Hours Of Hydration Research Articles

THE IMPACT OF THE C12A7/CA RATIO AND THE FLUORIDE CaF2 AND AlF3 ON THE PROCESS OF HYDRATION AND HARDENING OF ALUMINA CEMENT

The effect of the ratio CaO.Al2O3/12CaO.7Al2O3, AlF3 and CaF2 on the formation of the structure and phase composition of clinker minerals of aluminate cement during hydration has been studied. It is found that after 24 hours of hydration, the main hydraulic phases in the studied cement stones are CAH10, C2AH8, AH3. It has been shown that the introduction of AlF3 and CaF2 fluorides reduces the liquidus temperature of the systems and increases the rate of CA formation. Scanning electron microscopy has revealed that the process of hydration of calcium aluminates of cement at low temperatures can be considered as simultaneous reactions.

Sulfate consumption during the hydration of Alite and its influence by SCMs

AbstractSCMs with a large specific surface area, such as calcined clays or fine limestone powder, can significantly accelerate the occurrence of the aluminate heat flow peak during the early hydration of blended cements. These systems therefore require a higher amount of sulfate. While this effect has been drawn back to the sulfate incorporation into C‐S‐H, which is formed more rapidly due to the filler effect, it has been recently shown that in systems with high amounts of metakaolin, the sulfate balance is influenced by further mechanisms. This study provides new results on the influence of aluminum‐rich and aluminum‐free SCMs on the early hydration of alite in presence of calcium sulfate. A synthesized alite was blended with 5 wt% of anhydrite and its hydration was investigated by isothermal calorimetry and in‐situ XRD at a w/b ratio of 0.5. It was shown that the formed C‐S‐H is able to take up the calcium and sulfate ions, indicated by a depletion of the solid anhydrite after approximately 20 hours. This process is significantly accelerated by incorporating 30 wt% of a fine limestone filler. The addition of metakaolin leads to an acceleration of the alite hydration compared to the reference as well, but to a significantly lower extend compared to the limestone. However, this system requires a lower degree of alite reaction to reach sulfate depletion. This indicates that in metakaolin‐rich systems, the sulfate demand is influenced by further effects. The results from in‐situ‐XRD reveal that significant ettringite formation is taking place in the metakaolin‐blended system already during the first hours of hydration. Correlations between the degree of alite hydration and the rate of sulfate depletion provide new insights into the mechanisms affecting the sulfate balance and early hydration of blended cements.

Increasing the Hydration Activity of Tricalcium Silicate by Adding Microdispersed Ettringite as a Nucleating Agent.

Tricalcium silicate (C3S) as a binder material has a decisive influence on the processes of hardening and strength gain of cements and concretes. One of the promising directions is the introduction of dispersed additives into cement mixtures, which allow micro-level control of the composition of hydration products and change the dynamics of the structure formation of cement stone. In this paper, the effect of a microdisperse ettringite additive on the kinetics of the hydration and hardening process of tricalcium silicate was studied. It was shown that ettringite crystals selectively adsorb Ca2+ and OH- ions from a saturated solution of calcium hydroxide, which contributes to the formation of hydrosilicate nuclei on their surface during cement hydration. Hydration of C3S in the presence of ettringite proceeds more intensively; the addition of ettringite contributes to an increase in the content of calcium hydrosilicates in hydration products at the initial stage of the process. Addition of 10 wt.% ettringite to C3S reduces the induction period of the beginning of the main phase of heat release by around two times and increases the amount of heat released on the 1st day of hydration by 15% compared to the control sample. According to electron microscopy data, it was found that during the first hours of hydration of modified C3S, a significant number of nuclei of fibrous particles of calcium hydrosilicates with sizes of 0.2-2 microns were formed on the surface of ettringite crystals. According to the results of kinetic modeling of the setting process of cement pastes using the Avrami-Erofeyev model, it was shown that in the presence of the addition of microcrystals of ettringite, the setting rate is characterized by a slowdown in nucleation, whereas for a sample without an additive, this process proceeds with an acceleration of the formation of solid-phase nuclei. Based on the comparison of kinetic results and mechanical measurements, it is concluded that needle crystals of ettringite during C3S hydration and cement stone hardening are preformed centers for the growth of hydrosilicate nuclei, and they also act as a reinforcing filler, increasing the bending strength of modified samples. The results of the work can be used in practice in the development of methods for controlling the processes of hydration and hardening of cements, as well as for controllable structure formation of cement stone which is important in particular for 3D printing of building products and constructions.

