Multicomponent Hydrate Research Articles

Think Drink: Feasibility trial of a multicomponent hydration care intervention for people living with dementia in care homes

Background and aimPeople with dementia, and particularly those living in care homes are at risk of suboptimal hydration and dehydration. Individual, contextual and staffing factors affect drinking behaviour in this population, hence multicomponent hydration care interventions have been promoted. The aim was to assess the feasibility and acceptability of a multicomponent Think Drink intervention for supporting hydration for people living with dementia in English care homes. MethodsA cluster randomised controlled feasibility study compared 6 intervention care homes and 5 control homes, over 3-months. Data (fluid intake; admission to hospital/dehydration; falls; laxative use; urinary tract infection and upper respiratory tract infection) was collected from 50 residents living with dementia in the intervention group and 37 control group pre and post intervention. Post intervention, 45 care home staff took part in 9 individual and 17 small group interviews. ResultsThink Drink was feasible and acceptable to participating care home staff. The findings highlighted how Think Drink changed staff knowledge of hydration requirements and new hydration practices were implemented in care homes. No significant positive change in fluid intake was found in the intervention group in terms of mean and median fluid intake in previous seven days, and proportion of population achieving an intake greater than 1,600mls per day. This could be attributed to improvement in recording fluid intake following the intervention. ConclusionsWhilst Think Drink is acceptable to care home staff further research is required to address methodological issues in assessing efficacy in supporting fluid intake.

The effect of multi-component Inhibitor systems on hydrate formation

Based on the existing components of drilling fluids, the construction of a multi-component hydrate inhibitor system is essential for building a high-performance hydrate drilling fluid system and reducing production costs. The constant rate cooling method are performed to investigate the effect of different inhibitor systems on hydrate formation. The results indicate that thermodynamic inhibitors exhibit enhanced effectiveness in inhibiting hydrate formation at higher mass concentrations. In contrast, kinetic inhibitors demonstrate superior performance at lower mass concentrations, and their inhibitory efficacy does not scale up with concentration. Kinetic inhibitors can synergize with other components of the drilling fluid that have thermodynamic inhibitor effects. In particular, the ternary composite system has better synergistic effects compared to the binary composite system. It is of great significance for the construction of efficient hydrate drilling fluid systems in the future.

Modeling the thermal and mechanical properties of early age concrete containing ground granulated blast furnace slag

In this study, a multi-component hydration model of cementitious material was applied to estimate the heat of hydration, adiabatic temperature rise (ATR), and compressive strength of concrete containing ground-granulated blast furnace slag (GGBFS). Different types of GGBFS were hydrated in limewater solution to measure their heat generations. The reference heat of slag in the multi-component hydration model (DuCOM) was revised using the heat measured from each type of GGBFS. Hence, the revised model is sensitive to the chemical compositions of slag. Isothermal and adiabatic heat measurements, as well as compressive strength experiments, were conducted using concrete with four different types of GGBFS. Results show that the proposed model is able to estimate the heat of hydration, adiabatic temperature rise, and compressive strength of concrete mix using different types of GGBFS with various w/cm ratios and air contents. The model predictions versus experimental results show reasonable agreement with the maximum average error percentage of 6.8% and 11% for the heat of hydration and compressive strength, respectively. The proposed method can be a useful technique to obtain the thermal and mechanical properties of GGBFS blended concrete with different cement and GGBFS sources.

Empirical Compression Model of Ultra-High-Performance Concrete Considering the Effect of Cement Hydration on Particle Packing Characteristics.

The mix design of UHPC has always been based on a large number of experiments; in order to reduce the number of repeated experiments, in this study, silica fume (SF), fly ash (FA), and limestone powder (LP) were used as the raw materials to conduct 15 groups of experiments to determine the particle size distribution (PSD) properties of UHPC. A model of multi-component hydration based on the SF, FA, and LP pozzolanic reactions was devised to quantify the rate and total heat release during the hydration process. Additionally, a microscopic pore development model, which was based on the accumulation of hydration products, was established to measure the effect of these products on the particle-packing properties. Utilizing this model, a UHPC strength prediction technique was formulated to precisely forecast the compressive strength based on a restricted experimental data set. The applicability of this prediction method was verified using 15 sets of existing experimental data along with the data collected from 4 research articles. The results show that the prediction method can predict the strength values of different mix proportions with an accuracy rate of over 80%.

