Search

In this work Mg(OH) 2, Ca(OH) 2, CaCO 3, SrCO 3 and BaCO 3 nanoparticles were synthesized via a simple sonochemical reaction at room temperature. Nanoparticles were synthesized via a surfactant-free reaction solvent water. Nanostructures materials were characterized by scanning electron microscopy, X-ray diffraction and fourier transform infrared spectroscopy. The photocatalytic behavior of nanoparticles was evaluated using the degradation of a methyl orange aqueous solution under ultraviolet light irradiation. The results show that metal hydroxide and metal carbonate nanoparticles are promising materials with excellent performance in photocatalytic applications. [ABSTRACT FROM AUTHOR]

Abstract: Lime putty is a traditional binder, experiencing a new advent in the preservation of historical buildings. Recently it was shown that lime putty microstructure evolves with ageing time, generally resulting in a continuous quality improvement, but possibly also passing a minima/maxima. Hence, periodical quality checks during ageing are needed to optimize quality and avoid excessive storage. The specific surface area (SSA) of lime putty is a potentially valuable parameter for quality control as it influences the workability and setting of lime mortars. Gas adsorption and the Brunauer–Emmet–Teller (BET) theory is a popular method for its determination, requiring a dry powder. Generally, freeze-drying is used for powder preparation as this method is assumed to diminish particle aggregation. However, no systematic investigation of the effect of powder preparation method on BET SSA has previously been reported. In addition, reproducibility evaluations of such methods are also lacking. This work was aimed to fulfil these gaps, using both calcitic and dolomitic lime putties. Freeze-drying was compared to heat-induced drying (105°C) under air as well as at low pressure. In addition, sample microstructure was evaluated using X-ray Powder Diffraction data and Rietveld refinements as well as Electron Microscopy techniques (SEM, TEM). It was statistically proven that freeze-drying, compared to the other dehydration methods, resulted in a 20–35% higher BET SSA for calcitic lime putties consisting mainly of nanoparticles. Instead, BET SSA of a dolomitic lime putty containing micrometre-sized hexagonal platelet crystals was not influenced by drying method. No statistically significant difference in phase composition was found between the samples dried by the different methods, excluding carbonation of the hydroxides as influencing factor. Finally, high reproducibility of BET specific surface area was obtained regardless of drying method which is an important characteristic of a standard test method for quality control. [Copyright &y& Elsevier]

The study aimed to evaluate the nutrients intake and performance of Nellore heifers fed with chopped sugarcane, fresh (FS) or treated (HS) with 0.5% of Ca(OH)2 and stored during 24, 48 or 72 hours. It was used twenty-four heifers with nine months age and 119.6±8.1kg of initial body weight. The experimental design was completely randomized with four treatments and six replications. The dry matter intake showed an average reduction of 29% by adding Ca(OH)2 , and didn't change with the storage period. Calcium intake was increased by the use of HS in the diet, while maintaining acceptable levels of intake. Heifers fed with HS stored during 24, 48 and 72 hours had, respectively, average daily weight gain of 41, 30 and 35% lower than those fed with FS. The treatment of sugarcane with Ca(OH)2 is not recommended for feeding Nellore heifers, due to limited intake and lower weight gain. [ABSTRACT FROM AUTHOR]

Abstract: Reducing greenhouse gas has been important issue in recent years. Capturing CO2 gas in polymer matrix is attractive method to reduce the greenhouse gas and uses as a natural resource, such as polymer–CaCO3 composite. Calcium carbonate (CaCO3) and cellulose composite have been synthesized by bubbling CO2 gas into the mixture of cellulose acetate (CA) and Ca(OH)2 solution. Completely dissolved and transparent Ca(OH)2 solution was prepared to react stoichiometric reaction of Ca(OH)2 and CO2. Since the strong absorption peak of the CA in infrared spectra, it is difficult to identify the existence of the CaCO3. To confirm the existence of CaCO3 in the cellulose matrix, the CA was removed by dissolving the reaction composite and by centrifuging the solution to separate CaCO3 particles. The characteristic absorption peaks of CaCO3 at 1450, 875 and 712cm−1 were obtained for the particles. Field emission scanning electron microscope images show the shape and size of the CaCO3 particles in the cellulose matrix. Therefore, using cellulose and Ca(OH)2 is one of the effective method capturing the CO2 greenhouse gas. [Copyright &y& Elsevier]

Abstract: Dry Sorbent Injection (DSI) is a process used to control sulfur dioxide (SO2) by injecting a powdered alkaline sorbent into the flue gas stream. The present paper uses Computational Fluid Dynamics to analyze the dry scrubbing process of an industrial plant made up of a short ductwork followed by a holding vessel. The resulting complex flow field strongly impacts the desulfurization efficiency, evaluated with the adsorption model proposed by Gutierréz Ortiz et al. [1,2]. A modified system’s configuration is also simulated and compared to the previous one in terms of a newly defined mixing efficiency parameter. The latter compares the calculated SO2 removal efficiency with the maximum efficiency achievable under the same operating conditions affecting the adsorption process and is helpful in the design of DSI plants. [Copyright &y& Elsevier]

