Articoli di riviste: "Carbonation in air"

1

Khan, Mohammad Iqbal. "Carbonation of High Strength Concrete". Applied Mechanics and Materials 117-119 (ottobre 2011): 186–91. http://dx.doi.org/10.4028/www.scientific.net/amm.117-119.186.

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High strength concrete consisting of binary and ternary blended cementitious systems based on ordinary Portland cement, pulverised fuel ash and silica fume were investigated for carbonation. PFA up to 40% was used and to these blends 0, 5, 10, and 15% SF was incorporated as partial cement replacement. Results of carbonation of concrete cured in mist and air are reported. It was found that carbonation linearly increases with an increase in PFA content. Concrete with OPC only and concrete with 10% SF content showed insignificant change in carbonation when comparing air cured and mist cured concrete. The maximum carbonation depth observed for air cured concrete (containing 40% PFA) was less than 4 mm while in the case of mist cured concrete it was less than 2 mm. This depth is still far less than the cover of reinforced steel bars to cause corrosion.

2

Zhao, Wei Xia, Juan Hong Liu, Ping Yang, Xiao Ning Yuan e Min Chen. "Effect of Aggregate Pre-Wetting and Air-Entraining Agent on Durability of Lightweight Aggregate Concrete". Advanced Materials Research 335-336 (settembre 2011): 1163–67. http://dx.doi.org/10.4028/www.scientific.net/amr.335-336.1163.

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Rapid carbonation test and gas permeability radio method are used to study the durability of lightweight aggregate concrete. The concrete includes foam,lightweight aggregate，pre-wetting and air entraining. The test results show that The combined-effect of air entraining agent(AEA)and aggregate pre-wetting can increase permeability. The anti-carbonation capacity of pre-wetting and air entraining lightweight aggregate concrete is 40% greater than that of ordinary concrete.gas permeability radio of pre-wetting and air entraining lightweight aggregate concrete is half of that foam concrete and expanded pearlite concrete.

3

Dheilly, Rose-Marie, Yahya Sebaibi, Joseph Tudo e Michèle Queneudec. "Importance de la présence de magnésie dans le stockage de la chaux: carbonatation de l'oxyde et de l'hydroxyde de magnésium". Canadian Journal of Chemistry 76, n. 8 (1 agosto 1998): 1188–96. http://dx.doi.org/10.1139/v98-126.

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The influence of relative air moisture, temperature, and concentration of carbon dioxide on the carbonation of magnesium oxide and hydroxide have been studied in normal climatic conditions. The MgO and Mg(OH)2 used for this original work are pure granular materials. The different species that appear during the process of carbonation and the most stable form in usual conditions of storage were identified. Moreover, the study of the different climatic factors showed that the carbonation is never complete even after a prolonged exposure.Key words: carbonation, magnesium oxide, magnesium hydroxide, storage, climatic conditions.

4

FAUSTINO, Pedro, Fábio GONÇALVES, Ana BRÁS e Ângela NUNES. "LIFETIME PREDICTION OF REINFORCED CONCRETE STRUCTURES IN CARBONATION ENVIRONMENTS CARBONATION MODELLING VS AIR PERMEABILITY MODELLING". JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 23, n. 2 (6 febbraio 2017): 283–91. http://dx.doi.org/10.3846/13923730.2015.1068849.

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This article compares two models for the prediction of lifetimes of reinforced concrete structures in carbonation environments based on different tests: carbonation test-based modelling and air permeability test-based modelling. The study also includes experimental testing of five concrete mixes with different types of cement in order to validate the models using safety factors. The tests included compressive strength, accelerated carbonation and air permeability. Both models are defined in a European standard as being alternative to each other, meaning that their results for the same concrete composition and the same environment should converge. The results show that both current models can scarcely constitute alternative to each other. Design lifetime results are far from similar for each concrete mix and each exposure class. The different nature of each test – accelerated carbonation and air permeability – and their different characteristic such as the scattering of results and the unrelated parameters of the modelling equations are some of the features discussed, including the possibility of using different safety factors as function of the model and definition of possible correlation between tests.

5

Tassos, Christos, Kosmas Sideris, Alexandros Chatzopoulos, Nikolaos Pistofidis e Emmanouil Chaniotakis. "Influence of cement type on carbonation of concrete mixtures". MATEC Web of Conferences 163 (2018): 05005. http://dx.doi.org/10.1051/matecconf/201816305005.

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This research aims to investigate the influence of cement type to carbonation. For this purpose mixtures of four different cement mortars and eight different concretes that have been prepared with four different cements were left exposed for one year in open air in northern Greece. Results indicate that the type of cement influences the carbonation rate. Concrete mixtures produced according to the definitions of EN 206 standard perform lower service life against carbonation induced corrosion if the choice of the cement type is not carefully examined.

6

Schmitt, Lucie, Jena Jeong, Jean-Marc Potier, Laurent Izoret, Jonathan Mai-Nhu, Nicolas Decousser e Thomas Pernin. "Using an analysis of concrete and cement epd: verification, selection, assessment, benchmarking and target setting". Acta Polytechnica CTU Proceedings 33 (3 marzo 2022): 546–51. http://dx.doi.org/10.14311/app.2022.33.0546.

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Carbonation of concretes is a natural physico-chemical process that can be described as a reaction between the carbon dioxide contained in the air and the cement matrix. Carbonation concerns all concretes types in contact with the ambient air but also concretes in ground, from production stage to use and end-of-life stages. The amount of carbon dioxide bound varies according to the type of binder, the compacity of concrete and the environmental conditions during the use and the end-of-life stages. To consider the re-carbonation of concrete, works have been carried out within the framework of the European standardization group CEN/TC229/WG5 and in CEN/TC104. A methodology to consider the re-carbonation of concrete structures has been proposed in the NF EN 16757 standard on environmental product declarations for concrete and concrete elements. In addition, FD CEN/TR 17310 provides detailed recommendations regarding carbonation and absorption of carbon dioxide in concrete and give some precisions for application of NF EN 16757. This is an important topic towards a sustainable development in the current context of circular economy and CO2 uptake related to the French energy labelling (E+C-). In this paper, numerical and analytical carbonation models are used to estimate the CO2 binding ability of concrete structures. The obtained results are compared to the methodology proposed in Appendix BB of NF EN 16757 standard. They confirm that the methodology described in the NF EN 16757 standard leads to estimated degree of carbonation of the same order of magnitude. The advantage of using more advanced models lies in a better consideration of environmental parameters, the possibility to simulate the behaviour of crushed concrete, its reuse in new concrete as recycled aggregate and the possibility to simulate the carbonation of concretes in ground. This is an immediate perspective in the ongoing work in the French national project FastCarb on accelerated carbonation of recycled concrete aggregates.

