Bibliography - George Scherer

1. Matteo, Edward, George Scherer, Bruno M. Huet, and Leo Pel, 2011: Understanding Boundary Condition Effects on the Corrosion Kinetics of Class H Well Cement. Energy Procedia, Elsevier, 4, doi:10.1016/j.egypro.2011.02.520 5370-5376
   [ Abstract ]

   Storing carbon dioxide in depleted petroleum reservoirs is a viable strategy for carbon mitigation, but ensuring that the sequestered CO₂ remains in the formation is vital to the success of such projects. There is great concern for the development of leakage pathways through annuli between the well cement and the formation or the casing. Predicting the behavior of such potential leakage pathways is critical. Numerical simulations conducted using a reactive transport module match well with experimental studies [1], but also show the necessity of quantifying the transport and mechanical properties of the leached solid cementitious solids--predominantly silica gel-- produced by carbonic acid corrosion of well cement. Bench-top experiments have been performed with the following goals in mind: 1) to investigate the parameter space of relevant corrosion boundary conditions, e.g. pH, CO₂ concentration, and calcium ion concentration, 2) to produce samples that can be used to quantify the transport and mechanical properties of acid corroded Class H well cement, and 3) to validate and improve the accuracy of numerical simulations of the reaction of well cement with carbonic acid. Class H cement samples were uniaxially corroded via exposure to a brine of constant composition. Constant composition is ensured by constant renewal of the brine at a rate larger than cement reaction rate. H⁺, Ca²⁺ and CO₂ total aqueous concentration in the NaCl brine are controlled independently by adding known amounts of NaCl, HCl, CaCl₂ and NaHCO₃ and by controlling CO₂ partial pressure. Microscopic (30X) time-lapse videos were taken of each sample so that corrosion front movements could be accurately measured. These experiments have yielded corrosion front measurements that clearly show that corrosion front advancement is diffusion controlled (i.e., linear as a function of the square root of time). The uniaxial corrosion of these samples has not only allowed for detailed measurements of the corrosion front, but also affords the opportunity to measure the mechanical properties of the corroded samples as a function of depth. The one-dimensional corrosion also allows for measuring the diffusion coefficient of the outer layer of silica gel by low field Nuclear Magnetic Resonance (NMR). Measuring the kinetics under various boundary conditions has validated the modeling results reported by Huet et al. [1]. The measurements of mechanical and transport properties can now be used to improve the predictive power of these simulations by providing much needed information on the exterior layer of corroded Class H well cement. Additionally, these experiments offer experimental validation that the corrosion kinetics are enhanced by the presence of CO₂ and open the door to better understanding of the mechanism of, and boundary conditions that might lead to, "pore-plugging" by the corrosion products, which in turn leads to a drastic retardation of the corrosion reaction.

2. Peters, Catherine A., P. F. Dobson, C. M Oldenburg, Joseph S.Y. Wang, T. C. Onstott, George Scherer, B. Freifeld, T. S. Ramakrishnan, Eric L. Stabinski, Kenneth Liang, and Sandeep Verma, 2011: LUCI: A facility at DUSEL for large-scale experimental study of geologic carbon sequestration. Energy Procedia, Elsevier, 4, doi:10.1016/j.egypro.2011.02.478 5050-5057
   [ Abstract ]

   LUCI, the Laboratory for Underground CO₂ Investigations, is an experimental facility being planned for the DUSEL underground laboratory in South Dakota, USA. It is designed to study vertical flow of CO₂ in porous media over length scales representative of leakage scenarios in geologic carbon sequestration. The plan for LUCI is a set of three vertical column pressure vessels, each of which is ∼500 m long and ∼1 m in diameter. The vessels will be filled with brine and sand or sedimentary rock. Each vessel will have an inner column to simulate a well for deployment of down-hole logging tools. The experiments are configured to simulate CO₂ leakage by releasing CO₂ into the bottoms of the columns. The scale of the LUCI facility will permit measurements to study CO₂ flow over pressure and temperature variations that span supercritical to subcritical gas conditions. It will enable observation or inference of a variety of relevant processes such as buoyancy-driven flow in porous media, Joule-Thomson cooling, thermal exchange, viscous fingering, residual trapping, and CO₂ dissolution. Experiments are also planned for reactive flow of CO₂ and acidified brines in caprock sediments and well cements, and for CO₂-enhanced methanogenesis in organic-rich shales. A comprehensive suite of geophysical logging instruments will be deployed to monitor experimental conditions as well as provide data to quantify vertical resolution of sensor technologies. The experimental observations from LUCI will generate fundamental new understanding of the processes governing CO₂ trapping and vertical migration, and will provide valuable data to calibrate and validate large-scale model simulations.

3. Scherer, George, B. Kutchko, N. Thaulow, A. Duguid, and Bryant Mook, 2011: Characterization of cement from a well at Teapot Dome Oil Field: Implications for geological sequestration. International Journal of Greenhouse Gas Control, Elsevier, (5), doi:10.1016/j.ijggc.2010.06.010 115-124
   [ Abstract ]

   Wellbores represent the weakest link in terms of CO₂ storage permanence. As a result, special attention to the numerous existing wells that perforate storage formations is needed. The pre-injection condition of the cement can influence the rate (and type) of alteration by the injected CO₂ plume. The condition of the existing well cement depends on a variety of factors including wellbore/formation and wellbore/brine interactions as well as the composition and type of cement placed in the well (i.e. type of admixtures used, water/solids ratio, sulfate resistant mixes, etc.). In this paper, the details of recovering wellbore cement from an older well to determine pre-injection seal integrity are described. Petrographical and chemical analyses are presented for samples of cement that were retrieved from a 19-year-old well at Teapot Dome in Wyoming. Examination revealed that the retrieved cement had altered as a result of original slurry composition and with respect to the local downhole wellbore environment. Although samples were obtained from a single well, significant differences were observed in their alteration and condition. Sulfate attack resulted in abundant ettringite formation in a cement sample taken adjacent to the Wall Creek sandstone (3060 ft), while cement taken adjacent to the Tensleep formation (5478 ft) was decalcified and enriched in magnesium, owing to reaction of calcium hydroxide in the cement with the dolomitic formation.

4. Thomas, Jeffrey J., Joseph J. Biernacki, J.W. Bullard, Shashank Bishnoi, Jorge S. Dolado, George Scherer, and Andreas Luttge, 2011: Modeling and simulation of cement hydration kinetics and microstructure development. Cement and Concrete Research, doi:10.1016/j.cemconres.2010.10.004
   [ Abstract ]

   Efforts to model and simulate the highly complex cement hydration process over the past 40 years are reviewed, covering different modeling approaches such as single particle models, mathematical nucleation and growth models, and vector and lattice-based approaches to simulating microstructure development. Particular attention is given to promising developments that have taken place in the past few years. Recent applications of molecular-scale simulation methods to understanding the structure and formation of calcium-silicate-hydrate phases, and to understanding the process of dissolution of cement minerals in water are also discussed, as these topics are highly relevant to the future development of more complete and fundamental hydration models.

