The role of calcium silicates and quicklime on the reactivity of rehydrated cements

Angulo, Sérgio Cirelli; Guilge, Mario Sergio; Quarcioni, V. A.; Cincotto, Maria Alba; Nobre, Thiago Ricardo Santos; Pöllmann, Herbert

doi:10.1016/j.conbuildmat.2022.127625

Cited by 13 publications

(33 citation statements)

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“…This generates C-A-H (calcium aluminate hydrate) and C-S-H (calcium silicate hydrates), filling the pores in the curing of the material between the curing of the graphite tailing sand to become more dense and improve the permeability of the curing of the material. Its chemical reaction equation can be expressed as follows [34,35]:…”

Section: Analysis Of Permeability Coefficients Gt-clay Impermeability...mentioning

confidence: 99%

Performance and Heavy Metal Analysis of Graphite Tailings Cured Using Cementitious Materials

Jiang,

Wang

2024

Buildings

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The massive accumulation of graphite tailings causes serious environmental pollution, mainly from heavy metal pollution. Therefore, this article introduces a method of using graphite tailings as a high-content main material, cement as a small component of the auxiliary cementitious material, and clay as a substitute for cement. The compressive strength and permeability of graphite tailing–solidified material (GT, GT–Clay) were tested, and the effect of clay partially replacing cement as an auxiliary cementitious agent on GT–Clay performance was compared. In addition, inductively coupled plasma mass spectrometry (ICP) was used to analyze the effect of the graphite tailing placement time on the heavy metal content, as well as the changes in the GT heavy metal leaching concentration and its heavy metal content under outdoor freeze–thaw conditions. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to elucidate the microstructural changes in the GT–Clay. The experimental results show that, as the substitution of clay for cement increased from 0 to 50%, the compressive strength of the 90% GT–Clay gradually decreased, and the permeability also increased. The compressive strength of 95% GT–Clay did not show significant changes, but the permeability increased, and when mixed with quicklime, gypsum, and silica fume, the permeability decreased. The Ni and As in graphite tailings fluctuated significantly with the placement time. The heavy metal leaching concentrations of the 90% GT and 95% GT were below the standard limit, and Cd, As, and Ni in GT were potential sources of pollution. The analysis of the microscopic test results showed that the hydration products of the GT–Clay included ettringite, Ca(OH)2, and calcium silicate hydrates. The hydration product stabilized and filled the gaps between the tailing particles, thereby cementing them together. Not only did it improve the mechanical strength of GT, it also reduced the permeability and heavy metal leaching rate. This study provides a new analytical approach to applying graphite tailings for environmental treatment.

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Section: Analysis Of Permeability Coefficients Gt-clay Impermeability...mentioning

confidence: 99%

Performance and Heavy Metal Analysis of Graphite Tailings Cured Using Cementitious Materials

Jiang,

Wang

2024

Buildings

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“…Comparing to in situ mineralization, where CO 2 is mineralized in subsurface geological formations, ex situ mineralization often utilizes readily accessible industrial byproducts such as coal ash, iron, and steel slags, mine wastes, and tailings. − These byproducts represent significant CO 2 storage potentials, with mine wastes and tailings alone estimated to have a potential to sequester 1.1–4.5 Gt CO 2 per year . Furthermore, they tend to exhibit high reactivity because these mineral byproducts often contain finely ground particles and, in some cases, also a high amorphous content (e.g., high-temperature processed byproducts such as coal ash and slag), − which could facilitate CO 2 storage at reduced costs. As such, ex situ mineralization has been widely investigated. , …”

Section: Introductionmentioning

confidence: 99%

Enhancing Aqueous Carbonation of Calcium Silicate through Acid and Base Pretreatments with Implications for Efficient Carbon Mineralization

Zhai,

Chen,

Yilmaz

et al. 2023

Environ. Sci. Technol.

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Carbon dioxide (CO 2 ) mineralization based on aqueous carbonation of alkaline earth silicate minerals is a promising route toward large-scale carbon removal. Traditional aqueous carbonation methods largely adopt acidification-based approaches, e.g., using concentrated/pressurized CO 2 or acidic media, to accelerate mineral dissolution and carbonation. In this study, we designed and tested three distinctive routes to evaluate the effect of pretreatments under different pH conditions on aqueous carbonation, using amorphous calcium silicate (CS) as an example system. Pretreating CS with high concentrations (100 mM) of HCl (Route I) or NaOH (Route II and III) enhanced their carbonation degrees. However, NaOH pretreatment overall yielded higher carbonation degrees than the HCl pretreatment, with the highest carbonation degree achieved through Route III, where an extra step is taken after the NaOH pretreatment to remove the solution containing dissolved silica prior to carbonation. The HCl and NaOH pretreatments formed different intermediate silica products on the CS surface. Silica precipitated from the HCl pretreatment had a minimal effect on the carbonation degree. The high Ca/Si ratio intermediate phases formed from the NaOH, on the other hand, can be readily carbonated. In contrast to commonly utilized acidification-based approaches, basification offers a more promising route to accelerate aqueous carbonation as it can mitigate the need for costly pH swing and high-concentration/pressurized CO 2 . The key to aqueous carbonation under basic conditions, as suggested by this study, is the control of aqueous silica species that have a suppressing effect on carbonation. Overall, this study highlights the critical needs for investigations of aqueous mineral carbonation in a broader pH region.