The effect of heat treatment on the kinetics of the delayed ettringite formation – An improved chemo-thermal-hygral model

This study investigates the effect of heat treatment on the kinetics of precipitation of the delayed ettringite in concrete structures and a chemical model for concrete expansion due to delayed ettringite formation (DEF). The expansion of concrete structures due to DEF majorly depends on the amount of sulfate, aluminate, and alkali content present in the cement. Apart from these parameters, environmental conditions like saturation, temperature, and duration of heat treatment also play a major role in the kinetics of the formation of delayed ettringite. The thermal energy, which is a function of concrete’s high temperature and its duration, can change the concrete’s microstructures affecting the kinetics of release of sulfate from the C-S-H gel. Such high temperature curing can also affect the leaching of alkali by modifying the pore structure. A comprehensive chemo-thermo-hygral model for DEF is discussed in this study based on study conducted by previous research. The previous model defines the kinetics of three major phenomenon related to DEF: dissolution of ettringite and monosulfate at high temperature; fixation of aluminate into hydrogarnet during the high-temperature curing; precipitation of delayed ettringite. In the current work, the model is integrated with a multi-component hydration heat model and a new thermal energy factor governing the precipitation kinetics which not only correlates well the final expansion with experimental values, but also closely simulates the kinetics of expansion. A multi-ionic transport model is considered for alkali equilibrium. Finally, the kinetics of DEF along with the chemical expansion is validated with the experimental results from literature.

Time-dependent retardation effect of epoxy latexes on cement hydration: Experiments and multi-component hydration model

The kinetics and thermodynamics of the retardation effect of epoxy latexes on cement hydration were investigated using isothermal calorimetry and in-situ x-ray diffraction. The experimental results showed that the retardation effect of epoxy latexes on cement hydration was time-dependent. When the epoxy latexes were added to cement pastes, heat-generation rate was slowed, the hydration induction and acceleration periods were delayed, and the heat-flow maxima were suppressed. The addition of epoxy latexes markedly retarded silicate and aluminate hydrations by retarding both the dissolution of cement clinker minerals and the precipitation of hydration products. Higher epoxy latex content led to even slower cement hydration. Based on these results, a multi-component hydration model for composite cementitious materials, considering the time-dependent retardation effect of epoxy latexes on cement hydration, was established. The numerical results showed that the model showed great potential to predict the kinetics and thermodynamics of cement hydration with different epoxy latex contents, and provided more details about the phase evolution of the clinker minerals during cement hydration.

Implementation of a multi-layer radiation propagation model for simulation of microwave heating in hydrate reservoirs

PurposeThis paper aims to present the implementation of a multi-layer radiation propagation model in simulations of multi-phase flow and heat transfer, for a dissociating methane hydrate reservoir subjected to microwave heating.Design/methodology/approachTo model the induced heterogeneity due to dissociation of hydrates in the reservoir, a multiple homogeneous layer approach, used in food processes modelling, is suggested. The multi-layer model is incorporated in an in-house, multi-phase, multi-component hydrate dissociation simulator based on the finite volume method. The modified simulator is validated with standard experimental results in the literature and subsequently applied to a hydrate reservoir to study the effect of water content and sand dielectric nature on radiation propagation and hydrate dissociation.FindingsThe comparison of the multi-layer model with experimental results show a maximum difference in temperature estimation to be less than 2.5 K. For reservoir scale simulations, three homogeneous layers are observed to be sufficient to model the induced heterogeneity. There is a significant contribution of dielectric properties of sediments and water content of the reservoir in microwave radiation attenuation and overall hydrate dissociation. A high saturation reservoir may not always provide high gas recovery by dissociation of hydrates in the case of microwave heating.Originality/valueThe multi-layer approach to model microwave radiation propagation is introduced and tested for the first time in dissociating hydrate reservoirs. The multi-layer model provides better control over reservoir heterogeneity and interface conditions compared to existing homogeneous models.