Intravenous hydration station in the chemotherapy infusion unit: A feasibility pilot study to improve efficiency, capacity, and wait times.

44 Background: Intravenous hydration (IVH) is frequently administered to oncology patients in outpatient chemotherapy infusion units. High demand for IVH often leads to capacity restraints in the chemotherapy infusion unit, negatively impacting the availability of infusion chairs for cancer-directed therapy, causing long wait times and patient dissatisfaction. This feasibility study aimed to expand the capacity for IVH and chemotherapy at a regional site of an academic medical center, through a dedicated hydration station outside of the conventional infusion chairs. Methods: A mobile space adjacent to a nurses’ station, within the chemotherapy infusion unit, was designated and converted to accommodate two patients simultaneously for IVH. Privacy screens separated this area from the rest of the infusion unit. Patients were directly scheduled into hydration station chairs. One nurse provided patient monitoring within the hydration station. The hydration rate was standardized to 1 liter per hour, subject to change at the discretion of treating physicians. Outcomes collected included the number of patients treated, total hours of hydration, wait times, and patient satisfaction, which was ascertained by a survey administered during February 2023 of the pilot phase. Results: Over a six-month period from December 2022 through May 2023, a total of 784 patients received IVH in the hydration station. This equates to 11 hours of IVH per day, and a cumulative total of 1,590 hours over the course of six months. The average wait time from check-in to starting IVH was 7 minutes. During the same period, the average wait time for chemotherapy was halved to 16 minutes. Among 28 patients who completed the satisfaction survey and had previously received IVH in a conventional infusion chair, 24 (86%) reported that the hydration station was either better or equivalent to their prior hydration experience. 23 (82%) patients reported a shorter or similar wait time compared to the conventional process. Overall, 84% were satisfied with their experience. Importantly, no patient safety issues were reported during the six-month period. Conclusions: IVH can be safely and effectively administered outside the conventional infusion chair, resulting in decreased wait times and high patient satisfaction. This IVH model increased the capacity for cancer-directed therapy in the chemotherapy infusion unit, with no reported safety issues. It is being standardized and implemented across other infusion units across our institution.

Effects of bacteria-based self-healing nutrients on hydration and rheology of cement pastes

Crack openings in concrete lead to a reduction in its lifespan. Many authors have analysed different techniques that could repair cracks autonomously, being the use of bacteria one of the most promising approaches. Bacteria are often introduced with nutrients in the concrete mixes, and they may alter the cement hydration.In this study, the effects that calcium lactate, calcium nitrate, and yeast extract have on cement pastes during the early hours of hydration were analysed. To accomplish this, calorimetry, in situ X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Vicat and rheology techniques were employed. The results demonstrated that the addition of calcium lactate led to higher values of ettringite, which altered the rheological behaviour of the pastes. Moreover, when added at 4%, calcium lactate also delayed the setting time by inhibiting the reaction of silicates, a similar effect was observed when yeast extract was added. Lastly, the incorporation of nitrate accelerated the setting time.

Direct observation of C3S particles greater than 10 μm during early hydration

Fast tomography, a non-destructive imaging technique, was used to study the spatial behavior of monoclinic tricalcium silicate (mC3S) from the first few seconds to one hour of hydration at a water to solids ratio of 0.43. The microstructure evolution of over 9,000 individual particles was directly observed and analyzed at 1 μm per pixel. These particles have an estimated diameter of 10 to 31 μm. These particles occupy ≈ 70 % of the total solids volume of the paste sample and so understanding the changes during hydration is important. The results show that these mC3S particles dissolve and contribute a significant amount of ions that likely participate in subsequent reactions. The dissolution of these particles occurs in localized regions with an observed depth of up to 6 µm. The findings show that these particles cannot be ignored in hydration reactions and these observations can provide further insights into the mechanism of the initial dissolution of hydration.