Abstract: Cost-effective production of optically pure lactic acid from lignocellulose sugars is commercially attractive but challenging. Bacillus coagulans C106 was isolated from environment and used to produce l-lactic acid from xylose at 50°C and pH 6.0 in mineral salts medium containing 1–2% (w/v) of yeast extract without sterilizing the medium before fermentation. In batch fermentation with 85g/L of xylose, lactic acid titer and productivity reached 83.6g/L and 7.5g/Lh, respectively. When fed-batch (120+80+60g/L) fermentation was applied, they reached 215.7g/L and 4.0g/Lh, respectively. In both cases, the lactic acid yield and optical purity reached 95% and 99.6%, respectively. The lactic acid titer and productivity on xylose are the highest among those ever reported. Ca(OH)2 was found to be a better neutralizing agent than NaOH in terms of its giving higher lactic acid titer (1.2-fold) and productivity (1.8-fold) under the same conditions. [Copyright &y& Elsevier]

Abstract: This study aimed to evaluate the effects of three sodium hypochlorite (NaOCl)-endodontic irrigation procedures used alone or in combinations with two intermediate dressing materials on bond strengths of two adhesive composite systems to coronal dentin. Surfaces were treated with NaOCl or NaOCl–Glyde-File-Prep (H2O2 and EDTA) with or without chlorhexidine (CHX) as a final rinse. Intermediate dressing materials of calcium hydroxide (Ca(OH)2) and sodium perborate (SP) were combined with surface treatments. Surface treatment groups (n =10/group) included (1) distilled water (control), (2) 5.25% NaOCl (30min), (3) NaOCl/Glyde (30min), (4) NaOCl/Glyde (30min)+CHX (2min), (5) NaOCl/Glyde (30min)+Ca(OH)2 (5days)+CHX (2min), and (6) NaOCl/Glyde (30min)+SP (9days)+CHX (2min). For each surface treatment group, dentin shear bond strengths of two different composite systems (Excite/Tetric Flow Chroma, [EX/TFC], and Clearfil Protect Bond/Protect Liner F [PB/PLF]) were evaluated. Median shear bond strengths (EX/TFC, PB/PLF) for each surface treatment group in MPa were (1) 21, 18; (2) 26, 18; (3) 21, 17; (4) 22, 16; (5) 17, 11; and (6) 14, 11, respectively. NaOCl significantly increased the bond strength of EX/TFC (p <0.05), but did not significantly affect that of PB/PLF. The use of NaOCl/Glyde with CHX did not significantly affect EX/TFC (p >0.05), whereas it significantly decreased PB/PLF (p <0.05). Ca(OH)2 and SP significantly decreased the bond strengths of both adhesive systems (p <0.05). Adhesion to coronal dentin is dependent upon the irrigation regimen and the type of adhesive. [Copyright &y& Elsevier]

Background The long-term use of calcium hydroxide, or Ca(OH)2, on dentin has been established in the literature. However, scarce data is available on dentin wettability with Ca(OH)2. Aim The present study was conducted to assess the outcomes of Ca(OH)2 use on the wettability of dentin following two and four weeks of using sealers of bioceramic (BC) and Tubli-Seal™ in the root canal. Methods In this study, 168 specimens were divided into 12 groups of 14 specimens each and were numbered from G1 to G12. G1-G6 groups were tested with Tubli-Seal. Sterile water irrigation was reserved for G1 for two weeks (14 days) followed by two minutes treatment with 6% sodium hypochlorite (NaOCl) chemical irrigation and 17% EDTA (10 ml). G2 and G3 were subjected to Ca(OH)2 (0.1 ml of UltraCal) for two weeks followed by 10ml sterile water irrigation for two minutes with chemical irrigation. G4 to G6 were given similar treatment for four weeks. G7-G12 were assessed for BC sealer similarly to G1-G6. Two and four weeks of incubation with sterile water or Ca(OH)2 was done in 100% humidity at 37°C. SEM and EDX were done to evaluate the surface morphology of G1 and G6, and results were formed.  Results Significantly smaller contact angles were seen for Tubli-Seal (G1 to G6) compared to BC (G7 to G12) with p<0.05. Application of water irrigants and Ca(OH)2 (in G2, G5, and G11) showed a smaller (p<0.05, statistically significant) contact angle compared to the use of chemical irrigation agents and Ca(OH)2 (in G3, G6, and G12) except for G8 and G9. Based on EDX and SEM, compared to the use of chemical irrigation with Ca(OH)2, higher remnants of Ca(OH)2 were seen in the water irrigation, whereas, no remnant was seen with chemical irrigants.  Conclusion Better dentin wettability is seen with Tubli-seal compared to BC sealer. A smaller contact angle between root canal sealers and dentin is seen in the remaining calcium hydroxide samples. Also, calcium hydroxide can be removed from the polished dentin surface with two minutes of irrigation with 17% EDTA and 6% NaOCl., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2022, Babu et al.)

