Hydration Agent Research Articles

Evaluation of the technical properties of reactive-MgO cements produced by solar calcination of magnesite in a fluidized bed reactor

Magnesium oxide (MgO)-based cements display very interesting technical properties and environmentally-friendly features. The novel idea investigated in this study is to synthesize MgO cements, using as raw material natural magnesite calcined in fluidized bed heated by concentrated solar energy. Calcination was performed in a lab-scale system equipped with a concentrated solar simulator, operated under different process conditions. The most reactive MgO was mixed with 3% by weight of MgCO3 (nucleation agent) and four different solutions containing magnesium acetate or chloride. The binders were hydrated in air or 20% CO2 atmosphere (accelerated carbonation conditions) until 28 days. X-ray diffraction, differential-thermal and mercury intrusion porosimetry analyses, and compressive mechanical strength tests, were performed on the hydrated systems. Solar calcination produced a highly reactive MgO. The performance of the cement pastes improved at higher curing times, and when using magnesium acetate as hydration agent, as also witnessed by the application of a kinetic model. Accelerated carbonation conditions further enhanced the mechanical properties of the cements thanks to the formation of nesquehonite, allowing to reach a mechanical strength comparable to that of ordinary Portland cements class 32.5. The achieved outcomes encourage the production of low-CO2 magnesite cements from solar calcined magnesite, boosting the green aspect of the entire process.

Influence of nesquehonite seeds on hydration and carbonation of reactive magnesia cement

Among all carbonation products of reactive magnesia cement (RMC), nesquehonite exhibited the highest CO2 amount of sequestration per molar. Inducing the nesquehonite formation may improve the CO2 sequestration capacity of RMC. In this paper, nesquehonite seeds were introduced to promote the formation of nesquehonite in RMC. The performances of RMCs with 0%, 0.5%, 1%, 1.5% and 2% nesquehonite seeds were studied and compared with that of RMC mixed with hydromagnesite seeds. It was found that the hydration of RMC could be facilitated by nesquehonite seeds, resulting in reduced setting times. The nucleation effect of nesquehonite seeds was demonstrated, resulting in increased nesquehonite formation and carbonation degree. Nesquehonite seeds combined with hydration agent can further promote the compressive strength of RMC through forming more amounts of nesqeuhonite crystals and amorphous hydrated magnesium carbonates. Compared with the hydromagnesite seeds, the nesquehonite seeds showed a more significant increase in the CO2 sequestration capacity of RMC.

Multiple effects of glycine on stability and rheology behavior of hydrated Mg(OH)2 slurry

Hydration of MgO is a potential technology for economically preparing Mg(OH)2 slurry. Understanding the rheological behavior evolution of the slurry during MgO hydration, particularly in the presence of hydration agent, is essential for better control of the hydrated Mg(OH)2 slurry’s rheology. In this work, Mg(OH)2 slurry was prepared by hydrating MgO in the presence of glycine. The effect of glycine on the rheological behavior of the hydrated Mg(OH)2 slurry have been investigated by means of viscosity, shear stress, sedimentation measurements, particle size distribution, 1H nuclear magnetic resonance relaxometry and zeta potential. Results showed that shear thinning rheological slurry could be made by hydration at 80 °C for 1 h. The yield stress of the slurry is 27.49 ± 0.81 Pa, and no settling occurs within 7 days. Yet, in the absence of glycine, the structure of the slurry was unstable and easily settled even after 8 h of hydration. Glycine has multiple effects on the slurry’s solid loading, particle morphology, particle size distribution, and zeta potential of the slurry. In addition, the neutral zwitterionic form of glycine may serve as an inter-particle lubricant, reducing viscosity.

