Sulfate Dehydrate Research Articles

Chemotherapy Options in New Patients with Drug Susceptible Tuberculosis and Concurrent HIV Infection

The objective: to compare effectiveness and safety of isonicotinoylhydrazine-O,N' iron (II) sulfate dihydrate with the drug of isonicotinic acid hydrazide group in the complex therapy of patients with drug susceptible tuberculosis and HIV infection.Subjects and Methods. In 2020-2021, 40 patients with HIV infection and drug susceptible respiratory tuberculosis with a positive sputum test were examined in Moscow Regional Clinical TB Dispensary as a part of the post-registration observational study. The subjects were randomized into two groups – Main Group (MG) and Comparison Group (CG). Isonicotinoylhydrazine-O,N' iron (II) sulfate dihydrate was administered to the patients from MG as a part of regimen 1 of chemotherapy (instead of isoniazid). The effectiveness and safety of the investigational drug and comparator were evaluated. The primary effectiveness criteria included resolution of clinical symptoms of intoxication and sputum conversion. The secondary effectiveness criterion was positive X-ray changes. The safety criterion was the absence of adverse reactions.Results. During the study period, no adverse reactions were registered when isonicotinoylhydrazine-O,N' iron (II) sulfate dehydrate was used, as well as isoniazid. Good tolerability was noted as well as high compliance to treatment by patients. Thus, both in terms of effectiveness and safety, isonicotinoylhydrazine-O,N' iron (II) sulfate dihydrate is comparable to isoniazid as part of anti-tuberculosis chemotherapy for patients with drug susceptible tuberculosis and concurrent HIV infection.

Determination of Micro Amounts of Promethazine Hydrochloride in Pure and Pharmaceutical Samples Using UV- Visible Spectrophotometry

This study presents the development of a novel, facile, and overly sensitive spectrophotometric approach for quantifying promethazine hydrochloride (PRO) within its pharmaceutical formulations. The method capitalizes on an oxidative coupling reaction, achieved through the oxidation of the compound in an acidic milieu utilizing ammonium cerium (IV) sulfate dehydrate (Ce+4) solution. This process leads to the creation of a green-colored solution, which, upon conjugation with 5-aminosalicylic acid, exhibits maximum absorption at a wavelength of 598 nm. The methodology investigated several parameters, encompassing oxidation duration, temperature, quantities of oxidizing agent and coupling reagent, and determining the stoichiometric ratio between promethazine hydrochloride and 5-aminosalicylic acid. The established ratio was confirmed to be 1:1. Numerous organic solvents were evaluated, with water emerging as the optimal choice due to its pronounced absorption characteristics at the 598 nm wavelength. The applicability of Beer's law was verified over a concentration range of 2 - 28 μg/mL of promethazine hydrochloride, with a calculated molar absorption coefficient of 1.9606 x 104 L/mol∙cm. The Sandell sensitivity index was determined as 0.0164 μg/cm2, while the relative standard deviation (RSD) ranged from 0.8553- 1.2671%. Notably, recovery percentages were also within the 99.88 – 100.34% range. The efficacy of this technique was effectively demonstrated through its successful application in the analysis of pharmaceutical formulations containing promethazine hydrochloride, employing the standard method as a benchmark.

Annual Performance Evaluation of a Novel Industrial-scale Solar Dryer for Phosphogypsum Waste