The structural modifications of desulfurant sorbents synthesized by hydration of calcium hydroxide, magnesic smectite and lignosulfonates was investigated. The aim of the work was to know if the structural properties of the raw materials suffer modifications during the preparation of the sorbents or when the sorbents are used at medium temperature. The smectite, a magnesic smectite or saponite, used as support in the sorbents preparation was subjected at different temperatures and the structural modifications were studied by X-Ray diffractometry, thermogravimetry and Nitrogen adsorption-desorption technique. This last technique was also used to study the modifications of the isotherm of the support in the process of preparation of the sorbents. Results show that up to 600° C, the structure of smectite does not change and neither change in the preparation of the sorbent. Because of that these solids can be used in a desulfurization reaction at low or medium temperature. [ABSTRACT FROM AUTHOR]

In the present work, reoxidation of Al-killed steel by Ca(OH)2 in high basicity slag was investigated by using laboratory experiments at 1873 K in MgO crucibles with various amount of Ca(OH)2 addition into slag. The CaO-SiO2-Al2O3-MgO-Ca(OH)2 slags were used to study the effect of Ca(OH)2 on total oxygen content, aluminum loss, and FeO content in the slag. It was shown that total oxygen content decreased with the time when no Ca(OH)2 was added into the slag, but it first increased and then decreased with the time when the addition of Ca(OH)2 was made. Moreover, aluminum loss and FeO content in the slag increased with increasing Ca(OH)2 content. [ABSTRACT FROM AUTHOR]

Abstract: The groundwater of Fourchi which feeds the town of Ain M’lila in the Eastern region of Algeria is derived from limestone. This water have a hardness of 87 ¡ F and give rise to compact and adherent deposits of calcium carbonate in the drinking water distribution network. To inhibit the furring of this water some chemical and electrochemical treatments (chronoamperometry) were applied in the presence of (Ca(OH)2, Na2CO3 and KH2PO4) to eliminate the scale precipitation. The use of Lime and sodium carbonate is encouraged due to their very low prices. The scale inhibitor KH2PO4 has the property to adsorb on the nuclei of calcium carbonate and modify their growth and morphology at a very low concentration (0.05mg/L). The tests were performed on the Fourchi water in the presence of (Ca(OH)2, Na2CO3 and KH2PO4) allowed us to make partial softening treatment and help solve the problem of scaling. [Copyright &y& Elsevier]

Aims: Comparing the calcium concentration and pH levels of Ca(OH)2 medicament placing in pulp chamber and root canal. Materials and Methods: Ninety-nine extracted human mandibular second premolars were instrumented to size #40 k file. Nine teeth served as the control group and the remaining teeth were assigned into two groups. Group 1-Ca(OH)2 was placed in the dried pulp chamber, while root canals remained wet with normal saline; group 2-Ca(OH)2 was placed in dried root canals. In control group, canals remained wet without medication. Each group was divided into 3 subgroups of 15 teeth in which pH and calcium concentration were measured in three intervals of 2 days, 1 week, and 2 weeks by pH meter and atomic absorption spectrometer system, respectively. Findings were assessed using Kruskal-Wallis and t-test. Results: At 1 and 2 weeks, the calcium concentration had increased without being significantly different from Ca(OH)2 placed either in the root canal or in the pulp chamber. Ca(OH)2 placed in the pulp chamber or root canal provided similar pH values (P=0.362). Conclusions: Placing Ca(OH)2 in pulp chamber is as effective as placing it in the root canal. [ABSTRACT FROM AUTHOR]

Abstract: Experimental work has been done to determine changes in the particle shape of portlandite grown in the presence of different ions. To quantify the experimentally observed changes in morphology a new analysis tool was developed, allowing the calculation of the relative surface energies of the crystal facets. The observed morphology in the presence of chlorides and nitrates was facetted particles of a similar shape, the addition of sulfates leads to hexagonal platelet morphology and the addition of silicates leads to the formation of large irregular aggregates. In addition to the experimental work, the surfaces of portlandite were studied with atomistic simulation techniques. The empirical force field used has first been validated. The equilibrium morphology of portlandite in vacuum and in water was then calculated. The results indicate that the presence of water stabilizes the [20.3] surface and changes the morphology. This is consistent with the experimental observation of [20.3] surfaces. [Copyright &y& Elsevier]

Objectives: To determine the direct effect of hydroxide compounds on dermatophytes, four chemicals containing hydroxide ions within their structure were selected to investigate their effect on two species of dermatophytes. Methods: Different percentages of potassium hydroxide (KOH), sodium hydroxide (NaOH), magnesium hydroxide (Mg(OH)2) and calcium hydroxide (Ca(OH)2) were dissolved in two forms of fungal media (solid and liquid). Results: KOH and NaOH (down to 1.25%) showed the ability to completely inhibit the growth of both strains of dermatophytes (Trichophyton mentagrophytes and Epidermophyton floccosum). The pH value of medium found to be influenced by sterilization process and by media form. Conclusion: Maintenance the growth and viability of dermatophytes required their cells not to be exposure to strong alkaline of hydroxide ions containing chemicals such as KOH and NaOH for long periods of time. [ABSTRACT FROM AUTHOR]

