The Experts below are selected from a list of 24741 Experts worldwide ranked by ideXlab platform
Zuhua Zhang - One of the best experts on this subject based on the ideXlab platform.
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Carbonation induced phase evolution in alkali activated slag fly ash cements the effect of silicate modulus of activators
Construction and Building Materials, 2019Co-Authors: Jian Zhang, Caijun Shi, Zuhua ZhangAbstract:Abstract In this study, the effects of silicate modulus of activators (Ms) on Carbonation of alkali-activated slag/fly ash cements are studied and compared between natural (0.03–0.04% CO2) and accelerated (1% CO2) Carbonation conditions, via XRD, FTIR and TG/DTG techniques. Carbonation results in the decalcification of the C-A-S-H gels and the formation of calcium carbonates and silica gels, while the N-A-S-H gels are essentially constant after Carbonation. The main calcium carbonate phase after Carbonation is calcite, and the increase of Ms leads to the generation of vaterite and aragonite. The Carbonation behaviors of low-calcium system (20% slag) are different from the high-Ca systems (100% and 60% slag), while the Carbonation rate and the amount of calcium carbonates generally decrease with the increase of Ms in all of the studied systems. This investigation provides an in-depth understanding of Carbonation mechanisms of alkali-activated cements, and is essential for the establishment of Carbonation models and prediction of long-term performances.
Nele De Belie - One of the best experts on this subject based on the ideXlab platform.
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Effect of the Mechanical Load on the Carbonation of Concrete: A Review of the Underlying Mechanisms, Test Methods, and Results
'MDPI AG', 2021Co-Authors: Zhiyuan Liu, Philip Van Den Heede, Nele De BelieAbstract:As one of the major causes of concrete deterioration, the Carbonation of concrete has been widely investigated over recent decades. In recent years, the effect of mechanical load on Carbonation has started to attract more attention. The load-induced variations in crack pattern and pore structure have a significant influence on CO2 transport which determines the Carbonation rate. With different types of load, the number, orientation, and position of the induced cracks can be different, which will lead to different Carbonation patterns. In this review paper, the Carbonation in cracked and stress-damaged concrete is discussed first. Then, literature about the effect of sustained load during Carbonation is compared in terms of load type and load level. Finally, the advantages and disadvantages of possible test methods for investigating the effect of sustained load on Carbonation are discussed with respect to loading devices, load compensation, and specimen size
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Carbonation resistance of high volume fly ash hvfa mortar effect of applied co2 concentration
Synercrete 2018 Interdisciplinary approaches for cement-based materials and structural concrete, 2018Co-Authors: Philip Van Den Heede, Nele De BelieAbstract:To save time, the Carbonation resistance of cementitious materials is usually assessed in an accelerated manner by exposing the material to CO2 levels that highly exceed the atmospheric CO2 concentration. However, a too high acceleration of the Carbonation reaction could induce chemical, microstructural and mineralogical changes and excess production of the water reactant that are unrealistic. In this paper, it was evaluated whether the outcome of colorimetric Carbonation experiments at 10% CO2 for High-Volume Fly Ash (HVFA) mortar could still be used for calculating natural Carbonation rates and to do an adequate service life assessment. This seems not true. The effect of full Carbonation at 10% CO2 on the capillary water uptake was found to be significantly lower than after full Carbonation at only 1% CO2.
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Carbonation of slag concrete effect of the cement replacement level and curing on the Carbonation coefficient effect of Carbonation on the pore structure
Cement & Concrete Composites, 2013Co-Authors: Elke Gruyaert, Philip Van Den Heede, Nele De BelieAbstract:Abstract Concrete containing supplementary cementitious materials as, e.g. fly-ash (FA) or blast-furnace slag (BFS) is more vulnerable to Carbonation than ordinary Portland cement concrete. In order to know whether Carbonation-initiated corrosion is a risk within the life span of the concrete structure, the Carbonation depth after several years (e.g. 50 years) is mostly predicted based on accelerated Carbonation tests on young concrete specimens. However, these predictions do not take into account the positive effect of the continuing hydration of slag and fly-ash particles over a longer time. In this study, accelerated Carbonation tests (10 vol.% of CO 2 ) were performed on concrete specimens containing different amounts of blast-furnace slag (slag-to-binder ratios of 50%, 70% and 85%) after different curing times (1, 3, 6 or 18 months). Based on these tests, a new method, which takes into account the effect of the ongoing hydration, is described in order to predict the Carbonation depth of these special types of concrete over a long time more realistically. The tests revealed that, although BFS concrete has a lower Carbonation resistance than OPC concrete, the depth of Carbonation at the end of the concrete’s life (50 years) can still be acceptable in normal environments.
