Academic literature on the topic 'Hydration degree'

The cement hydration is an exothermic reaction. The hydration heat is characterizing quantitatively the clinker hydration degree. Monitoring its time response makes it possible to determine not only the heat released during a certain time interval but also the concrete mix setting onset, the cement hydration degree (when evaluating the cement applicability after a long storage period) etc. The measurement of the hydration heat or the temperature versus time plot for a hydrating mix makes it possible to identify the effect of the different additives and admixtures on the mix hydration kinetics. This paper deals with the effect of adding two different super-plasticizers (lignin-sulphonate-based and naphthalene-sulphonate-based) on the hydration heat development progress. A set of iso-peribolic calorimeters was used to measure the hydration heat development process. The measurement proper consisted in monitoring and recording the temperature versus time plot for the specimen under test. The released heat amount was determined by calculation from the temperature gradient, the ambience specific thermal losses, the material thermal capacity and the test specimen mass.

To explore the hydration process of fly ash-cement blended mixtures, the degrees of the fly ash and cement reactions as well as the content of nonevaporated water were determined at various water to binder ratios, curing ages, and fly ash incorporation amounts. An equation describing the relationship between the degree of hydration and the effective water to binder ratio was established based on the experimental results. In addition, a simplified scheme describing a model of the degree of reaction in fly ash-cement mixtures is proposed. Finally, using reaction stoichiometry, quantitative equations for the hydration products of fly ash-cement blended pastes are proposed by considering the hydration reactions of fly ash and cement as well as their interactions. The predicted results of the enhanced degree of cement hydration, content of calcium hydroxide (CH), and porosity are consistent with the experimental data.

Abstract. The hydration degree of Portland cement-slag complex binders was investigated by hydration heat, chemically bound water amount, EDTA selective dissolution and mortar compressive strength. Different hydration degree of complex binders was obtained with different methods. Hydration heat and EDTA method indicated that reaction degree of slag was much lower than cement and the total reaction degree of complex binders was also lower than neat cement. However, chemically bound water amount and mortar compressive strengths of complex binders blended with slag within certain limit were higher than neat cement at late age.

The hydration degree of fly ash and the calcium hydroxide (CH) content were measured. Combined with the equilibrium calculation of cement hydration, a new method for assessment of the hydration degree of cement in the fly ash-cement (FC) pastes based on the CH content was developed. The results reveal that as the fly ash content increase, the hydration degree of fly ash and the CH content decrease gradually; at the same time, the hydration degree of cement increase. The hydration degree of cement in the FC pastes containing a high content of fly ash (more than 35%) at 360 days is as high as 80%, even some of which hydrates nearly completely. The effect of water-cement ratio to the hydration degree of cement in the FC pastes is far less distinct than that of the content of fly ash.

Slag is increasingly unitized for the production of sustainable concrete. This paper presents a procedure with which to analyze the property development of slag composite concrete. Experimental studies of the hydration heat and compressive strength development and simulation studies using a kinetic hydration model and a thermodynamic model were performed. First, we performed an experimental study of the isothermal hydration heat of cement–slag blends. Based on the results of the experimental study on cumulative hydration heat, the reaction degree of slag was determined. We found that the reaction degree of slag decreased as the slag content increased. Second, the reaction degree of slag and cement were used as the input parameters for the Gibbs energy minimization (GEM) thermodynamic equilibrium model. Moreover, the phase assemblage of hydrating cement–slag was determined. The trends of calcium silicate hydrate (CSH) are similar to those of strength. Based on the CSH content, the strength of hardening cement–slag blends was determined. In addition, the calcium hydroxide (CH) content resulting from the thermodynamic model shows good agreement with the experimental results. In summary, the integrated kinetic–thermodynamic model is useful for analyzing the properties of cement–slag blends.

Based on the multi-phase hydration dynamic model, taking into account the factors such as chemical composition of cement, curing temperature, water-cement ratio, the final hydration degree and fineness of cement, a theoretical hydration kinetics equation is established in this paper. It can be used to predict the hydration rate increases with the change of hydration degree. The results showed that: water-cement ratio will accelerate the phase boundary reaction, while not influence the early crystallization of nucleation and crystal growth; temperature can accelerate the hydration process, while it can not change the ultimate hydration degree.

Prediction of degree of hydration of concrete is very important on research of crack-resistance capability and durability of the structure. This article studied the relationship between degree of hydration and strength of concrete based on a large number of references, the results show that the compressive strength of concrete is closely related with the degree of hydration, and the correlation function is a function of water-cement ratio and has nothing to do with the temperature. The hydration degree and compressive strength of ordinary concrete is linear correlation, and the prediction model of degree of hydration of concrete was proposed based on BP Artificial Neural Networks.

AbstractA binary ion exchange of cationic pairs involving K, Na, Ba and Ca in clinoptilolite was investigated calorimetrically. The selected cations included two pairs equal in charge and two pairs similar in size. The heats of ion exchange and the degrees of exchange were determined at 30 and 95°C. The data obtained are discussed with respect to cationic interactions in the clinoptilolite structure and hydration characteristics (heats of hydration and hydration numbers) of competing cations in the solution. No correlation was found between the heat effects and the degree of exchange. The heat of exchange depends mainly on the difference between the hydration heats of the cations in the solution, whereas the degree of exchange depends on their positioning over the extraframework sites in the clinoptilolite structure. The heats of ion exchange are lower at 95°C than those measured at 30°C, which is due to a decrease of the hydration number with increasing temperature. In all cases the degree of exchange increases with increasing temperature.

This work examines the influence of zeolite saturated with zinc (SZ) on the early hydration of Portland cement. The measurements and results indicate that the microcalorimetric method allows continuous observation and determination of SZ’s influence on kinetic processes in the early stages of hydration. According to the total heat released after 48 hours of hydration, higher SZ content results in lower heat values, while the maximum hydration occurs earlier. As SZ proportion increases, the rate of heat release and the degree of hydration decrease. Measured hydration degrees differ significantly from the calculated values when SZ is added to Portland cement, especially later in the hydration process.

Hydration is a chemical reaction in which the major compounds in cement form chemical bonds with water molecules and become hydration products. By the process of hydration Portland cement mixed with sand, gravel and water produces the synthetic rock we call concrete. The Therefore, the concrete properties always accompanies with the hydration degree of cement. This paper presents some experimental test results on how silica fume affects the cement hydration in cement pastes of the Reactive Powder Concrete as increasing levels of silica fume addition with the content from 0% to 30% of cement mass. The hydration process of cement/silica fume paste was followed from the estimation of heat of hydration, rate of heat evolution, of binder pastes obtained by isothermal calorimetry (TAM-Air). In addition, the portlandite content, the hydration degree of pure cement, reaction degree of binder paste as well as reaction degree of silica fume were investigated. The quantitative assessment on these characteristics are due to the simulation of the hydration of Portland cement pastes containing silica fume.