Abstract: To explore the potential fate and transport of perfluorochemicals in the thermal treatment of sludge, perfluorooctanesulfonate (PFOS), a perfluorochemical species commonly dominant in wastewater sludge, was mixed with hydrated lime (Ca(OH)2) to quantitatively observe their interaction under different temperatures. The phase compositions of the mixtures after the reactions were qualitatively identified and quantitatively determined using X-ray diffraction technique. The results of the thermogravimetry and differential scanning calorimetry analyses indicate that PFOS gasified directly during the thermal treatment process when the temperature was increased to around 425°C. However, the formation of CaF2 at 350°C suggests that the presence of Ca(OH)2 in the mixture can lead to the decomposition of PFOS at 350°C, which is lower than the decomposition temperature of PFOS alone (425°C). The increase of temperature promoted a solid state reaction between PFOS and Ca(OH)2, and also enhanced the interaction between the gaseous products of PFOS and CaO (or Ca(OH)2). The preferred Ca/F molar ratio to achieve fluorine stabilization by Ca(OH)2 was above 1:1 in the experiment involving 400°C and 600°C treatment. It also showed that equilibrium efficiency is achieved within 5min at 400°C and within 1min above 600°C. [Copyright &y& Elsevier]

A design of a controlled cooking system (CCS) for corn flours production is presented. The system allows reproducibility in the samples preparation with control of the time and the temperature. The treatment of corn was performed with a cooking time of 120 minutes at 92.5°C, by adding calcium hydroxide (Ca(OH)2) in concentration between 0 and 0.5% compared to the corn weight. The cooking process was monitored via measures of moisture absorbed by the corn kernels and pH of the solution. The samples were manufactured by operation steps like wet milling, dehydration, dry milling and sieving. The samples were analyzed using modulated differential scanning calorimetry (MDSC) and thermogravimetric analysis (TGA) techniques, which were focused in the thermal stability of the flours and their physical variables: gelatinization range (ΔT), enthalpy (ΔH), change in heat capacity (ΔCp), temperature decomposition of maximum decomposition rate (Tmd) and residue after decomposition (Rs). The adding of Ca(OH)2 moves the peak gelatinization and the maximum peak of decomposition towards higher temperature. The TGA analysis showed that the addition of calcium hydroxide improves the thermal stability of the flour, since the degradation temperature shifts to higher temperatures as the amount of calcium hydroxide increases. The results were compared with the same analysis performed on raw corn. This study proposes an experimental method, including a controlled cooking system for the production of flour enriched with calcium, which could have a major impact in the field of nutrition. [ABSTRACT FROM AUTHOR]

Abstract: The aim of the study is to investigate the calcium hydroxide (Ca(OH)2) contents in pozzolanic cement pastes analyzed by the chemical extraction method and thermal analysis (DTA/TG). The second part of the study involves the carbonation of pozzolanic cement pastes and its influence on Ca(OH)2 reduction. The Ca(OH)2 contents in cement pastes after being subjected to accelerated carbonation were investigated by a chemical extraction method and compared to those values from DTA/TG analysis. The experimental results show that the chemical method reveals overall results comparable to those from DTA/TG analysis. However, in case of pastes containing high amounts of mineral admixtures or pastes subjected to carbonation which contain very low Ca(OH)2, only the chemical method yields precise reliable results by showing the pseudo-negative contents. [Copyright &y& Elsevier]

Abstract: Catalytic pyrolysis of pine wood was carried out in a fixed-bed reactor heated slowly from room temperature to 700°C under a stream of purging argon to examine the effects of the physically mixed K2CO3 or Ca(OH)2 on the pyrolysis behaviors. K2CO3 demonstrated a stronger catalysis for decomposition of hemicellulose, cellulose and lignin constituents, leading to the reduced yield of liquid product in conjunction with the increased yields of gaseous and char products because of the promoted secondary reactions of liquid product. With the addition of 17.7wt.% of K2CO3, none of saccharides, aldehydes and alcohols was formed and the formation of acids, furans and guaiacols was substantially reduced, whereas the yields of alkanes and phenols were increased. Potassium led to an increase in the cumulative yields of H2, CO2 and CO at 700°C. Ca(OH)2 somewhat promoted the decomposition of cellulose and lignin constituents, and the effect of Ca(OH)2 on the yields of liquid and char was opposite to that of K2CO3. With the addition of 22.2wt.% Ca(OH)2, some groups of liquid product such as acids and aldehydes disappeared completely and the yields of saccharides, furans and guaiacols were somewhat reduced, while the yield of alcohols was remarkably increased in contrast to the result of K2CO3. The addition of Ca(OH)2 did not significantly change the total yield of gaseous product at 700°C but enhanced the yield of H2. [Copyright &y& Elsevier]

Calcium hydroxide nanostructures have been synthesised by the reaction of calcium acetate with sodium hydroxide or tetramethylammonium hydroxide by a sonochemical method. Reaction conditions, such as the concentration of the Ca2+ ion, ageing time and power of the ultrasonic device show important roles in the size, morphology and growth process of the final products. The calcium oxide nanoparticles have been obtained by heating of calcium hydroxide nanostructures at 600°C. The calcium hydroxide and calcium oxide nanostructures were characterised by transmission electron microscopy, scanning electron microscopy and X-ray powder diffraction. [ABSTRACT FROM AUTHOR]