5. Bullard, J.W., Hamlin M. Jennings, Richard A. Livingston, Andre Nonat, George Scherer, Jeffrey S. Schweitzer, Karen L. Scrivener, and Jeffrey J. Thomas, 2010: Mechanisms of Cement Hydration. Cement and Concrete Research, Elsevier, doi:10.1016/j.cemconres.2010.09.011
   [ Abstract PDF ]

   The current state of knowledge of cement hydration mechanisms is reviewed, including the origin of the period of slow reaction in alite and cement, the nature of the acceleration period, the role of calcium sulfate in modifying the reaction rate of tricalcium aluminate, the interactions of silicates and aluminates, and the kinetics of the deceleration period. In addition, several remaining controversies or gaps in understanding are identified, such as the nature and influence on kinetics of an early surface hydrate, the mechanistic origin of the beginning of the acceleration period, the manner in which microscopic growth processes lead to the characteristic morphologies of hydration products at larger length scales, and the role played by diffusion in the deceleration period. The review concludes with some perspectives on research needs for the future.

6. Duguid, A., and George Scherer, 2010: Degradation of oilwell cement due to exposure to carbonated brine. International Journal of Greenhouse Gas Control, 4, doi:10.1016/j.ijggc.2009.11.001 546–560
   [ Abstract ]

   The growing interest in geologic carbon sequestration has highlighted the need for more data on how well cements react to CO₂ exposure. This paper describes a series of experiments that was conducted to examine the effects of flowing carbonated brine on well cements. Class H cement pastes were exposed to the ranges of temperature (20–50 °C) and pH (2.4–5) characteristic of geosequestration conditions at a depth of about 1 km. The exposed cements and the reactor effluents were analyzed using multiple techniques including optical microscopy, X-ray diffraction, EPMA, and ICP-OES. The results showed that if the solution was pre-equilibrated with calcium carbonate, as would be expected in a limestone formation, there was no detectable attack. However, under the pH and temperature conditions to be expected in a sandstone formation, the initial rate of attack was on the order of millimeters per month. The outer layers of the cements reacted under sandstone-like conditions were fully degraded based on the results of the XRD and EPMA analyses. Inside the degraded layers there was a calcium carbonate-rich layer, a layer depleted of calcium hydroxide, and an unreacted cement core. The rate of degradation of the cement in these experiments was controlled by the rate of dissolution of the calcium carbonate-rich layer, after its formation, and diffusion through the fully degraded layers.

7. Huet, Bruno M., Jean Hervé Prévost, and George Scherer, 2010: Quantitative reactive transport modeling of Portland cement in CO₂-saturated. International Journal of Greenhouse Gas Control, 4, doi:10.1016/j.ijggc.2009.11.003 561-574
   [ Abstract ]

   A modular reactive transport model, Dynaflow^TM, is used to simulate the reactivity of cement in CO₂- saturated water of intermediate salinity (0.5 M). Methodology for coupling transport and geochemical modules is derived and its assumptions are discussed. The modules are coupled in a sequential iterative approach to accurately model: (1) mineral dissolution/precipitation (2) aqueous phase speciation and (3) porosity-dependent transport properties. Simulation results reproduce qualitatively the dissolution of cement hydrates (CH, C-S-H, AFm, AFt) and intermediate products (CaCO₃) that have been observed experimentally. However, when using a standard power law to relate effective transport properties to porosity, modeling and experimental results do not coincide; here, agreement between simulations and observations is obtained by modifying the functional dependence of effective diffusivity on mineralogy. Furthermore, for this particular system for which concentration gradients are the only driving force, the assumption of neglecting the mass balance of water or density changes might show its limits. Therefore, future work should investigate the likely need to account for reaction-driven advection.

8. Matteo, Edward, George Scherer, Bruno M. Huet, and Leo Pel, 2010: Understanding Boundary Condition Effects on the Corrosion Kinetics of Class H Well Cement. International Conference on Greenhouse Gas Technologies (GHGT 10), Elsevier/Energy Procedia,
   [ Abstract ]

   Storing carbon dioxide in depleted petroleum reservoirs is a viable strategy for carbon mitigation, but ensuring that the sequestered CO₂ remains in the formation is vital to the success of such projects. There is great concern for the development of leakage pathways through annuli between the well cement and the formation or the casing. Predicting the behavior of such potential leakage pathways is critical. Numerical simulations conducted using a reactive transport module match well with experimental studies [1], but also show the necessity of quantifying the transport and mechanical properties of the leached solid cementitious solids -- predominantly silica gel -- produced by carbonic acid corrosion of well cement. Bench-top experiments have been performed with the following goals in mind: 1) to investigate the parameter space of relevant corrosion boundary conditions, e.g. pH, CO₂ concentration, and calcium ion concentration, 2) to produce samples that can be used to quantify the transport and mechanical properties of acid corroded Class H well cement, and 3) to validate and improve the accuracy of numerical simulations of the reaction of well cement with carbonic acid. Class H cement samples were uniaxially corroded via exposure to a brine of constant composition. Constant composition is ensured by constant renewal of the brine at a rate larger than cement reaction rate. H⁺, Ca2+ and CO₂ total aqueous concentration in the NaCl brine are controlled independently by adding known amounts of NaCl, HCl, CaCl₂ and NaHCO₃ and by controlling CO₂ partial pressure. Microscopic (30X) time-lapse videos were taken of each sample so that corrosion front movements could be accurately measured. These experiments have yielded corrosion front measurements that clearly show that corrosion front advancement is diffusion controlled (i.e., linear as a function of the square root of time). The uniaxial corrosion of these samples has not only allowed for detailed measurements of the corrosion front, but also affords the opportunity to measure the mechanical properties of the corroded samples as a function of depth. The one-dimensional corrosion also allows for measuring the diffusion coefficient of the outer layer of silica gel by low field Nuclear Magnetic Resonance (NMR). Measuring the kinetics under various boundary conditions has validated the modeling results reported by Huet et al. [1]. The measurements of mechanical and transport properties can now be used to improve the predictive power of these simulations by providing much needed information on the exterior layer of corroded Class H well cement. Additionally, these experiments offer experimental validation that the corrosion kinetics are enhanced by the presence of CO₂ and open the door to better understanding of the mechanism of, and boundary conditions that might lead to, “pore-plugging” by the corrosion products, which in turn leads to a drastic retardation of the corrosion reaction.