Introduction: Solar drying is considered one of the most promising technologies for drying the phosphogypsum “Calcium Sulfate Dehydrate” material as a clean source of energy and saving the environment from its negative impact if it is dried in an open landfill. Method: The dried phosphogypsum (PG) may be recycled and utilized in many useful applications. The presented design of the trapezoidal-shaped greenhouse solar dryer is the preferable solution to perform the drying process in the daytime with solar energy. It may be usable at night, during cloudy and rainy periods, using evacuated tube solar collectors via sensible heat solar thermal energy storage. The system can be operated for 24 hours by solar energy. From theoretical calculations, it was found that the drying time decreased as the gypsum layer in the drying trays decreased due to the improvement of the heat transfer mechanism. The designed solar dryer was studied at various loading capacities depending on the gypsum thickness on the dryer trays. Capacities were 8280 kg, 6624 kg, 4968 kg, 3312 kg, and 1656 kg, corresponding to gypsum thickness of 5 cm, 4 cm, 3 cm, 2 cm, and 1 cm, respectively. The daily collected amount of water and the daily moisture content were estimated with different gypsum thicknesses during all months of the year. Result: It was found that the solar dryer with a capacity of 1,656 kg weight was technically and economically feasible. It was also found that the maximum reduction of moisture content occurred during the summer season, while the minimum values were achieved during winter. Conclusion: With a mass of gypsum equal to 1,656 kg weight, the moisture content of gypsum started to decrease from its initial value (35%) until it reached the final value (10%) in 4 scenarios: the first one, 2 days from April to September, 3 days from March to November, more than 3 days in other months while the minimum moisture content, i.e., 20%, was reported in the first day in June.

Recycling thermal modified phosphogypsum in calcium sulfoaluminate cement: Evolution of engineering properties and micro-mechanism

The phosphogypsum (PG) can be used as a substitute for calcium sulphoaluminate cement (CSC) due to its high content of calcium sulfate dehydrate. In this study, the engineering properties including setting time, compressive strength and fluidity index of CSC with addition of thermal modified phosphogysum (MPG) were experimentally investigated. Furthermore, the micro-mechanisms including crystalline phase and microstructure evolutions of CSC incorporating MPG under different thermal treatment temperatures were analyzed via conducting X-ray diffraction (XRD), heat of hydration, thermogravimetry (TG) and scanning electron microscopy (SEM) tests. The results show that the optimum PG content and thermal modification temperature were respectively 10% and 300℃, which achieved the maximum compressive strength of 41.59 MPa. The hydration heat release peak of CSC with 300℃ MPG was advanced, contributing to shorter setting time and poor fluidity of CSC. Whereas after incorporating untreated and 100℃ MPG, the hydration exothermic peak of CSC lagged behind, causing higher retarding effect and better fluidity. The main hydration products of ettringite (AFt) and alumina gel (AH3) in CSC-MPG mixture were respectively produced in the early and later stages, which were similar to that in pure CSC. The amount of AFt was the most under the optimum incorporation of 10% MPG at 300℃, which was mainly responsible for the highest structure density. The key findings in this study can achieve the double benefits of utilizing waste PG and improving the engineering properties of CSC.

Preparation of calcium carbonate nanoparticles from waste carbide slag based on CO2 mineralization

This study proposes a novel method for simultaneously dealing with the waste carbide slag (WCS) and CO2 mitigation. In addition, the ultrafine vaterite CaCO3 with high economic value was produced under mild conditions of 25 °C and 0.1 MPa. Ammonium sulfate ((NH4)2SO4) was employed to efficiently extract calcium from WCS into the solid phase calcium sulfate dehydrate (CaSO4·2H2O). Subsequently, it was subjected to “dropwise carbonation” leading to the formation of a calcium carbonate with controllable particle size between 100 nm–1 μm through multiple crystalline phase transformations. The results showed that nano-sized CaCO3 with nearly 90% purity and whiteness was prepared at 25 °C, CO2-500 mL/min, and NH4+/Ca2+ = 2.4 conditions. Results of TG and FTIR analyses confirmed that CaCO3 polymorphs with vaterite and metastable were formed. Based on the calcium conversion ratio of the entire process, treatment with 1 ton of WSC captured ∼0.5 tons of CO2 and yields about 1.15 tons of nano-sized CaCO3 per each cycle operation. This study provides a valuable method for identifying potential application for scale preparation of vaterite nanoparticles from low cost but abundant calcium resource such as WCS and gypsum.