Abstract: Potential-time curves are constructed for the steel electrode in naturally aerated Ca(OH)2 solutions simulating the corrosion behavior in concrete. Cl− and SO4 2− ions cause the destruction of passivity and initiation of pitting corrosion. The rate of oxide film growth by Ca(OH)2 and oxide film destruction by Cl− and SO4 2− ions follows a direct logarithmic law as evident from the linear relationships between the open-circuit potential and the logarithm of immersion time. Chromate, phosphate, nitrite, tungstate and molybdate ions inhibit the pitting corrosion of steel. The rate of oxide film healing and thickening increases with their concentrations. In presence of constant inhibitor concentration, the efficiency of pitting inhibition increases in the order: (weak) CrO4 2−

In microcosm experiments, the use of inorganic and organic amendments has been studied as potential agents to reduce heavy metal bioavailability in an acidic soil highly contaminated by Cu, Zn and Ni, that has to be remediated by phytoremediation. The concentrations of heavy metals in the original soil (O-Soil) produced phytotoxic effects with a strong reduction in biomass yield that hinder the utilization of this technology. To overcome phytotoxicity the use of three immobilizing agents was evaluated. The results obtained showed that all the strategies decreased the mobile fractions of heavy metals in soil and increased the metal removal efficiency. In the case of Brassica juncea the best results for Zn and Ni were obtained after zeolites addition (Z-Soil) with an increase of about 6 times with respect to the value found in the O-Soil. In the case of Cu, the more efficient treatment was Ca(OH)2 addition (Ca-Soil). The B. juncea plants accumulated Cu amounts 8 times greater than in the O-Soil. For this metal, relevant results were obtained also with compost, that increased the amount of Cu in the plants of 7 times with respect to the O-Soil. Similar results were obtained with Helianthus annuus the highest Zn and Ni accumulation was detected in the Z-Soil and compost-treated soils (C-Soil), with an increase of nearly 11 times with respect to the accumulation in the O-Soil. In the case of Cu the highest increase of total uptake was found in the C-Soil: 28 times higher than in the O-Soil. Total accumulation in Poa annua plants showed the highest removal efficiency in the Z-Soil for all metals. The values obtained increased of 4, 11 and 12 times for Cu, Zn and Ni, respectively. [Copyright &y& Elsevier]

Abstract: The pozzolanic reaction between portlandite and different types of nearly pure natural zeolites was studied. Analcime, phillipsite, chabazite, erionite, mordenite and clinoptilolite-rich tuffs were mixed with portlandite and water (1:1:2 by weight), and the progress of the pozzolanic reaction was quantitatively determined by thermogravimetrical analyses from 3 to 180 days. A thorough characterization of the raw materials was performed by quantitative XRD, XRF, SEM-EDX, BET specific surface area measurements, grain-size analyses, FTIR and Cation Exchange Capacity measurements. The difference in reactivity of the samples containing zeolites with varying Si/Al ratios, as well as between clinoptilolite-rich samples exchanged with different cations or ground to different grain sizes was assessed. The results indicate that the external surface area only influences the short-term reactivity, whereas the cation content has an effect on both the long- and short-term reactivity. The early reactivity of the unexchanged samples can be explained by these two parameters, but their long-term reactivity is mainly related to the Si/Al ratio of the zeolites. Samples with zeolites rich in Si react faster then their Al-rich counterparts. [Copyright &y& Elsevier]

This study aimed to test the biocompatibility and antibacterial properties of Salvadora persica (S. persica) extract, a natural product, as an intracanal medication in comparison with calcium hydroxide (Metapaste, META BIOMED, Cheongju, Korea). The pH values of both materials were tested. The biocompatibility of S. persica extract and Metapaste was determined using light microscopy and MTT assays. The antibacterial action was tested using the zone of bacterial inhibition on four common bacterial species. In addition, intracanal medication was administered using 68 extracted single-rooted teeth contaminated with Enterococcus faecalis (E. faecalis), and the percentage reduction in colony count (% RCC) at 1, 3, and 7 days was measured. The extension of activity for both materials was assessed using histological sections and scanning electron microscopy. S. persica was found to be acidic in nature. Both materials showed significantly lower cell viability than the positive control cells on days 1 and 3 but not on day 7. S. persica showed better antibacterial effects against E. faecalis and S. mutans. S. persica extract showed 97.6%, 98.9%, and 99.3% RCC values at 1, 3, and 7 days, respectively, which are comparable to those of Metapaste. S. persica herbal extract is a promising material that can be utilized as an intracanal medication, but its use requires further research. [ABSTRACT FROM AUTHOR]

Abstract: A thermochemical cyclic process and associated reactor is presented for the continuous removal of CO2 from ambient air via consecutive CaO-carbonation and CaCO3-calcination steps using concentrated solar energy as the source of high-temperature process heat. A fluidized-bed solar reactor is applied to accomplish the carbonation at 365–400°C and the calcination at 800–875°C, with reacting particles directly exposed to high-flux solar irradiation. Water vapor was introduced during the carbonation step to enhance its kinetics. Five consecutive cycles were performed, yielding complete removal of CO2 from a continuous airflow containing 500ppm of CO2 within a residence time of 1.3s during each carbonation step, and subsequent complete release of CO2 and regeneration of the CaO reacting particles during the calcination step. The reactor design, set-up, and experimentation using a high-flux solar simulator are described. [Copyright &y& Elsevier]