9. Peethamparan, S., E. Weissinger, J. Vocaturo, J. Zhang, and George Scherer, 2010: Monitoring Chemical Shrinkage Using Pressure Sensors. American Concrete Institute, http://www.concrete.org/PUBS/JOURNALS/OLJDetails.asp?Home=SP&ID=51663740, SP-270, 77-88
   [ Abstract ]

   This paper discusses the design and development of an automated test device for measuring the chemical shrinkage of hydrating cements. The device uses a very sensitive pressure sensor to determine water level drop in an open capillary tube, from which the volume change due to chemical shrinkage can be calculated continuously. The repeatability of the measurements and the stability of the measuring device have been demonstrated. The comparison of the result produced by the new device with that of a standard ASTM test showed excellent matching. The range of applicability of this device was demonstrated by obtaining shrinkage measurements for different types of cements, such as ordinary portland cement, Class H oil well cement and white portland cements, and for different temperatures.

10. Peters, Catherine A., P. F. Dobson, C. M Oldenburg, Joseph S.Y. Wang, and George Scherer, 2010: LUCI: A Facility at DUSEL for Large-Scale Experimental Study of Geologic Carbon Sequestration. International Conference on Greenhouse Gas Technologies (GHGT 10), Elsevier/Energy Procedia,
    [ Abstract ]

    LUCI, the Laboratory for Underground CO₂ Investigations, is an experimental facility being planned for the DUSEL underground laboratory in South Dakota, USA. It is designed to study vertical flow of CO₂ in porous media over length scales representative of leakage scenarios in geologic carbon sequestration. The plan for LUCI is a set of three vertical column pressure vessels, each of which is ~500 m long and ~1 m in diameter. The vessels will be filled with brine and sand or sedimentary rock. Each vessel will have an inner column to simulate a well for deployment of down-hole logging tools. The experiments are configured to simulate CO₂ leakage by releasing CO₂ into the bottoms of the columns. The scale of the LUCI facility will permit measurements to study CO₂ flow over pressure and temperature variations that span supercritical to subcritical gas conditions. It will enable observation or inference of a variety of relevant processes such as buoyancy-driven flow in porous media, Joule- Thomson cooling, thermal exchange, viscous fingering, residual trapping, and CO₂ dissolution. Experiments are also planned for reactive flow of CO₂ and acidified brines in caprock sediments and well cements, and for CO₂ -enhanced methanogenesis in organic-rich shales. A comprehensive suite of geophysical logging instruments will be deployed to monitor experimental conditions as well as provide data to quantify vertical resolution of sensor technologies. The experimental observations from LUCI will generate fundamental new understanding of the processes governing CO₂ trapping and vertical migration, and will provide valuable data to calibrate and validate large-scale model simulations.

11. Scherer, George, Gary P. Funkhouser, and S. Peethamparan, 2010: Effect of pressure on early hydration of class H and white cement. Cement and Concrete Research, 40, doi:10.1016/j.cemconres.2010.01.013 845-850
    [ Abstract ]

    The change in viscosity of cement slurry with temperature and pressure can be predicted by assuming that hydration can be treated as an activated process and that a given viscosity corresponds to a fixed degree of reaction. For Class H and White cements, chemical shrinkage experiments indicate that the activation energy is 33.8 kJ/mole and rheological measurements yield an activation volume of -30 cm³/mole. With these parameters, it is possible to predict the limit of pumpability of the slurry (which corresponds to a viscosity of about 2.5 Pa s) for arbitrary temperature and pressure cycles. This method of prediction requires that the physics of the process remain the same, but simply change in rate; therefore, the range of applicability is expected to be limited to temperatures below about 100 °C, since new phases occur at higher temperatures.

12. Sun, Zhenhua, and George Scherer, 2010: Pore size and shape in mortar by thermoporometry. Cement and Concrete Research, 40, doi:10.1016/j.cemconres.2009.11.011 740-751
    [ Abstract ]

    The pore structure of mortar (w/c = 0.55) was examined using thermoporometry (TPM), nitrogen adsorption/desorption (NAD), and mercury intrusion porosimetry (MIP). The TPM measurements were calibrated by comparison to NAD and MIP measurements on porous glass; similar comparisons were made on dried and resaturated mortars. For undried mortars, TPM provides the size of pore entries (from the freezing cycle) and interiors (from the melting cycle). In keeping with previous studies, we find that there is an unfrozen layer of water between the ice and the pore wall in porous glass that is about 0.8 nm thick; when lime-saturated water is used, the thickness of that layer increases by about 10%. In mortar, the unfrozen layer is about 1.0–1.2 nm thick, so no freezing occurs in pores with diameters ≤ 4.5 nm, at least down to − 40 °C (where the radius of the crystal/liquid interface is ~1.5 nm). Based on the hysteresis in the freezing and melting curves, the larger mesopores in mortar were found to be rather spheroidal, while the smaller ones were more cylindrical.

13. Zhang, J., E. Weissinger, S. Peethamparan, and George Scherer, 2010: Early hydration and setting of oil well cement. Cement and Concrete Research, 40, doi:10.1016/j.cemconres.2010.03.014
    [ Abstract ]

    A broad experimental study has been performed to characterize the early hydration and setting of cement pastes prepared with Class H oil well cement at water-to-cement ratios (w/c) from 0.25 to 0.40, cured at temperatures from 10 to 60 °C, and mixed with chemical additives. Chemical shrinkage during hydration was measured by a newly developed system, degree of hydration was determined by thermogravimetric analysis, and setting time was tested by Vicat and ultrasonic velocitymeasurements. A Boundary Nucleation and Growth model provides a good fit to the chemical shrinkage data. Temperature increase and accelerator additions expedite the rate of cement hydration by causing more rapid nucleation of hydration products, leading to earlier setting; conversely, retarder and viscosity modifying agents delay cement nucleation, causing later setting times. Lower w/c paste needs less hydration product to form a percolating solid network (i.e., to reach the initial setting point).However, for the systems evaluated, at a givenw/c, the degree of hydration at setting is a constant, regardless of the effects of ambient temperature or the presence of additives.

