Increase Of Hydration Time Research Articles

Performance evaluation of structurally modified wellbore cement with graphene nanoplatelets undergone thermal cyclic loading

Geothermal energy is identified as one of the alternatives to fossil fuels in global climate crisis and the effective efforts for net-zero carbon emissions by 2050. The potential of geothermal heat at high temperatures is yet to be unlatched thus requiring a novel approach in all aspects of wellbore technology including cementing. Understanding the characteristics of the geothermal system is critical as we aim to develop wellbore materials for these thermally and chemically challenged wells. Materials used require stability at high temperatures and chemical resilience in contact with geofluids, where ordinary Portland cement (OPC) is deteriorating due to low pH that leads to loss in overall mechanical strength. Recent studies have shown that adding graphene nanoplatelets (GNP) to OPC based materials can improve properties and reduce risks from mechanical failures. GNP effect on overall cement properties has been studied and experimental results show promising outcomes at very low concentrations (<1% bwoc), significantly impacting strength and stiffness of the cement. The Class-H cement is hydrated with and without, liquid and powdered GNP at 0.008% and 0.1% concentrations each and cured in approximately pH 13 Ca(OH)2 solution to examine the influence of GNP on cement hydration. All the samples were subjected to cyclic temperature loading between 20 °C and 110 °C at 95% RH following an 8-hour cycle for 7 and 28 days in an environmental chamber. These temperature cycles help us evaluate close to the subsurface conditions where enhanced geothermal systems undergo thermal changes over tens of thousands of times during a lifetime of a well. Following API RP-10B specifications, GNP in the powdered form (PG) prepared from environmental waste and a 99.5% carbon purity lab grade liquid dispersion GNP (LG) were used. 0% GNP (neat) control, 0.008%, 0.1% of PG and LG mix design cement samples were prepared. Results show that 0.1%LG samples hydrated for 28 days had greater dispersion of GNP with a notable increase in the ductile behavior out of all the designs tested. There is a 13.21% decrease in permeability, 27.77% decrease in hardness and 50.71% decrease in elastic modulus when compared to neat sample hydrated for 28 days thus proving its effectiveness for wellbore integrity with increase in hydration time.

Effect of aggregate size on water distribution and pore fractal characteristics during hydration of cement mortar based on low-field NMR technology

The influence of aggregate size (AS) on the hydration of cement mortar is very important for improving the quality and stability of cement mortar. This study aims to study the effect of AS on water distribution and pore structure characteristics on the early-age hydration of cement mortar by low-field NMR technology. The hydration degree and fractal dimension of the hydration process were calculated by the T2 spectrum. The water distribution models at different times and locations during the hydration process were established based on the MRI bitmap data. The variation law of water volume at different locations was studied. The results indicate that: In the process of hydration, some of the water is consumed by the hydration reaction, and some of the water oozes out. The water in the large pores flows to the small pores under the action of hydrostatic pressure. AS affected the uniformity of the cement mortar at the initial state, and the gradation of the sand could improve the uniformity. The smaller AS was, the more complex the pore water distribution and changed during hydration. The bleeding mass was directly proportional to the porosity and inversely proportional to the specific surface area of particles. The effect of porosity on bleeding mass was more significant than AS. Pore fractal dimension was negatively correlated with aggregate diameter. In the initial stage, when the aggregate composition became complex, the change of fractal dimension with time also became complex. The fractal dimension increased gradually with the increase of hydration time. The gel pores (G) did not have fractal characteristics from beginning to end, capillary pores (C) and transition pores (T) had fractal characteristics after a particular time of hydration reaction. Although the air-voids (A) had fractal characteristics from beginning to end, they were not continuous.

