Alkali-activated calcined smectite clay blended with waste calcium carbonate as a low-carbon binder

Valentini, Luca; Contessi, Silvia; Dalconi, Maria Chiara; Zorzi, Federico; Garbin, Enrico

doi:10.1016/j.jclepro.2018.02.249

Cited by 42 publications

(29 citation statements)

References 46 publications

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“…The results obtained are within the accepted limits for semi-adiabatic calorimetry (RILEM, 1997). The detailed procedure is described elsewhere (Valentini et al , 2018). The remaining paste was placed in Teflon moulds and cured at 95% relative humidity and ambient temperature for 3 days.…”

Section: Experimental Methods and Materials Characterizationmentioning

confidence: 99%

Potential use of Kebilian clay reserves(southern Tunisia)for the production of geopolymer materials

et al. 2020

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The aim of this study was to help drive the Tunisian construction industry towards a more sustainable approach given the existence of abundant local raw material deposits that could be exploited for the production of low-CO2 binders. Various clay sediments from the Kebili region (southern Tunisia) were characterized by chemical analysis, X-ray diffraction, thermal analysis and geotechnical tests to determine their suitability for the preparation of geopolymer binders. The clays consist of illite and kaolinite with other accessory minerals. To test the possibility of using these materials as precursors for the production of low-CO2 and low-cost geopolymers, the raw samples were calcined and activated by addition of solid sodium silicate. Compressive strength tests performed on four alkali-activated clays show that promising mechanical performance may be achieved, with mechanical strength values as high as 25 MPa after 7 days, depending on the clay composition. The mechanical strength is related to the SiO2:Al2O3 and Al2O3:(NaO2 + K2O) ratios. Careful selection of the raw materials is, therefore, an essential step in the exploitation of clay deposits to be used for the production of ecological materials such as geopolymers.

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Section: Experimental Methods and Materials Characterizationmentioning

confidence: 99%

Potential use of Kebilian clay reserves(southern Tunisia)for the production of geopolymer materials

et al. 2020

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“…The selection of precursors available for use in alkali-activation has also broadened significantly in recent years, with particular emphasis being placed upon the use of materials for which there is not strong competition in demand from utilization in blends with Portland cement. For example, calcined non-kaolinitic clays [17][18][19][20], palm oil fuel ash [21,22] or other minerals [23][24][25][26], have been shown to yield alkali-activated binder systems with technical properties that are attractive in given applications. Various industrial by-products or wastes without current large-scale utilization as supplementary cementitious materials have been tested and validated for use in alkali-activated binders, including red mud [27][28][29] and various glassy wastes including slags, some of which can benefit from thermal re-processing or modification to improve their reactivity before use [10,[30][31][32][33][34][35].…”

Section: Precursorsmentioning

confidence: 99%

Recent progress in low-carbon binders

Shi

Provis

2019

Cement and Concrete Research

467

131

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The development of low-carbon binders has been recognized as a means of reducing the carbon footprint of the Portland cement industry, in response to growing global concerns over CO2 emissions from the construction sector. This paper reviews recent progress in the three most attractive low-carbon binders: alkali-activated, carbonate, and belite-ye'elimite-based binders. Alkali-activated binders/materials were reviewed at the past two ICCC congresses, so this paper focuses on some key developments of alkali-activated binders/materials since the last keynote paper was published in 2015. Recent progress on carbonate and belite-ye'elimite-based binders are also reviewed and discussed, as they are attracting more and more attention as essential alternative low-carbon cementitious materials. These classes of binders have a clear role to play in providing a sustainable future for global construction, as part of the available toolkit of cements.

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“…Such a fast reaction, restricted to the very early stage and followed by a much slower rate of reaction, is commonly observed in indirect experimental methods based on calorimetry performed on alkali-activated metakaolin and other calcined clays. 52−54…”

Section: Results and Discussionmentioning

confidence: 99%

Modeling Dissolution–Precipitation Kinetics of Alkali-Activated Metakaolin

Valentini

2018

ACS Omega

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The numerical model HydratiCA was used to simulate the reaction kinetics of alkali-activated metakaolin, a material belonging to a class of sustainable binders alternative to Portland cement. The full chemistry of the system, including solid phases and aqueous species, is taken into account in these simulations. Specifically, metakaolin dissolution, reaction product nucleation and growth, and ion speciation, and diffusion in solution are simulated. The sodium aluminosilicate (N–A–S–H), formed by the reaction of metakaolin in alkaline solution, is implemented in the model as a combination of co-precipitating pseudo-zeolitic phases, with variable stoichiometry. The results show how variations of the reaction pathways, occurring when alkaline activators of different composition and concentration are used, can be associated with different macroscopic behaviors in terms of mechanical performance and durability. Reconciling these macroscopic properties with the basic chemical processes will be a fundamental technological challenge for the deployment of sustainable technologies in the construction industry.

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Alkali-activated calcined smectite clay blended with waste calcium carbonate as a low-carbon binder

Cited by 42 publications

References 46 publications

Potential use of Kebilian clay reserves(southern Tunisia)for the production of geopolymer materials

Potential use of Kebilian clay reserves(southern Tunisia)for the production of geopolymer materials

Recent progress in low-carbon binders

Modeling Dissolution–Precipitation Kinetics of Alkali-Activated Metakaolin

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