14. Peters, Catherine A., George Scherer, Michael Celia, Jean Hervé Prévost, T. C. Onstott, P. F. Dobson, C. M Oldenburg, B. Freifeld, J. Birkholzer, J. Wang, S. Benson, and T. J. Phelps, et al., in press: Collaborative Research: DUSEL CO₂, A Deep Underground Laboratory for Geologic CO₂ Sequestration Studies: A proposal for the conceptual design of the facility and experiments. NSF. 0/09.
    [ Abstract ]

    Princeton University and Lawrence Berkeley National Laboratory have forged a new collaboration to examine the feasibility and risks of carbon sequestration, a method of countering global warming by storing greenhouse gases deep underground. To develop a sound understanding of carbon sequestration, we will build a deep underground laboratory to study the processes of trapping and storing CO₂, including the risks of unintended leakage. It will be part of the new DUSEL facility at the Homestake mine in South Dakota. The “DUSEL CO₂, facility will make the United States the only country with a deep underground laboratory for controlled study of geologic carbon sequestration, providing a unique opportunity for global leadership. The findings from these unique experiments will advance carbon management technology worldwide and help reduce global greenhouse gas emissions. The features and capabilities of the planned facility are unprecedented. The experimental design exploits the nearly half-kilometer vertical extent of existing “sandline” borings at Homestake. Pipes will be installed within the sandlines to serve as long flow columns. These columns will contain the CO₂, and allow experimentation at the same pressure and temperature conditions as in deep subsurface reservoirs. Fill materials will mimic sedimentary layering, as well as cements in plugged wells. Instrumentation will enable detailed monitoring of flow, pressure, temperature, brine composition, geomechanics, and microbial activity. As part of the initial suite of experiments, we plan to simulate a leak in which CO₂, changes from a supercritical fluid to a subcritical gas as the pressure drops during upflow over tens to hundreds of meters. We will test for possible acceleration in CO₂, flow due to increasing buoyancy. Also, we will examine the interactions of CO₂, with cap-rocks and well cements, and determine whether CO₂, will enlarge flow pathways or cause selfsealing. Finally, we will investigate the effects of anaerobic, thermophilic bacteria on CO₂, conversion to methane and carbonate. This project is being led by researchers at Princeton and LBNL, and involves no-cost collaboration with individuals at ORNL, Stanford University, Schlumberger and the U.S. DOE NETL. During this three-year project, the team is working to (i) prioritize future experiments that will be conducted at DUSEL CO₂, (ii) build models that simulate experimental conditions and predict process dynamics, and (iii) develop a Work-Breakdown Structure (WBS) schedule for design, procurement, construction, operation and deconstruction of the facility over the facility lifetime. International awareness about DUSEL CO₂, is being fostered through international workshops and formation of an International Advisory Committee. Also, we are collaborating with other DUSEL scientists on education and outreach about “deep science,” with particular focus on climate change and energy solutions. DUSEL education and outreach activities are focused on Native American communities in South Dakota and operation of the Visitor Center at the Sanford Lab at Homestake. To inspire and educate the next generation of leaders, we are involving undergraduate and graduate students in DUSEL CO₂, research at Princeton University.

15. Scherer, George, and B. J. Huet, 2009: Carbonation of wellbore cement by CO₂ diffusion from caprock. International Journal of Hydrogen Energy, Elsevier, (G Model IJGGC-188), doi:10.1016/j.ijggc.2009.08.002
    [ Abstract ]

    To evaluate the risk of corrosion of cement by geosequestered CO₂, samples are being retrieved from wells placed in natural CO₂ deposits [e.g., Crowet al., 2009]. If the cement passing through the cap rock is carbonated, it may indicate that annular gaps or cracks have allowed carbonic acid to come into contact with the cement. However, it must be recognized that the pore water in the cap rock has become saturated with CO₂ over geological time. After the well is placed, the CO₂ will diffuse toward the cement and react with it. A simple analysis of the diffusion kinetics demonstrates that carbonation depths of millimeters to centimeters can be expected from this reaction within the lifetime of a well, in the absence of any cracks or gaps. Therefore, the occurrence of carbonation in cement sealing natural CO₂ deposits must be interpreted with caution.

16. Scherer, George, Jean Hervé Prévost, and Z. H. Wang, 2009: Bending of a Poroelastic Beam with Lateral Diffusion. International Journal of Solids and Structures, 46(18-19), doi:10.1016/j.ijsolstr.2009.05.016 3451-3462
    [ Abstract ]

    Bending an elastic beam leads to a complicated 3D stress distribution, but the shear and transverse stresses are so small in a slender beam that a good approximation is obtained by assuming purely uniaxial stress. In this paper, we demonstrate that the same is true for a saturated poroelastic beam. Previous studies of poroelastic beams have shown that, to satisfy the Beltrami–Michell compatibility conditions, it is necessary to introduce either a normal transverse stress or shear stresses in addition to the bending stress. The problem is further complicated if lateral diffusion is permitted. In this study, a fully coupled finite element analysis (FEA) incorporating the lateral diffusion effect is presented. Results predicted by the “exact” numerical solution, including load relaxation, pore pressure, stresses and strains, are compared to an approximate analytical solution that incorporates the assumptions of simple beam theory. The applicability of the approximate beam-bending solution is investigated by comparing it to FEA simulations of beams with various aspect ratios. For “beams” with large width-to-height ratios, the Poisson effect causes vertical deflections that cannot be neglected. It is suggested that a theory of plate bending is needed in the case of poroelastic media with large width-to-height ratios. Nevertheless, use of the approximate solution yields very small errors over the range of width-to-height ratios (viz., 1–4) explored with FEA.

17. Webb, M. B., S. H. Garofalini, and George Scherer, June 2009: Use of a Dissociative Potential to Simulate Hydration of Na+ and Cl−. Journal of Physical Chemistry, 113, doi:10.1021/jp901667c 9886–9893
    [ Abstract ]

    We have developed interatomic interaction parameters for Na+ and Cl- hydration using the dissociative water potential of Mahadevan and Garofalini [J. Phys. Chem. B 2007, 111, 8919] suitable for molecular dynamic simulations. Simulations were performed for small ion−water clusters Na(H₂O)_n + (n = 1−6) and Cl(H₂O)m − (m = 1−5), as well as dilute aqueous solutions of the ions in water, reproducing the structure and energies found in the literature. A simulation of an HCl molecule in water demonstrated the dissociation of the molecule. The Na+ and Cl- ion−ion interaction parameters also reproduce the energy and density of crystalline NaCl. A series of simulations of NaCl at progressively increasing temperatures from 300 to 1400 K produced solid densities varying by less than 1% from experiment.

18. Huet, B. J., Jean Hervé Prévost, and George Scherer, 2008: Reactive Transport Modeling of Cement Degradation in Brine: Effect of pH and CO₂ content. Geophysical Review, 10,
    [ Abstract ]

    As a CO₂ plume is moving into a reservoir, the chemistry of the fluid at the bottom of an abandoned well changes in successive stages. The first one consists in an increase of the CO₂ content of the brine, while brine saturation remains close to its initial value. A modular reactive transport model, Dynaflow, is used to analyze the reactivity of well cement paste during this first stage. The geochemical module accurately models aqueous speciation and mineral dissolution and/or precipitation within the porous material. Hydrated cement paste is found to dissolve in brines with various content in CO₂. Simulation of a reference case is successfully compared with experimental results, in terms of mineral zoning and dissolution rate. Between pH 2.4 and 5.0, the CO₂ content of a 0.5 M brine controls the degradation rate of cement whereas the pH does not affect it meaningfully. A minimum degradation rate is obtained when the CO₂ molality equals the total molality of aqueous calcium in equilibrium with portlandite. This minimum is related to the maximal amount of calcite precipitated and the relative decrease of the diffusivity within the calcite rich zone.