T. Leelawat - One of the best experts on this subject based on the ideXlab platform.
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A study on Carbonation depth prediction for fly ash concrete
Construction and Building Materials, 2006Co-Authors: Jittbodee Khunthongkeaw, Somnuk Tangtermsirikul, T. LeelawatAbstract:Abstract Carbonation of fly ash concrete is studied by using two types of fly ash with different CaO contents. It is observed that under natural exposure environments, the Carbonation rate is the highest when specimens are exposed in the city. The decreased ratio of water to binder and fly ash content leads to a better Carbonation resistance. For the same fly ash content, specimens of high-CaO fly ash show a better Carbonation resistance than those of low CaO fly ash. However, when compared at an equal strength, the effect of the type of fly ash on Carbonation becomes insignificant. When comparing the Carbonation results of concrete and mortar specimens, results of mortar show similar trends as those of concrete. However, the test results on mortar are worse by the use of fly ash than those of concrete. In addition, the Carbonation tests in an accelerated environment are also conducted. It is found that there exist strong relations between Carbonation depths of concrete exposed in natural and in accelerated environments. A mathematical approach to predict the Carbonation depth in the natural environments is proposed based on the accelerated tests and the square-root- t -law.
Dong Cui - One of the best experts on this subject based on the ideXlab platform.
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investigation on porosity of partly carbonated paste specimens blended with fly ash through dual ct scans
Construction and Building Materials, 2019Co-Authors: Dong Cui, Nemkumar Banthia, Qiannan Wang, Wei SunAbstract:Abstract Carbonation is one of the durability concerns for fly ash blended concrete. Unlike concrete made with ordinary Portland cement (OPC), the microstructure of fly ash blended concrete evolves in a different pattern during Carbonation. In this research, paste samples blended with variant amounts of fly ash were taken for accelerated Carbonation, and based on an extend X-ray attenuation method (XRAM), spatial distribution of porosity for partly-carbonated fly ash-blended pastes was investigated for the first time. Based on XRAM, the porosity before Carbonation is 0.42, 0.35, 0.36 and 0.46 respectively for OPC, FA30, FA50 and FA70, and the porosity changed to 0.36, 0.42, 0.46 and 0.49 respectively after Carbonation. The evolved microstructure subjected to Carbonation was verified by mercury intrusion porosimetry (MIP). For quantitative porosity results, very sharp porosity gradients were observed on the Carbonation front, which attests that all Carbonations in this study were diffusion controlling processes. The results of current research can be used for the verification of Carbonation models and for the understanding of Carbonation mechanism.
Xiao-yong Wang - One of the best experts on this subject based on the ideXlab platform.
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optimal mixture design of low co 2 high volume slag concrete considering climate change and co 2 uptake
International Journal of Concrete Structures and Materials, 2019Co-Authors: Hanseung Lee, Seungmin Lim, Xiao-yong WangAbstract:High-volume slag (HVS) can reduce the CO2 emissions of concrete, but increase the Carbonation depth of concrete. In particular, because of the effects of climate change, Carbonation will accelerate. However, the uptake of CO2 as a result of Carbonation can mitigate the harm of CO2 emissions. This study proposes an optimal mixture design method of low-CO2 HVS concrete considering climate change, Carbonation, and CO2 uptake. Firstly, net CO2 emissions are calculated by subtracting the CO2 emitted by the material from the uptake of CO2 by Carbonation. The strength and depth of Carbonation are evaluated by a comprehensive model based on hydration. Secondly, a genetic algorithm (GA) is used to find the optimal mixture. The objective function of the GA is net CO2 emissions. The constraints of the GA include the strength, Carbonation, workability, and range of concrete components. Thirdly, the results show that Carbonation durability is a control factor of the mixture design of low-strength HVS concrete, while strength is a control factor of the mixture design of high-strength HVS concrete. After considering climate change, the threshold of strength control increases. With the increase of strength, the net CO2 emissions increase, while the CO2 uptake ratio decreases.
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Evaluation of compressive strength development and Carbonation depth of high volume slag-blended concrete
Construction and Building Materials, 2016Co-Authors: Lee Han-seung, Xiao-yong WangAbstract:Abstract Compressive strength development and Carbonation are critical topics for using high volume slag concrete rationally. The objective of this study is to present a numerical procedure that evaluates compressive strength and Carbonation depth of high volume slag concrete. This numerical procedure consists of a blended hydration model and a Carbonation reaction model. The amount of carbonatable materials, such as calcium hydroxide (CH) and calcium silicate hydrate (CSH), is calculated using the blended hydration model. Compressive strength development of cement-slag blends is evaluated from CSH content. By considering the effects of material properties and environmental conditions, the Carbonation reaction model analyzes the diffusivity of carbon dioxide and the Carbonation depth of concrete. The results of the analysis show that regarding compressive strength, the contribution of slag mixes prepared at a lower water to binder ratio was greater than the contribution of slag mixes prepared at a higher water to binder ratio. Regarding Carbonation, with an increase in slag content or reducing the initial curing period, Carbonation depth increases. The results of this study are useful for optimum mixing proportional design and Carbonation durability design of concrete incorporating a high volume slag.