Capacitance-based compression self-sensing effectiveness of cement paste with curing time

Capacitance-based self-sensing properties of cement pastes at different curing times were studied in this work. Cement paste samples that did not require any functional materials were tested at 7, 14 and 28 days. Continuous and discontinuous loading cycles (minimum load of 21 kPa and maximum load of 98 kPa) were applied to the cement pastes. It was found that capacitance-based self-sensing is superior to resistance-based self-sensing owing to its greater dependence on stress and reversibility. The capacitance change was found to be irreversible for the 7-day cement paste sample owing to irreversible deformation. Over time, capacitive self-sensing became more effective. The stress sensitivity (fractional increase in capacitance divided by stress) for the 28-day cement paste sample was 2.54 × 10−8/Pa. It was also found that, with an increase in hydration time, the capacitance decreased, indicating the strength increase in cement paste can also be sensed with capacitance measurements.

Mechanical Properties of Lamellar Shale Considering the Effect of Rock Structure and Hydration from Macroscopic and Microscopic Points of View

It is well known that the effect of shale hydration causes wellbore instability due to water phase invasion of drilling fluid to lamellar shale rich formations. This is because of that the mechanical properties (compressive strength, elastic modulus, etc.) of lamellar shale surrounding the borehole, which is rich in clay minerals, will decrease significantly after hydration. In this study, using the lamellar shale in the continental stratum of the southern Ordos Basin, the mechanical properties of lamellar shale were studied by compression tests considering the effect of lamellar structure and hydration from a macroscopic point of view. In addition, the mechanical mechanism was discussed combined with the CT scanning tests results from a microscopic point of view. The results demonstrate the following points. Lamellar shale has stronger anisotropy than bedding shale, the compressive strength (deviatoric stress) and elastic modulus of lamellar shale are both lower than those of bedding shale, and it is more prone to tension fracture. With the increase in the angle (β) between the lamina and the axial direction from 0° to 90°, the compressive strength of lamellar shale decreases when β &lt; 30° and then increases, the elastic modulus of lamellar shale decreases greatly when β &lt; 30° and then tends to flatten. With the increase in hydration time, the compressive strength and elastic modulus of lamellar shale both gradually decrease, and the rates of their decrements reduce. The mechanical properties of lamellar shale are more affected by hydration than those of bedding shale. The hydration of lamellar shale leads to the formation of new fractures and the expansion of existing fractures in the junction area between the laminae and rock matrix, resulting in easy tension fracture along the laminae of shale.

Long-term effect of water chemistry on the swelling pressure and hydraulic conductivity of compacted claystone/bentonite mixture with technological gaps

A compacted mixture of Callovo-Oxfordian (COx) claystone/MX80 bentonite is a promising sealing material in the French Cigéo project for radioactive waste disposal at great depth. Over time, the sealing material will be saturated by the site water originating from the surrounding rock and the water chemistry can affect the performance of the sealing material. In this study, the effects of water chemistry and technological gaps on the hydro-mechanical property were investigated by performing hydration tests on the compacted claystone/bentonite mixture with technological gaps using deionised water and synthetic site solution for 10 and 590 days. After the tests, the dry density, water content and microstructure distributions were also determined to complement the program. Results show that the synthetic site solution did not affect the swelling pressure and hydraulic conductivity after a short term of 10 days. With the increase of hydration time, the specimens with technological gaps tended to be homogeneous, resulting in a reduction of hydraulic conductivity. Because of the cation exchanges and the decreased diffuse double layer thickness, the synthetic site solution reduced the swelling pressure and increased the hydraulic conductivity in long term, especially for the specimens with lower global dry densities.

Autogenous shrinkage and hydration property of alkali activated slag pastes containing superabsorbent polymer

In this paper, the superabsorbent polymer (SAP) was applied as internal curing agent to study its effect on the autogenous shrinkage and hydration property of alkali activated slag (AAS) pastes. Liquid absorption and release processes of SAP in AAS pastes were characterized by 1H nuclear magnetic resonance (1H NMR). Moreover, the microstructure and mechanical strength of AAS pastes containing SAP were also revealed. The results showed that the autogenous shrinkage of AAS pastes containing SAP was reduced by about 80.6%, 72.1% and 72.6%, respectively as the silicate modulus (Ms) increased from 0.8 to 1.4. The addition of SAP delayed the second exothermic peak, but increased the cumulative heat of AAS pastes. In addition, internal curing by SAP could promote the generation of C-A-S-H gels and hydrotalcite-like phases and increase the reaction degree of slag, particularly for AAS pastes with higher Ms, being attributed to the continuous release of entrained water and alkali activator solutions in SAP with the increase of hydration time. Furthermore, the addition of SAP would increase capillary pore size and pore volume of AAS pastes, and thus lead to the decrease of compressive strength.