L’utilisation de ciment à haute teneur en laitier est envisagée dans le cadre du conditionnement des déchets nucléaires. Dans ce contexte, il est nécessaire de connaître les propriétés structurales et de transport des gaz formés par la radiolyse de l’eau contenue dans cette matrice. Selon la littérature, ces propriétés sont impactées par l’ajout de laitier de haut-fourneau. L’objectif de cette thèse est de relier les processus d’hydratation des ciments au laitier aux propriétés de transport des gaz. La première partie de cette étude est consacrée à l’étude de l’hydratation des ciments au laitier. La Résonance Magnétique Nucléaire (RMN) du silicium et de l’aluminium a été utilisée pour suivre l’évolution de la quantité des différentes phases anhydres du clinker (C3S, C2S, C3A et C4AF) et des principaux oxydes de la phase vitreuse du laitier (SiO2, Al2O3, MgO et SO3). La quantité de calcium dissoute provenant du laitier a, quant à elle, été déduite en comparant la quantité de portlandite [Ca(OH)2] mesurée par ATG avec celle calculée par un logiciel de spéciation chimique (Phreeqc). Cette approche a permis de déterminer l’évolution du degré d’hydratation des principaux oxydes de la phase vitreuse du laitier dont une dissolution progressive (comparé au clinker) et incongruente (la vitesse de dissolution des différents oxydes et différente) a ainsi pu être mise en évidence. Cette plus faible réactivité du laitier a pu être mise en relation, pour un temps donné, avec la diminution de la quantité d’eau liée au ciment, de la contraction chimique et de la chaleur dégagée. La prise en compte quantitative de la dissolution des phases du clinker et des oxydes du laitier permet une description plus précise de la minéralogie. La deuxième partie de ce travail porte sur l’évolution de la microstructure et de son influence sur les propriétés de transport en phase gazeuse (diffusion et perméabilité). L’évolution du coefficient de diffusion effectif à l’hélium et à l’azote et de la perméabilité intrinsèque a été suivie au cours du temps et comparée à l’évolution de certaines grandeurs, telles que la porosité globale, le diamètre d’entrée critique, la surface spécifique et le degré de connectivité des pores. Les résultats montrent une diminution du coefficient de diffusion effectif et de la perméabilité au cours du temps, ce qui a pu être relié, pour un même matériau, à la diminution de la porosité totale. Une réduction de ces propriétés avec la teneur croissante de laitier a également été observée. Cette baisse est liée à une diminution de la porosité capillaire et à une augmentation de la nanoporosité, due à une modification de la microstructure des C-S-H. La dernière partie de ce projet concerne la relation entre les processus d’hydratation, la microstructure et les propriétés de transport. Dans ce but, des bilans volumiques des réactions d’hydratation ont été réalisés en considérant de façon indifférenciée ou séparée chaque phase du ciment. La prise en compte séparée des différentes phases du ciment permet d’évaluer avec une précision de 10 % la porosité totale, la teneur en eau liée et le volume de contraction chimique. Cette description permet d’expliquer les variations des propriétés de transport d’un même matériau dans la durée. Pour établir ce lien au cours du temps et pour tous les ciments, le volume apparent des C-S-H a été recalculé pour rendre compte de la microstructure de ces hydrates
Cements with high slag content are currently studied as possible candidate for nuclear waste containment materials. In this context it is important to know their microstructure and the transport properties (permeability and diffusion) of the gases that are formed by the radiolysis of the water present in this material. According to literature, these properties are strongly impacted by the addition of blast furnace slag. The aim of this work is to correlate the hydration processes of slag blended cements with their transport properties. In the first part of this work, the hydration of the slag blended cements, for which only few results have been reported to date, has been studied. Silicon-29 and aluminium-27 Magic-Angle Spinning Nuclear Magnetic Resonance (MAS NMR) were used to follow the variations of anhydrous phases of clinker (C3S, C2S, C3A and C4AF) and of the main oxides of the slag (SiO2, Al2O3, CaO, MgO and SO3). The quantity of calcium dissolved from slag was deduced by fitting the quantity of portlandite [Ca(OH)2] calculated by a geochemical software (PHREEQC - coupled to a thermodynamic database) with TGA measurements. Our approach enabled the evolution of the hydration degree (percentage of reacted material) of various oxides of slag to be determined. A progressive and an incongruent dissolution (the rate of dissolution of the oxides is different) of the slag is observed. The low reactivity of slag could be linked, at a hydration time, to a lower content of bound water, chemical shrinkage and heat of hydration. Quantitatively accounting for the dissolution of clinker and oxide of slag yields a more accurate description of the hydration process. The second part of this work is focused on the microstructure evolution and its influence on the transport properties (diffusion and permeability). Time-evolution of the diffusion coefficients and the intrinsic permeability could be monitored and were then compared to that of the microstructure (global porosity, pore entry size distribution, specific surface area and the degree of connectivity). The results showed a decrease in the diffusion coefficient and permeability over time which is due to the progressive filling of the porosity. A decrease of these parameters with the slag content increasing was also observed. This is a consequence of the diminution of the capillary porosity and augmentation of the nanoporosity resulting from changes in the microstructure of C-S-H. The last part concerns the relation between the hydration processes, the microstructure and the transport properties. To this aim, volumetric balances of reactions involved in the hydration processes were made by considering globally or specifically the hydration of the different phases. Accounting for the hydration of each phase of the cement allowed us to determine the global porosity, the bound water content and the chemical shrinkage with accuracy of the order of 10 %. This description allows the understanding of the transport properties variations in time for a same material To establish this time evolutions for all the cements, the apparent volume of C-S-H was recalculated to account for the microstructure of these hydrates