• An adsorption model of SO 3 and SO 2 by the Ca(OH) 2 particle is established. • The adsorption of SO 3 and SO 2 is found to involve two stages. • Internal pore diffusion and product-layer diffusion mainly dominate SO 3 adsorption. • SO 3 adsorption shows a shrinking core mode, while SO 2 adsorption shows a bulk mode. • Particle structure greatly affects the performance of SO 3 adsorption by Ca(OH) 2. SO 3 in coal-fired flue gas will cause equipment corrosion and the emission of sulfuric acid mist. The performance of injecting the alkaline adsorbent into the flue gas to remove SO 3 is affected by the adsorption of SO 2 in the flue gas. Taking Ca(OH) 2 as a typical alkaline adsorbent, a model describing the adsorption of SO 3 and SO 2 by Ca(OH) 2 particles was established, based on the combination of the product-island-growth model and the grain model. The parameters in the model were determined by the experimental data of adsorption in the fixed-bed reactor. The adsorption process of a single Ca(OH) 2 particle was studied by numerical simulation. The adsorption of SO 3 and SO 2 was found to involve two stages: (1) In the early stage when there existed unreacted grain surface in the particle, SO 3 and SO 2 mainly reacted with the left fresh grain surface. The SO 3 adsorption was controlled by internal pore diffusion and surface reaction, in which internal pore diffusion played a major role. The SO 3 adsorption showed a shrinking core mode. The SO 2 adsorption was controlled by internal pore diffusion and surface reaction and occurred throughout the entire particle. The SO 3 adsorption selectivity at the outer surface of the particle was the highest, and decreased with a decreasing dimensionless particle radius R / R 0. (2) In the later stage when the grain surface was completely reacted, the SO 3 adsorption was controlled by internal pore diffusion and product-layer diffusion, in which product-layer diffusion played a major role. The SO 2 adsorption was controlled by product-layer diffusion. The product-layer diffusion coefficient in the SO 3 adsorption process was significantly higher than that of the SO 2 adsorption, so SO 3 was still significantly adsorbed in the later stage. The adsorption process of Ca(OH) 2 under different particle structure parameters showed that decreasing the particle radius and increasing the particle porosity and specific surface area increased the SO 3 removal efficiency as well as the total conversion of Ca(OH) 2. Decreasing the particle radius and the specific surface area and increasing the particle porosity increased the SO 3 adsorption selectivity by Ca(OH) 2. When preparing industrial adsorbents, the optimization of the particle porous structure should be given attention. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study was to determine whether para-chloroaniline (PCA) and/or reactive oxygen species (ROS) are generated by chlorhexidine (CHX) alone or after CHX is mixed with calcium hydroxide at different time points. Mass spectrometry was performed to detect PCA in samples of 0.2% CHX and Ca(OH)2 mixed with 0.2% CHX. High-performance liquid chromatography was used to confirm the presence of CHX in the mixture with Ca(OH)2. The samples were analyzed immediately after mixing and after 7 and 14 days. During the intervals of the experiment, the samples were maintained at 36.5°C and 95% relative humidity. PCA was detected in the 0.2% CHX solution after 14 days. The mixture of CHX with Ca(OH)2 liberated ROS at all time points, but no traces of CHX were present in the mixture as a result of immediate degradation of the CHX. [Copyright &y& Elsevier]

Abstract: The single crystal elastic constants C ij and the shear and adiabatic bulk modulus of a natural portlandite (Ca(OH)2) crystal were determined by Brillouin spectroscopy at ambient conditions. The elastic constants, expressed in GPa, are: C 11 =102.0(±2.0), C 12 =32.1(±1.0), C 13 =8.4(±0.4), C 14 =4.5(±0.2), C 33 =33.6(±0.7), C 44 =12.0(±0.3), C 66 =(C 11–C 12)/2=35.0(±1.1), where the numbers in parentheses are 1σ standard deviations. The Reuss bounds of the adiabatic bulk and shear moduli are K 0S =26.0(±0.3) GPa and G 0 =17.5(±0.4) GPa, respectively, while the Voigt bounds of these moduli are K 0S =37.3(±0.4) GPa and G 0 =24.4(±0.3) GPa. The Reuss and Voigt bounds for the aggregate Young''s modulus are 42.8(±1.0) GPa and 60.0(±0.8) GPa respectively, while the aggregate Poisson''s ratio is equal to 0.23(±0.01). Portlandite exhibits both large compressional elastic anisotropy with C 11/C 33 =3.03(±0.09) equivalent to that of the isostructural hydroxide brucite (Mg(OH)2), and large shear anisotropy with C 66/C 44 =2.92(±0.12) which is 11% larger than brucite. The comparison between the bulk modulus of portlandite and that of lime (CaO) confirms a systematic linear relationship between the bulk moduli of brucite-type simple hydroxides and the corresponding NaCl-type oxides. [Copyright &y& Elsevier]