Experimental Study of the Mechanical and Microstructure Characteristics of Coal Gangue Road Stabilization Materials Based on Alkali Slag Cementation.

To accelerate the resource utilization of coal gangue and meet the strategic requirements of carbon neutralization, alkali-activated, slag-cemented coal gangue is applied in the preparation of solid waste-based road stabilization materials. Here, the cementation characteristics and microstructure characteristics of alkali-activated, slag-cemented coal gangue road stabilization materials are studied using the alkali equivalent and coal gangue aggregate ratio as experimental variables. The results show that with the increase in alkali equivalent from 1% to 7%, the unconfined compressive strength of the alkali-activated coal gangue road stabilization material initially increases and then decreases, with 3% being the optimal group in terms of stabilization, the aggregate ratio of coal gangue increases from 70% to 85%, and the 7-day unconfined compressive strength of the stabilized material decreases approximately linearly from 8.16 to 1.68 MPa. At the same time, the porosity gradually increases but still meets the requirements of the specification. With the increase in hydration time, a large number of hydration products are formed in the alkali slag cementation system, and they are closely attached to the surface of and interweave with the coal gangue to fill the pores, resulting in the alkali slag slurry and coal gangue being brought closer together.

Influence of extreme high-temperature environment and hydration time on the rheology of cement slurry

As a large number of projects are being constructed in deep rock masses, high ground temperatures and hot water disasters are inevitably encountered during construction. Considering the design of grouting parameters and the actual reinforcement effect, it is important to study rheology of grouting materials in high ground temperature environments. This study investigated the influences of temperature and hydration time on the rheology of Portland cement. The water-cement ratio (W/C) of Portland cement PO42.5 varied from 0.5 to 2.0. Through design experiments, the rheological models and parameters (yield stress, plastic viscosity) of cement slurry with different degrees of hydration were studied at different temperatures from 30°C to 80°C. The results show that cement slurries with different water-cement ratios (W/Cs) belong to three flow patterns in different temperature environments. The flow pattern hardly changed during grouting. The rheological model of slurry was controlled by W/C. In addition, the influence of temperature on shear stress varied with the change of W/C. The increase in hydration time increased the shear stress of the slurry for each W/C. The constitutive equation considering the effects of temperature and hydration time was established. This research can provide necessary guidance for the establishment of grouting diffusion theory and numerical model in high ground temperature environment.

Experimental Study on Physical and Mechanical Properties of Gypsum Rock During High-Temperature Dehydration–Hydration Expansion

In order to study the physical and mechanical properties of gypsum rock samples in three states (natural, high-temperature dehydration and hydration time), natural gypsum rock was put into high-temperature condition of 220°C for dehydration treatment, and then the high-temperature dehydrated gypsum rock was treated with different hydration time, and the gypsum rock samples in three states were subjected to ultrasonic test, density test and uniaxial compression test. The results show that the main components of natural gypsum minerals were gypsum dihydrate (71%), dolomite (27%) and potassium chloride (2%). The hydration of high-temperature dehydration samples was an extremely complex physical and chemical process. Hydration had a significant strengthening effect on gypsum rock, and the weak surface of the structure had a significant weakening effect on it during the hydration process. As hydration time increased, the apparent density increased gradually and the longitudinal wave velocity increased. The peak strength of the sample decreased first and then increased, and it generally had a logarithmic relationship with hydration time. The peak strain decreased first and then increased, then decreased and fluctuated, and the elastic modulus first increased and then decreased and then increased again. The expansion rate and limited expansion force of the sample increased with increase in hydration time. After a certain hydration time, the expansion rate of the sample tended to be stable, while the limited expansion force began to decrease slowly after reaching the maximum value.