Lorsque des déchets nucléaires irradiants sont conditionnés en matrice cimentaire, l’eau contenue dans la solution porale et dans les hydrates peut être radiolysée, conduisant notamment à la production de dihydrogène. Dans le cas de déchets fortement irradiants, la maitrise de ce terme source hydrogène dans un site d’entreposage et/ou de stockage peut constituer un enjeu de sûreté. Ce terme source hydrogène peut-être limité en diminuant la quantité d’eau mise en œuvre pour élaborer les matrices cimentaires de conditionnement, ou en choisissant un liant cimentaire dont les produits d’hydratation présentent un faible rendement de production radiolytique de dihydrogène. De ce point de vue, les ciments alumineux pourraient présenter un intérêt significatif par rapport aux ciments silico-calciques. En effet, l’hydratation des ciments alumineux conduit à des assemblages minéralogiques dont les hydrates présentent une bonne stabilité sous irradiation. Toutefois, la vitesse d’hydratation de ces ciments est parfois élevée et incompatible avec les contraintes d’un atelier de cimentation industriel. Il convient donc de mieux comprendre les mécanismes d’hydratation de ces phases pour éventuellement mieux les contrôler.Dans le cadre de ce travail, le déroulement de l’hydratation de quatre aluminates de calcium anhydres synthétiques, se distinguant l’un de l’autre par leur rapport C/A, a été étudié. En particulier, ont été examiné, leur vitesse d’hydratation, leur degré d’hydratation et l’assemblage minéralogique formé. Les suivis d’hydratation ont été réalisés par microcalorimétrie isotherme et conductimétrie quand les phases ont été caractérisées par analyse thermogravimétrique, par diffraction des rayons-x et par résonance magnétique du solide. Toutes les expériences ont été réalisées à 25 °C. Les résultats du suivi de l’hydratation de pâtes de ciment et de suspensions cimentaires nous ont permis de conclure que les vitesses d’hydratation sont d’autant plus grandes que le rapport C/A de l’anhydre considéré est élevé. De plus, l’étude de l’hydratation de ces phases anhydres en suspension a permis d’identifier les chemins réactionnels suivis par chacun des systèmes étudiés. Notamment, il a été démontré que la formation d'hydroxyde d'aluminium limite la cinétique d'hydratation des phases anhydres dont le rapport C/A est inférieur ou égal à 1. Les résultats obtenus dans le cadre de ce travail pourront permettre à terme d’orienter le choix du ciment alumineux à mettre en œuvre pour le conditionnement de déchets irradiants
This Ph-D project takes place in the framework of nuclear waste conditioning in cementitious matrices. When an irradiating nuclear waste is stabilized and solidified in a cementitious matrix, the radiolysis of water molecules from the pore solution and from the hydrates themselves yields dihydrogen. In the case of highly irradiating wastes, the release of dihydrogen raises safety issues for storage and/or disposal facilities. The release of hydrogen gas by radiolysis can be limited by reducing the amount of water used for the elaboration of the cement or by choosing a cement binder with hydrates showing a good stability under irradiation. As far as radiolysis is concerned, calcium aluminate-based cements are of significant interest in comparison to calcium silicate cements. The hydration of calcium aluminate cements leads to mineralogical assemblages with a low radiolytic yield of dihydrogen. However, the hydration of these cements is sometimes too fast and incompatible with the industrial process requirements. The objective of this thesis is thus to better understand the underlying mechanisms of the hydration of the calcium aluminates present in calcium aluminate-based cements.Specifically, the course of hydration of four synthetic anhydrous calcium aluminates, varying one from each other by their C/A ratio, is studied at 25°C from the point of view of their hydration rate, their degree of hydration and the resulting mineralogical assemblages by a combination of isothermal calorimetry, thermogravimetric analysis, x-ray diffraction and solid-state nuclear magnetic resonance. Monitoring the hydration by isothermal calorimetry in pastes and by conductimetry in suspensions show that the higher the C/A ratio of the considered anhydrous phase, the higher the hydration rate. Finally, studying the hydration of each of these phases in suspension makes it possible to point out the reaction path followed by each studied system. This work also demonstrated that aluminium hydroxide formation limits the kinetics of hydration of anhydrous phases with a C/A ratio lower than or equal to 1. The results obtained in the framework of this thesis can help optimizing the design of a calcium aluminate cement-based matrix to be used for the conditioning of irradiating wastes

Doctor of Philosophy
Department of Civil Engineering
Kyle A. Riding
Finely ground glass has the potential for pozzolanic reactivity and can serve as a supplementary cementitious material (SCM). Glass reaction kinetics depends on both temperature and glass composition. Uniform composition, amorphous nature, and high silica content of glass make ground glass an ideal material for studying the effects of glass type and particle size on reactivity at different temperature. This study focuses on how three narrow size ranges of clear and green glass cullet, 63–75 [mu]m, 25–38 [mu]m, and smaller than 25 [mu]m, as well as combination of glass types and particle sizes affects the microstructure and performance properties of cementitious systems containing glass cullet as a SCM. Isothermal calorimetry, chemical shrinkage, thermogravimetric analysis (TGA), quantitative analysis of X-ray diffraction (XRD), and analysis of scanning electron microscope (SEM) images in backscattered (BS) mode were used to quantify the cement reaction kinetics and microstructure. Additionally, compressive strength and water sorptivity experiments were performed on mortar samples to correlate reactivity of cementitious materials containing glass to the performance of cementitious mixtures. A recently-developed modeling platform called “[mu]ic the model” was used to simulated pozzolanic reactivity of single type and fraction size and combined types and particle sizes of finely ground glass. Results showed that ground glass exhibits pozzolanic properties, especially when particles of clear and green glass below 25 [mu]m and their combination were used at elevated temperatures, reflecting that glass cullet is a temperature-sensitive SCM. Moreover, glass composition was seen to have a large impact on reactivity. In this study, green glass showed higher reactivity than clear glass. Results also revealed that the simultaneous effect of sizes and types of glass cullet (surface area) on the degree of hydration of glass particles can be accounted for through a linear addition, reflecting that the surface area would significantly affect glass cullet reactivity and that the effects of SCM material interaction on reaction kinetics were minimal. However, mechanical properties of cementitious systems containing combined glass types and sizes behaved differently, as they followed the weaker portion of the two particles. This behavior was attributed to the pores sizes, distruibution, and connectiity. Simulations of combined glass types and sizes showed that more work on microstructural models is needed to properly model the reactivity of mixed glass particle systems.

