Recent progress in low-carbon binders

Shi, Caijun; Qu, Bo; Provis, John L.

doi:10.1016/j.cemconres.2019.05.009

Cited by 467 publications

(155 citation statements)

References 370 publications

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“…However, it is worth to notice the presence of belite in this sample. This phase was not found in previous works using the proposed stabilization methods [41] and is generally present as an additional main mineralogical component of calcium sulfoaluminate cement, which can be obtained by using FA [42]. Then its presence, although it was not expected, can be justified by previous works.…”

Section: Xrd Patternmentioning

confidence: 71%

A Circular Economy Virtuous Example—Use of a Stabilized Waste Material Instead of Calcite to Produce Sustainable Composites

et al. 2020

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This work reports and analyzes the mechanical properties of some composites obtained using stabilized waste with epoxy resins E-227. For comparison, correspondent composite samples were realized using calcite as a filler. The recovered stabilized waste was obtained by means of a new method to stabilize municipal solid waste incineration (MSWI) fly ash (FA), based on the use of bottom ash (BA). The aim of this paper is to show that the stabilization process, which can be considered a zero—waste treatment, produces inert materials, that can be reused as a filler. The production of new filler was made on a pilot plant, designed to verify the transferability of the proposed stabilization technology. Mechanical analysis revealed that flexural modulus raises by increasing the filler content around 30% wt, independently of filler type, stabilized sample or calcium carbonate. Mechanical properties are lower in the samples with the high amount of filler due to the crowding effect. The morphology of composite materials showed a non-homogeneous dispersion of particles in stabilized sample filler, characterized by large particle agglomerates. Finally, according to the ESCAPE simplified method, the obtained composites result more sustainable in comparison with the corresponding ones produced by using natural resources (like calcite). These findings open new possibilities for the reuse of the stabilized material, in frame of circular economy principles, with environmental and economic advantages.

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Section: Xrd Patternmentioning

confidence: 71%

A Circular Economy Virtuous Example—Use of a Stabilized Waste Material Instead of Calcite to Produce Sustainable Composites

et al. 2020

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“…In recent years, as cement production is facing challenges of CO 2 emission and a shortage of raw materials, alkali-activated materials (AAMs) or geopolymers are attracting increasing attention as an alternative binder to ordinary Portland cement (OPC) [1,2]. AAMs are developed via alkaline activating of the solid aluminosilicates, such as fly ash, blast furnace slag, and mine tailings, at a high pH.…”

Section: Introductionmentioning

confidence: 99%

Effect of the Sodium Silicate Modulus and Slag Content on Fresh and Hardened Properties of Alkali-Activated Fly Ash/Slag

Ouyang

Liu

et al. 2019

Minerals

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This paper presents the results of an experimental study performed to investigate the effect of activator modulus (SiO2/Na2O) and slag addition on the fresh and hardened properties of alkali-activated fly ash/slag (AAFS) pastes. Four activator moduli (SiO2/Na2O), i.e., 0.0, 1.0, 1.5, and 2.0, and five slag-to-binder ratios, i.e., 0, 0.3, 0.5, 0.7, 1.0, were used to prepare AAFS mixtures. The setting time, flowability, heat evolution, compressive strength, microstructure, and reaction products of AAFS pastes were studied. The results showed that the activator modulus and slag content had a combined effect on the setting behavior and workability of AAFS mixtures. Both the activator modulus and slag content affected the types of reaction products formed in AAFS. The coexistence of N–A–S–H gel and C–A–S–H gel was identified in AAFS activated with high pH but low SiO2 content (low modulus). C–A–S–H gel had a higher space-filling ability than N–A–S–H gel. Thus, AAFS with higher slag content had a finer pore structure and higher heat release (degree of reaction), corresponding to a higher compressive strength. The dissolution of slag was more pronounced when NaOH (modulus of 0.0) was applied as the activator. The use of Na2SiO3 as activator significantly refined the pores in AAFS by incorporating soluble Si in the activator, while further increasing the modulus from 1.5 to 2.0 prohibited the reaction process of AAFS, resulting in a lower heat release, coarser pore structure, and reduced compressive strength. Therefore, in view of the strength and microstructure, the optimum modulus is 1.5.

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“…X-ray absorption near-edge structure allows determine the coordination number of Ti ( [4] -, [5] -and [6] Ti). The low-energy side of the absorption edge ( Figure 3) corresponds to the pre-edge, which is a specific feature, the intensity of which is enhanced for [4] Ti and [5] Ti sites, as compared to a [6] Ti site. The sensitivity of XANES allows investigate the proportion of Ti coordination numbers, 25,26 as shown in Figure 4.…”

Section: Ti K-edge Xanesmentioning

confidence: 99%

“…2 Within the scope of a circular economy imposed by the future scarcity of primary raw materials, 3 the waste produced by other industries may be used as low-CO 2 binders. 4 Among these secondary raw materials, Ground Granulated Blast-furnace Slags (GGBS) from steelmaking industry can be used as supplementary cementitious materials (SCM) for producing low carbon footprint cements ("green cements"). GGBS is an amorphous by-product obtained by rapid cooling under water of high temperature molten silicate slags.…”

Section: Introductionmentioning

confidence: 99%

Structural role of titanium on slag properties

Cornec

Galoisy

Izoret³

et al. 2020

J. Am. Ceram. Soc.

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The presence of titanium in ground granulated blast-furnace slags (GGBS) has been suspected to modify cement properties. This study provides the first evidence of a relation between the TiO 2 content of slags and the mechanical properties of mortars based on slag cements. It is observed that only the slags containing less than 1%TiO 2 show a compressive strength at 28 days that remains within the 52.5 MPa norm with CEM III cements complying with the European Standard NF EN 197-1. The structural origin of this chemical dependence of the performance of cements is investigated by determining directly the titanium speciation in various European slags by spectroscopic methods. Electron paramagnetic resonance indicates that about 76% of Ti in slag occurs as Ti 4+. The atomic structure around Ti was determined by Ti K-edge X-ray absorption near edge structure, which shows that Ti is mainly five-fold coordinated in square-based pyramid geometry. Five coordinated Ti acts as networkstabilizer of the silicate network as it increases the polymerization. Requiring Ca 2+ for charge-compensation of the titanyl bond, it reduces the availability of Ca 2+ during glass alteration in a modified random model of glass structure, where Ca 2+ atoms are clustered in percolating cationic domains. As a consequence, the presence of fivecoordinated Ti results in a slower dissolution of the slag. These peculiar structural properties of titanium may explain the detrimental role of Ti above a 1% concentration, for many physical and chemical slag properties. This work provides a scientific ground for the technological acceptability of the upper limit of the Ti-content of GGBS.

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Recent progress in low-carbon binders

Cited by 467 publications

References 370 publications

A Circular Economy Virtuous Example—Use of a Stabilized Waste Material Instead of Calcite to Produce Sustainable Composites

A Circular Economy Virtuous Example—Use of a Stabilized Waste Material Instead of Calcite to Produce Sustainable Composites

Effect of the Sodium Silicate Modulus and Slag Content on Fresh and Hardened Properties of Alkali-Activated Fly Ash/Slag

Structural role of titanium on slag properties

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