19. Scherer, George, 2008: Poromechanics Analysis of a Flow-Through Permeameter with Entrapped Air. Cement and Concrete Research, 38(3), doi:10.1016/j.cemconres.2007.09.028 368-378
    [ Abstract ]

    In a standard flow-through permeameter, a hydrostatic head is applied to one side of a sample and the flux of fluid through the sample is measured. In this paper, we apply poromechanics to calculate the evolution of the pressure distribution and the flux through the sample. We allow for negative capillary pressure in the pores at the start of the experiment (owing to self-desiccation during hydration of cement), as well as entrapped air. The time required to reach steady state flow can increase by an order of magnitude by the presence of 1 vol.% of air in the pore liquid; the delay increases as the applied pressure decreases.

20. Duguid, A., M. Radonjic, and George Scherer, 2007: The Effect of Carbonated Brine on Well Cement Used in Geologic Formations. Proceedings of the 12th ICCC, eds. J.J. Beaudoin, J.M. Makar, L. Raki (Canada), paper TH4-10.2,
    [ Abstract ]

    Carbon sequestration in abandoned petroleum fields may be a short-term solution to reducing anthropogenic emissions of CO₂. If sequestration is adopted on a large scale, it will be important to understand how CO₂ may leak out of sequestration formations via abandoned wells. Within an abandoned petroleum well there are multiple pathways that CO₂ may use to escape to the atmosphere. These include leakage through the cement that makes up the primary and/or plug cement in the well, leakage through the interface between the primary cement and the geologic formation, and leakage through the interface between the well cement and the well casing. As the plume of carbonic acid created by sequestration reaches an abandoned well, the first potential pathway with which it come in contact is the interface between the geologic formation and the primary well cement. In order to better understand what takes place when carbonic acid reaches the cement-rock interface, a series of batch experiments was conducted. This paper describes experiments that were conducted on composite samples that were made from Class H well cement and Salem limestone or Berea sandstone.

21. Huet, B. J., Jean Hervé Prévost, and George Scherer, June 2007: Cement reactivity in CO₂ saturated brines: use of a reactive transport code to highlight key degradation mechanisms. Eurotherm Seminar N 81 Reactive Heat Transfer in Porous Media, Albi, France, http://eurotherm81.enstimac.fr/papers_pdf/22-Huet.pdf,
    [ Abstract ]

    A modular reactive transport code is proposed to analyze the reactivity of cement in CO₂ saturated brine. The coupling of the transport module and the geochemical module within Dynaflow^TM is derived. Both modules are coupled in a sequential iterative approach to accurately model: (1) mineral dissolution/precipitation and (2) porosity dependent transport properties. Results of the model reproduce qualitatively the dissolution of cement hydrates (C-H, C-S-H, AFm, AFt) and intermediate products (CaCO₃) into the brine. Slight discrepancies between modeling and experimental results were found concerning the dynamics of the mineral zoning. Results suggest that the power law relationship to model effective transport properties from porosity values is not accurate for very reactive case.

22. Scherer, George, J. J. Valenza II, and G. Simmons, 2007: New Methods to Measure Liquid Permeability in Porous Materials. Cement and Concrete Research, 37(3), doi:10.1016/j.cemconres.2006.09.020 386-397
    [ Abstract ]

    Several novel methods have recently been proposed for rapid measurement of the liquid permeability of saturated cement paste, mortar and concrete. The relative merits of the techniques are discussed, and some recent results obtained on pastes and mortars are presented. The low permeabilities seen in cement paste are inconsistent with the pore size distributions measured following drying, indicating that the pore structure is significantly changed by drying.

23. Duguid, A., M. Radonjic, and George Scherer, June 2006: The effect of carbonated brine on the interface between well cement and geologic formations under diffusion controlled conditions. Proceedings of the 8th International Conference on Greenhouse Gas Control Technologies (GHGT-8),
    [ Abstract ]

    A series of experiments was conducted on composite samples made from Class H well cement and either sandstone or limestone in order to determine the effect on the cement-stone interface in a petroleum well from exposure to carbonated brine. The experiments were carried out over the course of a year and showed that carbonated brines can degrade cement at the cement-stone interface.

24. Huet, B. J., R. Fuller, Jean Hervé Prévost, and George Scherer, May 2006: Numerical simulation of multiphase flow of CO₂ along low permeability path up the wells. Introduction of the interactions with cement. Proceedings of the Fifth Annual Conference on Carbon Capture & Sequestration, Alexandria, Virginia,
    [ Abstract ]

    This work aims at modeling well-bore leakage of Carbon Dioxide (CO₂) from sequestration reservoirs. The leakage of CO₂ is function of the geometry of the low permeability path and boundary conditions. However, the CO₂ flow can also be strongly influenced by the chemical reactivity of cement leading either to the sealing or to the widening of the annulus. This study presents results of the integration of a geochemical module into a robust three-phase transport module developed by Fuller et al. [1]. The numerical model assesses the chemical and physical integrity of cement in injection and/or abandoned sealed wells. The geochemistry part of the simulator assumes local chemical equilibrium. It takes into account the reactivity of cement, i.e. both mineral solid phase changes, like portlandite dissolution and calciium carbonate formation, and aqueous speciation in the interstitial solution. As a result of minerals dissolution and formation, the changes in porosity and the related changes in diffusion and permeability properties of cement are also evaluated. The simulator allows the study of the influence of the well geometry, e.g., the initial width of the annulus between hydrated cement and steel casing, or between hydrated cement and reservoir stone. Both diffusion and advection transport mechanisms are studied separately to account for the different cement pressure environments. Results indicate drastically different degradation rates for cement. Thus, the mean width of the annulus is a key parameter to assess the reliability of injection or abandoned wells.

25. Ciardullo, J. P., D. J. Sweeney, and George Scherer, 2005: Thermal expansion kinetics: Method to measure permeability of cementitious materials: IV, Effect of thermal gradients and viscoelasticity. Journal of the American Ceramic Society, 88(5), doi:10.1111/j.1551-2916.2005.00214.x 1213-1221
    [ Abstract ]

    When a porous material that is saturated with liquid is heated, the liquid expands much more than the solid phase. If the permeability is low, then the liquid may not be able to escape as it expands, so it expands within the pores and causes dilatation of the body. In that case, by analyzing the kinetics of dilatation during a change in temperature, it is possible to extract the permeability. Previous papers have examined the behavior of an elastic or viscoelastic (VE) porous solid subjected to a thermal cycle slow enough to avoid internal temperature gradients. However, for cementitious samples, the sample size must be large enough that thermal gradients are likely. In this paper, we show that the effect of the gradient can be readily incorporated into the analysis of experimental data. For cement paste, experiments reveal that VE relaxation has a greater influence on the results than the gradient in temperature.