7

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.

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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.

8

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.

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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.

9

Neves, R., B. Sena da Fonseca, F. Branco, J. de Brito, A. Castela e M. F. Montemor. "Assessing concrete carbonation resistance through air permeability measurements". Construction and Building Materials 82 (maggio 2015): 304–9. http://dx.doi.org/10.1016/j.conbuildmat.2015.02.075.

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Zhang, Donghao, e Wenbin Hu. "Improving Cycle Life of Zinc–Air Batteries with Calcium Ion Additive in Electrolyte or Separator". Nanomaterials 13, n. 12 (15 giugno 2023): 1864. http://dx.doi.org/10.3390/nano13121864.

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The electrolyte carbonation and the resulting air electrode plugging are the primary factors limiting the cycle life of aqueous alkaline zinc–air batteries (ZABs). In this work, calcium ion (Ca2+) additives were introduced into the electrolyte and the separator to resolve the above issues. Galvanostatic charge–discharge cycle tests were carried out to verify the effect of Ca2+ on electrolyte carbonation. With the modified electrolyte and separator, the cycle life of ZABs was improved by 22.2% and 24.7%, respectively. Ca2+ was introduced into the ZAB system to preferentially react with CO32− rather than K+ and then precipitated granular CaCO3 prior to K2CO3, which was deposited on the surface of the Zn anode and air cathode to form a flower-like CaCO3 layer, thereby prolonging its cycle life.

11

Lu, En Li, Guo Li, Ying Shu Yuan, Ou Geng e Jian Min Du. "Studies about the Initial Curing Conditions on the Carbonation Resistance of Fly-Ash Concrete". Advanced Materials Research 250-253 (maggio 2011): 920–24. http://dx.doi.org/10.4028/www.scientific.net/amr.250-253.920.

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Studies about the resistance of carbonation capability of fly-ash (FA) concrete at different initial curing regimes and exposure time through accelerated carbonation experiments were made. Firstly, 30% replacement ratio fly-ash concrete specimens were fabricated and cured in 20°C, 30°C and 40°C water for 3d, 7d, 14d and 28d respectively, and cured in a standard air environment (20±2°C, relative humidity ≥95% ) for 28d. As a comparison, ordinary Portland concrete (OPC) specimens were also made and cured in 30°C water for 7d, and standard curing for 28d. After the initial curing, all the specimens were taken out and placed indoor natural environment. When specimen age reach 30d, 60d and 120d, 2 weeks accelerated carbonation experiments were made and concrete carbonation depth were measured. In addition to this, hydration degrees of fly ash at different initial curing conditions were measured using the selective dissolve method. Results show that the initial curing conditions play an important role in the carbonation resistance of FA concrete. Initial water curing is beneficial to the development of carbonation resistance of FA and OPC concrete. Prolonging initial curing time and increasing curing temperature is beneficial for the carbonation resistance of FA concrete. For the same curing conditions, carbonation rate of FA concrete is usually higher than OPC concrete, but with the increase of initial curing temperature, the difference can be reduced.

12

Kim, Junho, Seunghyun Na e Yukio Hama. "Effect of Blast-Furnace Slag Replacement Ratio and Curing Method on Pore Structure Change after Carbonation on Cement Paste". Materials 13, n. 21 (27 ottobre 2020): 4787. http://dx.doi.org/10.3390/ma13214787.

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The frost damage resistance of blast-furnace slag (BFS) cement is affected by carbonation. Hence, this study investigates the carbonation properties of pastes incorporating BFS with different replacement ratios, such as 15%, 45%, and 65% by weight, and different curing conditions, including air and carbonation. The BFS replacement ratio properties, determined by the Ca/Si ratio of calcium silicate hydrate in the cement paste sample, were experimentally investigated using mercury intrusion porosimetry, X-ray diffraction, and thermal analysis. The experimental investigation of the pore structure revealed that total porosity decreased after carbonation. In addition, the porosity decreased at a higher rate as the BFS replacement rate increased. Results obtained from this study show that the chemical change led to the higher replacement rate of BFS, which produced a higher amount of vaterite. In addition, the lower the Ca/Si ratio, the higher the amount of calcium carbonate originating from calcium silicate hydrate rather than from calcium hydroxide. As a result of the pore structure change, the number of ink-bottle pores was remarkably reduced by carbonation. Comparing the pore structure change in air-cured and carbonation test specimens, it was found that as the replacement rate of BFS increased, the number of pores with a diameter of 100 nm or more also increased. The higher the replacement rate of BFS, the higher the amount of calcium carbonate produced compared with the amount of calcium hydroxide produced during water curing. Due to the generation of calcium carbonate and the change in pores, the overall number of pores decreased as the amount of calcium carbonate increased.

13

Niu, Jian Gang, Jia Lei Wang e Jian Bao. "Study on the Regularity of the Influence of Wind Pressure on the Properties of Concrete Carbonation". Applied Mechanics and Materials 341-342 (luglio 2013): 1453–57. http://dx.doi.org/10.4028/www.scientific.net/amm.341-342.1453.

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The distribution of surface pressure of columns in concrete bridge with the effect of wind load has been simulated by Ansys software. Carbonation model of concrete in windy environment has been established by analyzing the relationship between the wind pressure, carbonization time and carbonation depth. Furthermore, by Taking air pressure of concrete surface into the carbonation model, there is a good consistency between the test value and the measured value of the actual place. At last, the design method of the durability of concrete structures under wind loads, which is based on concrete durability limit state, has been putted forward to determine the expression of the breakdown coefficient.

14

Ye, Qing, Zhi Wei Song e Guo Rong Yu. "Variation of Carbonation Coefficient of Pumping Concrete with Moist-Curing Time at early Ages and Fly-Ash Content". Advanced Materials Research 287-290 (luglio 2011): 899–905. http://dx.doi.org/10.4028/www.scientific.net/amr.287-290.899.

