Fly ash effects

Wang, Aiqin; Zhang, Chengzhi; Sun, Wei

doi:10.1016/j.cemconres.2003.03.001

Cited by 141 publications

(80 citation statements)

References 1 publication

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“…The initial growth of this parameter in the studied grouts is in agreement with previously discussed impedance resistances results, and it could be related to the formation of solid phases due to the cement and slag hydration and fly ash pozzolanic reactions [4,27,28]. In addition to this, the slower increase of capacitance C 1 for CEM IV grouts also coincides with R 1 and R 2 results, revealing the abovementioned delay of fly ash pozzolanic reactions in comparison with slag and cement hydration [7]. Until 100 days, the capacitance C 1 showed a similar magnitude for all the grouts studied, which would suggest that they would have a similar solid fraction, independently of the refinement degree of their pore network, and consequently only little differences in porosity between them would be expected.…”

Section: Discussionsupporting

confidence: 90%

“…The slag reacts directly with the water since the mixing of the grouts [8,31], so the slag hydration initiates immediately and then, its benefits in the pore network of the grouts are produced sooner. However, the pozzolanic reactions of fly ash start once enough portlandite has been formed as a product of cement hydration [6,7], so these pozzolanic reactions are delayed compared to slag and cement hydration, and therefore it is necessary more time to observe the effects of fly ash in grouts microstructure. For that reason, the maximum R 1 for CEM IV samples was observed at a later age than for CEM III samples.…”

Section: Discussionmentioning

confidence: 99%

“…In general, many of these additions are wastes coming from other industries, so their reuse also has an added benefit. Furthermore, some of them can react directly with water or with portlandite formed during the cement hydration, producing new hydrated products which improve the properties of cement-based materials [6,7,8]. They are called active additions, and fly ash and ground granulated blast furnace slag are two of the most popular ones.…”

Section: Introductionmentioning

confidence: 99%

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Long-Term Behaviour of Fly Ash and Slag Cement Grouts for Micropiles Exposed to a Sulphate Aggressive Medium

et al. 2017

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Nowadays, one of the most popular ways to get a more sustainable cement industry is using additions as cement replacement. However, there are many civil engineering applications in which the use of sustainable cements is not extended yet, such as special foundations, and particularly micropiles, even though the standards do not restrict the cement type to use. These elements are frequently exposed to the sulphates present in soils. The purpose of this research is to study the effects in the very long-term (until 600 days) of sulphate attack in the microstructure of micropiles grouts, prepared with ordinary Portland cement, fly ash and slag commercial cements, continuing a previous work, in which these effects were studied in the short-term. The microstructure changes have been analysed with the non-destructive impedance spectroscopy technique, mercury intrusion porosimetry and the “Wenner” resistivity test. The mass variation and the compressive strength have also been studied. The impedance spectroscopy has been the most sensitive technique for following the sulphate attack process. Considering the results obtained, micropiles grouts with slag and fly ash, exposed to an aggressive medium with high content of sulphates, have shown good behaviour in the very long-term (600 days) compared to grouts made with OPC.

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Section: Discussionsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Long-Term Behaviour of Fly Ash and Slag Cement Grouts for Micropiles Exposed to a Sulphate Aggressive Medium

et al. 2017

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“…As has been previously explained, they could be due to the early solids formation, as a consequence of hydration and pozzolanic reactions, and the later appearance of expansive products produced during the sulphate attack. Furthermore, the different age when it was reached the maximum C 1 for each cement type, especially for CEM IV grouts, was also in accordance with R 1 and R 2 results, and reveals the delaying between the beginning of fly ash pozzolanic reactions and clinker and slag hydration [10,11]. The fact that there was not a great difference between the capacitance C 1 values obtained for the different grouts and exposure conditions studied (Figure 4 and Figure 5), could indicate that the solid phase of the samples was very similar for the three cement types, independently of the different pore size distribution for each one.…”

Section: Discussionsupporting

confidence: 64%

“…The subsequent rise of both resistances for CEM IV grouts hardened in this medium, could be explained because the pozzolanic reactions of fly ash start to develop later than slag and clinker hydration [10,11], so more time is needed to observe their effects in the porous network of fly ash grouts.…”

Section: Discussionmentioning

confidence: 99%

Microstructural Effects of Sulphate Attack in Sustainable Grouts for Micropiles

et al. 2016

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Nowadays, the use of micropiles has undergone a great development. In general, they are made with cement grout, reinforced with steel tubing. In Spain, these grouts are prepared using OPC, although the standards do not forbid the use of other cements, like sustainable ones. Micropiles are in contact with soils and groundwater, in which the presence of sulphates is common. Their deleterious effects firstly affect to the microstructure. Then, the aim of this research is to study the effects of sulphate attack in the microstructure of micropiles grouts, prepared with OPC, fly ash and slag commercial cements, compared to their behaviour when they are exposed to an optimum hardening condition. The microstructure evolution has been studied with the non-destructive impedance spectroscopy technique, which has never been used for detecting the effects of sulphate attack when slag and fly ash cements are used. Its results have been contrasted with mercury intrusion porosimetry and “Wenner” resistivity ones. The 28-day compressive strength of grouts has been also determined. The results of microstructure characterization techniques are in agreement, although impedance spectroscopy is the most sensitive for following the changes in the porous network of grouts. The results showed that micropiles made using fly ash and slag cements could have a good performance in contact with aggressive sodium sulphate media, even better than OPC ones.

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Enhancing the reliability and accuracy of machine learning models for predicting carbonation progress in fly ash‐concrete: A multifaceted approach

Uwanuakwa,

Akpınar

2024

Structural Concrete

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Existing machine learning models for carbonation in fly ash blended concrete, developed and validated using accelerated or combined datasets, lack validation against natural carbonation processes in concrete. Furthermore, the reliability and accuracy of these models are directly influenced by the sets of input variables used in model training. This research specifically aims to investigate the reliability and accuracy of machine learning models, trained with accelerated datasets, in predicting the natural carbonation process. Additionally, this study introduces Gaussian process regression (GPR) as an alternative modeling tool, due to its potential for enhanced prediction accuracy. The results of this study indicate that GPR can satisfactorily predict natural carbonation progress in fly ash concrete. Moreover, the study carried out a model interpretation to provide intuitive feature contributions in the black‐box model. The results indicate that the accuracy of the natural carbonation process evaluation of models trained with accelerated carbonation dataset is less than 0.2 R2 value, indicating the inappropriateness of using accelerated carbonation data to train reliable models. Additionally, the model interpretation shows a significant dependency of the natural carbonation process on the binder's chemical composition, highlighting key chemical factors influencing carbonation.

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Fly ash effects

Cited by 141 publications

References 1 publication

Long-Term Behaviour of Fly Ash and Slag Cement Grouts for Micropiles Exposed to a Sulphate Aggressive Medium

Long-Term Behaviour of Fly Ash and Slag Cement Grouts for Micropiles Exposed to a Sulphate Aggressive Medium

Microstructural Effects of Sulphate Attack in Sustainable Grouts for Micropiles

Enhancing the reliability and accuracy of machine learning models for predicting carbonation progress in fly ash‐concrete: A multifaceted approach

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