Microstructural characterisation of hybrid cement after exposure to high temperatures

Qu, Bo; Martı́n, A.; Pastor, J.Y.; Palomo, A.; Jiménez, Ana Fernández

doi:10.1016/j.conbuildmat.2020.120843

Cited by 20 publications

(7 citation statements)

References 52 publications

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“…The H-WG T25-2 pastes exhibited greater strength than the HN T25-2 pastes due to the extra soluble silica (sourced from the WG) in the medium and the early formation of reaction product [53,57,58]. As expected, an inverse relationship was observed between compressive strength and mean pore size (see Table 5), a finding consistent with earlier reports [59][60][61].…”

Section: Hybrid Cement Paste Compressive Strength and Mean Size Poresupporting

confidence: 90%

Hybrid Cements: Mechanical Properties, Microstructure and Radiological Behavior

et al. 2022

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The use of more eco-efficient cements in concretes is one of the keys to ensuring construction industry sustainability. Such eco-efficient binders often contain large but variable proportions of industrial waste or by-products in their composition, many of which may be naturally occurring radioactive materials (NORMs). This study explored the application of a new gamma spectrometric method for measuring radionuclide activity in hybrid alkali-activated cements from solid 5 cm cubic specimens rather than powder samples. The research involved assessing the effect of significant variables such as the nature of the alkaline activator, reaction time and curing conditions to relate the microstructures identified to the radiological behavior observed. The findings showed that varying the inputs generated pastes with similar reaction products (C-S-H, C-A-S-H and (N,C)-A-S-H) but different microstructures. The new gamma spectrometric method for measuring radioactivity in solid 5 cm cubic specimens in alkaline pastes was found to be valid. The variables involved in hybrid cement activation were shown to have no impact on specimen radioactive content. The powder samples, however, emanated 222Rn (a descendent of 226Ra), possibly due to the deformation taking place in fly ash structure during alkaline activation. Further research would be required to explain that finding.

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Section: Hybrid Cement Paste Compressive Strength and Mean Size Poresupporting

confidence: 90%

Hybrid Cements: Mechanical Properties, Microstructure and Radiological Behavior

et al. 2022

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“…Wollastonite formation from β-C 2 S and leftover silica in the raw materials was also responsible for the considerable decrease in belite peak intensity at the higher temperature of 1200 °C as explained in the study by El-Didamony et al [ 56 ]. As reported by Qu et al [ 57 ], a balance favoring β-C 2 S over wollastonite is related to a Ca/Si ratio of 3. For ordinary Portland cement (OPC), a Ca/Si ratio of 3.2 resulted in belite and lime, while a ratio lower than 2 resulted in gehlenite and wollastonite at 800 °C, as the alkali content lowered the crystallization temperature.…”

Section: Resultsmentioning

confidence: 53%

Production of Belite Based Clinker from Ornamental Stone Processing Sludge and Calcium Carbonate Sludge with Lower CO2 Emissions

et al. 2022

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Environmental concerns have come to the forefront due to the substantial role of the cement industry in the extraction and expenditure of natural resources. Additionally, industrial processes generate a considerable amount of waste, which is frequently disposed of inadequately. The objective of this study was to evaluate the simultaneous use of ornamental rock processing sludge and calcium carbonate sludge generated from the kraft process in the production of belitic clinker. These waste materials would be used in total or partial substitution of natural raw materials, namely, limestone and clay. Several formulations were produced and sintered at 1100 and 1200 °C. The raw materials were characterized physico-chemically and thermogravimetrically, with subsequent evaluation of the resulting dosed raw mixes. Mineral analyses determined that the mixtures with limestone and clay in substitution ratios of 95% and 100%, respectively, and sintered at 1100 °C have the potential to produce belite-rich clinkers. This temperature is considerably lower than those reported in reference studies. Additionally, full limestone and clay substitution could result in a 23.92% reduction in carbon dioxide in clinker production. The results confirmed the potential use of ornamental rock processing sludge and calcium carbonate sludge as viable alternative materials for cement production and, consequently, could contribute to a reduction in the negative environmental impacts of this industry.

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“…Qu et al determined the mineralogical and microstructural changes taking place in a hybrid alkaline cement exposed to high temperatures and the mechanical strength was determined after cooling. The results showed that the hybrid cement pastes had higher residual strength than the reference PC and better post-thermal performance after reaching temperatures of over 800 • C. The above was attributed to the recrystallization of scantly hydraulic phases, such as gehlenite and rankinite [34].…”

Section: Introductionmentioning

confidence: 95%

Hybrid Cements with ZnO Additions: Hydration, Compressive Strength and Microstructure

et al. 2022

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The effect of ZnO has already been studied for Portland cement, but the study of its impact on hybrid pastes is scarce. Thus, in this investigation, the influence of ZnO addition on hydration, compressive strength, microstructure, and structure of hybrid pastes is presented. The analyses were made by setting time tests, compressive strength tests, X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis with differential scanning calorimetry, and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. The results indicate that the setting time of the cements was delayed up to 39 min with additions of 3 wt% ZnO. Alternatively, the higher values of compressive strength were observed when 0.5 wt% ZnO was added to the cements for all curing days. In addition, no important differences in the microstructure of samples with different additions of ZnO were observed after 28 days of curing. It is expected that the use of ZnO contributes to the delay of the setting time and the increase of the compressive strength without negatively modifying the microstructure of hybrid pastes.

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Microstructural characterisation of hybrid cement after exposure to high temperatures

Cited by 20 publications

References 52 publications

Hybrid Cements: Mechanical Properties, Microstructure and Radiological Behavior

Hybrid Cements: Mechanical Properties, Microstructure and Radiological Behavior

Production of Belite Based Clinker from Ornamental Stone Processing Sludge and Calcium Carbonate Sludge with Lower CO2 Emissions

Hybrid Cements with ZnO Additions: Hydration, Compressive Strength and Microstructure

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