and carbonation and chloride ion ingress depths measurements were taken. Phase change due to carbonation and chloride ion attack was monitored by XRD analysis, and microstructures and interfacial transition zones were studied by implementing SEM as well as mercury intrusion porosimetry. It was expected to have a synergistic effect in the tidal zone where simultaneous carbonation and chloride ion attack happen. However, the observed reduced surface resistivity, compared to specimens maintained in CO2gas, could be due to the moisture that is available near the surface, hindering CO2from penetrating into the pores of the specimens. Moreover, the porosity analysis of the specimens showed that the sample containing silica fume cured in the tidal zone had 50.1% less total porosity than the plain cement paste cured in the same condition.
24
Kamaitis, Zenonas. "DAMAGE TO CONCRETE BRIDGES DUE TO REINFORCEMENT CORROSION". TRANSPORT 17, n. 5 (31 ottobre 2002): 163–70. http://dx.doi.org/10.3846/16483840.2002.10414037.
Testo completoAbstract (sommario):
The mechanisms of reinforcement corrosion in concrete are the subject of extensive research. Although reliable methods for predicting the corrosive deterioration of concrete structures do not yet exist. This paper describes the durability problem of reinforced concrete bridges based on the mechanisms of carbonation depth or chloride profile. The deterioration model considering concrete carbonation, chloride penetration and concrete cover cracking is adopted to describe the service life of concrete structures. The corrosion models include environmental conditions, concrete carbonation or chloride diffusion rates, quality of concrete cover, steel corrosion rates and many other factors that make the predicting of service life of structures extremely difficult. Finally, the author gives the details of the methods of durabilio/ verification and the proposals for its including in the national standards and practical guides.
25
Дронов e Andrey Dronov. "THE PROPERTIES OF PITTING CORROSION OF STEEL REINFORCEMENT OF REINFORCED CONCRETE BEAMS". Bulletin of Belgorod State Technological University named after. V. G. Shukhov 2, n. 3 (4 aprile 2017): 32–36. http://dx.doi.org/10.12737/24678.
Testo completoAbstract (sommario):
Two types of steel reinforcement depassivation process: carbonation of concrete and chloride penetration are considered in the article. The comparison between the corrosion due to carbonation of concrete and the chloride-induced corrosion was carried out. It was found out, that chlorides induced corrosion is potentially more dangerous than that resulting from carbonation. Method of durable tests of reinforced concrete structures under the action of the gravitational load and the corrosive chloride environment is described in the article. The results of experimental research on reinforced concrete structures with corrosive damages to steel reinforcement are given in the article. The properties of corrosion cracking in the case of the pitting corrosion were determined. The character of corrosive damage distribution along the reinforcement bars and its effect on the strength of reinforced concrete beams were determined.
26
Malheiro, Raphaele, Aires Camões, Gibson Meira, Rui Reis e Aline Nóbrega. "Impact of Combined Action of Chloride and Carbonation on Cement-Based Materials with Fly Ash". Sci 6, n. 1 (28 febbraio 2024): 13. http://dx.doi.org/10.3390/sci6010013.
Testo completoAbstract (sommario):
Integrating waste and industrial by-products into concrete is an alternative way to reduce global cement consumption, enhancing its eco-friendliness. In this context, residues with fly ash have been increasingly utilised. Considering the vulnerability of concrete with fly ash to carbonation and, at the same time, its high resistance to chlorides, it is important to investigate the behaviour of these concretes under their combined actions. For this purpose, an experimental investigation was conducted, studying mortar and concrete specimens with 40% replacement of cement with fly ash. These specimens were subjected to a combination of actions (Cl− and CO2) in two phases: initially through immersion and drying tests, and subsequently through a combination of accelerated tests. Concerning the chloride impact study, free and total chloride profiles were studied. Concerning the impact of carbonation, colourimetric and chemical tests were used. The results demonstrate a significant influence of combined action not only on chloride penetration in cement-based materials with fly ash but also on the development of a carbonation front. Exposure of cement-based materials with fly ash to environments with high Cl− and CO2 content sequentially may lead, on the one hand, to an increase in carbonation resistance. However, on the other hand, it may result in a substantial reduction in chloride penetration resistance.
27
Quan, Chang-Qing, Chu-Jie Jiao, Wei-Zhi Chen, Zhi-Cheng Xue, Rui Liang e Xue-Fei Chen. "The Impact of Fractal Gradation of Aggregate on the Mechanical and Durable Characteristics of Recycled Concrete". Fractal and Fractional 7, n. 9 (31 agosto 2023): 663. http://dx.doi.org/10.3390/fractalfract7090663.