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Based on accelerated carbonation test, the variation of carbonation resistance of pumping concrete (C40 grade) with moist-curing time at early ages and fly-ash content was studied. Results indicate that the carbonation coefficient and the accelerated carbonation depth of the concrete increased obviously with a reduction in the moist-curing time at early ages and with an increase in the fly-ash content. For example, in conditions of curing schedules with 28, 7, 3, 2 and 1 d moist-curing at 20 0C with above 95% RH at early ages and then 0, 21, 25, 26 and 27 d air curing at 20 0C with 60% RH, respectively, carbonation coefficients of the concrete incorporated with 30% fly-ash were 2.04, 2.49, 3.16, 3.86 and 5.42 mm/a0.5 respectively, and thus it can be seen that the calculated times when concrete cover (25 mm) was completely carbonated naturally in now atmosphere (0.04% CO2) were 164, 104, 66, 44 and 21 years respectively. The results suggest that for the carbonation resistance of the C40 concrete incorporated with up to 30% fly-ash, the moist-curing time of 7 days at early ages should be necessary.

15

Xia, Guo Ping. "A Study on Carbonization Performance of Concrete by Freeze-Thaw Action in Ningxia". Applied Mechanics and Materials 488-489 (gennaio 2014): 407–10. http://dx.doi.org/10.4028/www.scientific.net/amm.488-489.407.

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In this paper, the effect of carbonization performance of concrete by freeze-thaw action in Ningxia Hui Autonomous Region have been studied. Based on the concrete carbonation depth prediction model modified, the effects of the carbonation depth of concrete by freeze-thaw action with dry weather in Yinchuan and Yanchi County are studied. These influential factor include water-cement ratio, cement dosage, the air relative humidity, carbon dioxide concentration.

16

Ye, Qing. "Influence of Early Age Wet Curing Time, Clinker and CaO Content on the Carbonation Resistance of C40 Ordinary Concrete". Advanced Materials Research 311-313 (agosto 2011): 1894–900. http://dx.doi.org/10.4028/www.scientific.net/amr.311-313.1894.

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Based on accelerated carbonation test, the variation of the carbonation resistance of ordinary concrete (C40 grade) with early age wet curing time, clinker and CaO content was studied. Results indicate that the carbonation coefficient and the accelerated carbonation depth of the concrete increased obviously with a reduction in the wet curing time at early ages, the clinker or CaO content in binder and the compressive strength at 28 d age. For example, in conditions of curing schedules with 28, 7, 3, 2 and 1 d wet curing at 20 °C with above 95% RH at early ages and then 0, 21, 25, 26 and 27 d air curing at 20 °C with 60% RH, respectively, carbonation coefficients of the concrete incorporated with 15% fly-ash and 25% slag were 1.83, 2.71, 3.61, 4.67 and 5.50 mm/a0.5 respectively, and thus it can be seen that the calculated times when concrete cover (25 mm) was completely carbonated naturally in now atmosphere (0.04% CO2) were 191, 104, 52, 31 and 20 years respectively. It is possible to predict the potential carbonation coefficient of the concrete from its clinker or CaO content in binder and from its compressive strength at 28 d age in conditions of the certain wet curing time at early ages.

17

Zhu, Jing Song, Ya Li Sun, Yue Feng Zhu e Dan Fei Chen. "Experimental Study on Carbonation Resistance of Ready-Mixed Concrete". Applied Mechanics and Materials 174-177 (maggio 2012): 152–58. http://dx.doi.org/10.4028/www.scientific.net/amm.174-177.152.

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By means of accelerated carbonation tests, the carbonation resistance of concrete in relation to the variation of water-cement ratio, fly ash content and curing conditions is studied in this article. The results show that under the standard curing conditions, with the fly ash content of 20%, in response to different water-cement ratio, the carbonation depth of concrete and the water-cement ratio are presented more or less in a linear relationship. At the water-cement ratio of 0.40, there is hardly any carbonation effect onto the concrete. However, at the ratio of bigger than 0.60, the carbonation depth of concrete increases in a speedy way. Under the standard curing conditions, at the water-cement ratio of 0.55, with the fly ash content of lower than or equal to 30%, the carbonation resistance of concrete is good enough to fulfill the design criteria of 50~100 years for service life of important and general buildings, while the compressive strength declines by less than 10%. But under the condition of 1d curing with retention of moisture followed by curing in the air until 28d, with no fly ash content, the carbonation depth of concrete has reached 35mm, which fails to fulfill the design criteria of 50 years for service life of general buildings. It is therefore concluded that the control of water-cement ratio, the control of fly ash content, and the sufficient curing with retention of moisture in early stage are all the essential factors to ensure the durability against carbonation for the concrete with fly ash content.

18

Zhang, Hua, Pin-Jing He, Li-Ming Shao e Duu-Jong Lee. "Temporary stabilization of air pollution control residues using carbonation". Waste Management 28, n. 3 (gennaio 2008): 509–17. http://dx.doi.org/10.1016/j.wasman.2007.02.005.

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Yu, Qi, Bingbing Guo e Changjiang Li. "Effects of CO2 Concentration and the Uptake on Carbonation of Cement-Based Materials". Materials 15, n. 18 (16 settembre 2022): 6445. http://dx.doi.org/10.3390/ma15186445.

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Carbonation seriously deteriorates the durability of existing reinforced concrete structures. In this study, a thermodynamic model is used to investigate the carbonation reactions in cement-based materials. The effects of the concentration and amounts of CO2 on the carbonation behaviors of mortar are discussed. The simulation results show that the mechanisms of the carbonation reaction of cement-based materials at different CO2 concentrations may be different. Nearly all of the hydrate phases have a corresponding CO2 concentration threshold, above which the corresponding carbonation reaction can be triggered. The thresholds of the C-S-H phases with different Ca/Si ratios are different. The calculation results also show that the phase assemblages in cement paste after being completely air-carbonated, primarily consist of a low-Ca/Si ratio C-S-H, strätlingite, CaCO3 and CaSO4. The pH of the pore solution exhibits a significant decrease when a higher Ca/Si ratio C-S-H phase is completely decalcified into a lower Ca/Si ratio C-S-H phase, by increasing the CO2 uptake. Additionally, the experimental results and the previously published investigations are used to validate the simulation results.

20

Thiel, Charlotte, Johanna Kratzer, Benedikt Grimm, Thomas Kränkel e Christoph Gehlen. "Effect of Internal Moisture and Outer Relative Humidity on Concrete Carbonation". CivilEng 3, n. 4 (17 novembre 2022): 1039–52. http://dx.doi.org/10.3390/civileng3040058.