Kinetic modelling of polyphenol degradation during common beans soaking and cooking

Phenolic compounds are phytonutrients with anti-inflammatory attributes that are significant for brain, heart and gut health. Losses of natural phenolic compounds in foods occur due to degradation during processing. The extent of degradation depends on the processing conditions applied. In this study, the degradation of total phenolic compounds during the processing of common beans (Phaseolus vulgaris L.) cultivars was investigated. The effects of soaking time, soaking water temperature and cooking conditions on polyphenol degradation were examined. The total phenolic compounds were determined as gallic acid equivalents. The result shows that increase of hydration time and process water temperature significantly (p < 0.05) increased polyphenol degradation. There was a strong positive Pearson correlation (r > 0. 85) between the rate of water uptake and polyphenol degradation regardless of the water temperature and cultivar. The rate of degradation varied from 0.041 – 0.098 and 0.014–0.069 mg/g per hour for Kabulangeti and Maine cultivar, respectively. The addition sodium chloride (NaCl) and potassium carbonate (K2CO3) during cooking to soften the beans significantly increased the degree of degradation. The activation energy for degradation was estimated as 45.4 and 26.3 kJ/mol for Kabulangeti and Maine cultivar, respectively.

Enhancement of electromagnetic shielding and piezoelectric properties of White Portland cement by hydration time

Effect of hydration time on the structural and physical properties of White Portland Cement (WPC) is considered to be a critical and essential factor. In this study effect of hydration time (360, 720, 1260, and 1450) min on the dielectric, electromagnetic shielding and piezoelectric properties of WPC at room temperature were investigated. Amorphous crystal structure of WPC has been detected by X-ray diffraction. Meanwhile dielectric and permeability properties of the present samples were investigated from frequency 9–11.5 GHz in X- band at room temperature (RT). At lower hydration time (360 min), the permittivity increases rapidly with frequency, however an anomalous peak has been observed at (720–1450 min) owing to the relaxor behaviour. The dielectric properties are explicitly improved by hydration time due to the enhancement of the mechanical properties. Furthermore, scattering parameters (Reflection coefficient (S11) and Transmission coefficient (S12)) in addition to electromagnetic shielding have been studied for the present samples. The transmission coefficient tends to decrease significantly with hydration time due to enhancement of the sample consolidation. The shielding effectiveness increases with increase in hydration time which indicates internal consolidation of WPC sample. Moreover, the hydration time shows an enhancement both of leakage current and piezoelectric properties of WPC at room temperature.

A study on the CO2 capture and attrition performance of construction and demolition waste

CaO-based sorbent deactivation is one of challenges to develop CaO-based chemical looping technology. The replacement of non-renewable natural or expensive synthetic CaO-based sorbents with cheap and environmental CaO-based waste sorbents is an effective way to overcome this challenge. As high CaO content, construction and demolition waste (CDW) has ability to capture CO2. Due to the rapid development of cities, a great deal of CDW is produced every year. According to the characteristics of CDW, six components were selected in this paper. From the initial CO2 carrying capacity, hydrated limestone had the highest initial CO2 carrying capacity, about 0.592 g CO2/g sorbent in TGA and 0.414 g CO2/g sorbent in fluidized bed system, followed by limestone, cement-based limestone, hydrated cement, cement-based sand, cement raw and sand. For multiple carbonation-calcination cycles, cement played a positive role in maintaining high cyclic CO2 carrying capture. Hydration degree and free lime content increased with the increase of hydration time, which improved the CO2 capture performance of CDW. For cement-based sorbents, evidence from this study suggested that extending hydration time played a positive role in improving the attrition resistance and maintaining the initial specific surface area in fluidized bed system.

