Calcined Illitic Clays as Portland Cement Replacements

Lemma, Roxana; Irassar, Edgardo F.; Rahhal, Viviana Fátima

doi:10.1007/978-94-017-9939-3_33

Cited by 17 publications

(11 citation statements)

References 6 publications

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“…For these two ICCs, the Frattini test was positive after 14 days. Additionally, strength tests were performed and presented in another publication (Lemma et al, 2015). Physical characteristic of the materials are summarized in Table 2.…”

Section: Methodsmentioning

confidence: 99%

“…Illite is one of the most abundant clayed minerals of the earth's crust coming from the alteration of feldspars and micas of rocks due to the weathering process. Illite clays develop pozzolanic properties when are thermally treated at 950 °C (Lemma et al, 2015) causing dehydroxylation and collapse of its structure to form a metastable or amorphous aluminosilicate (Ramachandran, 1995). These pozzolanic properties combined with the large availability of this mineral place illite calcined clays as a key supplementary material for the future mineral admixtures used in concrete.…”

Section: Introductionmentioning

confidence: 99%

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Sulfate Resistance of Blended Cements (Limestone Illite Calcined Clay) Exposed Without Previous Curing

Rossetti¹,

Ikumi²,

Segura³

et al. 2020

XV International Conference on Durability of Building Materials and Components. eBook of Proceedings

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Durability in aggressive environments is an important factor to extend the service life of concrete and the use ternary blended cements (limestone filler + calcined clays) can contribute to this purpose. In sulfate environments, the effects of supplementary cementing materials depend on the concentration, Portland cement and the progress of hydration reactions. Low level of limestone filler replacement influences the stabilization of AFt due to formation of monocarboaluminate, but high replacement increases the effective w/c and the capillary porosity promoting sulfate penetration. The use of active pozzolans suppresses the sulfate attack by minimizing both ettringite and gypsum formation. It is generally assumed that curing prior to sulfate exposure should be extended to allow the development of the pozzolanic reaction and subsequent reduction of portlandite content, pore size structure refinement and permeability reduction. However, in most field applications, concretes exposed to sulfate attack are cast in situ and thus, these are exposed to sulfate since early ages. This paper evaluates the sulfate resistance of an illitic-calcined clay and limestone filler when the cement is exposed immediately to aggressive environments. In this paper, the external sulfate resistance of blended cements containing 30% replacement of limestone filler and/or calcined clay (C30F, C30CC and C15F15CC) are analysed. Two different calcined clays from Buenos Aires, Argentina were selected. Mortar prisms and cement paste cubes were fabricated and exposed to a sodium sulfate solution after 2 days. Comparison of sulfate resistance was based on the expansion, mass variation, visual appearance and compressive strength. Furthermore, the evolution of microstructure of blended cements exposed to sodium sulfate solution was characterized by XRD tests on the external surface and the core of cementblended pastes.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Sulfate Resistance of Blended Cements (Limestone Illite Calcined Clay) Exposed Without Previous Curing

Rossetti¹,

Ikumi²,

Segura³

et al. 2020

XV International Conference on Durability of Building Materials and Components. eBook of Proceedings

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show abstract

“…The illitic calcined clay (ICC) meets the chemical requirements for Class N pozzolan (ASTM C 618): S+A+F > 70 %; SO3 < 4 % and LOI < 10 %. For this ICC, the Frattini test was positive after 14 days also strength test was made in another paper [6]. For this study, the SCM replacement in all binders was set to 30% by cement weight.…”

Section: Methodsmentioning

confidence: 99%

“…Illite is one of the most abundant clayed minerals of the earth's crust coming from the alteration of feldspars and micas of rocks due to the weathering process. Illite clays develop pozzolanic properties when clays are thermally treated at 950 °C [1] causing dehydroxylation and collapse of structure to form a metastable or amorphous aluminosilicate [2]. These pozzolanic properties combined with the large availability of this mineral place illite calcined clays as a key supplementary material for the future mineral admixtures used in concrete.…”

Section: Introductionmentioning

confidence: 99%

Performance of Blended Cements with Limestone Filler and Illitic Calcined Clay Immediately Exposed to Sulfate Environment

et al. 2020

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The use of ternary blended cements with limestone filler and calcined clays can improve the durability of concrete structures exposed to aggressive environments and extend their service life. In sulfate-rich environments, the effects of supplementary cementitious materials depend on the replacement level and the progress of hydration. Low level of limestone filler contributes to the stabilization of AFt due to formation of monocarboaluminate. However, high replacement increases the effective w/c ratio and the capillary porosity, favoring the sulfate penetration. The use of active pozzolans improves sulfate resistance by reducing portlandite content and the permeability, which minimize ettringite and gypsum formation and sulfate penetration. It is generally assumed that curing prior to sulfate exposure should be extended to allow the pozzolanic reaction to progress. It is currently uncertain the effectiveness of calcined clay in combination with limestone filler when the cement is exposed immediately to aggressive environments. Typical structures affected by sulfate attack are commonly build in situ, thus being exposed to the aggressive environment since casting. This paper analyses external sulfate attack of blended cements with 30 % replacement by combinations of limestone filler and/or calcined clay exposed to Na2SO4 solution at two days after casting. For that, expansions, mass variation, visual appearance and compressive strength are monitored in mortars and pastes during 6 months. The evolution of microstructure was evaluated with XRD. Despite the lack of curing prior to sulfate exposure, cement with calcined clay showed an excellent resistance to external sulfate attack, while limestone cements presented a worse performance.

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“…Illit is one of the minerals which show practically no pozzolanic properties in their raw state. Heat treatment carried out at high temperatures (930–950 °C) both pure mineral with small admixtures [ 33 ] as well as clays with a dominant share of illite [ 34 ] leads to a material with moderate pozzolanic activity. The dehydroxylation process itself, occurring at a lower temperature, does not lead to activation of the illite and formation of a material with a positive value of hydraulic index whereas, at the temperature that causes the destruction of its structure, a partial recrystallization of the resulting amorphous phase takes place at the same time, which reduces the potential pozzolanic activity of this mineral.…”

Section: Characteristic Of Clay Mineralsmentioning

confidence: 99%

Calcined Clay as Supplementary Cementitious Material

2020

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Calcined clays are the only potential materials available in large quantities to meet the requirements of eco-efficient cement-based materials by reducing the clinker content in blended cements or reducing the cement content in concrete. More than 200 recent research papers on the idea of replacing Portland cement with large amounts of calcined clay are presented and discussed in detail. First, the fundamental information about the properties and structure of clay minerals is described. Then, the process of activation and hydration of clays is discussed, including the methods of pozzolanic activity assessment. Additionally, various testing methods of clays from different worldwide deposits are presented. The application of calcined clay in cement and concrete technology is then introduced. A separate chapter is devoted to lime calcined clay cement. Then an influence of calcined clay on durability of concrete is summarized. Finally, conclusions are formulated.

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Calcined Illitic Clays as Portland Cement Replacements

Cited by 17 publications

References 6 publications

Sulfate Resistance of Blended Cements (Limestone Illite Calcined Clay) Exposed Without Previous Curing

Sulfate Resistance of Blended Cements (Limestone Illite Calcined Clay) Exposed Without Previous Curing

Performance of Blended Cements with Limestone Filler and Illitic Calcined Clay Immediately Exposed to Sulfate Environment

Calcined Clay as Supplementary Cementitious Material

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