Influence of Impurities on the Process of Obtaining Calcium Carbonate during the Processing of Phosphogypsum.

The article is devoted to the study of the influence of residual sulfuric and phosphoric acids on the process of processing large-tonnage phosphogypsum (PG) waste into calcium carbonate. In the Russian Federation, about 10 percent of existing phosphogypsum waste is processed into construction materials. Acidic impurities (phosphoric and sulfuric acids) in their composition are an obstacle to the use of phosphogypsum for the production of binders. This study finds that impurities also reduce the chemical activity of phosphogypsum. At the same time, the paper focuses on the potential of phosphogypsum for the production of calcium carbonate. This article investigated the amount of impurities in phosphogypsum. The results show that during automatic washing of phosphogypsum, losses are approximately 30–35 wt. %. It was also found that phosphogypsum by 22% consists of impurities of phosphoric and sulfuric acid. These acids are characteristic waste products of extraction phosphoric acid (EPA) production. By ASTM C471M-20ae1, the content of calcium sulfate dehydrate and hemihydrate before and after washing was determined. A thermodynamic calculation of the proposed interaction of phosphogypsum with carbonates showed that the characteristic reaction is possible. The conversion process of phosphogypsum to get the corresponding calcium carbonate was carried out at 70 °C. Data on the chemical composition of the reaction products, obtained by X-ray fluorescence analysis on a Shimadzu EDX-7000 spectrometer, showed that some reactions proceed incompletely and need the selection of optimal conditions. The potential commercial benefits of processing phosphogypsum by carbonization were defined for products such as calcium carbonate or its derivatives.

The Influence of Organic Vanadium Complexes on an Antioxidant Profile in Adipose Tissue in Wistar Rats.

One of the aspects of biological activity of vanadium is its influence on carbohydrate metabolism. For more than 30 years, various vanadium complexes have been tested as antidiabetic agents. This study researched organic vanadium complexes with bipyridinium ligands and their influences on metabolic rate, as well as on the antioxidant activity of adipose tissue. The effects of sodium (2,2′-bipyridine) oxidobisperoxovanadate (V) octahydrate (known as the V complex), bis(2,2′-bipyridine) oxidovanadium (IV) sulfate dehydrate (known as the B complex), and bis(4.4′-dimethyl-2,2′-bipyridine) oxidovanadium (IV) sulfate dihydrate (labelled as the BM complex) were assessed. Solutions of the tested complexes were introduced intraperitoneally with a probe to animals fed with either a control diet or a high-fat diet. The BM complex had a significant influence on the increase in ferric reducing antioxidant power, as well as on the concentration of glutathione in the adipose tissue of rats fed with a high-fat diet. The V complex increased the concentration of glutathione in the adipose tissue of rats fed with control fodder, as well as significantly reduced the relative change in rat weight for the high-fat diet. Furthermore, the presence of each tested vanadium complex had an impact of statistically significant increase in basal metabolic rate, regardless of applied diet. Further research on these organic vanadium complexes is necessary to understand the mechanisms responsible for their ability to affect adipose tissue.

Phase Transformation of FGD By-Product into Plaster Mould via Heat Treatment Process

Flue Gas Desulfurization (FGD) is a waste incineration process commonly used to eliminate sulfur dioxide (SO2) from flue gas power plants. FGD by-product recorded a rich gypsum content, also known as calcium sulfate dehydrate (CaSO4•2H2O), which has promising practical applications in plaster mould production. Plaster of Paris (POP) with a chemical composition of calcium sulfate hemihydrate (CaSO4•0.5H2O) is widely used in plaster mould production because of its quick setting and hardening upon moistened. Naturally, gypsum with 2 molecules of crystalline water can change to 1.5 molecules via the dehydration process. Various dehydration methods were conducted to transform FGD gypsum to hemihydrate. After undergoing different autoclave processes, the phase transition of FGD by-products was identified by X-ray diffraction (XRD) mode and compared with commercial POP. Chemical composition of FGD sludge contains a high amount of calcium oxide (CaO), sulfur trioxide (SO3) and boron trioxide (B2O3), as well as other impurities such as fluorine (F), chlorine (Cl), and magnesium oxide (MgO). Based on phase analysis, sample H1 to H5 show the percentage of hemihdyrate is 1.5%, 19.7%, 2.8%, 1.2%, and 46.1%, respectively, after different dehydration methods.