Testo completoAbstract (sommario):
Properties of recycled aggregate concrete (RAC) are influenced by the composition and particle size distribution of recycled coarse aggregate (RCA). The study herein designed seven distinct groups of RACs with varying aggregate fractal dimensions (D) and one group of natural concrete (NAC). The impact of D on the workability, compressive strength, resistance to chloride ion penetration, and carbonation resistance of RAC was measured. It was found that an increase in the D value led to a decrease in the slump and slump flow, with the compressive strength and chloride ion penetration increasing and then decreasing, and carbonation gradually declined. The optimal fractal dimension was thereby determined to be 2.547 by a strength model accommodating two parameters of D and the curing age. Additionally, the mass percentage of each particle size for the corresponding gradation was presented. The compressive strength and chloride permeation resistance of RAC (D = 1.0) relative to RAC (D = 2.5) was increased by 16.7% and 13.3%, respectively. Furthermore, the carbonation depth of RAC (D = 2.5) was comparable to that of NAC. Additionally, the carbonation resistance of RAC was influenced by both the size distribution and the degree of natural carbonation of RCA, resulting in four distinct features relative to NAC. It is thereby feasible to enhance RAC performance through the manipulation of RCA’s fractal dimensions.
28
Zong, Lan, Shi Ping Zhang e Pei Xin Liang. "Experiment Study on the Durability of Dry-Mixing Self-Compacting Concrete". Advanced Materials Research 250-253 (maggio 2011): 493–96. http://dx.doi.org/10.4028/www.scientific.net/amr.250-253.493.
Testo completoAbstract (sommario):
Durability of dry-mixing self-compacting concrete was evaluated through carbonation testing, freeze-thaw testing and chloride ions diffusion testing. The results indicate that carbonation resistance, frost resistance and chloride ions diffusion of durability of dry-mixing self-compacting concrete are excellent, compared with normally vibrated concrete (NVC). Durability of dry-mixing self-compacting concrete shows a better pore structure. Furthermore, the more the content of coarse aggregates is, the poorer the pore structure becomes.
29
Singh, Navdeep, Anjani Bhardwaj e Shehnazdeep. "Permeation Behaviour of Coal Bottom Ash Concretes". Journal of Solid Waste Technology and Management 48, n. 3 (1 agosto 2022): 353–61. http://dx.doi.org/10.5276/jswtm/2022.353.
Testo completoAbstract (sommario):
Low volume Coal Bottom Ash (CBA) was introduced as a substitute for Portland Cement (PC) and Fine Natural Aggregates (FNA) in concretes that were tested for permeation performance. Carbonation and chloride resistance was measured through accelerated carbonation tests and rapid chloride tests respectively while water penetration was evaluated through capillary water absorption tests for the aforesaid concretes. This paper particularly investigates the effectiveness of CBA in regard of permeation behaviour in concrete. The experimental investigation inferred that as level of CBA increases, the resistance towards carbonation, chloride penetration and water penetration decreases to some extent for low volume alterations while higher decrements were observed for higher replacements. The joint replacement of CBA as PC and FNA for the level of 10% and 25% respectively resulted in satisfactory behaviour comparing to control concrete demonstrating the efficacy and potential of CBA for its successful application in concrete.
30
Mejía de Gutiérrez, Ruby, Cesar Rodríguez, Erich Rodríguez, Janneth Torres e Silvio Delvasto. "Metakaolin concrete: Carbonation and chloride behavior". Revista Facultad de Ingeniería Universidad de Antioquia, n. 48 (24 luglio 2013): 55–64. http://dx.doi.org/10.17533/udea.redin.16019.
Testo completoAbstract (sommario):
The purpose of this paper is to present the results obtained in an experimental study that analyzed the performance of different concrete mixes. These mixes were produced with 90% of ordinary Portland cement (OPC) and the other 10% with the additions of metakaolin (MK) and silica fume (SF). Four types of MK were tested; two of these were produced by a thermal treatment on Colombian kaolin. The others two were imported from the international commercial market. The factors evaluated in all the concrete mixes were the following: compressive strength, water absorption and total volume of permeable porosity, capillary absorption, carbonation depth and chloride penetration. The concrete samples were submitted into an accelerated carbonation process inside a climatic chamber (30º C, 70% H.R. and 2.25% CO2 ). At 28 days of curing the carbonation depths for the blended concrete mixtures were greater than the one obtained in the OPC concrete without addition. With a prolonged curing age in all samples, with or without mineral additions, tend to slow the carbonation rate in the concrete. The resistance of the concrete to the chloride penetration was evaluated according to ASTM standard C1202. This study proved that blended concrete specimens have a lower capillary absorption and a higher chloride penetration resistance once these were compared with OPC concrete specimens without addition.