A simple Ca(OH)2-based replacement-precipitation process was applied to the removal of EDTA-chelated copper from wastewaters. The effect of initial pH of the solution, molar ratio of Ca2+ to Cu(II), the presence of CO2 on the removal efficiency was investigated. The experimental results showed that the Ca(OH)2-based replacement-precipitation process could efficiently remove the chelated copper from wastewaters. When 12⩽pH⩽13 and molar ratio of Ca2+ to Cu(II)⩾2, the removal efficiency could reach 99% above, also being close to the theoretically simulated results. The presence of CO2 in the air would exert negative effect on the removal efficiency, but the side effect could be effectively eliminated by the addition of flocculation agent polyacrylamide. Compared with Fe2+-based replacement-precipitation technique applied in industrial practice, the method possesses the advantages of less sludge, lower cost, higher removal efficiency and higher controllability. [Copyright &y& Elsevier]

Abstract: A process to produce hydrogen from polyethylene [–CH2–] n (PE) is developed by milling with Ca(OH)2 and Ni(OH)2 followed by heating the milled product. Characterizations by a set of analytical methods of X-ray diffraction (XRD), infrared spectroscopy (FT-IR), thermogravimetry–mass spectroscopy (TG/MS) and gas chromatography (GC) were performed on the milled and heated samples to monitor the process. It has been observed that addition of nickel hydroxide as well as increases in milling time and rotational speed of the mill is beneficial to the gas generation, mainly composed of H2 and CH4, CO, CO2. Gaseous compositions from the milled samples vary depending on the added molar ratio of calcium hydroxide. H2 emission occurs between 400 and 500°C, and H2 concentration of 95% is obtained from the mixture of PE/Ca(OH)2/Ni(OH)2 (C:Ca:Ni=6:14:1) sample, and the concentrations of CO and CO2 remain below 0.5%. The process offers a novel approach to treat waste plastic by transforming it into hydrogen. [Copyright &y& Elsevier]

Abstract: This paper studies Roman mortars to demonstrate that petrographic analysis provides valuable information on ancient mortar technology. Facts on lime technology relating calcination and slaking were obtained through petrographic analysis. The analysis also revealed the composition and origin of raw materials, pozzolanic additions and mortar hydraulicity. The results were contrasted with ancient Roman technology records including Cato, Pliny, Vitruvius, Palladius and Faventinus. The binders’ petrofabric suggests a high reactivity and water retention capacity and a low shrinkage for the lime. These agree with the long slaking and soft burning advised by the Romans. The strong binder cohesion and perfect aggregate-binder bond of most mortars together with the presence of aggregate-binder reaction denotes a high reactivity for the lime which also agrees with soft burning. The mortars were probably made with a non-hydraulic or feebly-hydraulic lime and their hydraulicity is mainly due to the addition of pozzolans (ceramics). These agree with Roman authors consistently advising to use a pure carbonate rock for lime making. The pozzolanic additions are probably responsible for the good durability of the mortars. [Copyright &y& Elsevier]

Abstract: This paper has been written to provide a realistic approach to modeling an in-duct desulfurization process and because of the disagreement between the results predicted by published kinetic models of the reaction between hydrated lime and SO2 at low temperature and the experimental results obtained in pilot plants where this process takes place. Results were obtained from an experimental program carried out in a 3-MWe pilot plant. Additionally, five kinetic models, from the literature, of the reaction of sulfation of Ca(OH)2 at low temperatures were assessed by simulation and indicate that the desulfurization efficiencies predicted by them are clearly lower than those experimentally obtained in our own pilot plant as well as others. Next, a general model was fitted by minimizing the difference between the calculated and the experimental results from the pilot plant, using Matlab™. The parameters were reduced as much as possible, to only two. Finally, after implementing this model in a simulation tool of the in-duct sorbent injection process, it was validated and it was shown to yield a realistic approach useful for both analyzing results and aiding in the design of an in-duct desulfurization process. [Copyright &y& Elsevier]

Investigated herein is the effect of temperature on heat development in cement pastes and concretes with and without silica fume cured at relatively high temperatures often encountered in tropical environment. With an initial temperature of 30°C, adiabatic temperature rise of the concrete with 8% silica fume as cement replacement was similar to that of the control Portland cement concrete up to about 18 h. After 24 h, however, the temperature of the silica fume concrete was lower than that of the control concrete. Since the concrete with 8% silica fume had a higher 28-day compressive strength (72.5 MPa) than the control concrete without silica fume (59.2 MPa), the concrete with silica fume is likely to have a lower temperature rise as compared with the control concrete of equivalent 28-day strength by reducing cementitious materials content with the same water content. The extent of heat evolution in the silica fume pastes was generally greater at lower temperatures of 20-50°C, but less at 65°C than in the control paste. At the relatively high curing temperatures, the degree of cement hydration in the paste with silica fume was lower than that in the control cement paste at early ages. However, the pozzolanic reaction started even before 24 h after water was added. [ABSTRACT FROM AUTHOR]