26. Duguid, A., M. Radonjic, and George Scherer, 2005: Degradation of well cements exposed to carbonated brine. Proceedings of the 4th Annual Conference on Carbon Capture and Sequestration, http://www.netl.doe.gov/publications/proceedings/05/carbon-seq/Tech%20Session%20Paper%20186.pd,
    [ Abstract ]

    With increased attention on how people affect the climate, interest has grown in the anthropogenic emissions of greenhouse gases such as carbon dioxide. Subsurface carbon sequestration in abandoned petroleum fields may represent a chance to reduce CO₂ emissions. In order to understand how CO₂ may escape from the storage formation back to the atmosphere through abandoned wells, a set of four experiments was conducted. The experiments looked at how well cements reacted to carbonated brines at 20° and 50°C at pH 2.4 and 3.7. The results showed severe degradation to samples made from Class H well cement. The degradation occurred over the course of 31 days.

27. Duguid, A., M. Radonjic, and George Scherer, April 2005: Durability of well cements: corrosion by carbonic acid. Proceedings of the 107th Annual Meeting of the American Ceramics Society,
    [ Abstract ]

    With an increased focus on how people affect the climate, interest has grown in the anthropogenic emissions of greenhouse gases such as carbon dioxide. Subsurface carbon sequestration in abandoned petroleum fields may represent a chance to reduce CO₂ emissions. In order to understand how CO₂ may escape from the storage formation back to the atmosphere through abandoned wells, a set of four experiments was conducted. The experiments looked at how well cements reacted to carbonated brines at 20° and 50°C at pH 2.4 and 3.7. The results showed severe degradation to samples made from Class H well cement, the degradation occurring over the course of 31 days.

28. Prévost, Jean H., R. Fuller, A. Altevogt, R. Bruant, and George Scherer, 2005: Numerical Modeling of Carbon Dioxide Injection and Transport in Deep Saline Aquifers. Proceedings of the 7th International Conference on Greenhouse Gas Control Technologies, (GHGT-7), http://www.princeton.edu/~cmi/research/Storage/Papers/NumericalModelingCarbonDioxide.pdf, 2189-2193
    [ Abstract ]

    We describe the development of a compositional resevoir simulator capable of modeling multiphase transport of CO₂ in a brine aquifer, and results are provided which illustrate the evolution of a 2-phase fluid system in which the injected CO₂ resides in a dense supercritical phase and also dissolves into the liquid phase. Salt precipitation into a solid phase is found to occur close to the injection well where the gas phase dominates.

29. Scherer, George, Michael Celia, Jean Hervé Prévost, , R. Bruant, A. Duguid, R. Fuller, S. Gasda, M. Radonjic, and W. Vichit-Vadakan, 2005: Leakage of CO₂ through Abandoned Wells: Role of Corrosion of Cement. The CO₂ Capture and Storage Project (CCP), Volume II, Chapter 10, 823-844
    [ Abstract ]

    The potential leakage of CO₂ from a geological storage site through existing wells represents a major concern. An analysis of well distribution in the Viking Formation in the Alberta basin, a mature sedimentary basin representative of North American basins, shows that a CO₂ plume and/or acidified brine may encounter up to several hundred wells. A review of the literature indicates that cement is not resistant to attack by acid, but little work has been reported for temperatures and pressures comparable to storage conditions. Therefore, an experimental program has been undertaken to determine the rate of corrosion and the changes in properties of oil well cements exposed to carbonated brine. Preliminary results indicate a very high rate of attack, so it is essential to have accurate models of the composition and pH of the brine, and the time that it will remain in contact with cement in abandoned wells. A model has been developed that incorporates a flash calculation of the phase distribution, along with analysis of the fluxes and pressure of the liquid, solid and vapor phases. A sample calculation indicates that wells surrounding the injection site may be in contact with the acidified brine for years.

30. Scherer, George, and I. Jimenez Gonzalez, 2005: Characterization of Swelling in Clay-Bearing Stone. Stone decay and conservation, 390, doi:10.1130/0-8137-2390-6.51 51-61
    [ Abstract ]

    Many sedimentary rocks contain clays that cause differential swelling upon exposure to moisture, and the resulting internal stresses are blamed for the deterioration of buildings and monuments. To predict the likelihood of damage from this mechanism, it is necessary to characterize the magnitude of the swelling and the mechanical properties of the stone. Stones that swell also exhibit viscoelastic behavior, probably owing to sliding of the clay layers. In this paper we discuss the characterization of the relaxation and swelling behavior and the estimation of stresses resulting from swelling. A new method for measuring swelling is introduced, in which warping of a plate of stone is produced by wetting one side. This method is faster than the traditional direct measurement of swelling pressure, and it also yields information about the permeability and the influence of wetting on the elastic modulus. Sample results are presented for Portland Brownstone.

31. Scherer, George, and J. J. Valenza II, 2005: Mechanisms of Frost Damage. Materials Science of Concrete, American Ceramics Society, VII(ISBN:978-1-57498-210), 209-246
    [ Abstract ]

    The mechanisms responsible for damage from internal freezing and salt scaling are reviewed. The primary cause of internal damage is crystallization pressure, and the role of the air voids is to provide sites for nucleation of macroscopic ice. The thermodynamics of the stress development are reviewed, and the predicted pressures are shown to be in quantitative accord with measured contraction of frozen bodies (including porous glass and cement paste). The origin of salt scaling damage is less clear. We examine two mechanisms that seem to account for most of the experimental observations: the bimaterial effect (i.e., thermal expansion mismatch between ice and cement paste) and salt-induced swelling. A sensitive experiment, in which a layer of water is frozen on top of a thin plate of cement paste and the deflection of the plate is measured, reveals the large stresses produced by these mechanisms. Cracking of the ice layer is promoted by brine pockets, and this may account for the pessimum concentration for scaling damage. Salt-induced swelling, which seems to result from a combination of crystallization pressure and ion exchange, also contributes to the superficial stresses and may exacerbate scaling.

32. Valenza II, J. J., and George Scherer, 2005: Evidence of anomalous thermal expansion of water in cement paste. Cement and Concrete Research, 35(1), doi:10.1016/j.cemconres.2004.08.022 57-66
    [ Abstract ]

    A comparative study of permeability measurement by thermopermeametry (TPA) and beam bending was performed on cement paste. To bring the two measurements into agreement, it is necessary to recognize that the pore solution has a thermal expansion coefficient about one and a half times that of bulk liquid and to account for viscoelastic stress relaxation during TPA experiments. The anomalous thermal expansion is not accounted for by the presence of ions in the cement paste pore solution.