31
Khartabil, Ahmad, e Samer Al Martini. "Carbonation Resistance of Sustainable Concrete Using Recycled Aggregate and Supplementary Cementitious Materials". Key Engineering Materials 803 (maggio 2019): 246–52. http://dx.doi.org/10.4028/www.scientific.net/kem.803.246.
Testo completoAbstract (sommario):
Green concrete is a recent sustainable practice in UAE that was enforced by Dubai Municipality in construction field within the emirate of Dubai to reduce the carbon foot print in construction industry and to increase the durability of the structures. This led the construction industry to reduce the usage of ordinary portland cement by replacing it with supplementary cementitious materials (SCMs) such as Grand Granulated Blast Furnace Slag (GGBS) and flyash (FA). Incorporating GGBS or FA in concrete mixtures can improve durability parameters of hardened concrete, such as resistance to water permeability, reduced water absorption and chloride penetration. This ultimately increases the structure’s service life by increasing the threshold of concrete mixture for chloride induced corrosion. On the other hand, carbonation induced corrosion to concrete is usually being ignored or forgotten generally, due its usual slow rate ingression in plain portland cement concrete mixtures. Several studies showed that incorporating some types of SCM – especially at high percentage - can reduce the concrete resistance to carbonation. Additionally and for concrete with recycled aggregate, carbonation investigation should be taken into consideration. This is since recycled aggregates are reused aggregates that are extracted from demolished structures and buildings which were already subjected to different environmental exposures and deteriorations. Unlike chloride penetration, there is no direct ASTM standard test to anticipate the concrete mixture resistance to carbonation at early ages. In this study, concrete mixtures with flyash and different recycled aggregate replacement percentages are investigated for carbonation resistance in accelerated proposed method, considering concrete mixtures’ key parameters like water-cement ratio, and total cement content. The results are analyzed to arrive to pertinent conclusions for the best utilization of sustainable concrete for carbonation resistance.
32
Wu, Jian Hua, e Yun Lan Liu. "Influence of Mineral Admixtures on the Carbonation Resistance and Chloride Permeability of Steam-Cured HPC". Key Engineering Materials 477 (aprile 2011): 366–74. http://dx.doi.org/10.4028/www.scientific.net/kem.477.366.
Testo completoAbstract (sommario):
This paper studies the influence of different mineral admixtures（fly ash and ground granulated blast furnace slag）on the carbonation resistance and chloride permeability of steam-cured HPC. The test results show that under the condition of steam-cured and standard-cured, incorporating 20-30% of the ground granulated blast furnace slag or 15-20% of fly ash decreased the alkalinity and the carbonation resistance of the concrete; with the increase of the proportion of the mineral admixture in concrete, carbonation resistance of HPC was decreased; incorporating 20-30% of the ground granulated blast furnace slag or 15-20% of fly ash improved the chloride permeability of steam-cured concrete, and the influence of ground granulated blast furnace slag is better than that of the fly ash.
33
Malheiro, Raphaele, Aires Camões, Rui Miguel Ferreira, Gibson Meira, Teresa Amorim e Ruis Rei. "Carbonation Front Progress in Mortars Containing Fly Ash Considering the Presence of Chloride Ions". Key Engineering Materials 634 (dicembre 2014): 214–21. http://dx.doi.org/10.4028/www.scientific.net/kem.634.214.
Testo completoAbstract (sommario):
The incorporation of fly ash (FA) in cementitious matrices have been frequently used in order to make the matrix more resistant to the action of chlorides. On the other hand, it is known that Ca (OH)2 existing in the matrix is partially consumed by the pozzolanic reactions, which facilitates the advancement of carbonation. Given that the combined action between carbonation and chloride penetration is a fact little known, we speculate about the behaviour of the matrix in this context. This study investigates the influence of the presence of chlorides on the carbonation in mortars with FA. Samples with 0% and 40% replacement of cement CEM I 42.5 R for FA were molded with water/binder 0.56 and 0.52 respectively. After 90 days of curing the specimens were subjected to cycles of immersion/drying for 56 days. Half of the samples was subjected to the following cycle: two days in a solution containing NaCl (concentration equal to 3.5 %); 12 days in the carbonation chamber (4% of CO2). The other half was: two days in water; 12 days in the carbonation chamber. Then, the development of carbonation was evaluated. The results indicate that the presence of chlorides influences the carbonation. The specimens submitted to the exclusive action of CO2 showed a greater depth of carbonation compared to that presented by the specimens subjected to combined action. This may be related to changes in properties of the matrix which may lead to further refinement of the pores and related to the presence of the salt that can lead to partial filling of the pores and the increase in moisture content .