Compressive resistance of concrete produced with recycled concrete aggregate and sugarcane vinasse waste-water

Vinasse is the main by-product of the sugar and alcohol industry. For each liter of ethanol produced from sugarcane, approximately 12–18 L of vinasse are generated. Being such, its use as a hydration agent in concretes may be useful to save drinking water. This work analyzed the compressive strength of concrete manufactured with vinasse and recycled concrete aggregates (RCA), as a substitute for water (100%) and sand (50 and 100%), respectively. At the initial periods (7 and 14 days), the compressive strength of specimens hydrated with water was higher than those hydrated with vinasse due to the delay in hydration of the cement caused by the sucrose present in the vinasse. Therefore, in these stages, the hydration agent is the main contributor for the differences in the compression strength ( p < 0.05, Two-way ANOVA). In the later stages (21 and 28 days), the RCA content was that which most contributed to the differences in the compressive strength. Specimens with 50% RCA showed the highest values ( p < 0.05), independently of the hydration agent; the specimens with vinasse reached the same resistance as that of the reference. After 63 days of curing, the concrete with water replaced by vinasse acquired higher resistance in relation to the reference due to continuity of curing. As both residues proved to be viable in the composition of concretes, they were applied in a precast concrete panel, that presented satisfactory results, enabling its use as a non-structural wall. It can be concluded that sugarcane vinasse with recycled concrete aggregate (RCA) is a suitable solution to achieve better reuse of construction and agroindustry waste as a new building materials compound. • Sugarcane vinasse waste water was used in concrete admixtures replacing water. • Concretes with vinasse and RCA acquired same compressive strength of reference at 28-days. • Concrete with vinasse reach higher compressive strength than reference at 63-days curing.

Fresh state properties and compressive strength development of reactive MgO-based systems

In this study, flowability, setting time, and strength gain of mortars containing reactive magnesium oxide cement (RMC) and a combination of micro-silica (MS), nano-silica (NS), slag, and fly ash (FA) as precursors without employing accelerated carbonation have been investigated. To increase the flowability and hydration degree, sodium hexametaphosphate (SHMP) was incorporated. The series containing RMC and MS simultaneously, had the greatest 3-day compressive strength value of about 25 MPa, whereas further strength gains in all the mixtures until the 7th day was minimal, which establishes that strength gains were due to hydration degree, not carbonation. RMC and MS simultaneously in a series, a combination of extremely high fineness materials dropped the flowability; the presence of slag and FA, on the other hand, enhanced it. The inclusion of NS in the mix didn’t demonstrate a perceptible change in any of the properties measured in this study; its inertness could be attributed to the unsuitable dispersion method. Setting time of reference mix was the shortest, which was in conformity with its fast initial strength gain. Replacement of RMC with any other binder extended both the initial and final setting time. It was hypothesized that a major difference in this study is the use of SHMP as a dispersant and hydration agent. The outcomes of this study confirm that RMC can be a potential binder material to be used in mortar productions.

Potential additives for magnesia-based concrete with enhanced performance and propensity for CO2 sequestration

This study focuses on the development of carbonated reactive magnesia cement (RMC) concrete formulations involving hydromagnesite (H), magnesite (M) and hydration agent (HA). Partial replacement of RMC by H and M stimulated the formation of hydrate and carbonate phases. Use of H increased the rate and degree of hydration, resulting in the formation of a bird nest-like structure containing poorly-crystalline brucite. The higher propensity of this poorly-crystalline phase for carbonation increased the utilisation of RMC as a binder and facilitated its conversion into strength-providing HMCs. Synergistic combination of M and HA led to significant strength gain via increased carbonate content and reduced w/b ratio. Presence of M provided micro-aggregates that facilitated the enhanced formation of large carbonate crystals with improved morphologies, resulting in microstructure densification and 113 % strength increase. Furthermore, partial replacement of RMC with M enabled reduction of natural resources, CO2 emissions and energy consumption associated with RMC production.

Use of microbial carbonation process to enable self‑carbonation of reactive MgO cement mixes

The low hydration and carbonation of reactive MgO cement (RMC) under ambient conditions causes prolonged setting and low compressive strengths (~4 MPa). This study proposed a unique technique which led to the enhancement of the hydration and carbonation processes via the synergistic combination of microbial carbonation process (MCP) with a hydration agent (HA) that enabled the self‑carbonation of RMC-based mixes without using of any special curing environments. Through hydrolysing urea (CO(NH2)2) using ureolytic bacteria, CO32− ions were produced to facilitate the carbonation of dissolved Mg2+ ions to form hydrated magnesium hydroxy carbonates (HMHCs). The self‑carbonation of RMC enabled by the MCP resulted in formation of brucite with a poor crystallinity and its rapid conversion into HMHCs, which improved the setting time and compressive strength of RMC-based samples. The simultaneous use of MCP with 2 M urea and HA revealed HMHCs with improved morphologies, resulting in the highest compressive strength (~15 MPa).