La production de dattes ne cesse d’augmenter d’une saison à une autre ce qui engendre des pertes essentiellement lors des étapes de manutention et de commercialisation. De plus, l’étape de manutention post-récolte joue un rôle important dans le maintien de la qualité des dattes. Dans ce cadre et afin de préserver les qualités organoleptique et nutritionnelle des dattes après récolte tout en améliorant leur valeur commerciale, des essais de conservation et de traitement post-récolte ont été mis en place. L’effet de la conservation des dattes en fonction de la température, du temps, de l’utilisation d’atmosphère modifiée lors du stockage et d’un traitement thermique sur la fermeté, la couleur, et les teneurs en sucres, acides organiques, polyphénols et parois cellulaires a été étudié. Les dattes du cultivar ‘Deglet Nour’ récoltées en 2017 et 2018 au stade Tamr ainsi que les dattes communes ‘Arichti’, ‘Bouhattam’, ‘Bser Hlou’ consommées à un stade de maturité précoce (stade Khalal) ont été conservées à -18, 0, 2 et 4 °C pendant 3, 6 et 9 mois et à 2 °C pendant 30 et 60 jours, respectivement. La spectroscopie Moyen Infrarouge (MIR) en tant que méthode non destructive et non ciblée a permis de mettre en évidence l’effet de l’année de récolte par rapport à la composition chimique et de discriminer les échantillons de dattes ‘Deglet Nour’ conservés à 4 et 2 °C. Le rendement en parois cellulaires assimilées aux fibres, ainsi que les procyanidines représentant 98% des polyphénols totaux sont stables durant la conservation du cultivar ‘Deglet Nour’ et du cultivar ‘Arichti’ quel que soit la température et la durée de conservation. En revanche, ces composants sont ceux qui sont les plus affectés par les conditions de conservations dans le cas des cultivars ‘Bouhattam’ et ‘Bser Hlou’. Ce dernier est le cultivar le plus ferme et le plus apprécié par les consommateurs, en raison notamment de l’augmentation des teneurs en sucres réducteurs affectant son goût sucré lors de la conservation. De ce fait, une conservation des dattes ‘Deglet Nour’ à -18 °C pourrait être une solution pour un stockage à long terme, par contre en raison des coûts énergétiques élevés, 2 °C est la température optimale de conservation. En outre, afin de bien valoriser les dattes communes et prolonger leur durée de vie, la durée de conservation peut être prolongée pour le cultivar ‘Arichti’, une optimisation de la température de conservation pour le cultivar ‘Bser Hlou’ et ‘Bouhattam’ sera cependant nécessaire. Les dattes précédemment citées ont été également conservées dans différents types d’emballages à atmosphère modifiée (EAM) à 2 °C pendant 3, 6 et 9 mois pour le cultivar ‘Deglet Nour’ et pendant 30 et 60 jours pour les cultivars ‘Arichti’, ‘Bouhattam’ and ‘Bser Hlou’. D’une façon générale, ces résultats ont montré que les EAM ont le même impact que la température et la durée de conservation sur la qualité des dattes. Par conséquent, leur utilisation dans les industries de conditionnement de dattes va entrainer des coûts supplémentaires sans effets bénéfiques. L’impact d’un traitement d’hydratation sur les qualités organoleptique et nutritionnelle des dattes a également été évalué. Le traitement des dattes ‘Deglet Nour’ de trois usines de conditionnement différentes, à une vapeur d’eau saturée à 60-62 °C pendant 4 heures a montré qu’elles deviennent plus souples comme attendu, tandis que les paramètres nutritionnels sont resté stables. La spectroscopie Moyen Infrarouge (MIR) a permis de discriminer les dattes des trois usines et il est suggéré qu’elle soit adoptée par les stations de conditionnement comme une nouvelle technique prédictive et non destructive. Ce résultat confirme que le traitement d’hydratation pourrait être fortement recommandé pour valoriser les dattes sèches de faible valeur commerciale, cependant il doit être optimisé pour les dattes très sèches
The production of dates is increasing every season, causing losses especially during post-harvest handling andmarketing. Post-harvest handling plays an important role in maintaining date palm. In order to preserve organolepticand nutritional quality of date palm fruits after harvest with improving their commercial value, storage experiments andpost-harvest treatments have been assayed.The effect of different storage conditions of temperature, time and modified atmosphere, as well as the effectof heat treatment of dates, on firmness, colour, sugars, organic acids, polyphenols and cell walls and compositions havebeen studied.‘Deglet Nour’ date palm fruits of two harvest seasons (2017 and 2018) as well as common date cultivars‘Arichti’, ‘Bouhattam’ and ‘Bser Hlou’ consumed at early maturity stage (Khalal stage), were stored at -18, 0, 2 and 4°C for 3, 6 and 9 months and at 2 °C for 30 and 60 days, respectively. Mid Infrared Spectroscopy (MIR) as a nontargetedmethod allowed to highlight a year effect on 'Deglet Nour’ chemical composition and to discriminate samplesstored at 4 and 2 °C regarding to major components (moisture, sugar, organic acids...). Cell wall yields (assimilated tofiber) as well as procyanidins, accounting for 98% of total polyphenols, were stable during ‘Deglet Nour’ and ‘Arichti’cultivars storage regardless of temperature and time conditions. However, these same components were the mostaffected by storage conditions for ‘Bouhattam’ and ‘Bser Hlou’ cultivar. This latter, was the softest cultivar and themost appreciated by consumers, may be because of reducing sugars increase affecting its sweet taste. Thus, stored fruitsat -18 °C