34
Zhang, Ke Feng. "Research on Durability Design of Concrete Structure under Chloride Environment". Advanced Materials Research 926-930 (maggio 2014): 623–26. http://dx.doi.org/10.4028/www.scientific.net/amr.926-930.623.
Testo completoAbstract (sommario):
For concrete structure durability increasingly highlight of problem, focus description has chlorine ion on concrete structure of erosion mechanism, and invaded model and effects factors, derivation out integrated consider concrete of chlorine ion combines capacity, and chlorine ion proliferation coefficient of time dependence, and concrete structure micro-defects effects and the mixed coagulation s performance of practical proliferation equation, established has for forecast concrete using life of chlorine ion proliferation theory model, made intends built structure in chlorine ion environment Xia durability design thought and design method, Perfected design theory of durability of concrete and carbonation model design based on Carbonation depth of concrete during the period, compared with the concrete cover thickness, for engineering design and revision of the specification reference.
35
Lozano-Valcarcel, Juan M., David Ov, Thomas Kränkel, Christoph Gehlen e Rolf Breitenbücher. "Bridging the Gap: Assessing Material Performance of Laboratory Specimens and Concrete Structures". Materials 16, n. 12 (10 giugno 2023): 4306. http://dx.doi.org/10.3390/ma16124306.
Testo completoAbstract (sommario):
Chloride ingress and carbonation pose a significant risk of steel rebar corrosion in concrete structures. Various models exist to simulate the initiation phase of rebar corrosion, addressing both carbonation and chloride ingress mechanisms separately. These models also consider the environmental loads and material resistances, typically determined through laboratory testing based on specific standards. However, recent findings show significant differences between material resistances obtained from standardized laboratory specimens and those extracted from real structures, with the latter exhibiting inferior performance on average. To address this issue, a comparative study was conducted between laboratory specimens and on-site test walls or slabs, all cast using the same concrete batch. This study encompassed five construction sites featuring different concrete compositions. While laboratory specimens adhered to European curing standards, the walls were subjected to formwork curing for a predetermined period (typically 7 days) to simulate practical conditions. In some instances, a portion of the test walls/slabs received only one day of surface curing to emulate inadequate curing conditions. Subsequent testing of compressive strength and resistance to chloride ingress revealed that field specimens exhibited lower material resistance compared to their laboratory counterparts. This trend was also observed in the modulus of elasticity and carbonation rate. Notably, shorter curing periods further compromised performance, particularly resistance to chloride ingress and carbonation. These findings highlight the importance of establishing acceptance criteria not only for concrete delivered to construction sites but also for ensuring the quality of the actual structure.
36
Zhou, Wei, Peng Zhu, Wenjun Qu, Wu Yao e Shengji Wu. "Study on the Influence of Calcined Underground Ant Nest Powder on the Durability of Concrete". Materials 13, n. 9 (2 maggio 2020): 2119. http://dx.doi.org/10.3390/ma13092119.
Testo completoAbstract (sommario):
Ants have strict requirements on the building materials of the nest, such as the size, weight, luster and color of soil particles. The soil of underground ant nests is composed of clay particles cemented together to form a hard brick-like material. The ant nest powder shows pozzolanic activity after calcination, which can meet the requirements for active admixture of concrete. Under the standard curing condition, the influence of calcined ant nest clay powder (CANCP) on the durability of concrete is evaluated by chloride penetration resistance, carbonization resistance and freeze–thaw resistance, and the influence of the powder content is investigated. The results show that when the content of CANCP is less than 10%, the chloride penetration resistance of concrete increases with content of CANCP. In the early stage of carbonation, the greater the content of CANCP, the higher the carbonization rate of concrete. In the middle and later stage of carbonation, the carbonation rate of CANCP concrete is significantly lower than that in the early stage, and the carbonation depth is linearly related to the carbonation time. When the content of CANCP is less than 20%, the freeze–thaw resistance of CANCP concrete is better than that of the reference concrete.
37
Sahani, Kameshwar, Shyam Sundar Khadka e Suresh Kumar Sahani. "Influence of Corrosion on Lifespan of Reinforced Concrete Structures: A Comprehensive Review". Kathmandu University Journal of Science, Engineering and Technology 18, n. 1 (29 giugno 2024): 1–14. http://dx.doi.org/10.3126/kuset.v18i1.67503.