Influence of Zinc-Saturated Zeolite on Portland Cement Hydration Kinetics

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.

Chemical and thixotropic contribution to the structural build-up of cementitious materials

The structural build-up of fresh cement paste is often considered as a purely thixotropic phenomenon in literature even though cementitious materials undergo a non-reversible hydration process that can have an influence on the structuration process. In the current paper a method is proposed to validate the impact of the non-reversible structural build-up. It is shown that fresh cement paste samples lose their structural gain almost completely due to thixotropy while the structural build-up due to hydration can be observed but occurs in a significantly lower order of magnitude over the course of the first hours of hydration. In addition, it is shown, that the chemical component of the structural build-up accelerates with the onset of the acceleration period of hydration, while its contribution in the entire structural build-up remains constant.

In‐depth understanding the hydration process of Mn‐containing ferrite: A comparison with ferrite

AbstractManganese (Mn) is inevitably incorporated into cement from raw materials, and is mainly incorporated into the ferrite phase of cement. In this paper, the hydration kinetic was investigated for Mn‐containing ferrite and unmodified ferrite. The evolution of the solid phases, aqueous species, and both conductivity and pH were investigated for unmodified ferrite and Mn‐containing ferrite by a diluted suspension experiment. Isothermal calorimetry, transmission electron microscopy, and mechanical property measurements were conducted to explore the influence of Mn on the hydraulic activity of ferrite. The results showed that the incorporation of Mn enhances the hydraulic activity, alleviates the influence of gypsum on the retardation of ferrite, and improves the early strength in the presence of gypsum. Mn‐containing ferrite also accelerates dissolution, influencing the initial sulfate adsorption. Mn ions eventually incorporate into (Al, Fe)‐AFt and (Al, Fe)‐AFm. During the first several hours of hydration of ferrite, there is no sulfate consumption after the initial adsorption, accompanied by a decrease of Ca2+ and Al3+ concentration. And an “adsorption‐barrier” hypothesis is proposed to explain the dormant period of sulfate consumption.

Hydration Processes of Four-Component Binders Containing a Low Amount of Cement.

Results of research on hydration of four-component binders containing very high amounts of supplementary cementitious materials were presented. The samples were composed of blended pozzolana (a mix of conventional fly ash and spent aluminosilicate catalyst), cement (about 20 wt.% in the binder) and Ca(OH)2. Spent aluminosilicate catalyst was proposed as activating component which can improve properties of low-cement blends, while the role of Ca(OH)2 was to enhance pozzolanic reaction. Early and later hydration periods of such blends were investigated by calorimetry, TG/DTG, FTIR and X-ray diffraction. Initial setting time as well as compressive strength were also determined. It was concluded that enhancement of reactivity and improvement of properties of fly ash–cement binders are possible by replacing a part of fly ash with more active fine-grained pozzolana and introducing additional amounts of Ca(OH)2. The spent catalyst is mainly responsible for accelerating action during the first hours of hydration and for progress of early pozzolanic reaction. Fly ash develops its activity over time, thus synergic effect influences the later properties of composites. Samples containing blended pozzolana exhibit shorter initial setting times and higher compressive strength, as well as faster consumption of Ca(OH)2 compared to the reference. Investigated mixtures seem to be promising as “green” binders, alternatives to cement, after optimizing their compositions or additional activating procedure.

Feasibility and safety of outpatient administration of ifosfamide and etoposide for pediatric patients with Ewing sarcoma in a resource-limited setting amid the COVID-19 pandemic.

