Incorporation of Al in C-A-S-H gels with various Ca/Si and Al/Si ratio: Microstructural and structural characteristics with DTA/TG, XRD, FTIR and TEM analysis

Kapeluszna, Ewa; Kotwica, Łukasz; Różycka, Agnieszka; Gołek, Łukasz

doi:10.1016/j.conbuildmat.2017.08.091

Cited by 315 publications

(122 citation statements)

References 49 publications

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“…Samples synthesized using three different K 2 O/SiO 2 ratios were cured for 7 days at 95 • C, and the TG/DTG curves showed small mass loss peaks at 190 • C, 200 • C, and 250 • C, separately. Combined with the XRD results, the samples contained crystalline zeolite phases, indicating more tightly physically bound and/or loss of zeolite water [2,24]. These peaks were not present before 7 days of curing time, which indicates that rearrangement and structural ordering of the water-containing phases (e.g., zeolites) persisted from the 3rd day to the 7th day of curing time as the reaction progressed.…”

Section: Thermogravimetric Analysismentioning

confidence: 81%

Insights into the Microstructure of Hydrothermal Synthesized Nanoscale K2O-Al2O3-SiO2-H2O Particles

et al. 2019

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K-A-S-H (K2O-Al2O3-SiO2-H2O) gel is a key phase that forms in most alkali-activated binders (eco-friendly binders which utilize a substantial amount of industrial by-product). An in-depth understanding of the microstructure and performance of this nano-sized key phase facilitates better application to alkali-activated binders. However, such studies remain little and undetailed. Therefore, our research aims to provide insights into the microstructure of K-A-S-H particles synthesized with accurate stoichiometric control by the hydrothermal method through thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and BET surface area. The results show that for materials prepared at the curing temperature lower than 80 °C, the K-A-S-H products were completely amorphous. With increased curing temperature and time, the K-A-S-H products were transformed from the amorphous phase to the crystalline zeolite phase structure, with a reduction in the specific surface area. The TG results indicate that the crystalline phase contains more non-evaporated water or zeolite water for structural rearrangement. The degree of tetrahedral polymerization slightly decreased with an increase of the K2O/SiO2 ratio as the amount of non-bridged oxygen atoms increased, whereas it gradually increased with an increase of curing temperature and time, as suggested by the FTIR and NMR results. Various K2O/SiO2 ratios resulted in the formation of zeolite K-H and K-G zeolite, both of which exhibited highly polymerized three-dimensional network structures. However, there was no significant effect of the SiO2/Al2O3 ratio on the structure of K-A-S-H products. Overall, these results provide insight into understanding the chemical stability of K-A-S-H.

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Section: Thermogravimetric Analysismentioning

confidence: 81%

Insights into the Microstructure of Hydrothermal Synthesized Nanoscale K2O-Al2O3-SiO2-H2O Particles

et al. 2019

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“…As reported, the primary cement hydration products are C–S–H and C–A–S–H gels . In addition, many works found that C–A–S–H gels could effectively increase both average chain length and toughness of C–S–H gels . Interestingly, the pozzolanic reaction of LWFA dissolved large amounts of Al 3+ ions, which made it necessary to determine whether the Al 3+ ions could participate in cement hydration to modify the C–S–H gels.…”

Section: Resultsmentioning

confidence: 98%

“…30,31 In addition, many works found that C-A-S-H gels could effectively increase both average chain length and toughness of C-S-H gels. 32,33 Interestingly, the pozzolanic reaction of LWFA dissolved large amounts of Al 3+ ions, which made it necessary to determine whether the Al 3+ ions could participate in cement hydration to modify the C-S-H gels. For this purpose, 29 Si NMR was carried out for cement pastes Figure 5.…”

Section: Pozzolanic Reactivity Of Lwfamentioning

confidence: 99%

Heat‐cured concrete: Improving the early strength and pore structure by activating aluminosilicate internal curing agent with triisopropanolamine

Liu

et al. 2019

J Am Ceram Soc

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Although heat‐cured concrete (HCC) has received extensive research interests in recent years, it still suffers from problems including coarsened microstructure, low cement hydration degrees, etc, which limited its application. Some of these problems can be solved by internal curing method resulting in low early strength of HCC and low‐production efficiency. This study addressed this issue by activating the aluminosilicate internal curing agent (lightweight fine aggregate, LWFA) with triisopropanolamine (TIPA). The results indicated that more Al3+ and Fe3+ ions were dissolved from LWFA by TIPA, which assisted the formation of hydrates with cement ions in interfacial transition zone (ITZ), and enhanced the density of ITZ in the early stage. The introduction of TIPA was found to increase the early compressive strength of HCC, by approximately 15.3%, 25.9% and 28.0%, respectively for the cement cured for 1, 3, and 7 days compared with control samples. Moreover, the results of rapid chloride migration and water absorption depth also suggested that coupling the aluminosilicate internal curing agent with TIPA improved the pore structure of HCC.

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“…Intuitively, these films can obstruct the dissolution of Ca 2+ and its diffusion outward the particle on one hand. On the other hand, the bond of calcium with the polymers (eg, acetate anions (CH3COO) − ) will restrict more calcium in the hydration products layer, and reduce the calcium for CH formation . Both the surface barrier and chemical bond effect eventually lead to the higher Ca/Si ratio in the hydration products layers and the less CH forming in the surrounding areas.…”

Section: Xrd/eds/sem Results and Further Discussionmentioning

confidence: 99%

BSE‐IA reveals retardation mechanisms of polymer powders on cement hydration

Zeng

et al. 2020

J Am Ceram Soc

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The retardation effects of two polymer powders, styrene butadiene rubber and ethylene‐vinyl acetate, on cement hydration and the mechanisms in terms of hydration degree and microstructure characteristics were investigated by the combination of backscattered electron image analysis, scanning electron microscopy, energy dispersive spectrometer, and X‐ray diffraction. Results show that the cement hydration can be significantly retarded by both polymers with the reductions in cement hydration degrees and hydration products thickness. Polymers retard cement hydration by agglomerating the polymer particles on the surfaces of cement grains, forming films in different thickness and bonding the calcium ions in the pore solutions. Consequentially, the formation of C‐S‐H and CH is depressed and the Ca/Si ratios in the hydration product layer are raised. The retardation is enhanced with the increase in polymer content. This work helps understand the retardation effect of polymers on cement hydration in depth, which enables rational development of polymer‐modified cement‐based materials for further applications.

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Incorporation of Al in C-A-S-H gels with various Ca/Si and Al/Si ratio: Microstructural and structural characteristics with DTA/TG, XRD, FTIR and TEM analysis

Cited by 315 publications

References 49 publications

Insights into the Microstructure of Hydrothermal Synthesized Nanoscale K2O-Al2O3-SiO2-H2O Particles

Insights into the Microstructure of Hydrothermal Synthesized Nanoscale K2O-Al2O3-SiO2-H2O Particles

Heat‐cured concrete: Improving the early strength and pore structure by activating aluminosilicate internal curing agent with triisopropanolamine

BSE‐IA reveals retardation mechanisms of polymer powders on cement hydration

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