Mechanical and microstructural changes in reactive magnesium oxide cement-based concrete mixes subjected to high temperatures

Hay, Rotana; Dũng, Nguyễn Tiến; Lesimple, Alain; Unluer, Cise; Çelik, Kemal

doi:10.1016/j.cemconcomp.2021.103955

Cited by 42 publications

(2 citation statements)

References 80 publications

(135 reference statements)

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“…The thermal destruction of serpentines leads to the formation of magnesium-containing phases prone to hydration [30]. In studies on optimizing the composition of magnesia binders, magnesium oxide hydration is considered a key link in the formation of the strength of magnesia stone [31]. When interacting with water vapors, the amount of adsorbed water depends on the chemical nature of the magnesium-containing phases and the value of the particle's surface [30,32].…”

Section: Interaction Of Heat-treated Serpentines With Water Vaporsmentioning

confidence: 99%

Magnesium Silicate Binding Materials Formed from Heat-Treated Serpentine-Group Minerals and Aqueous Solutions: Structural Features, Acid-Neutralizing Capacity, and Strength Properties

et al. 2022

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The influence of structural features of three serpentine-group minerals (antigorite, chrysotile, and lizardite) on the hydration of heat-treated materials and the formation of magnesium silicate binder has been studied. Initial serpentine samples have been fired in the interval 550–800 °C with a step of 50 °C; acid neutralization capacity (ANC) values have been determined for all samples. Antigorite samples (SAP) have exhibited a maximum reactivity at a temperature of 700 °C (ANC 7.7 meq/g). We have established that the acid-neutralizing capacity of chrysotile and lizardite samples in the temperature range of 650–700 °C differ slightly; the capacity varied in the interval of 19.6–19.7 meq/g and 19.6–19.7 meq/g, respectively. The samples obtained at optimal temperatures (antigorite—700 °C, lizardite, and chrysotile—650 °C) have been studied. Heat-treated serpentines have interacted with water vapor for a year; serpentine hydration has been investigated. The strength characteristics of the resulting binder agents were studied after 7, 28, 180, and 360 days. Upon hardening within 7 days, the strengths of the SAP and SCH samples have been almost the same (2.2 MPa), whereas this indicator for the SLH and SLK samples has been significantly lower (0.5 MPa). After hardening for over a year, the chrysotile sample SCH had the highest strength (about 8 MPa), whereas the strength of antigorite SAP was 3 MPa. The samples of initial, heat-treated, and hydrated heat-treated serpentines have been studied using XRD, differential scanning calorimetry, and surface texture analysis. The serpentine structure is crucial in destroying the mineral crystal lattice during heat treatment. In contrast to heat-treated chrysotile and lizardite, antigorite did not adsorb water. Structural features of chrysotile provided the highest compressive strength of the binding agent compared with antigorite and lizardite. The acid-neutralizing ability of lizardite was noticeably higher than antigorite, whereas its compressive strength was lower due to the layered mineral structure and impurities. We have established that the minerals’ structural features are crucial for the hydration of heat-treated serpentines; the structure determines material utilization in various environmental technologies.

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Section: Interaction Of Heat-treated Serpentines With Water Vaporsmentioning

confidence: 99%

Magnesium Silicate Binding Materials Formed from Heat-Treated Serpentine-Group Minerals and Aqueous Solutions: Structural Features, Acid-Neutralizing Capacity, and Strength Properties

et al. 2022

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“…Their results showed clearly defined data assignments for each phase, though this may also be attributed to the morphology of phases in the material's microstructure. 5 SNI and other grid nanoindentation methods continue to be a relevant tool for evaluating cementitious materials as seen in a number of recent studies, 6,[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] and this study seeks to improve the reliability of these methods without the use of complimentary microscopy of each indent that has previously been recommended. 39,40 We hypothesize that violations of continuity assumptions (i.e., additional sources of structural compliance, C s ) can have a significant effect on the outcomes of SNI methods in materials where the complexity is on the same scale as the interaction volume of indents.…”

Section: F I G U R Ementioning

confidence: 99%

On the role of continuity in statistical nanoindentation of composite microstructures

2022

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The validity of the statistical nanoindentation (SNI) technique for cementitious materials has been questioned by numerous researchers; however, it is still a commonly used method in literature. This study revisits assumptions pertaining to continuum mechanics of the method by using a well-established selective SNI method to evaluate continuity in the mechanical response of each indent. Ordinary portland cement (OPC) was investigated alongside a two-phase aluminosilicate ceramic (Al-Si). Filtering for continuity of indents eliminated a majority of indents in each sample. The indents meeting continuity requirements in the OPC sample had moduli values in the range of documented calcium silicate hydrates and portlandite-the predominant hydration phases in OPC. In the Al-Si sample, 73% of continuous indents were assigned to a mullite phase, although the chemical analysis showed only 42% mullite. This was attributed to the embedded morphology of the mullite phase, which made it more susceptible to structural compliance. These observations suggest that SNI may be ineffective for measuring the mechanical properties of individual phases in a microstructure if they are not prolific enough to exhibit a continuous indent response. Discontinuous indents due to microstructural interaction between phases were also shown to have a potential influence on the number of clusters (i.e., phases) suggested by the deconvolution algorithms.

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Atmospheric Corrosion of AZ31B Magnesium Alloy in the Antarctic Low-Temperature Environment

Shi,

Cui,

et al. 2023

Acta Metall. Sin. (Engl. Lett.)

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Mechanical and microstructural changes in reactive magnesium oxide cement-based concrete mixes subjected to high temperatures

Cited by 42 publications

References 80 publications

Magnesium Silicate Binding Materials Formed from Heat-Treated Serpentine-Group Minerals and Aqueous Solutions: Structural Features, Acid-Neutralizing Capacity, and Strength Properties

Magnesium Silicate Binding Materials Formed from Heat-Treated Serpentine-Group Minerals and Aqueous Solutions: Structural Features, Acid-Neutralizing Capacity, and Strength Properties

On the role of continuity in statistical nanoindentation of composite microstructures

Atmospheric Corrosion of AZ31B Magnesium Alloy in the Antarctic Low-Temperature Environment

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