BackgroundTo assess feasibility and safety of outpatient administration of ifosfamide and etoposide (IE) for pediatric Ewing sarcoma (EWS) patients in a resource‐limited setting amid the COVID‐19 pandemic.Materials and MethodsRetrospective study of patients with EWS who received outpatient IE from January 2020 until January 2021 at our institution. Ifosfamide 1800 mg/m2 was given for 5 days with MESNA (2‐mercaptoethane sulfonate sodium) infusion and additional boluses before and after 9 hours of hydration. Patients >10 years of age with the ability to drink orally at home, no pre‐existing renal dysfunction or history of hematuria were included. They were monitored for hemorrhagic cystitis with a urine dipstick before, midway, and at end of infusion. A urine analysis was done 24 hours after the last dose of ifosfamide.ResultsForty‐seven (100%) cycles were given as outpatient during the study period. Thirty‐five (74%) cycles were given on time, two (4%) cycles were delayed due to mucositis, two (4%) due to delayed count recovery, and eight (18%) due to unavailability of outpatient appointments. The median interval between these cycles was 15 days (range 14–44 days). No episode of hemorrhagic cystitis was reported. Urine analysis was not done at 24 hours for 27 (58%) cycles, so microscopic hematuria may have been missed. This outpatient protocol saved 32% (USD 299) per cycle in cost and 282 days of hospitalization.ConclusionOutpatient administration of IE for pediatric patients with EWS is feasible, safe, and cost‐effective during the COVID‐19 pandemic.

The hydration of fast setting spray binder versus (aluminum sulfate) accelerated OPC

The (early) hydration mechanisms of two different binder systems used for shotcrete were investigated: the so far almost unexplored low sulfate binder (spray binder), used in the field of dry-mix shotcrete; and ordinary Portland cement, accelerated by aluminum sulfate, widely used for wet-mix shotcrete. The basis for the fast setting of the spray binder is the rapid dissolution of C3A and the subsequent formation of flaky CO3-AFm phases. Thereby induced high aluminum concentrations in the pore solution lead to a blockage of alite dissolution during the first hours of hydration. At later stages, higher amounts of portlandite are formed in the dry-mix, compared to the wet-mix system. The lower calcium availability for portlandite formation in the wet-mix system is explained by an enhanced formation of C–A–S–H phases with a higher Ca:Si ratio. Additionally, wet-mix systems show lower porosity and higher compressive strength after 1 d of hydration and beyond.Graphical abstract

Features of using cement suspension in concrete mixture recycling technology

Introduction. Recycling technologies may solve the problem of landfill waste. The problem of hydraulic active cement waste using not fully resolved in concrete mixtures recycling technologies. Using hydraulic active cement waste as an addition directly influences the technological and mechanical characteristics of new concrete mixtures. That requires additional research.
 
 Materials and methods. The cement waste obtained after recycling was simulated by pre-hydrated cement suspension produce at V/C equal to 0.7 for 6 hours of hydration. Different compositions of cement mixtures were investigated. The difference of which was amount of introduced pre-hydrated cement additive, both in the presence and without plasticizer. Technological properties, namely the normal consistency and setting time of cement compositions were investigated by standard methods of GOST 30744-2001. Mechanical properties, namely the compressive strength at the age of 28 days, were determined by destructive method on a hydraulic press PSU-10.
 
 Results. The introduction of a pre-hydrated suspension causes an increase in normal consistency, a reduction in the setting time and a decrease in strength with an increase in its quantity. The use of such a suspension in conjunction with a superplasticizer can level out the increase in normal density, as well as increase the strength of the samples. Timing of setting remained similar to the results of the test without the plasticizer.
 
 Conclusions. The results of the study show influences of cement waste obtained after recycling on the technological and mechanical characteristics of new mixtures. These influences are important and must be taken into account in the design of new concretes and mortars.