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With steadily rising CO2 concentrations in the ambient air and fast-changing concrete compositions with reduced clinker contents, the availability of reliable and accelerated concrete carbonation tests is of crucial importance to design durable structures. This paper focuses on the effects of moisture under accelerated conditions and the effects of different CO2 exposure conditions. Mortar prisms incorporating three different cement types were cured and stored at either 50% or 65% relative humidity (RH). Afterwards, the prisms were carbonated at different ambient humidities (50, 57 and 65%), different CO2 concentrations (0.04, 1 and 3 vol.%) and complemented by a series of tests at increased gas pressure (2 barg). High-resolution test methods were used to explain the underlying carbonation mechanisms. The results show that pre-conditioning for two weeks—as currently suggested by the European Standard—seems to be too short because the initial inner moisture content severely affects the carbonation rate. Relative humidity during carbonation of 57% led to higher carbonation rates compared to 50% and 65%. In addition, climate data needs to be periodically (preferably permanently) recorded in research experiments and in laboratory testing to ensure fair interpretation of experimental results.

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Aminu Alhassan, Yunusa, e Sunday Apeh. "Effect of micro-climate variations on carbonation rate of concrete in the inland environment". MATEC Web of Conferences 289 (2019): 02001. http://dx.doi.org/10.1051/matecconf/201928902001.

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In an inland environment, carbonation is the primary cause of initiation for potential corrosion of steel in reinforced concrete. This problem has been exacerbated over recent years by increased urbanisation and vehicular traffic, resulting in higher atmospheric carbon dioxide contents – a problem typical of economically active cities throughout the world. It is important that designers of reinforced concrete structures respond to these variations through appropriate specifications to ensure that structures perform satisfactorily over their intended service lives. This paper is part of a study undertaken to assess the carbonation of concretes exposed to a range of micro-climate variations in inland environments, particularly with variations in carbon dioxide content, temperature and relative humidity conditions with the intent of developing a prediction model for the rate of carbonation. Concretes samples were prepared using three binder types representing variations of blends with FA, GGBS and four w/b ratios ranging from 0.4 to 0.75 and subjected to different degrees of initial water curing (3, 7, 28 days). These samples were placed in three exposure conditions: indoors in laboratory air, outdoors sheltered from rain and sun and outdoors fully exposed to the elements. The depths of carbonation of these samples were monitored over a period of 24 months in order to determine the rates of carbonation. Concrete samples in the outdoor sheltered sites presented the highest rate of carbonation. Although samples in this exposure site carbonated faster, the risk of reinforcement corrosion is likely to be low because the samples are protected from direct moisture effect. Keywords: Carbonation, Corrosion, Reinforced concrete, Micro climate, Inland environments

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Zheng, Yiwei, Lyzmarie Nicole Irizarry Colón, Noor Ul Hassan, Eric R. Williams, Morgan Stefik, Jacob M. LaManna, Daniel S. Hussey e William E. Mustain. "Effect of Membrane Properties on the Carbonation of Anion Exchange Membrane Fuel Cells". Membranes 11, n. 2 (31 gennaio 2021): 102. http://dx.doi.org/10.3390/membranes11020102.

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Anion exchange membrane fuel cells (AEMFC) are potentially very low-cost replacements for proton exchange membrane fuel cells. However, AEMFCs suffer from one very serious drawback: significant performance loss when CO2 is present in the reacting oxidant gas (e.g., air) due to carbonation. Although the chemical mechanisms for how carbonation leads to voltage loss in operating AEMFCs are known, the way those mechanisms are affected by the properties of the anion exchange membrane (AEM) has not been elucidated. Therefore, this work studies AEMFC carbonation using numerous high-functioning AEMs from the literature and it was found that the ionic conductivity of the AEM plays the most critical role in the CO2-related voltage loss from carbonation, with the degree of AEM crystallinity playing a minor role. In short, higher conductivity—resulting either from a reduction in the membrane thickness or a change in the polymer chemistry—results in faster CO2 migration and emission from the anode side. Although this does lead to a lower overall degree of carbonation in the polymer, it also increases CO2-related voltage loss. Additionally, an operando neutron imaging cell is used to show that as AEMFCs become increasingly carbonated their water content is reduced, which further drives down cell performance.

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Kasina, Monika, Piotr R. Kowalski e Marek Michalik. "Mineral carbonation of metallurgical slags". Mineralogia 45, n. 1-2 (1 giugno 2015): 27–45. http://dx.doi.org/10.1515/mipo-2015-0002.

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Abstract Due to increasing emissions of greenhouse gases into the atmosphere number of methods are being proposed to mitigate the risk of climate change. One of them is mineral carbonation. Blast furnace and steel making slags are co-products of metallurgical processes composed of minerals which represent appropriate source of cations required for mineral carbonation. Experimental studies were performed to determine the potential use of slags in this process. Obtained results indicate that steel making slag can be a useful material in CO2 capture procedures. Slag components dissolved in water are bonded as stable carbonates in the reaction with CO2 from ambient air. In case of blast furnace slag, the reaction is very slow and minerals are resistant to chemical changes. More time is needed for minerals dissolution and release of cations essential for carbonate crystallisation and thus makes blast furnace slags less favourable in comparison with steel making slag.

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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.

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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.

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Abanades, J. Carlos, Yolanda A. Criado e José Ramón Fernández. "An air CO2 capture system based on the passive carbonation of large Ca(OH)2 structures". Sustainable Energy & Fuels 4, n. 7 (2020): 3409–17. http://dx.doi.org/10.1039/d0se00094a.

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Passive direct air capture by the carbonation of large scale Ca(OH)₂ porous structures that can be regenerated by means of well-tried technologies, while producing a pure CO₂ stream ready for storage.

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Jia, Mengjun, Yifan Zhao, Xuan Wu e Xiao Ma. "The effect of carbonation accelerator on enhancing the carbonation process and mechanical strength of air-hardening lime mortars". Construction and Building Materials 425 (aprile 2024): 136067. http://dx.doi.org/10.1016/j.conbuildmat.2024.136067.

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Liang, Kaikang, Kai Cui, Mohanad Muayad Sabri Sabri e Jiandong Huang. "Influence Factors in the Wide Application of Alkali-Activated Materials: A Critical Review about Efflorescence". Materials 15, n. 18 (16 settembre 2022): 6436. http://dx.doi.org/10.3390/ma15186436.