could be the solution for a long-term storage but due to its high energetic costs, 2 °C must be the optimaltemperature. Moreover, in order to valorize common dates palm and prolong their shelf life, storage time could beprolonged for ‘Arichti’ cultivar with temperature storage ptimization for ‘Bser Hlou’ and ‘Bouhattam’ cultivars.Date palm fruits mentioned above, were also stored under Modified Atmosphere packaging (MAP) at 2°Cduring 3, 6 and 9 months for ‘Deglet Nour’ and during 30 and 60 days for commons cultivars (‘Arichti’, ‘Bouhattam’and ‘Bser Hlou’). In general, differences were observed on physical and chemical parameters using different MAPstreatments for ‘Deglet Nour’date palm fruits. Dates became darke with MAPT and MAPA storage. Dates palm storedunder this latter MAP bag showed an increase on procyanidins, some cell walls compositions, fructose and citric acid.Firmness loss of this cultivar was delayed with MAPZ storage with polyphenols stability. This latter bag type conservedfirmness and colour of the three studied cultivars (‘Arichti’, ‘Bouhattam’ and ‘Bser Hlou’) were stabe with no differencecomparing to control (without MAP). Organic acids, cell walls yield and composition, polyphenols were also stableduring storage. Only sugars contents of every cultivars had different behaviour.These results showed that MAP bags had very lower benefical effects than storage time and temperature on ‘date palmquality. So, their use in date processing industries could have more costs with no apparent effects.The organoleptic and nutritional quality of ‘Deglet Nour’ date palm was also evaluated before and afterhydration treatment commonly used in date prcessing units (DPU), in order to become more commercially valued andto minimize waste generated along the date palm fruit supply chain. Hydration treatment under saturated steam at 60-62°C for 4 hours impoved date fruits texture as expected while nutritional parameters were quite stable. Mid InfraredSpectroscopy (MIR) allowed to discriminate samples from the three DPUs suggesting to be adopted in DPU as a newpredictive and no destructive technique. So, hydration treatment could be highly recommended to valorize fruit byproducts.However, it needs to be optimized for the very hard-type dates
انتاج التمور في ارتفاع مستمر من موسم الى اخر مما يجعل مراكزالفرز و التخزين تتخلص من كميات هائلة من التمور المتضررة أثناءعمليات الفرز والتسويق. هذه العمليات تلعب دورا هاما في الحفاظ على جودة التمور. ومن أجل الحفاظ على الجودة الغذائية للتمور بعد الجنيمع تحسين قيمتها التسويقية، تم القيلم بتجارب التخزين وبعض معالجات ما بعد الجني.وقد تم دراسة تأثير ظروف التخزين المختلفة من درجة الحرارة، مدة الخزن وتقنية الجو الهوائي المعدل، وكذلك تأثير معالجة التمور الجافةعلى الصلابة، اللون، السكريات، الأحماض العضوية، البوليفينول وجدران الخلايا النباتية (الالياف) ومكوناتها.تم تخزين تمور ’ دقلة النور’ لصابة 2017 و 2018 والأصناف الأخرى من التمور الأقل انتشارا مثل ’ الارشتي’، ’ بو حتم’، ’ بسر حلو’18 درجة مائوية وفي 2 درجة مائوية لمدة - ,0 ,2 , التي تستهلك في مرحلة متقدمة من النضج (خلال)، لمدة ثلاثة، ستة وتسعة أشهر في 430 و 60 على التوالي. اثبت التحليل الطيفي بالأشعة تحت الحمراء الوسطى ان سنة الجني لها تاثير على العناصر الكيميلئية للتمور’ دقلةالنور’ وقامت بتمييز التمور المخزنة في 2 و 4 درجة مائوية بالنسبة لاهم مكوناتها (الماء، السكريات، الأحماض العضوية...). اثبت النتائجان جدران الخلايا النباتية (الالياف) وان أكبر مكونات البوليفينول (بروسيانيدين) كانت مستقرة اثناء تخزين تمور’ دقلة النور’ و ’ الارشتي’،بغض النظر عن درجة حرارة ومدة التخزين. نفس هذه العناصر كانت الأكثر تاثرا بعوامل التخزين بالنسبة لاصناف’ بو حتم’ و ’ بسرحلو’. هذا الصنف الأخير كان الأكثر ليونة مع تغير بنية جدران الخلايا على الرغم من انه أكثر صنف قابلية لدى المستهلك، من الممكنبسبب ارتفاع كمية السكريلت السريعة التي اثرت على مذاقه الحلو.فبحيث ان تخزين التمور ’ دقلة النور’ في - 18 درجة مائوية من الممكن ان يكون أحسن حل على مدى طويل، لكن نظرا لتكاليفة الطاقيةالباهضة، تخزين التمور في 2 درجة مائوية يجب ان يكون أفضل حل. بصفة عامة لم يكن هناك خسائر هامة للقيمة الغذائية بالنسبة لاصنافالتمور الاخرى اثناء التخزين، مما يجعل التمديد في مدة التخزين ممكنا بالنسبة اصنف’ الارشتي’ مع البحث عن درجة حرارة تخزين ناجعةالصنف ’ بسر حلو’ و’ بو حتم’.تم ايضا تخزين انواع التمور المذكورة اعلاه بتقنية الجو الهوائي المعدل في 2 درجة مائوية لمدة ثلاثة، ستة وتسعة أشهربالنسبة ’ لدقلةالنور’ ولمدة 30 و 60 يوم بالنسبة للاصناف الأخرى. بصفة عامة هناك اختلافات في العناصر الفيزيلئية والكيميلئية ’ لدقلة النور' المخزنةفي كل أنواع تقنيات الجو الهوائي. ' دقلة النور' المخزنة في أكياس ترندلايف و ايباك. أصبحت داكنة الون.دقلة النور المخزنة في أكياس ' سجلت ارتفاعا في مكونات جدران الخلايل, بروسيانيدين, الفروكتوز و حامض السيتريك. تخزين' دقلة النور'في أكياس زويباك اخرت في ليونتها مع استقرار في البوليفينول. هذه النتائج اثبتت ان تخزين التمور في اكياس الجو الهوائي المعدل لم تكنذو نجاعة عالية مقارنة بعوامل الحرارة والمدة الزمنية.لون وصلابة التمور من اصناف ’ الارشتي’، ’ بو حتم’، ’ بسر حلو’ اثبتت استقرارها بعد تخزينها في أكياس زويباك, لكن بعدم ايجاد فرقمقارنة بالتمور المخزنة بدون اكياس الجو الهوائي المعدل, مثلها مثل بقية العناصر الفيزيلئية والكيميلئي بصفة عامة. هذا يثبت ان استعمالهافي مصانع تخزين التمور ليس له جدوى اقتصادية واضحة.تم دراسة مدى تاثر القيمة الغذائية لتمور ’ دقلة النور’ الجافة على إثر معالجتها وترطيبها بالطريقة الهعتدة في اغلب مصانع تخزين التمور62 درجة مائوية لمدة 4 ساعات - لتكون ذات قيمة تسويقية عالية ولتقليص كمية الخسائر. تقنية ترطيب التمور على طريقة البخار في 60اثبتت نتائج ناجعة كما كان متوقع مع المحافضة على استقرار المكونات الغذائية. طريقة معالجة التمور بترطيبها هي طريقة متصوح بهالكنها غير ناجة للتمور الأكثر جفافا التي تحتاج تطوير في هذه التقنية