Composition and properties of cement system with glutaraldehyde

The experience of operating livestock farms shows that periodic reorganization does not prevent biological corrosion of building structures. In this work, the possibility of using glutaraldehyde as a fungicide for volumetric administration in the preparation of biostable concrete was investigated. The study aims to minimize the adverse effects of the components of commercial biocidal products on the physical and mechanical characteristics of products. For research, we used an aqueous solution of glutaraldehyde with an active substance concentration of 0.5 and 1 %, which was introduced into Portland cement CEM I 42.5 N as mixing water. The degree of influence of the active substance on the properties of cement paste and mortar was estimated according to data on heat release during hydration, strength, and phase composition. The fungicidal activity evaluation of glutaraldehyde in cement systems and the degree of their growth with the Aspergillus niger test culture were evaluated. It was established by isothermal calorimetry that, in mixtures with glutaraldehyde, a delay in the achievement of the main hydration peak is observed-by 30 minutes for 0.5 %, by 1 hour for 1 %. After 72 hours of hydration, a lower total amount of released heat of hydration is observed-for 0.5 and 1% solutions by 6.8 and 5.8 %, respectively. According to X-ray phase and differential thermal analyzes, the phase composition of the initial and aldehyde-modified cement stone on day 28 does not differ and consists of the following phases: ettringite, portlandite, calcite and clinker minerals. Varying the phase composition leads to a change in strength: when using a 0.5 % solution of aldehyde, the power of the cement-sand mortar increases by 6.5 %, and a 1 % solution decreases by 6.7 %. The use of a 0.5 % solution of glutaraldehyde provides a decrease in the intensity of fungal development and the formation of a fungistatic effect. Based on the results, a 0.5 % solution of glutaraldehyde can be recommended for the development of cement composites with prolonged bioresistance.

Hydration of sustainable ternary cements containing phosphogypsum

Phosphogypsum (PG) is a large environmental issue generated by phosphate fertilizer industries. Its annual disposal worldwide is about 160 million tons, representing a high risk of contamination of the environment. The content of dihydrate (CaSO4.2H2O) in PG is generally above 90%, presenting recycling potential in cement production. The objective of this research is to investigate the applicability of unprocessed PG in the composition of sustainable ternary cement (TC) containing Portland cement (PC) and wastes of marble and clay brick. The effects on hydration properties and phase contents of PG added in ratios 1, 3, 5, and 10 wt% to cement were studied. The technical feasibility of applying PG in TC with different WCB/WM ratios (2.0 and 3.6) was also evaluated. Isothermal calorimetry was applied to study the hydration kinetics of the TC pastes. The hydration products were evaluated using Fourier transform infrared spectroscopy (FTIR), thermal analysis (TG/DTG/DTA), and X-ray diffractometry using the Rietveld method. The evolution of axial compressive strength was assessed at ages 1, 3, 7, 28, and 91 days. The increase in PG content satisfactorily prolonged the cement setting time and the induction period. Phosphorus impurities in the form of CaHPO4.2H2O did not cause any deleterious effects in the first hours of hydration. Although the presence of PG affects the hydration reactions by leading to higher levels of hydrated calcium silicate (C-S-H) and monocarboaluminate (Mca). TC pastes are mainly composed of C-S-H gel, portlandite, ettringite, Mca, calcite, quartz, dolomite, β-belite, and periclase. TC pastes after 28 days reached at least 70% of the PC compressive strength. The WCB/WM ratio affected the compressive strength, although it did not significantly influence the formation of phases. By evaluating the properties of TC paste it was concluded that the unprocessed PG can sustainably be used as an alternative to a natural source of calcium sulfate in the manufacture of the ternary cement.

Mortar pore pressure prediction during the first hours of cement hydration

During cement hydration, solid, fluid, and total volumes vary as water is consumed by chemical reactions. Those volume variations lead to pore water pressure decrease during the first hours of hydration. The deformations induced by early hydration are quantified in order to understand their consequences on the internal stress state within the hardening material.This paper aims to link pore water pressure with autogenous and chemical shrinkage during the first hours of hydration in the bulk of early setting cement mortar. It is demonstrated that specific volume variations are compensated by an increase of air-entrained volume. The variation of the volume of air is used to predict the air pressure. Using the size of a maximum capillary pore diameter filled with water, the capillary pressure is estimated using the Young-Laplace equation. In order to validate the approach, the pore water pressure is measured and compared to the thermodynamic prediction and air content.