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Applications related to alkali-activated materials (AAMs) have received much attention due to their excellent mechanical properties and low-energy production. Although much research has focused on developing AAMs, their application is still limited. One of the primary reasons is the efflorescence. Not only does efflorescence affect the material aesthetics, but it also affects the mechanical performance, leading to a decrease in material quality. This paper first summarizes the current research on AAMs efflorescence. The formation process of efflorescence is divided into three parts: alkaline cation leaching, air carbonation, and efflorescence formation. Furthermore, the influences caused by different factors, including raw materials, curing conditions, AAMs modalities, etc., on the efflorescence are proposed. This paper highlights the solutions for efflorescence by avoiding free alkaline cation leaching and preventing air carbonation. The advantages and disadvantages of efflorescence are discussed in-depth, showing that it can be exploited under certain conditions, such as in wastewater treatment. This paper has important implications for the practical preparation and application of AAMs.

28

Arizzi, Anna, Javier Martínez Martínez, Giuseppe Cultrone e David Benavente. "Mechanical Evolution of Lime Mortars during the Carbonation Process". Key Engineering Materials 465 (gennaio 2011): 483–86. http://dx.doi.org/10.4028/www.scientific.net/kem.465.483.

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Lime mortar is one of the most ancient and durable building materials. It is characterized by a slow carbonation during which Ca(OH)2 reacts with CO2 present in air and forms calcite, giving rise to a stronger and more compact material. This process takes place from the surface to the interior of the material and it is strongly affected by the reaction conditions. The aim of this study is to quantify the increase in strength and elasticity of different lime mortars according to their carbonation degree. For that, six types of mortars were elaborated, with different lime/aggregate proportions and aggregate mineralogy and grading. Mineralogical and textural studies were carried out to follow the carbonation process. Each mortar was tested in a uniaxial compression press after 15, 28, 60 days from the elaboration. In order to differentiate the mechanical behaviour of the external and internal parts of the mortars, two micro-samples (10×10×10 mm) were obtained from the first 10 mm and from the core of each prism. Results show that an increase in strength and especially in the elastic modulus is associated to the carbonation process, but it is different depending on the composition and compactness of the mortars.

29

Qin, Hong Yan, Peng Zhi Zhang, Si Si Zhang e Xiang Peng Wang. "Experimental Study on Regularities of Carbonation for CO₂ Capture Using Ammonia Solution". Advanced Materials Research 800 (settembre 2013): 62–66. http://dx.doi.org/10.4028/www.scientific.net/amr.800.62.

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The regularities of carbonation in the process of CO2 capture were investigated using ammonia solution by laboratory-scale and bench-scale device. The research showed that the lower volatility of NH3 and higher rate of carbonization in solution could be achieved with ammonia concentration ranging from 10 to 16 wt%. The emission of ammonia accelerated with the increasing of flow of flue gas, and the bubbling function of air was apparent in a lower CO2 volume fraction, which has an adverse effect on carbonation of solution. Benefits of environment and economic could be achieved in CO2 capture using ammonia solution so long as appropriate ammonia concentration, the flue gas flow and volume fraction of CO2 were determined.

30

Coppola, Luigi, Denny Coffetti, Elena Crotti, Raffaella Dell’Aversano, Gabriele Gazzaniga e Tommaso Pastore. "Influence of Lithium Carbonate and Sodium Carbonate on Physical and Elastic Properties and on Carbonation Resistance of Calcium Sulphoaluminate-Based Mortars". Applied Sciences 10, n. 1 (25 dicembre 2019): 176. http://dx.doi.org/10.3390/app10010176.

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In this study, three different hardening accelerating admixtures (sodium carbonate, lithium carbonate and a blend of sodium and lithium carbonates) were employed to prepare calcium sulphoaluminate cement-based mortars. The workability, setting times, entrapped air, elasto-mechanical properties such as compressive strength and dynamic modulus of elasticity, free shrinkage, water absorption and carbonation rate were measured and mercury intrusion porosimetry were also performed. Experimental results show that a mixture of lithium carbonate and sodium carbonate acts as a hardening accelerating admixture, improving the early-age strength and promoting a remarkable pore structure refinement. Finally, sodium carbonate also reduces the water absorption, the carbonation rate and the shrinkage of mortars without affecting the setting times and the workability.

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Berber, Hakan, Kadriann Tamm, Mari-Liis Leinus, Rein Kuusik, Kaia Tõnsuaadu, Peeter Paaver e Mai Uibu. "Accelerated carbonation technology granulation of industrial waste: Effects of mixture composition on product properties". Waste Management & Research 38, n. 2 (22 novembre 2019): 142–55. http://dx.doi.org/10.1177/0734242x19886646.

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The use of accelerated carbonation technology in combination with a granulation process was employed to produce aggregates from a variety of industrial wastes, which included municipal solid waste incineration fly ash and air pollution control residue, oil shale ash, cement kiln dust, and quarry fines that have been produced in Estonia. Focusing mainly on the effects produced by the content of municipal solid waste incineration ash in the admixtures, the granule compositions were varied in order to tailor granule properties on the basis of CO2 uptake, strength development, leaching behaviour, microstructure, and morphology. All the steps involved in the accelerated carbonation technology granulation process, from mixing with additives to granulation and carbonation treatment, were carried out in the same apparatus – an Eirich EL1 intensive mixer/granulator. The amount of CO2 that was bound ranged from 23 to 108 kg per tonne of waste. The granules that included the optimised mixture of municipal solid waste incineration air pollution control residue, oil shale ash, cement kiln dust, and ordinary Portland cement were characterised by the highest compressive strength (4.03 MPa) and water durability for the size range of 4–10 mm. In addition, the process was found to be effective in reducing alkalinity (pH < 11.5) and immobilising heavy metals (especially zinc) and chloride. The composition and properties of the respective waste materials and mechanisms associated with the characteristics of the resulting granules were also addressed.

32

NONAKA, Akira, e Noboru YUASA. "EVALUATION CARBONATION RESISTANCE OF STRUCTURAL CONCRETE BY RAPID AIR-PERMEABILITY TEST". Journal of Structural and Construction Engineering (Transactions of AIJ) 80, n. 711 (2015): 727–34. http://dx.doi.org/10.3130/aijs.80.727.