33. Duguid, A., M. Radonjic, R. Bruant, T. Mandecki, George Scherer, and Michael Celia, 2004: The Effect of CO₂ Sequestration on Oil Well Cements. Proceedings of the 7th International Conference on Greenhouse Gas Control Technologies, (GHGT-7), http://www.princeton.edu/~cmi/research/Vancouver04/GHGT7Duguid.pdf,
    [ Abstract ]

    Experiments were conducted to examine the effects of CO₂ sequestration conditions on cements used to construct and abandon oil and gas wells. The results showed that significant damage, complete loss of the calcium hydroxide phase, can take place over a time span as short as seven days.

34. Jimenez Gonzalez, I., and George Scherer, 2004: Effect of swelling inhibitors on the swelling and stress relaxation of clay-bearing stones. Environmental Geology, 46(3-4), doi:10.1007/s00254-004-1038-8 364-377
    [ Abstract ]

    Clay-containing stones such as Portland Brownstone (USA), Villarlod Molasse (Switzerland) and Tarifa Sandstone (Spain), are expected to weather as a result of wetting and drying cycles. During drying events, contraction of the drying surface leads to stresses approaching the tensile strength of the stone. However, we have found that the magnitude of these stresses is reduced by the ability of the stone to undergo stress relaxation. In this paper we describe novel methods to determine the magnitude of the stresses and the rate at which they develop and relax. We also discuss the influence of swelling inhibitors on the magnitude of swelling and the rate of the stress relaxation of these stones. The implications of our findings for the understanding of damage due to swelling of clays are discussed.

35. Scherer, George, 2004: Factors affecting crystallization pressure. Internal Sulfate Attack and Delayed Ettringite Formation, Proc. Int. RILEM 186-ISA Workshop, Paris, RILEM Publications, doi:10.1617/2912143802.009 139-154
    [ Abstract ]

    Crystallization pressure arises when the growth of a crystal is frustrated by an obstacle, such as a pore wall. At equilibrium, the crystallization pressure is inversely related to the size of the pore in which it grows. However, the equilibrium is unstable with respect to growth in a larger pore: if there is a path connecting small and large pores, small crystals will dissolve and the solute will diffuse to a larger pore where the chemical potential of the crystal will be lower. If the supersaturation is high, there can be abundant growth of small crystals that produce a high transient stress, while diffusion is transferring solute to the largest accessible pores. In the case of DEF, it is argued that expansion results from growth of crystals in mesopores, and macroscopic crystals appear subsequently as the solute redistributes.

36. Scherer, George, 2004: Characterization of Saturated Porous Bodies. Materials and Structures, 37(1), doi:10.1007/BF02481624 21-30
    [ Abstract ]

    Measurement of the response of a saturated body to mechanical and thermal strains can be used to determine the permeability and viscoelastic properties of the body. For example, bending a saturated beam creates a pressure gradient in the pores, and as the liquid flows to equilibrate the pressure, the force required to sustain a fixed deflection decreases. Analysis of the kinetics of force relaxation yields the permeability, in addition to the elastic modulus of the body; if viscoelastic relaxation of the solid phase occurs, it can also be measured. This method permits measurement of very low permeabilities in minutes or hours, but it is useful only for structurally homogeneous materials (such as cement paste) that can be formed into slender beams. For concrete, it is more practical to find the permeability by analysis of thermal expansion kinetics. When a saturated body is heated, the liquid expands more than the solid, and the expansion of the liquid stretches the solid network like a spring; consequently, the apparent thermal expansion coefficient is high. During an isothermal hold, the solid phase squeezes the liquid out of the pores and the body contracts. Analysis of the kinetics of thermal dilatation yields the permeability of the body. Recent experiments reveal an anomalously high thermal expansion coefficient for the water confined in the small pores of cement paste.

37. Scherer, George, 2004: Thermal expansion kinetics: Method to measure permeability of cementitious materials: III, Effect of viscoelasticity. Journal of the American Ceramic Society, 87(8), 1509-1516
    [ Abstract ]

    When a porous material that is saturated with liquid is heated, the liquid expands much more than the solid phase. If the permeability is low, then the liquid may not be able to escape as it expands, so it expands within the pores and causes dilatation of the body. In that case, by analyzing the kinetics of dilatation during a change in temperature, it is possible to extract the permeability. The behavior of an elastic porous solid was analyzed previously. In this paper, we consider the case of a viscoelastic material; for cementitious materials, the effect of relaxation is shown to be significant, but the elastic analysis will usually provide sufficient accuracy. If significant viscoelastic relaxation occurs, it is revealed by comparing the data from samples of different sizes.

38. Scherer, George, 2004: Measuring Permeability of Rigid Materials by a Beam-Bending Method: IV. Transversely Isotropic Plate. Journal of the American Ceramic Society, 87(8), 1517-1524
    [ Abstract ]

    A simple beam-bending measurement can be used to determine the permeability, as well as the modulus, of a saturated porous material. The procedure is to apply a constant deflection and measure the load decay as the pressure in the pores equilibrates; alternatively, an oscillatory deflection can be applied and the phase delay measured. The analysis of the experiment has been previously presented for beams with square or round cross sections. In this article, we consider the case of a saturated porous beam with a rectangular cross section and transverse isotropy; that is, the permeability and elastic properties are uniform in the x(1) - x(2) plane, but have different values in the x(3) direction. This is the case for a sedimentary stone or laminated composite, for example. The kinetics of hydrodynamic relaxation depend on the orientation of the planes with respect to the bending axis; consequently, three different solutions are presented that allow determination of the properties in etch direction. Exact solutions are obtained for elastic beams; in approximation for the case of a viscoelastic anisotropic beam also is presented. The relaxation kinetics of an isotropic rectangular plate are obtained as a special case; that geometry is convenient to use for isotropic materials, such as cement paste or mortar.

39. Scherer, George, 2004: Stress from crystallization of salt. Cement and Concrete Research, 34(9), doi:10.1016/j.cemconres.2003.12.034 1613-1624
    [ Abstract ]

    The thermodynamic and kinetic factors influencing crystallization pressure are reviewed for cases including capillary rise and evaporation, cyclic wetting and drying, and hydration of cement. Under equilibrium conditions, where the crystal is surrounded by a film of solution, high stresses are expected only in small pores, but when that film is discontinuous (as may occur during drying), high stresses can arise even in large pores. High crystallization pressure requires a substantial supersaturation of the pore liquid. In the case of sodium sulfate, supersaturation results from the difference in solubility between the anhydrate and decahydrate phases; for ettringite, supersaturation may develop following the cooling from elevated temperatures. During the hydration of Portland cement, crystallization pressure may result from the growth of ettringite and/or calcium hydroxide.