VOLATILITY OF CHEMICAL ELEMENTS DURING THE DEHYDRATION OF SECONDARY SULFATES

Link for citation: Bortnikova S.B., Abrosimova N.A., Devyatova A.Yu., Shevko E.P., Yurkevich N.V., Cherny N.K., Danilenko I.V., Palchik N.A. Volatility of chemical elements during the dehydration of secondary sulfates. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2022, vol. 333, no. 1, рр. 121-133. In Rus.
 The relevance. Air pollution due to the activities of the mining and metallurgical industries is a serious problem for the environment. This study was conducted to determine the possible mechanisms of migration and the sources of elements in the atmosphere above the surface of tailings. The main aim of the research is to show that chemical elements can be trapped by the water vapor and can migrate with the vapor phase during the desorption and dehydration of hydrous sulfates. Object: samples from the surface of the Belovo waste heaps (Belovo zinc processing plant, Belovo, Russia). Methods. Powder X-ray diffractometry (XRD) was used to determine the phase compositions of the crystalline substances, their quantitative phase relationships and transformations. An Agilent 8800 ICP-MS instrument (Tokyo, Japan), equipped with a MicroMist nebulizer, was used to determine the elements in the water samples (pore solution and condensates). Also, we used binocular microscope and physicochemical modeling methods. Results. By analyzing the condensates, it was determined that a wide range of chemical elements can migrate with vapor-gas streams from secondary hydrous sulfates under relatively low-temperature conditions (60 °C). Condensate from the wet sample contains high element concentrations due to the input of elements from the pore solution and hydrous sulfates. Alterations in mineral structure and water release are indicated by losses of sample weight. With dehydration, cations and trace elements can be extracted from the crystal lattice, replaced by protons, and can then enter the vapor-gas phase when the solution evaporates.

Application of Micro–Nano Bubbles to Improve the Performance of Reverse-Osmosis Membrane against the Gypsum Scaling

AbstractThe present study investigated the effects of air micro–nanobubbles (AMNBs) on calcium sulfate dehydrate (gypsum) scaling over a reverse-osmosis (RO) membrane in a lab-scale plate-and-frame...

Characterisation Of FGD Sludge From One of Glass Industrial in Malaysia and Their Potential as Ceramic Mould

Flue Gas Desulfurization (FGD) is a waste incineration process used to eliminate sulfur dioxide (SO2) from flue gas power plants. Limestone/gypsum was injected into the plant to trap sulfur dioxide and change their chemical composition from calcium carbonate to calcium sulfate dehydrate, known as FGD sludge wet scrubber. Nowadays, it is necessary to overcome the environmental pollution caused by the massive production of FGD sludge waste through recycling. In this research, FGD sludge was characterised to reveal its chemical composition, crystalline phase, and FTIR spectra characteristics. FGD sludge recorded a moderate alkaline with a pH of 8.24. Based on the XRD result, FGD sludge was mainly composed of gypsum (CaSO4•2H2O) and anhydrite (CaSO4). XRF analysis also shows that FGD sludge was mainly composed of calcium oxide, sulfur trioxide, silica, and potassium oxide.