The pore fillability of cementitious materials and its application in predicting compressive strength of gap-graded blended cements

To utilize cementitious materials efficiently, pore fillability was defined as volume expansion of cementitious materials during hydration, and calculated according to its chemical shrinkage and non-evaporable water content. Relationship between hydration characteristics of cementitious materials and porosity of cement pastes was established, and then the compressive strength of gap-graded blended cements was predicted based on the pore fillability of cementitious components and initial solid volume concentration of cement pastes. The results showed that the pore fillability of cementitious materials increased dramatically with the increase of hydration time and the decrease of particle size. For a given hydration degree, pore fillability of cementitious materials mainly dominated by the size of fraction, fine fraction presented a much higher pore fillability than coarse fraction as outer products contribute to a higher proportion in the hydration products. The compressive strengths measured and predicted were consistent with each other very well, indicating pore fillability can be used for the strength prediction of gap-graded blended cement (within 2.5% deviation).

Effects of different nanomaterials on hardening and performance of ultra-high strength concrete (UHSC)

Nanomaterials have attracted much interest in cement-based materials during the past decade. In this study, the effects of different nano-CaCO3 and nano-SiO2 contents on flowability, heat of hydration, mechanical properties, phase change, and pore structure of ultra-high strength concrete (UHSC) were investigated. The dosages of nano-CaCO3 were 0, 1.6%, 3.2%, 4.8%, and 6.4%, by the mass of cementitious materials, while the dosages of nano-SiO2 were 0, 0.5%, 1.0%, 1.5%, and 2%. The results indicated that both nano-CaCO3 and nano-SiO2 decreased the flowability and increased the heat of hydration with the increase of their contents. The optimal dosages to enhance compressive and flexural strengths were 1.6%–4.8% for the nano-CaCO3 and 0.5%–1.5% for the nano-SiO2. Although compressive and flexural strengths were comparable for the two nanomaterials after 28 d, their strength development tendencies with age were different. UHSC mixtures with nano-SiO2 showed continuous and sharp increase in strength with age up to 7 d, while those with nano-CaCO3 showed almost constant strength between 3 and 7 d, but sharp increase thereafter. Thermal gravimetry (TG) analysis demonstrated that the calcium hydroxide (CH) content in UHSC samples decreased significantly with the increase of nano-SiO2 content, but remained almost constant for those with nano-CaCO3. Mercury intrusion porosimetry (MIP) results showed that both porosity and critical pore size decreased with the increase of hydration time as well as the increase of nanoparticles content to an optimal threshold, beyond which porosity decreased. The difference between them was that nano-CaCO3 mainly reacted with C3A to form carboaluminates, while nano-SiO2 reacted with Ca(OH)2 to form CSH. Both nano-CaCO3 and nano-SiO2 demonstrated nucleation and filling effects and resulted in less porous and more homogeneous structure.

천연 수경성 석회의 수화특성에 미치는 석고의 영향

본 연구에서는 고로 수쇄 슬래그 및 석고를 혼합한 3성분계 천연 수경성 석회 페이스트에서 석고종류 및 혼합량에 따른 수화특성 변화를 확인하고자 하였다. 고로 수쇄 슬래그 20 %를 혼합한 천연 수경성 석회에 무수석고, 반수석고, 이수석고를 각각 3 %, 10%를 혼합하여 석고의 용해도 및 반응성에 따라 수화초기 생성되는 수화물의 종류와 생성량을 분석하였으며, 이에 따른 물리적 특성 변화거동에 대하여 조사하였다. 페이스트를 활용한 수화특성 결과 모든 샘플에서 수화초기 ettringite, C-S-H와 같은 수화물이 생성되었으며, 재령이 길어짐에 따라 수화물의 생성량이 증가하였다. 압축강도 측정결과, 석고 혼합량이 3 %일 때 더 높은 강도를 보였으며 재령 28일에서 무수석고 및 반수석고가 이수석고를 혼입할 경우 보다 높은 특성을 나타내었다. In this study, change of hydration property with contents and type of gypsum in ternary natural hydraulic lime containing blast furnace slag and gypsum was investigated. Anhydrite, hemihydrate and dihydrate were added 3 % and 10 %, respectively in natural hydraulic lime adding blast furnace slag 20 %. Hydration and physical behavior due to solubility and reactivity of different types of gypsum were analyzed in early hydration. As a result of analysis of hydration properties, in all samples, hydrates such as ettringite and C-S-H were produced in early hydration, and amount of hydrates with increase of hydration time was increased. In the case of compressive strength, when contents of gypsum are 3 %, it was higher compressive strength than other specimens. At hydration 28 days, for addition of anhydrite and hemihydrate, compressive strength was more than adding dihydrate.