Testo completoAbstract (sommario):
Carbonation-induced corrosion is a major concern for reinforced cement concrete (RCC) structures, impacting their long-term durability and structural integrity. This review synthesizes the findings on the deterioration mechanisms in concrete structures, focusing on carbonation, chloride-induced corrosion, and time-dependent deterioration. The analysis includes discussions on predictive likelihood methods for estimating bridge reliability, the impact of environmental factors on carbonation, and standardized testing methods for assessing concrete durability. The review highlights the importance of understanding material characteristics and environmental conditions in designing durable concrete structures, emphasizing the processes of carbonation, its impact on rebar corrosion, and strategies for mitigation. Sheltered concrete carbonation resistance in metropolitan tropical climates is 10-20% lower than open exposure. SCM concretes exhibit equivalent or greater long-term carbonation resistance to OPC concretes, as evidenced by the increase in carbonation depth ( Δ xd) at ages greater than 5 years. The paper concludes with recommendations for integrating advanced modeling techniques and empirical studies to develop robust maintenance strategies and improve concrete mix designs for enhanced durability.
38
Zhang, Peng, Huaishuai Shang, Dongshuai Hou, Siyao Guo e Tiejun Zhao. "The Effect of Water Repellent Surface Impregnation on Durability of Cement-Based Materials". Advances in Materials Science and Engineering 2017 (2017): 1–9. http://dx.doi.org/10.1155/2017/8260103.
Testo completoAbstract (sommario):
In many cases, service life of reinforced concrete structures is severely limited by chloride penetration until the steel reinforcement or by carbonation of the covercrete. Water repellent treatment on the surfaces of cement-based materials has often been considered to protect concrete from these deteriorations. In this paper, three types of water repellent agents have been applied on the surface of concrete specimens. Penetration profiles of silicon resin in treated concrete have been determined by FT-IR spectroscopy. Water capillary suction, chloride penetration, carbonation, and reinforcement corrosion in both surface impregnated and untreated specimens have been measured. Results indicate that surface impregnation reduced the coefficient of capillary suction of concrete substantially. An efficient chloride barrier can be established by deep impregnation. Water repellent surface impregnation by silanes also can make the process of carbonation action slow. In addition, it also has been concluded that surface impregnation can provide effective corrosion protection to reinforcing steel in concrete with migrating chloride. The improvement of durability and extension of service life for reinforced concrete structures, therefore, can be expected through the applications of appropriate water repellent surface impregnation.
39
Sosdean, Corina, Liviu Marsavina e Geert de Schutter. "Damage of Reinforced Concrete Structures due to Steel Corrosion". Advanced Materials Research 1111 (luglio 2015): 187–92. http://dx.doi.org/10.4028/www.scientific.net/amr.1111.187.
Testo completoAbstract (sommario):
Reinforced concrete (RC) became one of the most widely used modern building materials. In the last decades a great interest has been shown in studying reinforcement corrosion as it became one of the main factors of degradation and loss of structural integrity of RC structures. The degradation process is accelerated in the case of RC structures situated in aggressive environments like marine environments or subjected to de-icing salts. In this paper it is shown how steel corrosion of the embedded rebars occurs and how this affects the service life of reinforced concrete structures. Also, an experimental study regarding the combined effect of carbonation and chloride ingress was realized. Samples with and without rebars were drilled from a RC slab which was stored in the laboratory for two years. Non-steady state migration tests were realized in order to determine the chloride profile, while the carbonation depth was measured using the colorimetric method based on phenolphthalein spraying. It was concluded that carbonation has a significant effect on chloride ingress, increasing it.
40
Yuan, Yezhen, Kaimin Niu, Bo Tian, Lihui Li, Jianrui Ji e Yunxia Feng. "Effect of Metakaolin on the Microstructural and Chloride Ion Transport Properties of Concrete in Ocean Wave Splashing Zones". Materials 16, n. 1 (20 dicembre 2022): 7. http://dx.doi.org/10.3390/ma16010007.
Testo completoAbstract (sommario):
In order to address the problem of the durability deficiency of concrete in wave splash zones in a harsh marine environment, this paper investigates the effects of coupled carbonation, sulfate, and chloride salts on the strength, capillary water absorption, and ion migration properties of cement concrete incorporated with metakaolin, and characterizes the pore structural changes with the mercury-pressure method and AC impedance technique. The results show that, compared with a single chloride salt environment, the improvement in mortar strength and impermeability with carbonation coupling is almost positively correlated with the calcium content in the specimen, and renders its pore structure more refined and denser. In contrast, the presence of sulfate reduces mortar strength and increases the ion migration coefficient. When the three factors of sulfate, carbonation, and chloride salt were coupled, damage to the strength and pore structure of the specimens was the most significant, but the specimen incorporated with 30% metakaolin had its strength improved compared with the blank group specimen; from the perspective of pore structural parameters and transport coefficient, the microstructure was denser, and the impermeability was significantly improved.