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Monteiro, I., F. A. Branco, J. de Brito e R. Neves. "Statistical analysis of the carbonation coefficient in open air concrete structures". Construction and Building Materials 29 (aprile 2012): 263–69. http://dx.doi.org/10.1016/j.conbuildmat.2011.10.028.

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34

Bašić, Alma-Dina, Marijana Serdar, Ingrid Mikanovic e Gunther Walenta. "Impact of slag on carbonation rate of concrete based on calcium aluminate cement". MATEC Web of Conferences 364 (2022): 02020. http://dx.doi.org/10.1051/matecconf/202236402020.

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Throughout their service life, concrete structures are exposed to various environmental conditions that affect their durability. The cementitious matrix inevitably comes into contact with air, which leads to a progressive carbonation reaction. As a result of carbonation, changes occur in the microstructure and porosity of the cementitious matrix. Calcium aluminate cement is produced to increase the resistance of composites to aggressive environments, but its application is limited by the occurrence of conversion process. The addition of slag inhibits the conversion process of calcium aluminate cement and prevents a reduction in compressive strength due to the formation of C2ASH8 hydrate, while contributing to the net zero commitment of the cement industry. It remains an open question how these changes in microstructure caused by the addition of slag affect the carbonation rate of calcium aluminate cement-based concrete. Therefore, the objective of this study was to determine the effects of slag on the microstructure and porosity of calcium aluminate-based concrete before and after accelerated carbonation. For this purpose, the mechanical properties, porosity, and reaction product of a concrete mix containing 30% calcium aluminate cement replacement by slag were compared to calcium aluminate cement-based concrete before and after exposure to 3% CO2 for 7 and 28 days. Thermogravimetric analysis (TGA) and mercury intrusion porosimetry (MIP) were tested to understand the changes in reaction products and pore size distribution, respectively.

35

Lee, Jae-In, Chae-Young Kim, Joo-Ho Yoon e Se-Jin Choi. "Mechanical Properties of Cement Mortar Containing Ground Waste Newspaper as Cementitious Material". Materials 16, n. 4 (6 febbraio 2023): 1374. http://dx.doi.org/10.3390/ma16041374.

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In recent years, several studies have reported the recycling of by-products generated by the paper industry and their application to the construction industry. A majority of the existing studies used waste paper sludge ash, and considerable energy is consumed in such incineration processes. This may further contribute to air pollution. In this study, we used waste newspaper (WNP), which underwent a simple crushing process without a separate high-temperature treatment process, and we integrated it in cement mortar. We prepared mortars containing 0%, 0.2%, 0.4%, 0.6%, 0.8%, and 1.0% ground WNP as a cement substitute. Subsequently, the fluidity, compressive strength, tensile strength, carbonation depth, drying shrinkage, and microstructure of the mortars were compared and analyzed. The 28-day compressive strength of the mortar samples with WNP was approximately 3.2–16.1% higher than that of the control sample. The 28-day accelerated carbonation depth of the samples with WNP was approximately 1.03–1.61 mm. Furthermore, their carbonation resistance was approximately 5.2–39.4% higher than that of the control sample. Compressive strength, tensile strength, and carbonation resistance were improved by appropriately using ground WNP as a cement substitute in cement mortar. In this study, the appropriate amount of WNP according to the mechanical properties of cement mortar was found to be 0.4–0.8%, and considering the durability characteristics, the value 0.6 was the most ideal.

36

Udodov, Sergey, Dmitry Gura e Grigoriy Charikov. "Study of changes in concrete durability during the operation of buildings". Curved and Layered Structures 9, n. 1 (1 gennaio 2022): 193–201. http://dx.doi.org/10.1515/cls-2022-0016.

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Abstract The purpose of this study is to select the best methodologies for determining the condition of concrete structures. Semi-destructive concrete exposure methods were used to determine resistance parameters: the impact echo test to determine internal structure, the Figg test for air permeability, the initial surface adsorption test for water adsorption, titrimetric for chloride amounts, and a chemical and physical method to determine carbonation levels. In addition, two situations were simulated: a fire and a pipe burst and their impact on the condition of reinforced concrete structures. It was shown that the exposure to temperatures decreases the level of acidity, resulting in increased corrosion of steel. During a pipe burst, the amount of chlo-rides increases, which affects the reinforcement, oxidizing it. A search for possible correlation between concrete structure and carbonation, air permeability and water adsorption was also carried out. It was found that there is an almost linear dependence of these parameters on the presence of cracks, the deterioration of the structure leads to an increase in the transport properties of concrete, which becomes a danger to steel.

37

Boschmann Käthler, Carolina, Ueli M. Angst e Bernhard Elsener. "Towards understanding corrosion initiation in concrete – influence of local concrete properties in the steel-concrete interfacial zone". MATEC Web of Conferences 199 (2018): 04002. http://dx.doi.org/10.1051/matecconf/201819904002.

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Chloride-induced corrosion is the most common deterioration process for reinforced infrastructure objects. Improving the understanding of the conditions for initiation of localized corrosion is urgently needed. Research is focused on the influence of “defects” at the steel-concrete interface (SCI), as these weak points might be responsible for corrosion initiation. In contrast to numerous studies with “lab concrete”, this study reports results from reinforced concrete cores drilled from old infrastructure objects containing a non-corroding rebar. In contrast to laboratory studies, this guarantees real conditions at the SCI comprising also irregularities such as air voids, plastic settlement voids, cracks, etc. This allows to study chloride-induced corrosion in real conditions and to determine the so-called “critical chloride content” Ccrit. Visual inspection of the SCI enables to establish (or not) influences of the local conditions at the SCI and Ccrit. It was found that Ccrit strongly decreased with the carbonation depth, even if the carbonation front had not reached the steel. Moreover, coarse air voids and cracks were in this study not particularly susceptible sites for corrosion initiation.

38

Jankovský, Ondřej, Michal Lojka, Anna-Marie Lauermannová, Filip Antončík, Milena Pavlíková, Zbyšek Pavlík e David Sedmidubský. "Carbon Dioxide Uptake by MOC-Based Materials". Applied Sciences 10, n. 7 (26 marzo 2020): 2254. http://dx.doi.org/10.3390/app10072254.