Nous présentons une étude détaillée, non-perturbante, de la prise du plâtre par Relaxation Magnétique Nucléaire (RMN) du proton, à bas champ magnétique. Cette technique permet de quantifier en continu le degré d'hydratation et de déduire de manière non-destructive les paramètres microstructuraux d'une pâte de plâtre en cours de durcissement. La décroissance bi-exponentielle des signaux de relaxation de l'eau dans le plâtre prouve l'existence de deux populations d'eau différentes, en échange lent. A partir des mesures de relaxométrie RMN, deux modes d'organisation de la microstructure sont identifiés en fonction du rapport de gâchage initial eau/plâtre (e/p), pour 0.4 <= e/p <= 0.6 et 0.7 <= e/p <= 1. Un modèle original d'échange entre les populations d'eau dans un milieu poreux a été établi. Une nouvelle approche multi-échelles et multi-techniques de la prise et du durcissement des pâtes de plâtre est proposée, permettant de relier les mesures locales obtenues par RMN aux propriétés mécaniques du matériau (mesurées par ultrasons). La démarche expérimentale et la modélisation présentées dans cette étude peuvent être appliquées à une large gamme de matériaux poreux en évolution.

This item is only available electronically.
Biogenic silica is abundantly preserved in sediment and is found in diatoms and many higher plants. The isotopic composition (δ18Osilica) of biogenic silica is used widely in paleoclimate research to infer conditions in which the organism grew. However, previous studies show that secondary alterations within the matrix of biogenic silica complicate the structural and geochemical analysis of silica. This study investigates how the hydrated structure of silica changes at different temperature with time. A statistical model is constructed that quantifies the degree of silica hydration (Q4/Q3) by calibrating Fourier transform infrared (FTIR) measurements against nuclear magnetic resonance. This study also conducts an investigation of various oxidation techniques to find an optimal method to be used to remove organics within biogenic silica, although residual contamination proved challenging to remove in most cases. These contaminants hinder the quantification of silica hydration using FTIR which is also used in the statistical modelling of Q4/Q3 measurements. The experimental results showed a relationship between time and the relative increase of the relative hydroxylation/dehydroxylation of biogenic silica. However, silica condensation is not a linear reaction, but reversible, potentially implying that the structure of silica readily undergoes temporary absorption/desorption at its surface in the presence of water.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2016

Vigorous and prolonged physical exercise can produce a range of urinary abnormalities which would normally be considered alarming. They include haematuria, haemoglobinuria, the appearance in urine of red cells in urine, some fragmented in a ‘glomerular’ manner, red cell cast formation, and proteinuria. A variety of names have been given to these syndromes, including march haematuria and march haemoglobinuria. Mostly these changes seem benign and self-limiting. Rarely they are associated with acute kidney injury but this is often in the context of other renal insults, extreme dehydration, or hyperpyrexic conditions. Vigorous exercise is also commonly associated with various electrolyte changes related to both over- and under-hydration. These can complicate assessment. Transient proteinuria in the absence of haematuria appears to be a physiological response to even short-term exercise, its degree related to the intensity of the exercise. Causation of these syndromes is mixed and not fully explained. There is good evidence for physical trauma to red cells being a significant part, but this cannot explain the appearance of glomerular red cells and red cell casts. Exercise-related changes mostly resolve within less than a day, and almost all by 72 hours.

AbstractRenal diseases remain devastating illnesses with unacceptably high rates of mortality and morbidity worldwide. Animal models are essential tools to better understand the pathomechanism of kidney-related illnesses and to develop new, successful therapeutic strategies. Magnetic resonance imaging (MRI) has been actively explored in the last decades for assessing renal function, perfusion, tissue oxygenation as well as the degree of fibrosis and inflammation. This chapter aims to provide an overview of the preparation and monitoring of small animals before, during, and after surgical interventions or MR imaging. Standardization of experimental settings such as body temperature or hydration of animals and minimizing pain and distress are essential for diminishing nonexperimental variables as well as for conducting ethical research.This publication is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers.

Fluid and electrolyte emergencies are a common presenting complaint in the emergency department. Dehydration emergencies can occur as a complicating factor of another illness or due to vomiting and/or diarrhea. The recognition and management of dehydration in infants and children are of critical importance to the emergency department provider. The severity of dehydration requires a focused history and detailed examination, with multiple elements required to determine the degree of illness. Oral rehydration is the preferred method of treatment for mild and moderate dehydration. Intravenous hydration is preferred for severe dehydration and moderate dehydration that has failed traditional oral rehydration therapy. Electrolyte derangements should be considered in patients with moderate and severe illness or for whom the clinical picture is unclear.

The conformational dynamics and hydration of a DNA 14-mer containing the consensus Pribnow box sequence TATAAT have been measured using rotating frame T1 measurements and NOESY and ROESY in water. The H2 proton resonances of adenines show fast intermediate exchange behavior which can be attributed to a conformational transition that affects the distances between H2 protons of neighboring adenine residues, both sequential and cross-strand. The relaxation rate constant of the transition was measured at 4000s-1 at 25°C. Bound water close to the H2 proton of adenines was observed with residence times of >lns. At low temperature (5°C), the Pribnow box is in a closed state in which hydration water in the minor groove is tightly bound. At higher temperatures, the conformation opens up as judged by the increase in separation between sequential H2 protons of adenines and water exchanges freely from the minor groove. The conformational transition and the altered hydration pattern may be related to promoter function. The control of gene expression in procaryotes depends on the specific recognition by RNA polymerase of a six base-pair sequence (consensus: TTGACA) located at -35 from the transcription site, and a second one, named the Pribnow box (consensus: TATAAT) at about 10 base-pairs upstream the initiation site (Rosenberg and Court, 1979). It has been shown (Hawley and McClure, 1983) that strong promoters exhibit a high degree of homology with the consensus sequences, separated by an optimum consensus spacer length of 17 base pairs. The strength of a promoter depends on, among other thing, the rate of the initiation of transcription. This rate depends on the product between the thermodynamic and kinetic constants KB and k2 (McClure, 1980). The initial binding of RNA polymerase to the promoter results in the formation of a transcriptionally inactive ‘closed’ complex, characterized by the association constant KB. Isomerization to the active ‘open’ complex then occurs, and is characterized by the first order rate constant k2. Hence, the frequency of transcription initiation depends both on the strength of the polymerase-promoter interaction, and the ease with which this complex can isomerize to the productive state. Both of these events are likely to depend on the physical properties of the promoter.

Abstract To solve any problem, one must first assess what the problem is. Consequently, the nursing process dictates that the nurse begin care with an assessment of the patient’s health needs. Although palliative nurses are accustomed to assessing patients’ pain experiences, hydration status, and so forth, they less frequently participate in assessing patients’ and family members’ spirituality. Because spirituality is an inherent and integrating, and often extremely valued, dimension for those who receive palliative nursing care, it is essential that palliative care nurses know to some degree how to conduct a spiritual assessment. This chapter reviews models for spiritual assessment, presents general guidelines on how to conduct a spiritual assessment, and discusses what the nurse ought to do with data from a spiritual assessment. These topics are prefaced by arguments supporting the need for spiritual assessments, descriptions of what spirituality “looks like” among the terminally ill, and risk factors for those who are likely to experience spiritual distress. But first, a description of spirituality is in order.

Hard tissues are natural nanocomposites comprising collagen nanofibers that are interlocked with hydroxyapatite (HAp) nanocrystallites. This mechanical interlocking at the nanoscale provides the unique properties of hard tissues (bone and teeth). Upon fracture, cements are usually used for treatment of simple fractures or as an adhesive for the treatment of complicated fractures that require the use of metallic implants. Most of the commercially available bone cements are polymer-based, and lack the required bioactivity for a successful cementation. Besides calcium phosphate cements, gypsum is one of the early recognized and used biomaterials as a basi for a self-setting cementation. It is based on the controlled hydration of plaster of Paris at room temperature and its subsequent conversion to a self-setting solid gypsum product. In our work, we have taken this process further towards the development of a set of nanocomposites that have enhanced bioactivity and mechanical properties. This chapter will outline the formation, characterization, and properties of gypsum-based nanocomposites for bone cement applications. These modified cements can be formulated at room temperature and have been shown to possess a high degree of bioactivity, and are considered potential candidates for bone fracture and defect treatment.