41
Qian, Kuang Liang, Tao Meng, Xiao Qian Qian e Shu Lin Zhan. "Research on Some Properties of Fly Ash Concrete with Nano-CaCO3 Middle Slurry". Key Engineering Materials 405-406 (gennaio 2009): 186–90. http://dx.doi.org/10.4028/www.scientific.net/kem.405-406.186.
Testo completoAbstract (sommario):
Some long-term properties such as anti-carbonation properties, shrinkage, penetrability of chloride ion of fly ash concrete with nano-CaCO3 middle slurry were studied. Test results showed that the properties of anti-carbonation and impenetrability for chloride of fly ash concrete increased by adding nano-CaCO3 middle slurry because the tiny hole was filled by nano-CaCO3 and the density of concrete increased. But at the same time, the shrinkage of fly ash concrete with and without nano-CaCO3 was the same. Results of SEM also implied the hydration degree of fly ash could be increased by nano-CaCO3.
42
Hemkemeier, Thiago A., Fernando C. R. Almeida, Almir Sales e Agnieszka J. Klemm. "Carbonation and chloride penetration of repair mortars with water treatment plant sludge and sugarcane bagasse ash sand". MATEC Web of Conferences 364 (2022): 04011. http://dx.doi.org/10.1051/matecconf/202236404011.
Testo completoAbstract (sommario):
Water treatment plant sludge (WTPS) and sugarcane bagasse ash sand (SBAS) (wastes from water treatment and sugar/ethanol industries) can be used as replacements of natural sand in concrete. Thus, this paper aims to evaluate carbonation depth and chloride penetration of cementitious repair mortars produced with WTPS and SBAS. Three mortars compositions were analysed: plain reference sample (REF); sample with 3% of WTPS (3WTPS); and sample with 30% of SBAS (30SBAS). They were subjected to tests of accelerated carbonation and immersion in NaCl solution up to 84 days (12 weeks). The results showed that SBAS mortars had the best performance in relation to carbonation and chloride penetration tests. 3WTPS mortars had similar results to the reference sample. This is due to refinement of pores given by incorporation of fine waste materials making it difficult for aggressive agents to penetrate cement matrices. Therefore, 3WTPS and 30SBAS composites can be satisfactorily used in buildings repair services for more sustainable and durable construction.
43
Li, Guo, Zheng Zhuang, Yajun Lv, Kejin Wang e David Hui. "Enhancing carbonation and chloride resistance of autoclaved concrete by incorporating nano-CaCO3". Nanotechnology Reviews 9, n. 1 (20 ottobre 2020): 998–1008. http://dx.doi.org/10.1515/ntrev-2020-0078.
Testo completoAbstract (sommario):
AbstractThree nano-CaCO3 (NC) replacement levels of 1, 2, and 3% (by weight of cement) were utilized in autoclaved concrete. The accelerated carbonation depth and Coulomb electric fluxes of the hardened concrete were tested periodically at the ages of 28, 90, 180, and 300 days. In addition, X-ray diffraction, thermogravimetry, and mercury intrusion porosimetry were also performed to study changes in the hydration products of cement and microscopic pore structure of concrete under autoclave curing. Results indicated that a suitable level of NC replacement exerts filling and accelerating effects, promotes the generation of cement hydration products, reduces porosity, and refines the micropores of autoclaved concrete. These effects substantially enhanced the carbonation and chloride resistance of the autoclaved concrete and endowed the material with resistances approaching or exceeding that of standard cured concrete. Among the three NC replacement ratios, the 3% NC replacement was the optimal dosage for improving the long-term carbonation and chloride resistance of concrete.
44
Fedorov, Anatolii, Yurii Chekryshkin e Aleksei Gorbunov. "Studies of Recycling of Poly(vinyl chloride) in Molten Na, Ca ‖ NO3, OH Systems". ISRN Chemical Engineering 2012 (22 maggio 2012): 1–6. http://dx.doi.org/10.5402/2012/768134.