40. Valenza II, J. J., and George Scherer, 2004: Measuring Permeability of Rigid Materials by a Beam-Bending Method: V. Isotropic Rectangular Plates of Cement Paste. Journal of the American Ceramic Society, http://www3.interscience.wiley.com/cgi-bin/fulltext/118743577/PDFSTART, 87(10), 1927-1931
    [ Abstract ]

    Beam bending is an excellent method for measuring low permeabilities (<10^-18 m²) in homogeneous materials, because it is fast, requires no high pressure, and provides a concurrent measurement of the modulus of the material. The method was previously analyzed and substantiated for cylindrical or square beams. Recently, the analysis was extended to include isotropic and transversely isotropic rectangular beams. In this paper, the analysis is applied to measurements performed on cement paste, and it is shown that the solution for isotropic rectangular beams accounts for changes in the hydrodynamic behavior caused by changing the aspect ratio of the sample. The permeability and elastic modulus results are verified through comparison to previous measurements on cylindrical beams.

41. Xu, S., G. Simmons, and George Scherer, 2004: Thermal Expansion and Viscosity of Confined Liquids. Materials Research Society, http://www.mrs.org/s_mrs/sec_subscribe.asp?CID=2631&DID=116771&action=detail, 790, 85-92
    [ Abstract ]

    The thermal expansion and viscosity of water and salt solutions in porous silica glasses have been systematically investigated, and the effect of salts on the properties of water in confined geometry has been addressed. A dilatometric method has been devised and utilized to measure the thermal expansion of confined liquids. A beam-bending method that was developed to study the permeability of porous bodies has been used to measure the relative viscosity of salt solutions to water inside the silica pores. This work has demonstrated that water when confined in nanopores shows anomalous behavior and its thermal expansion is higher than bulk water. This work has also suggested that the presence of ions in water could enhance the anomaly of water in confined space and the extent of the ion effect is dependent on the ion charge.

42. Tsui, N., R. J. Flatt, and George Scherer, 2003: Crystallization damage by sodium sulfate. Journal of Cultural Heritage, 4(2), doi:10.1016/S1296-2074(03)00022-0 109-115
    [ Abstract ]

    Experiments demonstrate that a stone containing thenardite suffers great damage when exposed to water below the temperature limit of mirabilite stability. This is due to a transition between thenardite and mirabilite, and not to thenardite reprecipitation. Damage occurs whether or not thenardite was produced previously by mirabilite decomposition. Together with recent results from the literature, these results indicate that damage occurs because thenardite dissolution can produce solutions highly supersaturated with respect to mirabilite, so that precipitation of this mineral can lead to large crystallization pressures. Finally, it appears that there is a salt content threshold beyond which damage increases substantially.

43. Vichit-Vadakan, W., and George Scherer, 2003: Measuring permeability and stress relaxation of young cement by beam-bending. Cement and Concrete Research, 33(12), doi:10.1016/S0008-8846(03)00168-6 1925-1932
    [ Abstract ]

    When a saturated rod of a porous material is deflected in three-point bending, two types of time-dependent relaxation processes occur simultaneously: hydrodynamic relaxation, caused by the flow of liquid in the porous body, and viscoelastic (VE) relaxation of the solid network. By measuring the decrease in the force required to sustain a constant deflection, it is possible to obtain the permeability from the hydrodynamic relaxation function, in addition to the VE stress relaxation function of the sample. We report the early-age evolution of permeability, elastic modulus, and stress relaxation function for Type III Portland cement paste with water–cement (w/c) ratios of 0.45, 0.50, and 0.55. The stress relaxation function is shown to preserve its shape during aging; that function is numerically transformed into the creep function.

44. Vichit-Vadakan, W., and George Scherer, 2002: Measuring Permeability of Rigid Materials by a Beam-Bending Method: III. Cement Paste. Journal of the American Ceramic Society, 85(6), doi:10.1111/j.1151-2916.2002.tb00309.x 1537-1544
    [ Abstract ]

    The evolution of permeability and elastic modulus for Type III portland cement pastes with water/cement ratios varying from 0.4 to 0.6 were measured using a beam-bending method. Young’s modulus was independently verified by measuring the ultrasonic pulse velocity. The permeability ranged over 2 orders of magnitude, depending on the water/cement ratio and the age of the samples. The advantage of the beam-bending method is that the permeability results are obtained in a few minutes to a few hours, whereas conventional techniques take hours or days to measure permeability of this order of magnitude. More importantly, there is no need to maintain high pressure during the measurement period, so leaks are not a problem.

45. Ai, H., J. F. Young, and George Scherer, 2001: Thermal expansion kinetics: Method to measure permeability of cementitious materials: II, Application to hardened cement pastes. Journal of the American Ceramic Society, http://www3.interscience.wiley.com/journal/118965150/abstract, 84(2), 385-391
    [ Abstract ]

    A new approach to determine the permeability of cementitious materials is presented in this paper. The method involves the measurement of the thermal dilatation of thin slabs of saturated cement paste. On heating and subsequent isothermal holding, the sample first expands, then gradually contracts over time. The paste is treated as a porous solid with low permeability in which the initial expansion is partly due to the liquid expanding within the pores, putting both solid and liquid under stress. The time-dependent contraction is due to the liquid flowing out of the pores to restore the pressure to equilibrium. By analyzing the kinetics of the thermal expansion and contraction, the liquid permeability of the porous solid can be calculated. The theoretical analysis (presented in a previous paper) is applied to determine the water permeability coefficients of selected cement pastes modified with silica fume and made with different water/solid ratios.

46. Vichit-Vadakan, W., and George Scherer, 2001: Beambending method for permeability and creep characterization of cement paste and mortar. Creep, Shrinkage and Durability Mechanics of Concrete and Other Quasi-Brittle Materials, Amsterdam, Elsevier, 27-32
    [ Abstract ]

    When a saturated rod of Portland cement paste or mortar is deflected in 3-point bending, two types of time dependent relaxation processes occur simultaneously: hydrodynamic relaxation caused by the flow of liquid in the porous body and viscoelastic relaxation of the solid network. By measuring the decrease in the force required to sustain a constant deflection, it is possible to obtain the permeability and Young's modulus from the hydrodynamic relaxation function, in addition to the stress relaxation function of the sample. As shown in previous papers, the total relaxation can be very closely approximated as the product of the hydrodynamic and viscoelastic relaxation functions. We are reporting the evolution of permeability, elastic modulus, and stress relaxation function for Type III Portland cement pastes with water-cement ratio of 0.5 at early ages.

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