Effect of confined boundary and mud-layers on depressurization-based gas recovery and land subsidence in hydrate reservoirs

Hydrate reservoirs present numerous challenges due to their occurrence in ultra-deep regions, presence of mud-layers, unconfined boundaries, and complex morphological heterogeneities. Individual effect of some of these reservoir settings on overall production is known, however, a systematic assessment of their mutual impact on gas production and land subsidence is essential from production outcome point of view. In the present study, we address the mutual effect of confined boundaries and mud-layers, and their subsequent impact on depressurization induced gas recovery and land subsidence in hydrate reservoirs. Reservoir conditions are considered to be representative of Indian hydrate reservoirs. A numerical study is performed using a multiphase, multicomponent hydrate reservoir simulator externally coupled with a semianalytical subsidence model. Results indicate that the gas production vary by a large margin depending on whether the reservoir is confined or unconfined. Presence of mud-layers affects the overall gas production significantly, where, for an unconfined reservoir, hydrate dissociation is higher in reservoirs with thin mud-layers. Properly sealed reservoirs are more vulnerable to depressurization induced subsidence than poorly sealed reservoirs. Subsidence possibility for the reservoir with a higher number of mud-layers is lower and is the greatest for a reservoir with no mud-layers.

Enhanced hydration model of fly ash in blended cement and application of extensive modeling for continuous hydration to pozzolanic micro-pore structures

Fly ash (FA) concrete has many advantages of enhancing durability even in severe environmental conditions. If the long-term performance can be predicted with higher reliability, it greatly contributes to determination of proper mix proportions in structural design, with further application to practical structures being anticipated. Although the finding that peculiar slow-down hydration of FA in blended cement occurs according to the experimental conditions had been pointed out, the original multicomponent hydration model in DuCOM was not able to simulate a similar tendency. Hence, by simply considering morphology and intrinsic properties of precipitated C-S-H gels due to pozzolanic reactions, an enhanced hydration model was proposed. In addition, the original models, regarding compressive strength development and continuous hydration considering spatial condensed water in fine micro-pore structures, were extended to be applicable also to FA blended cement. Verification of the installation effect was revealed through good agreement with the peculiar experimental tendency.

Investigation of the performance of biocompatible gas hydrate inhibitors via combined experimental and DFT methods

In this work, three ionic liquids (ILs) from the bio-compatible family of choline cations attached to anions of varying hydrophobicity namely: choline acetate (ChOAc), choline bistriflamide (ChNtf2), and choline chloride (ChCl), have been tested for their gas hydrate inhibition properties for methane and a multi-component Qatari natural gas type mixture (QNG-S1). A rocking-rig assembly (RC-5) has been used to obtain the pressure-temperature (P-T) loops for the studied systems in absence/presence of inhibitors. Two concentrations of 1 and 5wt% for the choline IL-inhibitors have been chosen which shows distinct effectiveness towards studied single and multi-component hydrate systems. Hydrate suppression temperatures (ΔT) have been calculated from the obtained dissociation data for quantitative analysis of inhibition effect of ILs and its trends against pressure dependence were discussed. Further, to understand the mechanism of hydrate formation and dissociation, the imaging of a complete P-T loop for CH4+5wt% ChNtf2 system has been performed using a borescope camera attached to gas hydrate autoclave (GHA) apparatus. Furthermore, the main features of the interaction mechanism between selected ionic liquids and hydrate structures were elucidated at the molecular level through quantum chemical calculations by using density functional theory (DFT) methods. The results on the effectiveness of bio-compatible ILs as hydrate inhibitors compared to their conventional counterparts have been proposed in the manuscript.

Evaluation of the mechanical properties of concrete considering the effects of temperature and aging

This paper presents a procedure to evaluate the development of the mechanical properties of hardening concrete considering the effects of temperature and aging. The steps of this procedure are shown as follows: first, by using a multi-component hydration model, we evaluate the degree of hydration of cement as a function of the mineral compositions of cement, the water to cement ratio, curing temperature and particle size distribution; second, by using the modified Powers’ law, the development of the compressive strength of concrete is evaluated through the gel–space ratio and degree of hydration of cement; third, the development of the elastic modulus and splitting tensile strength of hardening concrete are evaluated by using empirical equations from the compressive strength. The proposed procedure is verified through experimental results on the mechanical properties of hardening concrete cured under constant and variable temperature conditions.