Growth and characterization of 4-(((4-aminophenyl)sulfonyl)oxy)-2,3-dihydroxy-4-oxobutanoic acid with Ce3+: for semiorganic nonlinear optical application

Abstract This work aims at the growth and characterization of novel semi-organometallic nonlinear optical (NLO) crystal 4-(((4- aminophenyl) sulfonyl) oxy)-2,3-dihydroxy-4-oxobutanoic acid (ASODA) with ammonium ceric (II) sulfate dehydrate (ACS). The crystal 4-(((4-aminophenyl) sulfonyl) oxy)-2,3-dihydroxy-4-oxobutanoic acid with Ce3+ (STA) was grown by slow evaporation solution growth technique using deionized water as a solvent. Crystalline system of the grown STA crystal was identified by a single crystal X-ray diffraction study and confirmed as monoclinic crystalline system with non-centrosymmetric space group P21/C. The powder X-ray diffraction study confirmed the purity and crystallinity of the crystal. The presence of functional groups and hydrogen bonds (–O–H–O–) was confirmed by FT-IR spectroscopy. UV-Vis spectra showed that the grown crystal had a low cutoff wavelength at 219 nm. The position of protons and carbons were determined by structural studies based on NMR technique. The grown crystal was thermally stable up to 130 °C and its melting point was 163 °C. The SHG studies were performed by Quanta Ray Model laser source using Kurtz powder technique. The NLO efficiency of the STA crystal was 0.5 times greater than that of standard KDP. The dielectric constant and dielectric loss of the grown crystal were studied at different temperatures. The surface morphology and the particle size of the crystal were determined by FE-SEM technique. From the mechanical studies, it was found that the grown crystal is a soft material.

Behaviour of Aquaporin Forward Osmosis Flat Sheet Membranes during the Concentration of Calcium-Containing Liquids.

This study aims to examine the scaling and performance of flat sheet aquaporin FO membranes in the presence of calcium salts. Experiments showed that the application of calcium sulphate (CaSO4) resulted in an 8–78% decline in the water flux. An increase in the cross-flow velocity from 3 to 12 cm/s reduced the decline in the flux by 16%. The deposition of salt crystals on the membrane surface led to the alteration in the membrane’s intrinsic properties. Microscopy, attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, and X-Ray fluorescence (XRF) analyses confirmed measurements of the zeta potential and contact angle. The use of a three-salt mixture yielded severe scaling as compared with the application of calcium sulphate dehydrate (CaSO4 × 2H2O), i.e., a result of two different crystallisation mechanisms. We found that the amount of sodium chloride (NaCl), saturation index, cross-flow velocity, and flow regime all play an important role in the scaling of aquaporin FO flat sheet membranes.

Gas Transfer of Metals during the Destruction of Efflorescent Sulfates from the Belovo Plant Sulfide Slag, Russia

This paper demonstrates the results of experiments for the determination of the composition of gases during the dehydration of sulfates (Na-jarosite, melanterite, and chalcanthite) collected at the surface of pyrometallurgical waste heaps. The volatilization of various elements, and vapor–gas phase transport from three sulfate groups were investigated by stepwise laboratory heating at 45, 55, and 65 °C. The sample of yellow efflorescence mainly consisted of Na-jarosite, the white efflorescence contained melanterite as the major mineral, and the blue efflorescence sample consisted of chalcanthite. These all contained a few impurities up to 5 %. The highest total dissolved solids (TDS) was found in the gas condensates from melanterite (59 mg/L), followed by chalcanthite (29 mg/L) and Na-jarosite (17 mg/L). It was determined that major and trace elements in the condensate can be trapped by water vapor and can migrate with the vapor phase during the desorption and dehydration of hydrous sulfates. X-ray diffractograms showed that Na-jarosite remained stable throughout the temperature range, whilst the separation of melanterite’s structural water occurred at 40 °C, and chalcanthite completely lost two water molecules at 50 °C. The gas condensates contained acetates and formates, which could be the fermentation products of bacterial communities. Some of the strains—Micrococcaceae sp., Bacillus sp., and Microbacteriaceae sp.—were cultivated.