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In this work, carbon dioxide uptake by magnesium oxychloride cement (MOC) based materials is described. Both thermodynamically stable magnesium oxychloride phases with stoichiometry 3Mg(OH)2∙MgCl2∙8H2O (Phase 3) and 5Mg(OH)2∙MgCl2∙8H2O (Phase 5) were prepared. X-ray diffraction (XRD) measurements were performed to confirm the purity of the studied phases after 7, 50, 100, 150, 200, and 250 days. Due to carbonation, chlorartinite was formed on the surface of the examined samples. The Rietveld analysis was performed to calculate the phase composition and evaluate the kinetics of carbonation. The SEM micrographs of the sample surfaces were compared with those of the bulk to prove XRD results. Both MOC phases exhibited fast mineral carbonation and high maximum theoretical values of CO2 uptake capacity. The materials based on MOC cement can thus find use in applications where a higher concentration of CO2 in the environment is expected (e.g., in flooring systems and wall panels), where they can partially mitigate the harmful effects of CO2 on indoor air quality and contribute to the sustainability of the construction industry by means of reducing the carbon footprints of alternative building materials and reducing CO2 concentrations in the environment overall.

39

Lyubomirskiy, N. V., S. I. Fedorkin, А. S. Bakhtin e Т. А. Bakhtina. "INTENSIVE WAYS OF PRODUCING CARBONATE CURING BUILDING MATERIALS BASED ON LIME SECONDARY RAW MATERIALS". Construction and industrial safety, n. 18 (70) (2020): 43–46. http://dx.doi.org/10.37279/2413-1873-2020-18-43-46.

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the article is dedicated to the research and development of intensive methods for curing products by capturing and binding CO2. It aims to improve and increase the productivity of technologies for the production of artificially carbonated building materials and products. Soda production wastes, limestone dust and finely dispersed limestone dust were used as the research objects. Secondary raw materials have been investigated using modern methods of phase composition and granulometry test. Intensive methods of production of accelerated carbonation of systems consisting of soda wastes were tested using multi-parameter optimization methods. The effects of recycled lime materials on the strength and hydrophysical properties of the obtained material were determined. The secondary raw materials effect depended on the composition of the raw mixture, molding conditions, CO2 concentration applied to the carbonate curing chamber, and the duration of exposure to environments with high CO2 content. It was found that the most effective way of providing accelerated carbonation curing of construction materials and products is a combined carbonation method, combining the principles of dynamic and static methods. It was concluded that the optimal CO2 concentration in the gas-air mixtures used for carbonate curing is 30%–40%.

40

Lyubomirskiy, Nikolai, Aleksandr Bakhtin, Stanisław Fic, Małgorzata Szafraniec e Tamara Bakhtinа. "Intensive Ways of Producing Carbonate Curing Building Materials Based on Lime Secondary Raw Materials". Materials 13, n. 10 (16 maggio 2020): 2304. http://dx.doi.org/10.3390/ma13102304.

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Abstract (sommario):

The article is dedicated to the research and development of intensive methods for curing products by capturing and binding CO2. It aims to improve and increase the productivity of technologies for the production of artificially carbonated building materials and products. Soda production wastes, limestone dust and finely dispersed limestone dust were used as the research objects. Secondary raw materials have been investigated using modern methods of phase composition and granulometry test. Intensive methods of production of accelerated carbonation of systems consisting of soda wastes were tested using multi-parameter optimization methods. The effects of recycled lime materials on the strength and hydrophysical properties of the obtained material were determined. The secondary raw materials effect depended on the composition of the raw mixture, molding conditions, CO2 concentration applied to the carbonate curing chamber, and the duration of exposure to environments with high CO2 content. It was found that the most effective way of providing accelerated carbonation curing of construction materials and products is a combined carbonation method, combining the principles of dynamic and static methods. It was concluded that the optimal CO2 concentration in the gas-air mixtures used for carbonate curing is 30%–40%.

41

Quan, Hong Zhu, e Hideo Kasami. "Effects of Change in Fineness of Fly Ash on Air-Entrained Concrete". Advanced Materials Research 168-170 (dicembre 2010): 2195–99. http://dx.doi.org/10.4028/www.scientific.net/amr.168-170.2195.

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In order to make clear of the effects of the change in fineness of fly ash on air-entrained concrete, 2 series of laboratory experiments were carried out using 6 kinds fly ash with the specific surface area in the range from 2500 to 4400cm2/g. The test results indicated higher slump and lower air-entraining content and higher dosage of air-entraining agent for fly ash with higher specific surface area. Compressive strength was found to increase with the increases of specific surface area of fly ash, while drying shrinkage and carbonation were found to show different tendency with change in fineness of fly ash.

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Pfleger, Marc-Patrick, e Markus Vill. "Forced carbonation of recycled concrete aggregates". Acta Polytechnica CTU Proceedings 33 (3 marzo 2022): 467–72. http://dx.doi.org/10.14311/app.2022.33.0467.

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The production of concrete, especially the contained cement clinker, causes a high proportion of the manmade gaseous air pollution. Studies show that the decarbonation of limestone effects roughly 8% of worldwide CO2 emissions, which underlines the need for action and research. Due to the present building and infrastructure stocks and their obsolescence, or rather replacement, the amount of demolition material is permanently increasing. In many cases the demolition material consists of high-quality concrete, which could be used again as recycled aggregate in the production process to conserve sources of raw materials. Most of the concrete waste is not carbonated which means that the potential as CO2 sink can be exploited in the course of the recycling process. Since the recycled and carbonated material is used as a replacement for primary raw material, the state of carbonation itself is irrelevant to any steel corrosion or associated problems. The main objective of this work was to investigate the CO2 absorption of concrete waste, to investigate and prove its use as a possible carbon sink. At this point, the carbonation velocity had to be optimised by the use of special equipment. First test series show that the ecological footprint of concrete can be significantly reduced if concrete waste is used for carbon storage and admixed as recycled aggregate during the production process. The aim of this study was to point out further possibilities for the ecological optimisation of concrete besides alternative binders, which are the subject of research in various projects worldwide.

43

Zhong, Yuwei, Bin Liu, Zequan Zhao, Yuanhao Shen, Xiaorui Liu e Cheng Zhong. "Influencing Factors of Performance Degradation of Zinc–Air Batteries Exposed to Air". Energies 14, n. 9 (2 maggio 2021): 2607. http://dx.doi.org/10.3390/en14092607.