Testo completoAbstract (sommario):
The interaction of poly(vinyl chloride) (PVC) with components of molten inorganic systems at the temperature range 200–500°C was studied by a combination of thermogravimetric and differential-thermal methods. The results of this study show that the melts of alkali and alkaline-earth metal nitrates can be used for utilization of wastes of halogen-containing polymeric materials. It was established that unique solid products of interaction of PVC with components of the Ca(NO3)2–Ca(OH)2 mixes are ecologically safe calcium chloride and carbonate. Their formation proceeds in three stages including reactions of PVC dehydrochlorination, interactions of formed hydrocarbon residue and hydrogen chloride with calcium hydroxide and calcium nitrate, oxidation of the hydrocarbon residue, and carbonation of calcium hydroxide. A scheme for the oxidative degradation of PVC and for the binding of chlorine and carbon from the polymer in the reactions with components of Ca(NO3)2–NaNO3 and Ca(NO3)2–Ca(OH)2 mixtures was suggested, involving a series of consecutive and parallel reactions.
45
Jiang, Zhilu, Siyao Li, Chuanqing Fu, Zheng Dong, Xuefeng Zhang, Nanguo Jin e Tian Xia. "Macrocell Corrosion of Steel in Concrete under Carbonation, Internal Chloride Admixing and Accelerated Chloride Penetration Conditions". Materials 14, n. 24 (13 dicembre 2021): 7691. http://dx.doi.org/10.3390/ma14247691.
Testo completoAbstract (sommario):
Steel corrosion has become the main reason for the deterioration of reinforced concrete structures. Due to the heterogeneity of concrete and the spatial variation of environmental conditions, macrocell corrosion is often formed by localized corrosion, which is more detrimental if the anode is supported by large numbers of cathodes. The macrocell corrosion caused by concrete carbonation has been seldom studied. Furthermore, the influence of geometrical conditions on cathode-controlled corrosion in the chloride environment needs to be further clarified. In this work, the macrocell corrosion of steel embedded in concrete specimens exposed to accelerated carbonation, chloride contamination, and chloride penetration is studied using a modified ASTM G109 method. Concrete specimens with various binder types, geometrical parameters (i.e., concrete cover thickness and the diameter of embedded steel), and boundary conditions were tested. A simplified mathematical model for the prediction of the steel corrosion rate was developed considering two-dimensional oxygen diffusion. The results showed that, at the same level of anodic potential drops, the corrosion current rate in chloride-induced corrosion is higher than that of carbonation-induced corrosion. Chloride contamination is less detrimental to concrete incorporated with slag and pulverized fly ash than it is to pure ordinary Portland cement (OPC), likely due to enhanced chloride binding capacity. The results also indicated that the model considering two-dimensional diffusion can accurately predict the cathodic reaction process on corroded steel bars, which provides a theoretical basis for considering the correction coefficient of steel bar position in the establishment of a steel bar corrosion rate model.
46
Saillio, Mickael, Véronique Baroghel-Bouny e Sylvain Pradelle. "Effect of Carbonation and Sulphate on Chloride Ingress in Cement Pastes and Concretes with Supplementary Cementitious Materials". Key Engineering Materials 711 (settembre 2016): 241–48. http://dx.doi.org/10.4028/www.scientific.net/kem.711.241.
Testo completoAbstract (sommario):
The main cause of premature deterioration of reinforced concrete structures is the corrosion of steel bars, induced by chloride ions (for example in marine environment) and/or by carbonation (atmospheric CO2). At the same time, environmental-induced degradations of concrete can also affect the structure, such as sulphate attack. This can lead to the formation of ettringite, inducing expansion inside the materials and finally degradation. Carbonation, chloride and sulphate ingress are usually studied separately in the literature. This is not representative of in-situ conditions since they can occur at the same time and can have an influence on each other. In this paper, chloride ingress are studied for concretes and cement pastes partially carbonated or/and in presence of sulphate in chloride contact solution. The mixtures contain OPC alone or with supplementary cementitious materials (SCM). SCMs are here pozzolanic materials (Fly Ash or Metakaolin) or alkali-activated materials such as ground granulated blast furnace slag (GGBS). The materials, partially carbonated (2 months in chamber at 1.5 % of CO2) or not, are put in contact with chloride solutions in presence of sulphate. This study focuses on the apparent chloride diffusion coefficients, as well as chloride binding isotherms which are obtained by the profile method. In addition, some aspects of the microstructure and of the pore structure are investigated, by using Mercury Intrusion Porosimetry and 27Al NMR, in order to better understand the results obtained relatively to the apparent chloride diffusion coefficients and to the chloride binding. Chloride ingress increases when sulphates are present in the contact solution for all cement materials tested (partially carbonated or not). In addition, chloride ingress is faster when the material is partially carbonated before contact with chloride solution. It appears that both carbonation or presence of sulphate decrease chloride binding, thus explaining the results. The results show an evolution of the properties as a function of the cement replacement ratio by SCMs.