Transfer of chemical elements in vapor-gas streams at the dehydration of secondary sulfates

The elemental composition of vapor-gas streams obtained during heating of secondary hydrous sulfates are presented. Samples of abundant sulfate intergrowth were collected at the Belovo waste heaps and heated at 60ºC in experiments to collect condensates of the releasing vapor-gas streams. A wide spectrum of major and trace elements was determined in the condensate. Chemical elements can be absorbed by the water vapor and migrate with this phase during the dehydration of hydrous sulfates. To determine the mechanisms of migration and the sources of elements in vapor-gas streams, a study of the features of certain hydrous sulphates (antlerite, goslarite, starkeyite, gunningite, siderotile, sideronatrite) by stepwise heating up to 60ºC was conducted. Alteration in the phase composition is controlled by powder X-ray diffractometry. It was determined, that antlerite and starkeite remain stable throughout the temperature range. The beginning of the separation of structural water in goslarite and siderotile occurs at 40°C. Goslarite and sideronatrite at 40°C lost water molecules and transformed to gunningite and Na-jarosite, correspondingly. Structure of siderotile was loosened. The modes of occurrence of the chemical elements in sulfates and pore solution determine the concentrations of elements in the condensates.

Effect of treatment time on development of gypsum carbonated apatite biphasic granules at different salt solution concentration

Abstract Sintering is the common method for heat treatment of bio ceramic implant. However this procedure is reported not appropriate for fabrication carbonated apatite due to carbonate ions are easily decomposed at above 600°C A carbonated apatite (CO3AP) ceramics was discovered to have a closer chemical composition which is similar to the bone mineral. These materials have high potential to be a good artificial bone substitute due good resorption and bioactivity properties. This study was to evaluate the effect of treatment time on phase transformation of gypsum-carbonated apatite biphasic granules which was prepared with salt solution at different concentration. Gypsum or also known as calcium sulphate dehydrate (CSD) granules were immersed into two different concentration of carbonated and phosphate mixture salt solution which is 0.5 molar and 2.0 molar respectively and undergo hydrothermal reaction at 50 °C at different treatment times. Characterization of the biphasic granules obtained were determined by multiple analytical methods such X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Fourier Transform Infra-red (FTIR), and CHN analysis. The experiment result has shown that the treated CSD was successfully transformed into carbonated apatite layer to form biphasic granules. The content of carbonated (CO32-) ion in biphasic granules prepared using salt solution at high concentration is higher than at low concentration. Thickness of carbonated apatite layer and the content of carbonated (CO32-) in biphasic granules were indicated to increase slowly by increasing hydrothermal heating time. Briefly, the concentration of salt solution and treatment time could influence the development of transformation phase of gypsum into gypsum-carbonated apatite biphasic granule.

Synthesis and characterization of nanocrystalline copper sulfide powders

Nanocrystalline copper sulphide (Cu2-xS) powders were synthesized by chemical precipitation from their aqueous solutions composed of different molar ratio of copper sulfate dehydrate (CuSO4.5H2O) and thiorea (NH2)2CS as source of Cu+2, S-2 ions respectively, and sodium ethylene diamine tetra acetic acid dehydrate (EDTA) as a complex agent. The compositions, morphological and structural properties of the nanopowders were characterized by energy dispersive spectroscopy (EDS), scanning electron microscope (SEM), and X-ray diffraction (XRD), respectively. The compositional results showed that the copper content was high and the Sulfur content was low for both CuS and Cu2S nanopowders. SEM images shows that all products consist of aggregate of fine nanospheres with uniform distribution and the size of the particles formed are in nanometer range. XRD results revealed that the obtained powders contains a mixture of copper sulfide phases specially the intermediate phases and the rough estimate of the average crystallite size using the Scherrer formula gives a range of values (4.1-36.9) nm.