Effect of pozzolanic micro and nanoparticles as secondary fillers in carbon nanotubes/cement composites

Incorporation of micro and nanoparticles as secondary fillers in cement based matrices improves the efficiency of self-sensing carbon nanotubes (CNT)/cement composites through the excluded volume effect. Pozzolanic particles can be seen as interesting secondary fillers for this purpose since they would increase the compacity of the granular matrix, increase the nanotube effective volume during the first hours of hydration, and densify the matrix through the growth of additional hydration products at latter ages. In this work, pozzolanic micro and nano particles (nanosilica, microsilica, metakaolin and nanoclay) were used as secondary fillers to investigate how their combined effect with CNT dispersion containing surfactant as dispersing agents affects the hydration kinetics, setting time and early strength development of Portland cement pastes. For this purpose, isothermal calorimetry and ultrasonic pulse velocity tests were performed. The change in solid fraction caused by the pozzolanic particles also was analyzed to understand the excluded volume effect in the matrix. It was found that the use of surfactants as dispersing agent for CNT has a retardation effect on the hydration and strength development of cement paste and this retardation is minimized by the presence of pozzolanic secondary fillers. It also was found that microparticles are much more effective than nanoparticles in increasing the compacity and effective nanotube volume in the matrix.

Spermidine priming promotes germination of deteriorated seeds and reduced salt stressed damage in rice seedlings

Deterioration of seeds is an important problem leading to low germination and uneven crop establishment causing poor crop growth and productivity. Soil salinity is another factor limiting crop cultivation. Spermidine (Spd) is a compound widely reported for diminishing adverse effects of salt stress in plants. In this study, the effects of Spd priming on normal and deteriorated rice seeds were investigated under salt stress during germination and young seedling stages. Rice seeds were primed with H2O and Spd solutions for 24 h before germination. All rice seeds were grown in Petri dishes containing 5 ml of deionized water with 0 (control) or 150 mM NaCl (salt treatment) for 1-10 d. The results showed that priming groups had higher germination percentage (GP) and germination index (GI) in both normal and deteriorated seeds. Moreover, deteriorated seeds primed with 0.5, 1.0 and 1.5 mM Spd showed significantly higher GP and GI than H2O-primed and non-primed seeds. During early hours of hydration, Spd-primed seeds produced reactive oxygen species (ROS) faster and at higher level than non-priming and H2O priming groups in both control and saline conditions. Earlier accumulation of ROS was associated with more rapid germination. In young seedlings, salinity stress caused a marked decrease in growth and increased membrane damage indicated by higher malondialdehyde (MDA) and electrolyte leakage (EL). Conversely, Spd priming increased growth and reduced membrane damage of rice seedlings established from normal and deteriorated seeds under salt stress. The finding suggested that Spd priming can effectively improve germination of deteriorated seeds and enhance seedling growth under control and salt stress conditions.

Influence of quartz powder and silica fume on the performance of Portland cement

Supplementary cementitious materials interact chemically and physically with cement, influencing the formation of hydrate compounds. Many authors have analyzed the filler and pozzolanic effect. However, few studies have explored the influence of these effects on hydration, properties in the fresh and hardened states, and durability parameters of cementitious composites separately. This study investigates the influence of the replacement of 20% of Portland cement for silica fume (SF) or a 20-µm medium diameter quartz powder (QP) on the properties of cementitious composites from the first hours of hydration to a few months of curing. The results indicate that SF is pozzolanic and that QP has no pozzolanic activity. The use of SF and QP reduces the released energy at early times to the control paste, indicating that these materials reduce the heat of hydration. The microstructure with fewer pores of SF compounds indicates that the pozzolanic reaction reduced pore size and binding capability, resulting in equivalent mechanical properties, reduced permeability and increased electrical resistance of the composites. SF and QP increase the carbonation depth of the composites. SF and QP composites are efficient in the inhibition of the alkali-aggregate reaction. The results indicate that, unlike the filler effect, the occurrence of pozzolanic reaction strongly influences electrical resistance, reducing the risk of corrosion of the reinforcement inserted in the concrete.

Experimental approach on a moving formwork

In a slipforming process, concrete is continuously poured and the formwork simultaneously raised so that the older concrete on the bottom supports the fresher on the top after a few hours of hydration. The objective of the present study is to examine the evolution of the concrete/formwork interface at very early age.An experimental device was designed to measure the evolution of the friction at this interface during the first hydration period. With cement hydration and thus water consumption, pore water pressure decreases and creates suction, which could increase granular stress on the formwork. The role of pore water pressure on formwork friction is investigated. The effect of mix-design parameter such as air content is described. Finally, a model that is able to predict the friction force at very early age (up to the initial setting time) is proposed.