Skin Hydration Effects of Scale-Up Fermented Cyclopia intermedia against Ultraviolet B-Induced Damage in Keratinocyte Cells and Hairless Mice.

Photoaging occurs by chronic skin exposure to the sun and ultraviolet irradiation and leads to skin aging accompanied by a lack of skin hydration. We previously demonstrated the photoprotective effect of fermented Cyclopia intermedia (honeybush) extract on the skin. In this study, we evaluated the skin hydration effects of scaled-up fermented honeybush extract (HU-018) against ultraviolet B (UVB) radiation in HaCaT immortalized human keratinocytes and hairless mice. Pretreating HaCaT cells with HU-018 attenuated the decreased hyaluronic acid (HA) levels and mRNA expression of genes encoding involucrin, filaggrin, and loricrin by UVB irradiation. HU-018 treatment also ameliorated the decreased stratum corneum (SC) hydration and the increased levels of transepidermal water loss (TEWL) and erythema index (EI) in hairless mice after UVB exposure. Microarray analysis revealed changes in gene expression patterns of hyaluronan synthase 2 (Has2), transforming growth factor-beta 3 (TGF-β3), and elastin induced by HU-018 in UVB-irradiated mice. Consistently, the mRNA expression of Has2, TGF-β3, and elastin was increased by HU-018 treatment. Moreover, HU-018 restored the increased epidermal thickness and collagen disorganization in skin tissue of UVB-irradiated mice. HU-018 treatment also decreased matrix metalloproteinase-1 (MMP-1) expression and increased procollagen type-1, elastin, and TGF-β1 expression. In conclusion, we found that HU-018 promoted skin hydration processes in UVB-irradiated keratinocytes and hairless mice by modulating involucrin, filaggrin, loricrin, and HA expression and ameliorating visible signs of photoaging. Thus, HU-018 may be a good skin hydration agent for skin care.

Correlation between microstructure and dissolution property of magnesium hydroxide synthesized via magnesia hydroxylation: Effect of hydration agents

The dissolution of magnesium hydroxide (MH) is a crucial process in its environmental protection application filed. In the present study, we attempted to improve the dissolution property of MH by changing the synthesis conditions. Various MH nanoparticles were prepared by MgO hydroxylation within hydration agents. The pH-stat method was applied to investigate the dissolution rate of the hydrate product. SEM, EDS-Mapping, FT-IR, and XRD technologies were utilized to gain surface and bulk structure information about the hydroxylation product. The dissolution property test results show that the average OH− released rate and Acid Neutralizing Capacity (ANC) in 120 min were promoted significantly form 27.7 ± 0.55 mmol/min/mol MH and 29.32 ± 0.59 mmol H+/g to 45.69 ± 1.37 mmol/min/mol MH (10 g NH4AC as hydration agent) and 31.31 ± 0.63 mmol H+/g (5g MgAC2 as hydration agent). The morphology and structure characterization results show that product with thin flake structure, large microscopic internal strain and low crystallinity would exhibit high dissolution activity. The present experimental results indicate that the curled sheet structure is an important reason for dissolution performance improvement, which is also proved by the Density-Functional Theory (DFT) calculation results of the affinity of H2O for uptake by the MH (001) surface. The results will be used to guide the synthesis of MH slurry with high activity and also provide valuable reference for the regulation of dissolution properties of other crystals.