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Zinc–air batteries feature high energy density, but they usually suffer from their short storage life after they start working, restricting their commercial applications. In the past, scholars did not reach an agreement on the influencing factors of the performance degradation of zinc–air batteries when exposed to air. Here, a series of comparative experiments were conducted to confirm the changes of the battery during storage after being exposed to air. The morphology and composition of the components of the battery were characterized by scanning electron microscopy (SEM) and X-ray diffraction analyses. SEM images revealed that with the increase of storage days, the corrosion of the zinc anode gradually deepens, but the surface morphology of the air cathode does not change much. The electrolyte of the batteries stored for different periods was examined through inductively coupled plasma spectroscopy and titration. After 20 days of storage, the concentration of CO32− reached 2.694 mol L−1, which indicates that more than 80% of the OH− in the electrolyte was consumed. The results show that after being exposed to air, the carbonation of the electrolyte is the main cause of the battery capacity decay.

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Baciocchi, Renato, Alessandra Polettini, Raffaella Pomi, Valentina Prigiobbe, Viktoria Nikulshina Von Zedwitz e Aldo Steinfeld. "CO2Sequestration by Direct Gas−Solid Carbonation of Air Pollution Control (APC) Residues". Energy & Fuels 20, n. 5 (settembre 2006): 1933–40. http://dx.doi.org/10.1021/ef060135b.

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Erans, María, Seyed Ali Nabavi e Vasilije Manović. "Carbonation of lime-based materials under ambient conditions for direct air capture". Journal of Cleaner Production 242 (gennaio 2020): 118330. http://dx.doi.org/10.1016/j.jclepro.2019.118330.

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46

Prigiobbe, Valentina, Alessandra Polettini e Renato Baciocchi. "Gas–solid carbonation kinetics of Air Pollution Control residues for CO2 storage". Chemical Engineering Journal 148, n. 2-3 (15 maggio 2009): 270–78. http://dx.doi.org/10.1016/j.cej.2008.08.031.

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47

Belgacem, M. E., R. Neves e A. Talah. "Service life design for carbonation-induced corrosion based on air-permeability requirements". Construction and Building Materials 261 (novembre 2020): 120507. http://dx.doi.org/10.1016/j.conbuildmat.2020.120507.

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Žižlavský, Tomáš, Martin Vyšvařil, Patrik Bayer e Pavla Rovnaníková. "Influence of Guar Gum Derivatives on Hardened Properties of Aerial Lime-Based Mortars". Key Engineering Materials 760 (gennaio 2018): 22–29. http://dx.doi.org/10.4028/www.scientific.net/kem.760.22.

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This paper studies the possibility of usage of the guar gum and its derivatives (carboxymethylhydroxypropyl guar (CMHPG) and hydroxypropyl guar (HPG)) as admixtures for aerial lime-based mortars. The influence on the properties of mortars was studied on the aerial lime –based mortars prepared with quartz fine grained sand and doses of admixtures ranging between 0,5 and 10‰. The hardened bulk densities, flexural and compressive strength, porosity, water absorption coefficient due to capillarity action and carbonation rate were studied. The addition of the hydroxypropyl guar lowered the bulk density (due to an air intake), improved workability, slightly increased the strength, slowed carbonation rate, and nobbled the water transport in the mortar. The addition of carboxymethylhydroxypropyl guar does not impact the bulk density, the strengths were increased similarly to HPG: it does not impact carbonation rate significantly, so the long term strengths were comparative with the HPG. The water transport was slightly better in lower doses and slightly worse in larger doses in comparison with the reference mortar. The pure guaran was found not to be beneficial for the lime mortars for its only advantage is in the water transport, where in any dose the transport was better than any other mortar, but the benefit of this is questionable.

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Saura Gómez, Pascual, Javier Sánchez Montero, Julio Emilio Torres Martín, Servando Chinchón-Payá, Nuria Rebolledo Ramos e Óscar Galao Malo. "Carbonation-Induced Corrosion of Reinforced Concrete Elements according to Their Positions in the Buildings". Corrosion and Materials Degradation 4, n. 3 (21 giugno 2023): 345–63. http://dx.doi.org/10.3390/cmd4030018.

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Most regulations on the manufacturing of concrete for reinforced concrete structures rest on durability models that consider the corrosion of reinforcements. Those models are based on factors such as humidity, frost, presence of chlorides, and internal characteristics of the concrete itself, like resistance, porosity, type of cement, water/cement ratio, etc. No regulations, however, adopt a purely constructive perspective when evaluating the risk of corrosion, i.e., the relative position of the reinforced concrete in buildings. The present work focuses on the relationship between the position of the damaged element and the building envelope. A total of 84 elements (columns and reinforced concrete beams) across twenty buildings were analysed in the provinces of Alicante and Murcia (Spain). The reinforcement concrete of these elements underwent carbonation-induced corrosion according to their positions in the buildings: (A) façade columns in contact with the ground; (B) interior columns in contact with the ground; (C) columns of walls in contact with the ground; (D) columns and external beams protected from rain; (E) columns and external beams exposed to rain; (F) columns and beams in air chambers under sanitary slabs; and (G), columns and interior beams. Of all types, elements (E) and (F) suffered carbonation-induced corrosion faster than the models used in the regulations, and type (G) underwent slower carbonation.

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Zhang, Cheng, Xinyu Shi, Ling Wang e Yan Yao. "Investigation on the Air Permeability and Pore Structure of Concrete Subjected to Carbonation under Compressive Stress". Materials 15, n. 14 (7 luglio 2022): 4775. http://dx.doi.org/10.3390/ma15144775.

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Concrete structures have to withstand the combined effects of external load and environmental factors. Therefore, it is meaningful to study the durability of concrete under compression and carbonation. The air permeability coefficient (kAu) and pore structure of concrete under uniaxial compression and carbonation were measured by the Autoclam method and mercury intrusion porosimetry (MIP). The Autoclam test results showed that the concrete kAu changed in a concave parabolic manner with the compressive stress level, and the inflection point of the stress level was 45%. The MIP results showed that the characteristic pore structural parameters (porosity, average pore diameter, median pore diameter by area, and median pore diameter by volume) first decreased and then increased with the stress level change. The change in concrete microstructure was a result of the combined effect of pore filling, decalcification, and densification, as well as the split effect. The key pore structural parameters affecting kAu were confirmed using gray relational analysis (GRA). The top three parameters with the highest correlation with the carbonated concrete kAu were porosity (gray relational grade γi = 0.789), median pore diameter by volume (γi = 0.763), and proportion of transition pore volume (γi = 0.827). Furthermore, the regression analysis showed a good linear relation between kAu and the important pore structural parameters.

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