Acute pancreatitis is a complex disease, and although most patients have a self-limiting illness, a minority of them develop severe disease and may need Intensive Care Unit admission. Regardless of severity degree, two cornerstones of acute pancreatitis multidisciplinary management are: fluid resuscitation and pain relief. These patients are frequently hypovolemic because of decreased oral intake, vomiting, fever, and fluid sequestration associated with pancreatic and systemic inflammation. Early intravenous volume resuscitation seems to reduce pancreatic hypoperfusion and multiorgan failure, but fluid overload has been associated with worse outcome, and maintaining proper hydration could be challenging. Acute pancreatitis is a very painful condition and effective analgesia is one of the priorities. Pain relief has a positive impact because of reduced stress response, sympathetic-induced vasoconstriction, and pulmonary complications. It is suggested to use a multimodal analgesic approach, to achieve patient’s satisfaction, minimize opioid consumption and side effects. A modern and effective approach involves the use of patient-controlled analgesia and thoracic epidural analgesia. We would revise these two items to offer early and better multidisciplinary management to patients with acute pancreatitis, including those with mild to moderate disease, who are managed in general surgical wards, with the aim to improve their outcome and hospital stay.

The shale hydration disturbance causes varying degrees of damage to the pore structure of surrounding rock of the borehole wall, deteriorates its mechanical properties, and reduces the safety and stability of the borehole wall. By using nuclear magnetic resonance (NMR) and triaxial compression test, the volume change and mechanical properties of rock samples versus different soaking time were tested and analyzed. Research results: (1) Through the increasing trend of signal intensity amplitude of T2 energy spectrum, the transformation and expansion rules of pores with different scales are analyzed, the mechanical mechanism of shale hydration damage and failure is revealed, and the change rules of shale void ratio and volume expansion rate are analyzed. (2) Through the curves of shear strength and elastic modulus of shale changing with soaking time, the evolution law of shale strength decline is analyzed, which revealed that shale hydration has obvious timeliness. (3) Based on the test results of shale hydration disturbance damage, using damage mechanics and strength statistics theory, and taking the volume expansion rate as the investigation variable, a statistical damage model of shale hydration disturbance is established to predict damage evolution law of shale hydration disturbance. The research results have important guiding significance for practical engineering.

This chapter discusses the addition of nucleophilic reagents to aldehydes and ketones. In the series formaldehyde–acetaldehyde–acetone, reactivity to nucleophiles decreases in that order. The electronic factor here is deactivating, but slight, because the additional Me groups are not attached directly to the carbonyl carbon. They are largely insulated from it by saturated carbon atoms. The chapter then considers high degrees of hydration at equilibrium, which generally result when the carbonyl group has strong electron-withdrawing substituents attached, and in extreme cases it is the hydrate which is the familiar form of the carbonyl compound. It also looks at hemiacetal and hemiketal formation; cyanohydrin formation; bisulfate addition; the Meerwein–Ponndorf–Verley reaction; the Cannizzaro reaction; and reaction with Grignard reagents.

In order to study the peculiarities of the interaction of hydrophobic particles with water, the binding of water in composite systems based on structurally modified mixtures of 1/1 hydrophilic (A-300) and hydrophobic (AM-1-300) silica was studied by low-temperature 1H NMR spectroscopy. It is shown that with equal amounts of hydrophobic and hydrophilic components, the dependence of the interfacial energy on the value of surface hydration has a bell-shaped appearance with a maximum at h = 3000 mg/g. The obtained dependence is explained from the point of view of restructuring of the composite system under the influence of mechanical loads and the possibility of air removal and adsorption processes in the interparticle gaps of hydrophobic and hydrophilic components, as well as the phenomenon of nanocoagulation. Increasing the concentration of the hydrophilic component does not increase the binding energy of water. Under the influence of liquid hydrophobic substances, depending on the bulk density of the composite, there may be an increase or decrease in interfacial energy. The growth is due to the restructuring of the hydrophobic and hydrophilic components (nanocoagulation), and the decrease is due to the displacement of water from the surface into pores of larger radius. For n-decane, the effect of increasing the melting temperature by several tens of degrees was registered in the interparticle gaps.

The Repository of LILW Radioactive Waste Morsleben (ERAM) is located in the Federal State Saxony Anhalt, Germany. After an operational phase of about 20 years it is now under licensing for closure. As the repository was erected in a former salt mine, there exists a void volume of approx. 6 million m3. Consequently, a closure concept was developed serving three main functional requirements: stabilization, limitation of leaching processes and sealing. It relies on a comprehensive backfilling of the openings using two mixtures of salt concretes. The concretes will be used to backfill cavities as well as to construct seals. As the salt concretes are used in the sense of a mass concrete the heat of hydration induces thermal restraint stresses inside the concrete bodies and the neighboring rocks. To show the integrity of the geological and technical barriers thermo-mechanical computations were carried out. In the numerical code which is used for safety analyses a so-called hydration model was implemented describing the evolution of strength and Young’s modulus of the concretes in relation to the degree of hydration. The hydration model includes a transformation of the temperature-dependent setting process from real time into an equivalent age, which is equal to the setting time at a temperature of 293 K. Thereafter, a coupling of the equivalent age to the degree of hydration leads to a temperature-independent description of the setting process. As the hydration of concretes strongly correlates with the amount of the generated hydration heat, the model parameters were derived from laboratory tests including measurements of the adiabatic temperature rise.

The secondary pozzolanic reaction mechanism has been modeled explicitly in the Delft hydration model Hymostruc. The model calculates the progress of the hydration process as a function of the particle size distribution, the water cement ratio, the temperature and the cement and pozzolanic chemistry. The consumption of portlandite due to the activation of the pozzolanic materials is shown in detail. The numerical results are validated by an experimental testing plan on G-cement and 8% of silica fume and a water to cementitious ratio of 0.44. The simulated development of portlandite and degree of hydration and the experimental results are in good agreement.