Fabrication of Al2O3-Bonded Fibrous Ceramics by An Aqueous Gel-Casting Process

The traditional gel-casting method mostly uses organic compounds, which are complex process, expensive and pollute the environment. In order to overcome the disadvantage of the traditional gel-casting method, an environment friendly aqueous gel-casting process is introduced in this paper. Al2O3-bonded fibrous ceramics with high porosity and low thermal conductivity have been prepared by a novel hydrated alumina gel-casting process using the ρ-Al2O3and mullite fibers or YSZ fibers as raw materials and the deionized water as hydration agent. A bird-nest-patterned three-dimensional reticular skeleton structure was established by the fibers to ensure a certain mechanical strength. The effects of the amount of mullite fibers andYSZ fibers on the properties of porous ceramic, such as phase composition, microstructure, sintering behavior and relative properties were investigated. Results showed that the as-prepared Al2O3-bonded fibrous mullite ceramics have high porosity of 66.9%∼78.6%, low thermal conductivity of 0.236∼0.479 W/m·K, and relatively high compressive strength of 0.80∼2.78 MPa. The as-fabricated fibrous YSZ ceramics had a high porosity (71.1%∼72.7%), a low thermal conductivity (0.209∼0.503 W/m·K) and a relatively high compressive strength (3.45∼4.24 MPa). Comparing to the as-fabricated fibrous mullite ceramics, the compressive strength of as-fabricated fibrous YSZ ceramics is promoted obviously.

A novel aqueous gel-casting for fabricating Al2O3-bonded fibrous mullite ceramics

Al2O3-bonded fibrous mullite ceramics with high porosity have been prepared by a novel aqueous gel-casting method using the ρ-Al2O3 and mullite fibers as raw materials and the deionized water as hydration agent. A bird nest structure with three-dimensional reticular skeleton was established by the fibers to ensure having a certain mechanical strength. The effects of the amount of mullite fibers on the properties of porous ceramic including phase composition, microstructure, sintering behavior, mechanical and thermal properties were investigated. The results showed that the fabricated Al2O3-bonded fibrous mullite ceramic had high porosity of 66.9%–78.6%, low density of 0.70 g/cm3 to 1.17 g/cm3, low thermal conductivity of 0.236 W/mK to 0.479 W/mK, and relatively high compressive strength of 0.80 MPa–2.78 MPa. With increasing the amounts of mullite fiber, the apparent porosity increased, the bulk density and thermal conductivity decreased. When the ratio of mullite fibers was 67%, the porous ceramic had the maximum porosity of 78.6%, the minimum thermal conductivity of 0.236 W/mK, and the relatively high compressive strength of 1.12 MPa, which could fully meet the application requirements of the thermal insulation materials.

Preparation of amphiphilic mesoporous carbon-based solid acid from kraft lignin activated by phosphoric acid and its catalytic performance for hydration of α-pinene

An amphiphilic mesoporous carbon-based solid acid (LCx-SO3H) with high specific surface area was prepared from kraft lignin that was carbonized using a phosphoric acid treatment. It was found that the specific surface area, pore structure, and amphiphilic nature of the catalyst was effectively controlled through adjusting the phosphoric acid dosage during lignin carbonization. Under optimum preparation conditions, the specific surface area, pore volume, and average pore size of the catalyst were 282.2 m2/g, 0.26 cm3/g, and 6.73 nm, respectively. The performance of this solid acid catalyst for the hydration of α-pinene was characterized via gas chromatography analysis. The conversion of α-pinene and the yield of α-terpineol during hydration reaction were as high as 95.3% and 55.3%, respectively; these results were greater than the results from other hydration methods with sulfuric acid and commercially available solid acid catalysts (e.g., Amberlyst-15). After five recycles of the carbon-based solid acid without regeneration, conversion of α-pinene decreased from 95.3% to 92.6%, and the yield of α-terpineol decreased from 55.3% to 47.6%. These observations indicated that the solid acid catalyst derived from kraft lignin carbonization has high potential as a hydration agent for α-pinene.

Fabrication and Characterization of Porous MgAl₂O₄ Ceramics via a Novel Aqueous Gel-Casting Process.

