Predicting Chemical Shrinkage in Hydrating Cements

Holmes, Niall; Tyrer, Mark; Kelliher, Denis

doi:10.3390/buildings12111972

Cited by 3 publications

(4 citation statements)

References 26 publications

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“…Indeed, it could be argued that the unwillingness to examine and change the consultation process stemmed at least in part from the active use of those very processes and systems to wear down community opposition through a process of attrition. It is a rare team of 'very determined' 70 volunteers, capable of 'intelligent lobbying', 71 who are willing and able to provide the time and effort necessary to challenge such large systems of statecraft -or, indeed, who have the skillset to do so effectively.…”

Section: Engagement With Decision-making Foramentioning

confidence: 99%

Ardagh Community Trust: transgressing boundaries, asserting community

Thomson¹,

Neuhaus²,

Franklin³

et al. 2023

Architecture_MPS

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Administrative boundaries are ubiquitous. A vital technology of power within the modern nation-state’s mode of bureaucratic governance, they carve up and abstract land and water alike into conceptual totalities that, in their simplification, render them legible to centralised administrative bodies. This is a foundational tool of state planning, the impact of which permeates all aspects of socio-economic life. These boundaries are not passive; they do not simply define a geographical area. Rather, they are selective in what they encompass and, as a result, what they include and exclude and what is rendered visible and, hence, valuable. This article describes an example of the real-world impact of this selectivity through discussion of the experiences of a community-led charity (Ardagh Community Trust) and the community group that founded it (Friends of Horfield Common). In their work to demonstrate that an administrative-boundary-spanning public green space (Horfield Common) and leisure facility (the Ardagh) was a vital community resource and hub, this article focuses on the work of Friends of Horfield Common/Ardagh Community Trust to ensure that their local community, one dissected by multiple administrative boundaries, was recognised and acknowledged when, in 2008, Bristol City Council in the UK proposed the sale of multiple publicly owned green spaces through their Parks and Green Space Strategy. Administrative boundaries played a key role in defining and determining which sites in the city were proposed for sale and in structuring the accompanying public consultation process, thereby determining which communities were recognised as communities in relation to this policy and, hence, which communities’ opinions were actively sought and heard. This article concludes by highlighting some of the potential political and economic costs attendant on reifying administrative boundaries rather than lived communities in both planning and consultation processes.

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Section: Engagement With Decision-making Foramentioning

confidence: 99%

Ardagh Community Trust: transgressing boundaries, asserting community

Thomson¹,

Neuhaus²,

Franklin³

et al. 2023

Architecture_MPS

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“…The thermodynamic modelling was undertaken using the PHREEQC geochemistry software [7] which, using appropriate input for the normative cement content, calculating the clinker dissolution rate while accounting for accessory phases, oversaturation and alkalis binding to the C-S-H, determines the equilibrium phase assemblages over time, as described in detail in [5,6,19,20]. Anhydrite (CaSO 4 ) is referred to here as gypsum.…”

Section: Thermodynamic Modelling Of Cement Hydrationmentioning

confidence: 99%

“…As may be seen in Figure 6, the three methods show excellent comparisons. The PHREEQC input file also accounts for the kinetic dissolution of the clinker phases as a function of time, oversaturation of the precipitating hydrates from 0-12 hrs and the release and uptake of alkalis by the C-S-H gel, as described in previous publications [5,6,19,20].…”

Section: Thermodynamic Descriptions Of So 3 Mgo and Periclasementioning

confidence: 99%

Comparing the Measured and Thermodynamically Predicted AFm Phases in a Hydrating Cement

et al. 2022

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In hydrating Portland cements, more than one of the AFm family of calcium aluminates may exist. Depending on the amount of carbonate and sulfate present in the cement, the most common phase to precipitate is monosulfate, monocarbonate and/or hemicarbonate. It has been reported in the literature that hemicarbonate often appears in measurements such as XRD but not predicted to form/equilibrate in thermodynamic models. With the ongoing use of commercial cements such as CEM I and CEM II containing more and more limestone, it is important to understand which hydrate solids physically precipitate and numerically predict over time. Using 27 cement samples with three w/c ratios analysed at 1, 3 and 28 days, this paper shows that although hemicarbonate was observed in a hydrating commercial Portland cement, as well as being predicted based on its carbonate (CO2/Al2O3) and sulfate (SO3/Al2O3) ratios, thermodynamic analysis did not predict it to equilibrate and form as a solid hydrate. Regardless of the w/c ratio, thermodynamic analysis did predict hemicarbonate to form for calcite contents < 2 wt.%. It appears that the dominant stability of monocarbonate in thermodynamic models leads to it precipitating and remaining as a persistent phase.

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“…Cracks caused by temperature drop and shrinkage of mass concrete during the process of concrete pouring and curing are reduced significantly [5]. Unlike ordinary Portland cement (OPC), the low hydration heat of LHP benefits from its high dicalcium silicate (C 2 S) content and low tricalcium silicate Thermodynamics is an important method for understanding chemical reactions of cement-based materials [12,13]. Lothenbach and Wieland [14] simulated the changes in the ion concentration of the pore solution of the Portland cement paste and the various substances in the phase dissolution and precipitation process by establishing a Portland cement thermodynamic database after evaluating the thermodynamic data of the Portland mineral phase.…”

Section: Introductionmentioning

confidence: 99%

Hydration and Fractal Analysis on Low-Heat Portland Cement Pastes Using Thermodynamics-Based Methods

Zhou

Peng

et al. 2023

Fractal Fract

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Low-heat Portland (LHP) cement is a kind of high-belite cement, which has the characteristic of low hydration heat. Currently, it is extensively used in the temperature control of mass concrete. Based on the thermodynamic database of OPC-based materials, the thermodynamic software GEM-Selektor (noted as GEMS) is used for simulating the hydration products of the LHP cement paste. Then, according to the GEMS thermodynamic simulation results, MATLAB is used to visualize the initial and ultimate stages of LHP cement pastes; the effects of curing temperature and water to cement (w/c) ratio on hydration products are addressed; and the porosity, fractal dimension, and tortuosity of different pastes are calculated. It is found that an appropriately high curing temperature is important for reducing porosity, especially in the early hydration stage. Hydration time also has a significant impact on the hydration of LHP cement paste; long hydration time may reduce the impact of temperature on hydration products. The w/c ratio is another important consideration regarding the hydration degree and porosity of LHP paste, and under different curing temperatures, hydration times, and w/c ratios, the porosity varies from 5.91–32.91%. The fractal dimension of this work agrees with the previous findings. From tortuosity analysis, it can be concluded that the high curing temperature may cause significant tortuosity, further affecting the effective diffusivity of LHP cement paste. For cement pastes with low w/c ratio, this high curing temperature effect is mainly reflected in the early hydration stage, for ones with high w/c ratio, it is in turn evident under long-term curing.

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Predicting Chemical Shrinkage in Hydrating Cements

Cited by 3 publications

References 26 publications

Ardagh Community Trust: transgressing boundaries, asserting community

Ardagh Community Trust: transgressing boundaries, asserting community

Comparing the Measured and Thermodynamically Predicted AFm Phases in a Hydrating Cement

Hydration and Fractal Analysis on Low-Heat Portland Cement Pastes Using Thermodynamics-Based Methods

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