Abstract The Fuman oilfield is the main block of the Tarim oilfield to increase reserves and production. However, the wells in this area are ultra-deep, and many sets of complex and difficult-to-drill formations are encountered in top-down drilling, which brings significant challenges to the drilling engineering. Based on triaxial and shear experiments, transverse isotropy theory and weak surface criterion, and integrating the mechanical damage under stress unloading and hydration in drilling wells, a well wall stability model under the synergistic effect of stress unloading and hydration has been established, and an analysis of the factors influencing the stability of the well wall of the formation has been carried out. The study shows that stress unloading occurs after drilling. The greater the confining pressure and axial stress, the more significant the shale strength weakening caused by stress unloading, and the magnitude of stress unloading is positively correlated with the degree of mechanical strength weakening. The more developed the laminations are, the easier it is to damage along the laminations. When stress unloading occurs, the weak structural surface acts synergistically with stress unloading, and the higher the degree of shale strength weakening is, the worse the mechanical stability is and the higher the risk of well wall instability. External fluids are prone to intrude along the bedding and promote shale hydration, making the shale mechanically less stable and reducing the well wall's stability. The effect of stress unloading on shale formation collapse pressure mainly occurs in the pre-drilling stage, and the effect of hydration damage on well wall instability mainly occurs in the late drilling stage. Beddings, stress unloading, and hydration affect the well wall stability together. The shale well wall stability model under stress unloading-hydration synergistic effect considers the influence of the three comprehensively. The prediction results align with the drilling actuality with good reliability after the field application test.

Abstract Yi 202 block has experienced multiple phases of tectonic movement, resulting in extensive development of natural fractures in the region. Actual drilling indicates that the presence of these natural fractures poses great challenges to drilling operations. However, the wells in this area are ultra-deep, and many sets of complex and difficult-to-drill formations are encountered in top-down drilling, which brings significant challenges to the drilling engineering. Based on triaxial and shear experiments, transverse isotropy theory and weak surface criterion, and integrating the mechanical damage under stress unloading and hydration in drilling wells, a well wall stability model under the synergistic effect of stress unloading and hydration has been established, and an analysis of the factors influencing the stability of the well wall of the formation has been carried out. The study shows that stress unloading occurs after drilling. The greater the confining pressure and axial stress, the more significant the shale strength weakening caused by stress unloading, and the magnitude of stress unloading is positively correlated with the degree of mechanical strength weakening. The more developed the laminations are, the easier it is to damage along the laminations. When stress unloading occurs, the weak structural surface acts synergistically with stress unloading, and the higher the degree of shale strength weakening is, the worse the mechanical stability is and the higher the risk of well wall instability. External fluids are prone to intrude along the bedding and promote shale hydration, making the shale mechanically less stable and reducing the well wall's stability. The effect of stress unloading on shale formation collapse pressure mainly occurs in the pre-drilling stage, and the effect of hydration damage on well wall instability mainly occurs in the late drilling stage. Beddings, stress unloading, and hydration affect the well wall stability together. The shale well wall stability model under stress unloading-hydration synergistic effect considers the influence of the three comprehensively. The prediction results align with the drilling actuality with good reliability after the field application test.

The behaviour of FBC ash/water systems is complex and the hydration behaviour of FBC ashes attracts attention both for environmental reasons and because hydration could be used to reactivate the ashes for further use in SO2 capture. In a recent study, hydration of 16 FBC bed and fly ashes from industrial installations firing high-ash coal and mine wastes was studied. Saturated steam at ∼165°C was employed; samples were analyzed chemically and investigated by X-ray diffraction (XRD) and thermal analysis (TGA). One of the more important results was that in some of the ashes there was no unreacted CaO and no Ca(OH)2 after hydration, and they could even consume CaO added to them before hydration. XRD evidence was also obtained to show that a hydrated calcium silico-aluminate (katoite) was formed during the hydration of ashes high in excess, unreacted CaO. The same ashes were used in the present study. The methods used were the same, but the bed ashes were divided into three size fractions and hydration by saturated steam at 100°C was employed. The results generally confirmed the earlier findings. Differences were small but could be significant. First, no katoite could be detected after hydration, so its formation (and possibly that of other compounds of that type) may require more drastic hydration conditions. Second, small quantities of Ca(OH)2 were detected in most hydrated samples. Third, systematic differences between bed ash size fractions were found. In particular, the proportion of anhydrite and the degree of CaO to CaSO4 conversion steadily increased with decreasing particle size fraction, but in the corresponding fly ash was lower and for lime-rich ashes, much lower.

Abstract Stability of nature gas hydrates (NGH) is greatly impacted by temperature. Because intense heat is released from cement hydration during well cementing, limiting the temperature rise of cement is critical for safe cementing of NGH well. The total heat release by cement slurry has a strong correlation with the mechanical properties of cement slurry. Consequently, reducing the heat of hydration of cement means typically results in lower strength of the cement stone. Traditional evaluation methods do not fully consider the complex interaction between cement hydration reaction and heat transfer in the wellbore, therefore, it is difficult to determine whether the cement slurry formula selected is suitable for well cementing in nature gas hydrates. In this paper, a model to predict cement wellbore temperature was developed by incorporating the complicated interactions between temperature and cement hydration reaction. The model established the relationship between degree of cement hydration and wellbore temperature based on the cement hydration reaction kinetics. Coupled with differential method and numerical calculation, the influence of wellbore temperature on NGH was analyzed during the cementing process. The newly developed model was used to predict the field performance. Model predicted data and field data are within 10.0%. By accurately predicting the change of NGH with wellbore temperature during the cementing process, the model in this paper can not only effectively guide the research and development of low hydration heat cement slurry for NGH well but also find and avoid safety hazards in time during the design process of NGH cementing slurry.

It was over 20 years ago that the first papers appeared proposing that terahertz time domain spectroscopy and imaging could be used in the medical arena due to the sensitivity of terahertz absorption to water content; and that the degree of hydration of tissue could be used as a measure of disease state [1].

Two commercial superabsorbent polymer (SAP) formulations were used to internally cure cement pastes, mortars, and concretes with a range of water-to-cement ratios (w/c 0.35–0.52). The following properties were determined as a function of cement chemistry and type, use of chemical admixtures, use of slag, and batching parameters: SAP absorption capacity, fresh mixture workability and consistency, degree of hydration, volumetric stability, cracking tendency, compressive and flexural strength, and pumpability. SAP internal curing agents resulted in cementitious mixtures with improved hydration, accelerated strength gain, greater volumetric stability, and improved cracking resistance while maintaining sufficient workability to be pumped and placed without sacrificing compressive or flexural strength. When using SAP, batching adjustments prioritized the use of water reducing admixture instead of extra water to tune workability. While the benefits of SAP internal curing agents for low w/c mixtures were expected, SAP-containing mixtures with w/c ≥ 0.42 displayed accelerated strength development and decreased cracking tendency.