Pressure induced reactions amongst calcium aluminate hydrate phases

Moon, Juhyuk; Oh, Jae Eun; Balonis, Magdalena; Glasser, F. P.; Clark, S. M.; Monteiro, Paulo J.M.

doi:10.1016/j.cemconres.2011.02.004

Cited by 37 publications

(36 citation statements)

References 22 publications

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“…The wider dispersion of cracks causes a load redistribution, so that additional energy is absorbed by a diffuse network of microcracks rather than a single localized macrocrack (46). Although strätlingite crystals have relatively low bulk modulus [about 23 GPa, compared with 34 GPa for C-A-S-H with Ca/(Si+Al) = 0.72 in slag concrete (47,48)] they evidently play a role in impeding the propagation of microcracks in Roman architectural mortar, similar to polypropylene microfibers with low elastic modulus interground with cement in present-day mortars (40). Three principal differences exist between authigenic strätlingite crystals in Roman mortar and microfiber additives in present-day cement pastes.…”

Section: Role Of Pyroclastic Rock In Concrete Durabilitymentioning

confidence: 99%

Mechanical resilience and cementitious processes in Imperial Roman architectural mortar

Jackson¹,

Landis

Brune

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

178

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The pyroclastic aggregate concrete of Trajan's Markets (110 CE), now Museo Fori Imperiali in Rome, has absorbed energy from seismic ground shaking and long-term foundation settlement for nearly two millenia while remaining largely intact at the structural scale. The scientific basis of this exceptional service record is explored through computed tomography of fracture surfaces and synchroton X-ray microdiffraction analyses of a reproduction of the standardized hydrated lime-volcanic ash mortar that binds decimeter-sized tuff and brick aggregate in the conglomeratic concrete. The mortar reproduction gains fracture toughness over 180 d through progressive coalescence of calcium-aluminum-silicate-hydrate (C-A-S-H) cementing binder with Ca/(Si+Al) ≈ 0.8-0.9 and crystallization of strätlingite and siliceous hydrogarnet (katoite) at ≥90 d, after pozzolanic consumption of hydrated lime was complete. Platey strät-lingite crystals toughen interfacial zones along scoria perimeters and impede macroscale propagation of crack segments. In the 1,900-y-old mortar, C-A-S-H has low Ca/(Si+Al) ≈ 0.45-0.75. Dense clusters of 2-to 30-μm strätlingite plates further reinforce interfacial zones, the weakest link of modern cement-based concrete, and the cementitious matrix. These crystals formed during long-term autogeneous reaction of dissolved calcite from lime and the alkali-rich scoriae groundmass, clay mineral (halloysite), and zeolite (phillipsite and chabazite) surface textures from the Pozzolane Rosse pyroclastic flow, erupted from the nearby Alban Hills volcano. The clastsupported conglomeratic fabric of the concrete presents further resistance to fracture propagation at the structural scale.Roman concrete | volcanic ash mortar | fracture toughness | interfacial zone | strätlingite

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Section: Role Of Pyroclastic Rock In Concrete Durabilitymentioning

confidence: 99%

Mechanical resilience and cementitious processes in Imperial Roman architectural mortar

Jackson¹,

Landis

Brune

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

178

View full text Add to dashboard Cite

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“…In this sense, the response under high pressures is important. Moon et al (2011) studied the effects of pressure on the structure of synthesised stratlingite (Matschei et al, 2007b) , contains only one molecule of water. Considering the hypothesis of pressure-induced dehydration, the stiffness of the crystal should increase once water molecules move out from the calcium aluminosilicate framework.…”

Section: Introductionmentioning

confidence: 99%

Structure of stratlingite and effect of hydration methodology on microstructure

Santacruz

Torre

Álvarez-Pinazo

et al. 2016

Advances in Cement Research

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Stratlingite, Ca 4 Al 2 (OH) 12 [AlSi(OH) 8 ] 2 ·2H 2 O, is an AFm phase which appears as a hydration product of aluminium-rich cements. These binders may be calcium aluminate cements, calcium sulfoaluminate cements and also belite calcium sulfo-aluminate (BCSA) cements. The structure of stratlingite is known from single-crystal studies of tiny minerals but their bulk formation, crystal structure and microstructure of powders is poorly understood. This paper reports on the synthesis of stratlingite and a complete structural and microstructural characterisation by synchrotron X-ray powder diffraction, nuclear magnetic resonance, scanning electron microscopy and thermal analyses. The structural and microstructural models have important implications for a correct quantitative phase analysis of stratlingite in cement pastes (for instance, in pastes of BCSA cements). The microstructure of stratlingite formed in cement pastes is highly dependent on the hydration conditions. In BCSA pastes, the (003) line position of stratlingite appears slightly shifted towards higher diffracting angles (lower inter-layered distance) after stopping hydration compared to that of a similar phase present in a paste analysed without stopping hydration. This is related to dehydration and disorder. This shift and peak broadening is even larger when the paste has suffered partial dehydration during curing (apart from stopping hydration). A microstructural study is presented.

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“…Other works reported the bulk modulus for selected samples of interest in cement chemistry like stratlingite: K o = 23 GPa, hemicarboaluminate: K o = 15 GPa, monocarboaluminate: K o = 54 GPa and hydrogarnet: K o = 70 GPa. [102,103] X-ray diffraction is the standard method for measuring the unit cell volume variation with the pressure of crystalline materials. For a pressure range where the composition of the phase is constant, this directly translates into the density variation with pressure.…”

Section: C-s-h(i) Does Not Significantly Affect the Bulk Modulus Of Cmentioning

confidence: 99%

Recent studies of cements and concretes by synchrotron radiation crystallographic and cognate methods

Aranda

2015

Crystallography Reviews

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The portfolio of available synchrotron radiation techniques is increasing notably for cements and pastes. Furthermore, sometimes the terminology is confusing and an overall picture highlighting similarities and differences of related techniques was lacking. Therefore, the main objective of this work is to review recent advances in synchrotron techniques providing a comprehensive overview. This work is not intended to gather all publications in cement chemistry but to give a unified picture through selected examples. Crystallographic techniques are used for structure determination, quantitative phase analyses and microstructure characterization. These studies are not only carried out in standard conditions but synchrotron techniques are especially suited to non-ambient conditions: high temperatures and pressures, hydration, etc., and combinations. Related crystallographic techniques, like Pair Distribution Function, are being used for the analysis of ill-crystalline phase(s). Furthermore, crystallographic tools are also employed in imaging techniques including scanning diffraction microscopy and tomography and coherent diffraction imaging. Other synchrotron techniques are also reviewed including X-rays absorption spectroscopy for local structure and speciation characterizations; small angle X-ray scattering for microstructure analysis and several imaging techniques for microstructure quantification: full-field soft and hard X-ray nano-tomographies; scanning infrared spectro-microscopy; scanning transmission and fluorescence X-ray tomographies. Finally, a personal outlook is provided.

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Pressure induced reactions amongst calcium aluminate hydrate phases

Cited by 37 publications

References 22 publications

Mechanical resilience and cementitious processes in Imperial Roman architectural mortar

Mechanical resilience and cementitious processes in Imperial Roman architectural mortar

Structure of stratlingite and effect of hydration methodology on microstructure

Recent studies of cements and concretes by synchrotron radiation crystallographic and cognate methods

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