Systematic kinetic studies on mixed gas hydrates by Raman spectroscopy and powder X-ray diffraction

This study presents results from systematic time-resolved experiments regarding the guest molecule geometry. The in situ observations of formation and dissociation processes of multicomponent hydrates were performed by means of Raman spectroscopy and a newly designed experimental setup including powder X-ray diffraction (PXRD) whose capabilities will be presented here in more detail. Both experimental setups allow investigating hydrate kinetics as a function of pressure, temperature, and feed gas composition. The unique feature of both setups is the continuous gas flow providing a constant composition of the gas phase during the whole experiment. This is crucial for the formation of mixed hydrates formed from feed gas mixtures that contain one or more components in low concentrations. The formation of structure II hydrates including C3H8, iso-C4H10, n-C4H10, or neo-C5H12 besides CH4 was analysed according to a multi-step model. For the initial phase it turned out that hydrates grown from the gas mixture containing 2% n-C4H10 and 98% CH4 have the highest formation rate at defined p, T conditions in comparison to other hydrates formed from gas mixtures containing about 2vol% of the above mentioned hydrocarbons besides CH4. But the reaction mechanisms for each hydrate system emerged to be different. Furthermore, Raman and time-resolved PXRD experiments were performed to study the formation of structure H hydrates with a low-concentrated large hydrocarbon guest molecule. In case of a gas mixture containing 1% iso-C5H12 and 99% CH4 the formation of a simple structure I CH4 hydrate was observed at first. Later on, structure H CH4+iso-C5H12 hydrate was formed resulting in a coexistence of both structures.

Using Water as a Design Element in Crystal Engineering. Host−Guest Compounds of Hydrated 3,5-Dihydroxybenzoic Acid

Thirteen host−guest compounds of 3,5-dihydroxybenzoic acid (DHBA) have been structurally characterized. Water molecules occupy the peripheries of a hexagonal void, created with DHBA molecules, and act as “hooks” to connect the guest molecules with the host-framework via hydrogen bonding. The “water hook” is an OH group acting as a donor. Consequently, the guest molecules were chosen so that they contain good hydrogen bond acceptor functionalities. A number of multicomponent hydrates were isolated with stoichiometries (DHBA)x(H2O)y(guest)z. Of these, compounds with the following as guests were obtained as crystals that were good enough for single crystal work: ethyl acetate (EtOAc), diethyl oxalate, dimethyl oxalate, di(n-propyl) oxalate, diethyl malonate, diethyl succinate, chloroacetonitrile, N,N-dimethyl formamide (DMF), acetone, dimethyl sulfoxide (DMSO), 1-propanol, and 2-butanol. From 2-butanol, a hemihydrate, (DHBA)2(H2O), was also obtained concomitantly. Further to guest stabilization, water acts as a good mediator of effective crystal packing and also determines the topology of the host framework. In the present series of compounds, the role of water is wide ranging, and it is not easy to classify it specifically as a host or as a guest.

A natural hydrate dissolution experiment on complex multi-component hydrates on the sea floor

Dissolution of natural hydrate cores was measured using time-lapse photography on the seafloor at Barkley Canyon (850 m depth and 4.17 °C). Two types of hydrate fabrics in close contact with one another were studied: a “yellow” hydrate stained with condensate oil and a “white” hydrate. From thermogenic origins, both fabrics contained methane as well as heavier hydrocarbons. These multi-component hydrates were calculated to be well within p– T stability conditions (<200 m water depth needed at 4.17 °C). While stable in pressure and temperature, the hydrates were bathed in under-saturated seawater, which promoted dissolution. The flux of gas from the shrinking yellow hydrate core was 0.15 ± 0.01 mmol gas/m 2 s, while the white hydrate dissolved faster at 0.25 ± 0.02 mmol gas/m 2 s. To determine the controlling mechanism for the observed changes in the hydrate cores, experimental results were compared with an engineering correlation for convective mass transfer. Using water velocity as a fitting parameter, the correlation agreed well with results from a previous dissolution experiment on well-characterized synthetic hydrates. Even with a number of other unknowns, when applied to the natural hydrate, the mass transfer correlation predicted the dissolution rate within 20%. This seafloor-based experiment, along with visual observations of seafloor hydrate dissolution over a 3-day period, were used to further understand the fate of natural seafloor hydrates exposed on the seafloor. By showing that mass transfer is the rate-controlling mechanism for dissolution of these natural hydrate outcrops, proper hydrodynamic calculations can be employed to give a refined estimate on hydrate dissolution rates.

