Internal sulfate attack in mortars containing contaminated fine recycled concrete aggregates

Colman, Charlotte; Bulteel, D.; Thiéry, Vincent; Rémond, Sébastien; Michel, Frédéric; Courard, Luc

doi:10.1016/j.conbuildmat.2020.121851

Cited by 29 publications

(15 citation statements)

References 28 publications

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“…The high concentration of ettringite in materials attacked by sulfates has also been confirmed in other studies, justifying the expansion tensions caused by the attack [17], [18], [42], [47].…”

Section: Xrdsupporting

confidence: 73%

“…Recent studies [17]- [19] related to the attack of sulfates investigate the impact that the presence of contaminants in recycled aggregates, such as gypsum, can cause on the properties of cementitious compounds such as: mechanics, microstructure, and porosity. Analyses analogous to those proposed in these studies were performed in the present study.…”

Section: Literature Reviewmentioning

confidence: 99%

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Influence of internal sulfate attack on cement paste properties: contamination by pyrite

Capraro

Filho

Medeiros

2021

Rev. IBRACON Estrut. Mater.

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The objective of this work was to evaluate the influence of the presence of sulfate in the microstructure and compressive strength of cement pastes. The lack of availability of more suitable aggregates, for reasons of distance or costs, sometimes leads to the use of materials that contain sulfate in their composition, which is harmful to cement mixtures. Currently, there are normative recommendations that limit the content of contaminants in the aggregates. However, there are still divergences as to the content that does not damage the concrete. In order to discuss the levels presented in the standards and the values above those allowed by them, tests were carried out on cementitious compounds contaminated by pyrite in different levels of sulfates (0.0%, 0.5%, 1.0% and 5.0% of SO3). SEM, XRD, compressive strength, ultrasonic pulse velocity and porosity analyses were performed in samples at different ages until 720 days of age. During early ages until the first year, the most contaminated samples presented an increase in their strength (1.0% and 5.0% of SO3). This behavior was explained by SEM, XRD and porosity analyses by filling the pores with products of sulfate attack, such as ettringite. At the end of the tests (720 days) the series that presented the lowest compressive strength, the presence of cracks and large amounts of ettringite was the one that had 5.0% SO3 contamination, proving the importance of a normative limit content.

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Section: Xrdsupporting

confidence: 73%

Section: Literature Reviewmentioning

confidence: 99%

Influence of internal sulfate attack on cement paste properties: contamination by pyrite

Capraro

Filho

Medeiros

2021

Rev. IBRACON Estrut. Mater.

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“…The mortars made with the reference FRA gained more mass, because of their irregular shape which captures more air into the mixture than a round aggregate [30,48]. For the reference FRA specifically, a high air content in mixes with this material was already observed [49]. Industrially fabricated FRA are rounder by nature than laboratory crushed FRA [50], explaining why their results lie between those of the natural aggregates and the reference FRA.…”

Section: Swelling Testsmentioning

confidence: 95%

“…To follow the development of the internal sulfate attack reaction, the mortar specimens were subjected to different tests. The mass, length [41], and resonance frequency were recorded weekly to observe features of sulfate attack such as swelling and possible internal cracking. Length measurements were performed with a digital length comparator, which gives the length of a mortar bar accurately up to 0.001 mm, relative to an Invar reference rod.…”

mentioning

confidence: 99%

Valorization of Fine Recycled Aggregates Contaminated with Gypsum Residues: Characterization and Evaluation of the Risk for Secondary Ettringite Formation

et al. 2020

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Fine recycled aggregates (FRA) (0/4 mm) are up to now not valorized on a high enough level because of characteristics like an elevated water absorption, higher fines content, and the presence of contaminations. Leftover gypsum residues from the construction site can cause internal sulfate attack when FRA are incorporated into new structures. Concern about this deteriorating reaction plays an important role in the rejection of FRA. In this study, samples of FRA from different recycling centers were characterized and incorporated into mortars. They were then subjected to swelling tests in order to evaluate the development of sulfate attack. Reference materials with different amounts of sulfates were used as a comparison. Results showed a variable sulfate content in industrial FRA, depending heavily on the source of the materials. In all but one case, the total amounts surpassed the acceptable sulfate contents specified in the European standard EN 206, meaning the FRA would be rejected for reuse in concrete. Nevertheless, swelling tests demonstrated that these contamination levels did not pose a risk for sulfate attack. These results indicated that the incorporation of FRA leads to acceptable mechanical performances and that the sulfate limit could be reviewed to be less strict.

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“…The expansion of mortars M-BS25 and M-BS50 after 77 days was 443 and 400 μm/m, respectively, while it was only 226 μm/m for reference mortar. The sulphate attack is defined as the sulphates reacting with aluminate hydrates and water to form secondary ettringite, which could cause a volumetric deformation [69,70]. The resistance to sulphate depends on the pore sizes, the total porosity and the permeability of concrete or mortar [4,70,71].…”

Section: Sulphate Resistance Of Mortarsmentioning

confidence: 99%

Performance and durability of self-compacting mortar with recycled sand from crushed brick

Zhao¹,

Duan²,

Hubert³

et al. 2022

Journal of Building Engineering

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Internal sulfate attack in mortars containing contaminated fine recycled concrete aggregates

Abstract: h i g h l i g h t s Gypsum residues in fine recycled aggregates can cause internal sulfate attack. Limited porosity or thaumasite formation had an aggravating role on the swelling. Increased alkalinity or limited sulfate contents inhibited the swelling response.

Cited by 29 publications

References 28 publications

Influence of internal sulfate attack on cement paste properties: contamination by pyrite

Influence of internal sulfate attack on cement paste properties: contamination by pyrite

Valorization of Fine Recycled Aggregates Contaminated with Gypsum Residues: Characterization and Evaluation of the Risk for Secondary Ettringite Formation

Performance and durability of self-compacting mortar with recycled sand from crushed brick

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