A novel upcycling technique of recycled cement paste powder by a two-step carbonation process

Fang, Xiaoliang; Xuan, Dongxing; Zhan, Baojian; Li, Weifeng; Poon, Chi Sun

doi:10.1016/j.jclepro.2020.125192

Cited by 50 publications

(14 citation statements)

References 35 publications

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“…The alumina-silica gel is amorphous in the view of powder XRD and exhibits a high surface area. Solid-state 27 Al and 29 Si NMR reveal that it is composed mainly of condensed Q 3 and Q 4 SiO4 tetrahedra with integrated AlO4 units in the structure. The carbonated cement paste can be successfully applied as a supplementary cementitious material to produce new composite cements.…”

Section: Discussionmentioning

confidence: 99%

“…The broad and featureless resonance after carbonation reflects the amorphous structure and is characteristic for alumina-silica gels formed by wet carbonation processes at the different conditions [30,46,47]. The decomposition of the C-(A)-S-H phase is also seen by 27 Al NMR (Figure 3) as the tetrahedral resonance (Al(IV)) from Al in this phase (~68 ppm) disappears upon carbonation and leads to the formation of a new resonance at approx. 58 ppm, which originates from Al(IV) sites in the alumina-silica gel (i.e., Al(O-Si)4 sites).…”

Section: Mechanisms Of Enforced Carbonationmentioning

confidence: 90%

“…The small Al(VI) peak after carbonation is attributed to hydrotalcite, which does not decompose up on wet carbonation [30,31]. The 27 Al and 29 Si NMR spectra clearly reveal the formation of an alumina-silica gel with Al(IV) integrated in the structure and not a pure silica gel as predicted by thermodynamic modelling [30] and proposed in an other study [29]. The formation of a similar gel has also been reported in a study of natural and accelerated carbonation of concrete [47].…”

Section: Mechanisms Of Enforced Carbonationmentioning

confidence: 99%

“…The enforced carbonation techniques were explored to modify the properties of the RCP, initially by Iizuka et al [20][21][22][23][24] and Ghacham et al [25,26]. Fang et al [27,28] have investigated a two-step wet-carbonation process which allows valorization of recycled cement paste into the added value products of calcite and alumina-silica gel. Lu et al [29] and Zajac et al [30][31][32][33] have applied CO2 mineralization to modify the recycled cement paste into a new supplementary cementitious material (SCM).…”

Section: Introductionmentioning

confidence: 99%

“…Figure3 13. C,27 Al and29 Si NMR spectra of a hydrated Portland cement (CEM-I) paste before and after enforced carbonation (360 min. ), acquired at 7.05, 14.09 and 7.05 T using spinning frequencies of 7.0, 13.0 and 7.0 kHz, respectively.…”

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CO2 mineralization of demolished concrete wastes into a supplementary cementitious material – a new CCU approach for the cement industry

2021

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This contribution discusses the carbon capture and utilization (CCU) approach based on CO2 mineralization of cement paste from recycled concrete as new approach to capture CO2 and significantly contribute to the reduction in CO2 emissions associated with cement production. The current literature suggests that all CO2 released from the decomposition of limestone during clinker production can be sequestered by carbonation of the end-of-life cement paste. This carbonation can be achieved in a few hours at ambient temperature and pressure and with a relatively low CO2 concentration (< 10 %) in the gas. The carbonation of cement paste produces calcite and an amorphous alumina-silica gel, the latter being a pozzolanic material that can be utilized as a supplementary cementitious material. The pozzolanic reaction of the alumina-silica gel is very rapid as a result of its high specific surface and amorphous structure. Thus, composite cements containing carbonated cement paste are characterized by a rapid strength gain. The successful implementation of this CCU approach relies also on improved concrete recycling techniques and methods currently under development to separate out the cement paste fines and such. Full concrete recycling will further improve the circular utilization of cement and concrete by using recycled aggregates instead of natural deposits of aggregates. Although the feasibility of the process has already been demonstrated at the industrial scale, there are still several open questions related to optimum carbonation conditions and the performance of carbonated material in novel composite cements.

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Section: Discussionmentioning

confidence: 99%

Section: Mechanisms Of Enforced Carbonationmentioning

confidence: 90%

Section: Mechanisms Of Enforced Carbonationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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CO2 mineralization of demolished concrete wastes into a supplementary cementitious material – a new CCU approach for the cement industry

2021

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Dissolution Behaviors of Recycled Cement Paste and Lime in EAF Slag Under Static Conditions

Yang,

Yan,

2024

Metall Mater Trans B

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Recycled cement paste (RCP) is a CaO-rich resource that is recycled from waste concrete and waste cement. For reducing environmental impact and promoting comprehensive resource utilization, RCP could partially replace lime as flux in electric arc furnace (EAF) steelmaking process. In this study, the dissolution behaviors of RCP and lime in EAF slag at 1400 °C and 1500 °C were investigated using static dissolution experiments. The measured dissolution rate constant of lime at 1400 °C and 1500 °C is 3.12×10−5 and 8.42×10−5 m/s, respectively, while that for RCP is 1.37×10−4 and 2.91×10−4 m/s, respectively. For the lime dissolution, a dense dicalcium silicate (C2S) product layer was generated at the dissolution interface, with the diffusion of Ca2+ in the C2S layer being the limiting step for the lime dissolution. However, for the RCP dissolution, no product layer was observed at the dissolution interface. Instead, a dissolution intermediate layer forms due to slag penetration. During the dissolution of RCP, Ca2+ and SiO44− diffuse from RCP layer to slag, while Fe2+ and AlO45− diffuse from slag to RCP layer accumulating in the dissolution intermediate layer. Furthermore, a dissolution model was developed based on current experimental results, which helps to predict dynamic dissolution process of lime and RCP in EAF slag. In general, the dissolution rate of RCP in EAF slag was much higher than that of lime, partially adding RCP as flux in EAF could accelerate the liquid slag formation in EAF steelmaking process.

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Microscopic mechanism analysis of the influence of stone powder with different replacement ratio on concrete performance

Tier

2022

Arab J Geosci

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A novel upcycling technique of recycled cement paste powder by a two-step carbonation process

Cited by 50 publications

References 35 publications

CO2 mineralization of demolished concrete wastes into a supplementary cementitious material – a new CCU approach for the cement industry

CO2 mineralization of demolished concrete wastes into a supplementary cementitious material – a new CCU approach for the cement industry

Dissolution Behaviors of Recycled Cement Paste and Lime in EAF Slag Under Static Conditions

Microscopic mechanism analysis of the influence of stone powder with different replacement ratio on concrete performance

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