Evaluation of chloride penetration in high performance concrete using neural network algorithm and micro pore structure

Chloride attack is one of the major causes of deterioration of reinforced concrete structures. In order to evaluate the chloride behavior in concrete, a reasonable prediction for the diffusion coefficient of chloride ion, which governs mechanism of chloride diffusion inside concrete, is basically required. However, it is difficult to obtain chloride diffusion coefficients from experiments due to time and cost limitations. In this study, a numerical technique for chloride diffusion in high performance concrete (HPC) using a neural network algorithm is proposed. In order to collect comparative data on diffusion coefficients in concrete with various mineral admixtures such as ground granulated blast-furnace slag (GGBFS), fly ash (FA), and silica fume (SF), a series of electrically driven chloride penetration tests was performed. Seven material components in various mix designs and duration time are selected as neurons in a back-propagation algorithm, and associated learning of the neural network is carried out. An evaluation technique for chloride behavior in HPC using the obtained diffusion coefficients from the neural network algorithm is developed based on, so-called, Multi-Component Hydration Heat Model (MCHHM) and Micro Pore Structure Formation Model (MPSFM). The applicability of the developed technique is verified by comparing the analytical simulation results and the experimental results obtained in this study. Furthermore, this proposed technique using the neural network algorithm and micro modeling is applied to available experimental data for verification of its applicability.

Numerical Simulation of Autogenous Shrinkage in High-Performance Cement Paste Based on a Multi-Component Hydration Model

Autogenous shrinkage is the term for the bulk deformation of a closed, isothermal, cement-based material system not subjected to external forces. It is associated with the internal volume reduction of cement/water mixture in the course of the hydration process. However, addition of blended components to cement, especially such as fly ash or silica fume, for the high-performance concrete will lead to a densification of the microstructure. The autogenous shrinkage deformation will increase and the following autogenous shrinkage crack will do harm to durability of concrete structure. In this paper, numerical simulation is suggested to predict autogenous shrinkage of high performance cement paste. The simulation is originated from a multicomponent hydration model. The numerical program considers the influence of water to cement ratio, curing temperature, particle size distribution, cement mineral components on hydration process and autogenous shrinkage. The prediction result agrees well with experiment result.

Numerical Simulation of Heat Evolution of Eco-Friendly Blended Portland Cements Using a Multi-Component Hydration Model

With the development of concrete industry, the necessity for utilizing waste materials and decreasing overall energy consumption is becoming increasingly obvious. Fly ash and granulated blast-furnace slag, which are used as blends of Portland cement, are waste materials produced in electric and energy industry, and concretes made with them can have properties similar to ones made with pure Portland cement at lower cost per unit volume. By using blended Portland cement, both ecology benefit and economic benefit can be achieved. Due to the pozzolanic reaction between calcium hydroxide and blended components, compared with ordinary Portland cement, hydration process of blended Portland cement is more complex. In this paper, based on a multi-component hydration model, a numerical model which can simulate heat evolution process of blended Portland cements is built. The influence of water to cement ratio, curing temperature, particle size distribution of cement paste and blended Portland material, and cement mineral components on heat evolution process is considered. The prediction result agrees well with experiment result.

Numerical Simulation of Autogenous Shrinkage of Eco-Friendly Blended Portland Cements Using a Multi-Component Hydration Model

Fly ash and granulated blast-furnace slag, which are used as blends of Portland cement, are waste materials produced in electric and energy industry. Due to excellent durability, low heat of hydration, energy-saving, resource-conserving, and generally less expensive than ordinary Portland cement, blends Portland cements is used increasingly in construction industry. Both ecology benefit and economic benefit can be achieved by using blended Portland cement. Addition of blended components to cement, especially such as fly ash or silica fume, will lead to a densification of the microstructure. The autogenous shrinkage deformation will increase and the following autogenous shrinkage crack will do harm to durability of concrete structure. In this paper, based on the multi-component hydration model, a numerical program is built to predict autogenous shrinkage of ordinary Portland cement and blended Portland cement. The numerical program considers the influence of water to cement ratio, curing temperature, particle size distribution, cement mineral components on hydration process and autogenous shrinkage. The prediction result agrees well with experiment result.