47
Chen, Peng, Zu Quan Jin e Jun Feng Fan. "Static Modulus of Ettringite in Different Environment". Key Engineering Materials 726 (gennaio 2017): 576–80. http://dx.doi.org/10.4028/www.scientific.net/kem.726.576.
Testo completoAbstract (sommario):
The pure ettringite, (Ca6Al2(OH)12(SO4)3· 32H2O), was synthesized by chemical reaction with saturation calcium hydroxide and aluminum sulfate. The ettringite in different environments including various concentration of sodium chloride, 5% magnesium sulfate and carbonation for 3 days were synthesized. And then these ettringtie specimens were prepared under different pre-loads. The static modulus and phase composites were tested. The experimental result shown that the influence of chloride ions concentration on the static modulus of ettringite could be ignored. And the magnesium ion reduced the generation of ettringite, and promoted the formation of gypsum. The static modulus of ettringite increased with carbonation time due to the formation of calcium carbonate.
48
TANAKA, RYOICHI, TAKASHI HABUCHI, TAKAHIKO AMINO e TSUTOMU FUKUTE. "A STUDY ON IMPROVEMENT AND ITS EVALUATION FOR THE SURFACE LAYER OF CONCRETE PLACED WITH PERMEABLE FORM". International Journal of Modern Physics: Conference Series 06 (gennaio 2012): 664–69. http://dx.doi.org/10.1142/s2010194512003947.
Testo completoAbstract (sommario):
Permeable form can improve the quality of the surface layer of concrete and can enhance the durability of concrete structures. In this study, the improvement and its evaluation for the surface layer of concrete placed with permeable form were investigated. For these purposes, accelerated carbonation test, chloride ion penetration test, air permeability test, rebound hummer test and water permeability test were conducted using the concrete specimen. As a result, it was found that the air permeability correlates the carbonation depth, chloride ion penetration depth, rebound number and water permeable volume of concrete. Moreover, the possibility that the improvement for the surface layer of concrete can be quantitatively evaluated by air permeability test was shown.
49
Wu, Ruidong, e Juanhong Liu. "Experimental Study on the Concrete with Compound Admixture of Iron Tailings and Slag Powder under Low Cement Clinker System". Advances in Materials Science and Engineering 2018 (23 settembre 2018): 1–7. http://dx.doi.org/10.1155/2018/9816923.
Testo completoAbstract (sommario):
In order to study the performance of concrete with compound admixture of iron tailings and slag powder under low cement clinker system, the mixture ratio of different iron tailings powder and slag powder was designed to prepare C30 and C50 concrete. The workability, strength, carbonation depth, chloride diffusion coefficient, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) of concrete were measured, respectively. The test results show that iron tailings powder is beneficial to improve the workability, and the strength of concrete decreases with the increase of iron tailings powder content, while the carbonation depth and chloride diffusion coefficient increase with the increase of iron tailings powder content. Under low cement clinker system, the iron tailings powder should not be used alone (below 70% of mineral admixture). When the ratio of iron tailings to slag powder is 1 : 1, the strength, carbonation depth, chloride ion permeation coefficient, and the microstructure of concrete are roughly the same to that of concrete with single slag powder. So, the iron tailings powder can replace S95 grade slag powder in the same quantity. Iron tailings powder does not take part in hydration reaction, but it can improve particle gradation, reach close accumulation, and increase the quantity of central grains.
50
Zhang, Junbo, Jigang Zhang, Weiwei Xiao, Qianying Wang e Feng Shao. "Experimental Study on the Effect of Expansive Agent on the Durability of Concrete in Civil Air Defense Engineering". Advances in Materials Science and Engineering 2021 (12 maggio 2021): 1–7. http://dx.doi.org/10.1155/2021/5598576.
Testo completoAbstract (sommario):
In this study, the effect of 8% UEA the reason why the UEA content is 8% is as follows: the expansion agent content in the actual mix proportion of the project is 8%, which is selected in this test to fit the reality better. expansion agent on the compressive strength, chloride ion penetration resistance, and carbonation resistance of civil air defense concrete were studied by simulating the rapid carbonation and chloride solution immersion of concrete structure in coastal civil air defense engineering environment. The results of this study show that the early compressive strength of concrete decreased by adding the UEA expansion agent and was also affected by the curing time. Moreover, the addition of UEA expansion agent decreased the content of free chloride ions and calcium carbonate in concrete and reduced the early compressive strength of concrete.