Effect of Temperature and Additives on the Hydration Behaviour of MgO Powders

High performance MgO-based castables have many advantages for refining clean steel. However, hydration of MgO powder limits the application of MgO-based castables. The effects of temperature, hydration time and additives (calcium aluminate cement and microsilica) on the hydration behaviour of MgO powders are investigated in this paper. The results show that the hydration content of MgO powders increases noticeably with an increase of hydration time and temperature, indicating that the intensity of brucite (Mg(OH)2) diffraction peaks and the brucite amount increase. With 5 mass-% microsilica or cement addition, the amount of hydrated product Mg(OH)2 decreases noticeably from 26 to 11 mass-% and 19 mass-%. Microsilica has a retarding influence on the hydration of magnesia.

Water Absorption Kinetics of Pearl Millet Grains

Water absorption characteristics of pearl millet (PC 443) were evaluated in the temperature range of ambient (16°C) to 100°C. Water absorption by the grain increased with increase in temperature. The increase in water absorption by the grain was more rapid at temperatures 70°C and above. The initial rates of hydration at temperatures 16, 30, 40, 50, 60, 70, 80, 90 and 100°C were 14.2, 20.5, 24, 32.9, 43.2, 47.6, 94.7, 136.3, and 142.7 g.kg.dm-1.min-1, respectively. The rate of hydration decreased with increase in hydration time and approached very low value (≤0.1 g.water.kg.dm-1.min-1) corresponding to the grain moisture contents 16, 19, 22, 25, 33, 39, 46% (wb), respectively, at 16, 30, 40, 50, 60, 70, 80°C. The maximum moisture content after the hydration of pearl millet grain could be 48%, beyond which bursting of grains was observed. Moisture diffusivity varied from 2.13x10-4 m2 .s-1 to 30.56x10-3 m2 .s-1, with average value of 9.99x10-3 m2 .s-1 during hydration. Activation energy for hydration of pearl millet was found to be 55.71 kJ.mol-1. Page model was found to be the best for modelling hydration characteristics of pearl millet.

Influence of drier inlet temperature during pilot‐scale manufacture of rennet casein on the hydration behaviour of the rennet casein in disodium orthophosphate solution

Rennet casein curds were dried in a pilot‐scale fluidized bed drier at air‐inlet temperatures of 80, 90, 110, 120 or 140°C. As the drier air‐inlet temperature was increased, there was a significant increase in hydration time and a significant decrease in hydrated viscosity and viscosity stability following hydration of the dried rennet caseins in 0.4% (w/w) disodium orthophosphate (DSP). The influence of air‐inlet temperature during drying on composition, the extent of Maillard reaction, the resolution of the proteins on urea–polyacrylamide gel electrophoresis (PAGE) and cation‐exchange fast protein liquid chromatography (FPLC), the dialysability of calcium and phosphorous from a 6 m urea dispersion at pH 4.6, and the particle‐size parameters of milled rennet caseins were determined. Relationships between all these latter parameters and the hydration behaviours of the rennet caseins in DSP solution were also studied. Results suggest that the increase in drier air‐inlet temperature resulted in a reduction in the mean particle size of milled casein, which was significantly correlated to the changes in hydration behaviour. Hydration times increased significantly and hydrated viscosities decreased significantly with increasing levels of fluorescent Maillard reaction products (MRPs) and with increasing levels of nondialysable calcium and phosphorous in the caseins. It appears that the increase in air‐inlet temperature during drying reduced the solubility of colloidal calcium phosphate (CCP), possibly through binding of CCP to the increased levels of MRPs. This change in CCP solubility led to increased difficulty in sequestering CCP from the curd when the pilot‐scale rennet caseins were dispersed in the DSP solution, leading to the changes in hydration behaviour.