수화물 및 공극률 관측 실험을 통한 시멘트모르타르의 탄산화 특성 변화에 대한 연구

Due to the increasing significance of durability, much researches on carbonation, one of the major deterioration phenomena are carried out. However, conventional researches based on fully hardened concrete are focused on prediction of carbonation depth and they sometimes cause errors. In contrast with steel members, behaviors in early-aged concrete such as porosity and hydrates (calcium hydroxide) are very important and may be changed under carbonation process. Because transportation of deteriorating factors is mainly dependent on porosity and saturation, it is desirable to consider these changes in behaviors in early-aged concrete under carbonation for reasonable analysis of durability in long term exposure or combined deterioration. As for porosity, unless the decrease in diffusion due to change in porosity is considered, the results from the prediction is overestimated. The carbonation depth and characteristics of pore water are mainly determined by amount of calcium hydroxide, and bound chloride content in carbonated concrete is also affected. So Analysis based on test for hydration and porosity is recently carried out for evaluation of carbonation characteristics. In this study, changes in porosity and hydrate under carbonation process are performed through the tests. Mercury Intrusion Porosimetry (MIP) for changed porosity, Thermogravimetric Analysis (TGA) for amount of are carried out respectively and analysis technique for porosity and hydrates under carbonation is developed utilizing modeling for behavior in early-aged concrete such as multi component hydration heat model (MCHHM) and micro pore structure formation model (MPSFM). The results from developed technique is in reasonable agreement with experimental data, respectively and they are evaluated to be used for analysis of chloride behavior in carbonated concrete.

Direct measurements of multi-component hydrates on the seafloor: Pathways to growth

The phase behavior of multi-component hydrate systems formed in the ocean has been studied using a sea-going in situ Raman spectrometer. Results from a field study using a synthetic hydrate sample and preliminary measurements of naturally occurring thermogenic hydrates at Barkley Canyon are reported and compared. This work follows early field trials using simple and binary synthetic hydrates and an expedition to Hydrate Ridge, studying natural hydrates primarily composed of methane. This refined Raman technique was combined with visual observations utilizing remotely operated vehicles as experimental platforms in an oceanic laboratory. Traditional laboratory Raman analysis was also performed on hydrate samples following recovery. A synthetic hydrate was first studied in Monterey Bay to characterize the formation, evolution, and dissociation of multi-component gas hydrates formed in the deep ocean as a guide to understanding complex behavior of natural hydrate systems. The gas mixture (92.5% CH 4, 3.8% C 2H 6, 1.9% C 3H 8, 0.4% i-C 4H 10, 0.4% n-C 4H 10, 0.1% i-C 5H 12, 0.1% n-C 5H 12, and 0.1% neo-C 5H 12) was chosen to simulate a typical natural gas composition. Regions of sII and mixed sI–sII hydrate were measured in situ after 65 days of formation. The presence of a heterogeneous inter-mixed sI–sII hydrate suggests a formation mechanism where hydrate growth proceeds from localized pockets of isolated gas, such as gas bubbles separated from the bulk vapor phase by hydrate membranes, where sI formation follows the depletion of sII-forming gases within these individual hydrate reactors. Unstable conditions during recovery led to significant hydrate dissociation, leaving only ice and a compositionally homogenous sII hydrate phase, with no evidence of the sI that had been observed at the seafloor. To investigate whether this process may operate in natural systems, a Raman investigation of the natural thermogenic hydrates at Barkley Canyon was carried out. Massive seafloor hydrate outcrops varied in appearance from yellow, due to oil staining, to white. While the yellow hydrate had significant interference due to fluorescence, detailed analysis of the in situ Raman data was possible for the white hydrate. This white hydrate was mainly sII, but the presence of sI was also detected. The heterogeneity in both structure and composition of these natural hydrates was similar to the synthetic hydrate formed in Monterey Bay. These similarities suggest that a controlled seafloor experiment was able to simulate a natural thermogenic hydrate with reasonable accuracy. Further development of theory and testing is needed to determine if the ‘individual hydrate reactor’ mechanism was indeed the pathway to growth in this natural system.