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“…Table 1 presents the composition of anhydrous OPC and OPC paste at 28 days (water/cement ratio of 0.80 g/g) through Rietveld refinement of XRD (ANGULO et al, 2022).…”

Section: Portland Cement Hydrationmentioning

confidence: 99%

“…However, a basic understanding of pure cementitious pastes is still required (XU et al, 2022). When subjected to heat treatment, the hydrated products (e.g., ettringite, other calcium aluminates, portlandite and C-S-H phases) have their free and chemically combined water partially or totally removed (CASTELLOTE et al, 2004;VYŠVAŘIL et al, 2014;REAL et al, 2020;ANGULO et al, 2022;BOGAS et al, 2022;LÜ;HU, 2008). Two critical temperatures and the associated processes were identified (ALONSO; FERNANDEZ, 2004): (i) above 450 °C, portlandite dehydrates may form quick lime (a high water reactive compound that is not always desirable as a cementitious material), and (ii) approximately 650 ºC, calcite decomposes to generate CO2 .…”

Section: Introductionmentioning

confidence: 99%

“…When anhydrous calcined fines are exposed to water again, they rapidly regain chemically bound water (XINWEI;ZHAOXIANG;XUEYING, 2010;ANGULO et al, 2015a;LIMA PACHECO et al, 2021). The R-PC generates a large amount of heat in the first few minutes of rehydration as ordinary Portland cement (OPC) (ANGULO et al, 2015a), recovering combined water in C-S-H (ANGULO et al, 2022), in part of the CaO (quicklime) formed (MENÉNDEZ;ANDRADE;VEGA, 2012). The morphologies of the hydrated and rehydrated phases are significantly different (WANG;MU;.…”

Section: Introductionmentioning

confidence: 99%

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Cimento Portland Reciclado (R-PC): redução da demanda de água, análise ambiental e uso como ligante otimizado.

Oliveira

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This part is mostly for my family, so it is written in Portuguese.Meu primeiro agradecimento é destinado à minha família. Sendo assim, eu gostaria de expressar minha mais profunda gratidão aos meus pais, Flávia e Paulo. Seu amor, apoio e ensinamentos são o alicerce sobre o qual construo minha jornada. Estendo este agradecimento inicial ao meu irmão, Lucas, por seu apoio que apesar de expresso de forma singular, se fez presente. Agradeço à minha noiva, Fernanda, por todo o apoio, presença, disponibilidade e amor ao longo desta trajetória repleta de desafios. Não tenho capacidade de expressar em palavras tamanha gratidão e amor por todos vocês. Meu segundo agradecimento é dedicado a todos os professores que desempenharam um papel fundamental na minha busca por conhecimento. Em especial, gostaria de expressar minha gratidão à Prof. Heloísa Cordon, que me apresentou ao fascinante mundo dos materiais cimentícios. Ao Prof. Leandro Sanchez, cujo intercâmbio foi um divisor de águas e me mostrou que o meu verdadeiro caminho era seguir com o mestrado. Ao Prof. Vanderley John, de quem sempre me inspirei a 'pensar fora da caixa.' E, sobretudo, ao Prof. Sérgio Angulo, meu orientador e amigo, que desempenhou um papel fundamental na minha evolução nessa área que tanto amo. Meu terceiro agradecimento é geral, direcionado a todos que, de alguma forma, contribuíram ao longo deste trabalho. Agradeço aos colegas de pós-graduação e aos profissionais da USP. Também gostaria de expressar minha gratidão ao Laboratório de Tratamento de Minérios e Resíduos Industriais (LTM) pelo auxílio na moagem das pastas. Ao Departamento de Engenharia Metalúrgica e de Materiais (PMT), agradeço a assistência na realização das porosimetrias de mercúrio. Quero também agradecer ao Instituto de Pesquisas Tecnológicas (IPT) pela disponibilidade na realização das calorimetrias. Por fim, um agradecimento especial ao Laboratório de Microestrutura (LME), ao Innovandi Global Cement and Concrete Research Network e ao National Institute on Advanced Eco-efficient Cementbased Technologies (CEMtec). EPIGRAPH"A curiosidade é a fome do intelecto."

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The role of calcium silicates and quicklime on the reactivity of rehydrated cements

Cited by 13 publications

References 46 publications

Performance and Heavy Metal Analysis of Graphite Tailings Cured Using Cementitious Materials

Performance and Heavy Metal Analysis of Graphite Tailings Cured Using Cementitious Materials

Enhancing Aqueous Carbonation of Calcium Silicate through Acid and Base Pretreatments with Implications for Efficient Carbon Mineralization

Cimento Portland Reciclado (R-PC): redução da demanda de água, análise ambiental e uso como ligante otimizado.

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