A novel and aqueous gel-casting process has been successfully developed to fabricate porous MgAl2O4 ceramics by using hydratable alumina and MgO powders as raw materials and deionized water as hydration agent. The effects of different amounts of deionized water on the hydration properties, apparent porosity, bulk density, microstructure, pore size distribution and compressive strength of the samples were investigated. The results indicated that the porosity and the microstructure of porous MgAl2O4 ceramics were governed by the amounts of deionized water added. The porous structure was formed by the liberation of physisorbed water and the decomposition of hydration products such as bayerite, brucite and boehmite. After determining the addition amounts of deionized water, the fabricated porous MgAl2O4 ceramics had a high apparent porosity (52.5–65.8%), a small average pore size structure (around 1–3 μm) and a relatively high compressive strength (12–28 MPa). The novel aqueous gel-casting process with easy access is expected to be a promising candidate for the preparation of Al2O3-based porous ceramics.

Development of MgO concrete with enhanced hydration and carbonation mechanisms

This study proposed the use of hydration agent (HA) and seeds to improve the hydration and carbonation of reactive magnesium cement (RMC)-based concrete formulations. Hydration of RMC was evaluated by isothermal calorimetry. Water absorption and compressive strength results were used to assess the mechanical performance of RMC-based concrete samples. Quantification of hydrate and carbonate phases was performed via XRD and TGA. Formation and morphology of carbonates were observed via BSE and SEM. In addition to increasing the utilization of RMC in the carbonation reaction and facilitating early strength development, the use of HA formed large carbonate phases, while the addition of seeds improved sample microstructures via the development of dense carbonate networks. The improvements in morphology, microstructure and carbonate content in samples involving the simultaneous use of HA and seeds resulted in 56% lower water absorption values and 46% higher 28-day compressive strengths (70MPa) in comparison to the control sample.

Carbonated MgO concrete with improved performance: The influence of temperature and hydration agent on hydration, carbonation and strength gain

Carbonation plays a key role in the strength gain of reactive MgO cement (RMC)-based concrete formulations. Low hydration of MgO limits the subsequent carbonation and associated strength gain. This study improves the mechanical performance of carbonated RMC concrete mixes with the introduction of a hydration agent (HA) and high temperature pre-curing (HTPC). The influence of HA and HTPC on hydration, carbonation and microstructural development was investigated through isothermal calorimetry, TGA, XRD, ATR-FTIR and SEM. Implementation of HA and HTPC increased the rate and degree of hydration. The increased brucite content led to higher carbonation degrees, accompanied by lower water absorption and higher density and strength values. Improvement of the morphology of carbonates resulted in 40% higher strengths than the control mix, reaching 56 MPa at 28 days. These mixes provided equivalent strengths to the 28-day strength of the control mix at 7 days, therefore shortening the curing period by 75%.

Three‐phase hydration of magnesium oxide using hydration agents

A gas‐liquid‐solid reaction system, named three‐phase reaction system, was firstly used for magnesium oxide (MgO) hydration in our previous research. In this paper, the effect of hydration agents on the MgO hydration in three‐phase reaction system was investigated experimentally. The hydration agents included magnesium acetate, acetic acid, and ammonium chloride. The variations of hydration degree (measured by thermogravimetric analysis), pH value, conductivity of different reaction system were studied. Furthermore, the final hydrated samples were characterized by X‐ray power diffraction (XRD), Scanning electron microscopy (SEM) and nitrogen sorption analyses. The results indicated that the hydration degree was 20%∼30% higher in hydration agent solution than that in deionized water. Hexagonal plate crystal was obtained in all reaction systems, while lager diameter and thinner crystallite was formed in the acetate system. The degree of hydration and the SEM analysis results indicated that the peel‐off phenomenon was more obvious in the present of CH3COO−.

Contrast-induced nephropathy

Contrast-induced nephropathy(CIN) is a common cause of hospital-acquired acute renal failure. Patients with chronic renal failure. diabetes mellitus， congestive heartfailure， older age，hypotension， and anemia are at particular risk. Typically. serum creatinine levels begin to increase at 48-72 hours. peak at 3 to 5 days ，and return to baseline within another 3 to 5 days. Although a variety of therapeutic interventions ， including saline hydration，diuretics，mannitol，dopamine agonist , and many other agent have been used to prevent the CIN. saline hydration is the sole efficacious therapy to protect against CIN. Recent advances have examined the effect of the antioxidant N-acetylcysteine，iso-osmolar nonionic contrast agents. hemodialysis and hemofiltration， erythropoietin to prevent the CIN. but there are many inconsistent trial results for unknown reasons.