Low-cost, shape-stabilized fly ash composite phase change material synthesized by using a facile process for building energy efficiency

Abstract With increasing building energy consumption, the use of phase change materials (PCMs) to store energy becomes particularly important. However, relatively complex packaging technology, high cost and unstable thermal performance constrain the use of PCMs in the field of building energy efficiency. In this study, co-soluble hydrous salt/fly ash composite PCMs (FA composite PCMs) were prepared by straight dipping using the relatively inexpensive sodium sulfate dehydrate (Na2SO4·10H2O) as the primary phase change energy storage agent and solid waste fly ash (FA) as a carrier material. The FA composite PCMs were fabricated with an optimal mass ratio of PCMs: FA = 1.7:1. The PCMs' chemical characteristics, morphology and thermal properties were systematically detected. It is shown that PCMs adsorbed to FA belong to physical adsorption according to FTIR and XRD analysis results. Confined in the microspores of fly ash, the phase separation phenomenon of FA composite PCMs is largely eliminated, and its undercooling has also been a certain degree of relief. In addition, the FA composite PCMs exhibit good thermal properties; for example, the latent heat reaches 106.9 J/g with a melting temperature of 25.3 °C and remains at 87.1 J/g even after 100 thermal cycles. Moreover, the FA composite PCMs exhibit excellent environmental sustainability evaluated using a new simple approach. Finally, no leakage was observed in the FA composite PCMs during the solid-liquid phase transition.

Rheological and Mechanical Properties of Thermoresponsive Methylcellulose/Calcium Phosphate-Based Injectable Bone Substitutes.

In this study, a novel injectable bone substitute (IBS) was prepared by incorporating a bioceramic powder in a polymeric solution comprising of methylcellulose (MC), gelatin and citric acid. Methylcellulose was utilized as the polymeric matrix due to its thermoresponsive properties and biocompatibility. 2.5 wt % gelatin and 3 wt % citric acid were added to the MC to adjust the rheological properties of the prepared IBS. Then, 0, 20, 30 and 50 wt % of the bioceramic component comprising tetracalcium phosphate/hydroxyapatite (TTCP/HA), dicalcium phosphate dehydrate (DCPD) and calcium sulfate dehydrate (CSD) were added into the prepared polymeric component. The prepared IBS samples had a chewing gum-like consistency. IBS samples were investigated in terms of their chemical structure, rheological characteristics, and mechanical properties. After that, in vitro degradation studies were carried out by measurement of pH and % remaining weight. Viscoelastic characteristics of the samples indicated that all of the prepared IBS were injectable and they hardened at approximately 37 °C. Moreover, with increasing wt % of the bioceramic component, the degradation rate of the samples significantly reduced and the mechanical properties were improved. Therefore, the experimental results indicated that the P50 mix may be a promising candidates to fill bone defects and assist bone recovery for non-load bearing applications.

Microstructural and Microanalytical Study on Concrete Exposed to the Sulfate Environment

Microstructural properties have been examined to investigate the effect of mineral admixtures on the sulfate resistance of concrete. Concrete and cement paste specimens made with ordinary Portland cement (OPC) or ordinary Portland cement incorporating 20% fly ash (FA) or 30% ground blast furnace slag (GBFS), were made and exposed to 250 cycles of the cyclic sulfate environment. Microstructural and Microanalytical study was conducted by means of x-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and mercury intrusion porosimetry (MIP). Results indicate that the pore structure of concrete after sulfate exposure possesses the fractal feature. The OPC concrete presents more complex pore internal surface, higher porosity and less micro-pores than the concrete incorporating fly ash and GBFS. Portlandite in OPC concrete and OPC-FA concrete is mainly converted to gypsum; while for OPC-GBFS concrete, both gypsum and ettringite are formed. In the cyclic sulfate environment, repeated hydration and dehydration of sulfates produce the expansive stress in pores, aggravating the demolishment of concrete structure.