Abstract
Coal fly ash (CFA), coal bottom ash (CBA) are residues produced in thermo-electrical power stations as result of the coal combustion in the same boiler. Therefore, some characteristics of the coal fly ash (CFA) are comparable with those of the coal bottom ash (CBA). Nevertheless, coal bottom ash size is larger than coal fly ash one. Consequently, it was found that it is necessary to grind the coal bottom ash (CBA) to reach a similar size to that one of the CFA. The objective of this paper is to evaluate the performance of Portland cement mortars made with coal fly ash (CFA), coal bottom ash (CBA) or mixes (CFA+CBA), against sulphate attack. The methodology is based on the expansion of slender bars submerged in a sodium sulphate solution (5%) according to the ASTM C-1012/C1012-13 standard. It has been found that mortars elaborated with CEM I 42.5 N (without ashes) presented the largest expansion (0.09%) after a testing period of 330 days. Mortars made with CEM II/A-V exhibited lower expansion (0.03%). Summing up, it can be established that mortar expansion decreases when the coal ash amount increases, independently of the type of coal ash employed. The novelty of this paper relies on the comparison between the performances of Portland cement mortars made with coal fly ash (CFA) or coal bottom ash (CBA) exposed to external sulphate attack. Doi: 10.28991/cej-2021-03091640 Full Text: PDF
Highlights
Portland cement is the material most widely used in the construction industry worldwide and it is estimated that its production releases approximately 7.4% of global anthropogenic emissions of carbon dioxide [1]
The objective of this paper is to evaluate the performance of Portland cement mortars made with coal fly ash (CFA), coal bottom ash (CBA) or mixes (CFA+CBA), against sulphate attack
The novelty of this paper relies on the comparison between the performances of Portland cement mortars made with coal fly ash (CFA) or coal bottom ash (CBA) exposed to external sulphate attack
Summary
Portland cement is the material most widely used in the construction industry worldwide and it is estimated that its production releases approximately 7.4% of global anthropogenic emissions of carbon dioxide [1]. The cement industry has an important role in reducing carbon dioxide emissions to minimize the climate change [3]. Coal fly ash use is still estimated to be just about half of the production level, mainly as cement and concrete constituent with replacement amounts between 15 and 25% [5]. Coal fly ash mitigates the damage of sulphate attack by reducing tricalcium aluminate hydrate, consuming Ca(OH) in the pozzolanic reaction and providing a denser matrix [7]. Concrete containing coal fly ash improves the resistance against sulphate attack of concrete made with plain concrete with 30% replacements [7]. Water-binder ratio is a control factor regarding the damage of concrete subjected to sulphate attack [7]
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