Quantification of tortuosity in hardened cement pastes using synchrotron-based X-ray computed microtomography

Promentilla, Michael Angelo B.; Sugiyama, Takafumi; Hitomi, Takashi; Takeda, Nobufumi

doi:10.1016/j.cemconres.2009.03.005

Cited by 246 publications

(127 citation statements)

References 37 publications

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“…8,17 Nevertheless, important properties of concrete, such as its elastic modulus and its permeability to liquids or gases, depend on various details of the cement paste microstructure. 3,4,19,20 Therefore, attempts to predict the durability and service life of cement-based materials should ideally capture the changes in cement paste microstructure.…”

Section: Introductionmentioning

confidence: 99%

Coupling thermodynamics and digital image models to simulate hydration and microstructure development of portland cement pastes

et al. 2011

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Equilibrium thermodynamic calculations, coupled to a kinetic model for the dissolution rates of clinker phases, have been used in recent years to predict time-dependent phase assemblages in hydrating cement pastes. We couple this approach to a 3D microstructure model to simulate microstructure development during the hydration of ordinary portland cement pastes. The combined simulation tool uses a collection of growth/dissolution rules to approximate a range of growth modes at material interfaces, including growth by weighted mean curvature and growth by random aggregation. The growth rules are formulated for each type of material interface to capture the kinds of cement paste microstructure changes that are typically observed. We make quantitative comparisons between simulated and observed microstructures for two ordinary portland cements, including bulk phase analyses and two-point correlation functions for various phases. The method is also shown to provide accurate predictions of the heats of hydration and 28 day mortar cube compressive strengths. The method is an attractive alternative to the cement hydration and microstructure model CEMHYD3D because it has a better thermodynamic and kinetic basis and because it is transferable to other cementitious material systems.

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Section: Introductionmentioning

confidence: 99%

Coupling thermodynamics and digital image models to simulate hydration and microstructure development of portland cement pastes

et al. 2011

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“…There is, however, a trade-off, such that the maximum sample size for the higher-resolution systems is limited to less than a few millimeters, whereas specimens on the scale of a few centimeters may be used with lower resolution systems. For cement-based materials, X-ray CT has been applied to a variety of research areas including pore structure characterization and freeze-thaw damage (Bentz et al 2000;Burlion et al 2006;Gallucci et al 2007;Helfen et al 2005;Lu et al 2006;Hitomi et al 2004;Promentilla et al 2008Promentilla et al , 2009Promentilla et al , 2010Sugiyama et al 2010).…”

Section: 3mentioning

confidence: 99%

“…For void space segmentation, global thresholding was used to separate the void from the "solid" matrix by defining the range of grayscale value (GSV) associated with void voxels. The lower bound of GSV associated with void voxels was set to 0 while the upper bound is set to the void threshold value on the basis of transition point in segmented porosity-threshold dependency curve (Promentilla et al 2007(Promentilla et al , 2009). …”

Section: Extraction Of 3d Crack Space From Microtomographic Imagesmentioning

confidence: 99%

“…It should be noted that the evaluation of pore structure parameters derived from microtomography images of cementitious material are also influenced by digital resolution (Garboczi et al 2001, Pignat et al 1996, Galluci et al 2007, Promentilla et al 2009). As for the crack geometry evaluation using X-ray microtomography, it is also influenced by digital resolution.…”

Section: Crack Geometry Parametersmentioning

confidence: 99%

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Application of X-Ray CT to Study Diffusivity in Cracked Concrete Through the Observation of Tracer Transport

Darma

Sugiyama

Promentilla

2013

ACT

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This paper demonstrates the application of microfocus X-ray computed tomography (CT) to study solute transport in cracked concrete. Cracks in a cylindrical specimen of ordinary Portland cement (OPC) and fly ash mortar were induced using a splitting tensile test. Cesium Carbonate (Cs 2 CO 3 ) was then used as a tracer in the in-situ diffusion test with the aid of X-ray CT. Image analysis was also employed to measure the 3D crack geometry and tracer diffusivity from these CT images. The geometric tortuosity of the crack was approximately 1.25 irrespective of the crack opening width and whether fly ash was added or not. On the other hand, the constrictivity increased for the fly ash mortar having roughly the equivalent crack opening width. The measured diffusivity in the crack was controlled by both crack opening width and constrictivity. Results obtained from microtomographic images suggest that the entire crack space may not always be filled with the tracer. The diffusive transport of solute in cracks thus can be restricted from microstructure's point of view. Smaller crack opening would increase such restricted diffusion. Indications also suggest that the addition of fly ash would lead to the reduction of diffusivity through uncracked body of the mortar.

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“…Thus, pore-scale analysis is one of the useful approaches to understanding the diffusive transport in porous media. Computer simulations are useful in investigating the pore-scale diffusion process in geo-materials (e.g., Nakano 1995; Nakashima et al 2004;Promentilla et al 2009;Han et al 2009;Sugiyama et al 2010). Thus, we performed extensive simulations to understand steadystate non-sorbing tracer diffusion in fluid-saturated porous geo-materials.…”

Section: Introductionmentioning

confidence: 99%

Steady-State Local Diffusive Fluxes in Porous Geo-Materials Obtained by Pore-Scale Simulations

Nakashima

Nakano

2012

Transp Porous Med

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Computer simulations of non-sorbing tracers diffusing in fluid-saturated porous sediment/rock were performed using pore-scale X-ray microtomographic images to reveal the following. (i) The histogram of the magnitude of the local diffusive flux vector obeys a unimodal log-normal distribution having a long positive tail. Simulations using model images were also performed to show that the flux broadening in large pores and the flux mixing at the pore network junctions are responsible for the log-normal shape. (ii) The simulation enabled us to directly visualize pore voxels with large and small fluxes, confirming the existence of transport pores and stagnant pores. Because of the unimodal nature, however, it was difficult to distinguish transport pores from stagnant pores using an objective threshold in the histogram. (iii) Another histogram of the flux vector component along the direction of the macroscopic concentration gradient was analyzed. A negative tail was found in the histogram, indicating that local counter diffusion exists in the porous geo-materials. However, the population and intensity of the counter diffusion fluxes are too small and weak to contribute to the overall diffusive transport across the porous media system. A long positive tail representing a large-flux diffusive pathway was also observed in the histogram. However, again, the population of the large-flux transport pores is small. As a result, the main conveyer of the tracer is the stagnant pores (not the transport pores), which have small positive flux values but a large population.

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Quantification of tortuosity in hardened cement pastes using synchrotron-based X-ray computed microtomography

Cited by 246 publications

References 37 publications

Coupling thermodynamics and digital image models to simulate hydration and microstructure development of portland cement pastes

Coupling thermodynamics and digital image models to simulate hydration and microstructure development of portland cement pastes

Application of X-Ray CT to Study Diffusivity in Cracked Concrete Through the Observation of Tracer Transport

Steady-State Local Diffusive Fluxes in Porous Geo-Materials Obtained by Pore-Scale Simulations

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