Small-Angle Neutron and X-ray Scattering from Amphiphilic Stimuli-Responsive Diamond-Type Bicontinuous Cubic Phase

The structural evolution of a diamond-type bicontinuous lipid cubic phase upon application of thermal and chemical (hydration agent) stimuli is investigated by means of small-angle neutron (SANS) and X-ray scattering (SAXS). The soft-matter cubic architecture responds by dramatic swelling (DLarge cubic structure) upon incorporation of a hydration-enhancing guest component (octyl glucoside) at low and ambient temperatures, the aqueous channel diameter increasing twice to approximately 7 nm. DLarge appears to be built up from an assembly of cubosomic domains, which may coexist with an amphiphilic lamellae domain at low temperatures. The chemical stimulus concentration can be selected as to tune the hydration of the nanochannels in the DLarge phase and its transformation into a DNormal phase at temperatures above the body temperature. Two-dimensional SANS images recorded upon heating scan reveal growth of spontaneously oriented domains of single-crystal cubic nature. Phase separation and squeezing out the guest-hydrating agent from the higher-curvature regions of the amphiphilic bilayer suggest a possible mechanism for the established transformations. The order-order structural transition, cubic DLarge-cubic DNormal, is found to be reversible upon cooling. The obtained results put forward a structure-based concept for release of encapsulated guest molecules from stimuli-responsive and self-regulated cubosomic nanocarriers.

Effect of seed disinfection for prevention against Bacterial Fruit Blotch of Cucurbitaceae vegetables by treatment with mixture of Copper hydration agent and Organic Acid, or with Peroxy acetic Acid

Effect of seed disinfection for prevention against Bacterial Fruit Blotch of Cucurbitaceae vegetables by treatment with mixture of Copper hydration agent and Organic Acid, or with Peroxy acetic Acid

Efficacy and safety of three ophthalmic inserts for topical anaesthesia of the cornea. An exploratory comparative dose‐ranging, double‐blind, randomized trial in healthy volunteers

Cataract surgery requires prolonged anaesthesia, concomitant with permanent hydration and lubrication of the cornea, in order to provide a clear view of the operation area. The primary objective of the study was to assess several formulae of a soluble ophthalmic insert: TOPICSERT [bupivacaine (Bupi) + hyaluronic acid (HA) or sodium hyaluronate] in terms of complete and long-lasting anaesthesia of the cornea. The hydration properties of HA were not assessed in this study. In a prospective double-blind, cross-over, randomized study, with latin-square allocation of treatments, 16 healthy volunteers received a single dose of each formula (A, 1 mg Bupi and 0.1 mg HA; B, 0.5 mg Bupi and 0.1 mg HA; C, 1 mg Bupi and 0 mg HA, and D acting as a placebo) via the ocular route with 1 week of wash-out between each period. Corneal anaesthesia was measured using a Cochet-Bonnet esthesiometer. There was a statistically significant difference between treatments with regard to the main criterion (complete anaesthesia lasting at least 20 min) when general association statistics were used (Mantel-Haenzel test, P < 0.0001): 68.75% (n = 11) of subjects receiving treatment A, 37.5% (n = 6) receiving treatment B, and 87.5% (n = 14) on treatment C reached complete and satisfactory anaesthesia, while this was not achieved in any of the subjects receiving placebo. Ninety-five percent confidence intervals of the difference between treatments were as follows: treatment A vs. B (-0.03, 0.66), treatment A vs. C (-0.47, 0.10), treatment B vs. C (-0.84, - 0.16). Only the difference between B and C was statistically significant (adjusted probability by the method of Bonferroni, P < 0.001). When complete anaesthesia was reached, mean (+/-SD) duration of anaesthesia was as follows: 20.7 (+/-6.5), 15.3 (+/-11.4) and 24.7 (+/-7.6) min for treatments A, B, C, respectively. Bupivacaine 1 mg seems to be the efficient and safe dose. The value of hyaluronic acid as a corneal hydration agent and used in association with bupivacaine will be the subject of further studies.