Aloe vera L. (Aloeaceae) has been extensively studied for anti-inflammatory, antimicrobial, and cellular regeneration properties. This work evaluated in vivo the effects of powder of freeze-dried Aloe vera on rat pulp tissue. Pulp tissue was mechanically exposed to Aloe vera, and it was evaluated at 1 to 30 days after the procedure by histopathologic examination. A predominant acute-moderate inflammatory infiltrate was observed in the Aloe vera-treated group 1 to 7 days after treatment. At 14 to 30 days, pulp tissue took a normal pattern when comparing Aloe vera treatment with the Ca(OH)2 treatment; it was found that both treatment groups stimulated reparative dentin and the formation of complete bridge. Strong superficial necrosis was detected exclusively for Ca(OH)2. It seems evident that application of Aloe vera in direct contact with the exposed pulp has acceptable biocompatibility and can lead to tertiary bridge formation. [ABSTRACT FROM AUTHOR]

Aim To evaluate the antioxidant and pro-oxidant properties of chlorhexidine (CHX). Methodology The scavenging and generation of reactive oxygen species (ROS) by CHX in the presence or absence of saturated Ca(OH)2 solutions was evaluated. The reaction emitted chemiluminescence in the presence of lucigenin thus was determined by a luminometer to evaluate the levels of ROS production. Changes in DNA conformation were analysed by agarose gel electrophoresis. Paired Student's t-test was used to compare the difference between groups. Results Chlorhexidine (0.00002–0.02%) effectively scavenged 56–88% of the superoxide radicals generated by the xanthine/xanthine oxidase reaction. Through analysis of PUC18 DNA conformation changes, CHX was shown to be a mild scavenger of hydroxyl radicals generated by H2O2 plus FeCl2. However, CHX (>0.083%) decreased the mobility of PUC18 plasmid DNA with potential production of DNA–DNA cross-link and severe DNA breaks (presence of DNA smear) at further higher concentrations. Furthermore, CHX induced ROS production including H2O2 and superoxide radicals in 0.1N NaOH (pH = 12.76) or Ca(OH)2 (pH = 12.5) solutions. Conclusion Chlorhexidine exhibited both antioxidant and pro-oxidant properties under different conditions. These events are possibly involved in the killing of root canal and periodontal microorganisms when CHX and Ca(OH)2 were used in combination or separately. Potential genotoxicity and tissue damage when extruded into the periradicular tissue and at higher concentrations should be considered during periodontal and endodontic practice. [ABSTRACT FROM AUTHOR]

Abstract: Studies monitoring the carbonation of NHL3.5 hydraulic lime are described. Weight-gain measurements, focused ion beam imaging, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy were used to monitor changes in structure and composition occurring in lime pastes after exposure to 100% carbon dioxide at relative humidities of 65 and 97%. Lime paste exposed to a relative humidity (R.H.) of 97% indicated a higher carbonation rate compared to paste exposed to 65% R.H. Surface analysis showed that the sample exposed to a relative humidity of 97% was completely carbonated. No calcium hydroxide was detected. A small amount of calcium hydroxide was, however, present at the surface of the sample exposed to 65% R.H. These observations suggest that high humidity results in the formation of a thin layer of crystalline calcium carbonate covering silicate and hydroxide phases. The actual mass increase of the sample also indicated that uncarbonated calcium hydroxide remained beneath the surface. [Copyright &y& Elsevier]

Abstract: This work studies the activity of activated CaO as a catalyst in the production of biodiesel by transesterification of triglycerides with methanol. Three basic aspects were investigated: the role of H2O and CO2 in the deterioration of the catalytic performance by contact with room air, the stability of the catalyst by reutilization in successive runs and the heterogeneous character of the catalytic reaction. The characterization by X-ray diffraction (XRD), evolved gas analysis by mass spectrometry (EGA-MS) during heating the sample under programmed temperature, X-ray photoelectron (XPS) and Fourier transform-infrared (FT-IR) spectroscopies allowed to concluding that CaO is rapidly hydrated and carbonated by contact with room air. Few minutes are enough to chemisorb significant amount of H2O and CO2. It is demonstrated that the CO2 is the main deactivating agent whereas the negative effect water is less important. As a matter of fact the surface of the activated catalyst is better described as an inner core of CaO particles covered by very few layers of Ca(OH)2. The activation by outgassing at temperatures ≥973K are required to revert the CO2 poisoning. The catalyst can be reused for several runs without significant deactivation. The catalytic reaction is the result of the heterogeneous and homogeneous contributions. Part of the reaction takes place on basic sites at the surface of the catalyst, the rest is due to the dissolution of the activated CaO in methanol that creates homogeneous leached active species. [Copyright &y& Elsevier]

With growing understanding of the differences between solid residues from the fluidized bed combustion of petroleum coke and of coal, the significance of fuel-derived and sorbent-derived components of the ash has become clearer It is well documented that hydration of the ashes is necessary prior to disposal or utilization or as a reactivation method. Initially, hydration of the lime was thought to involve water reacting only with CaO to form Ca(OH)2 but when the free lime content of the ashes is looked at before and after hydration, it is apparent that the process is more complex. Detailed analyses have shown that the free lime can decrease and vary within the same ash in different particle size ranges. The complexity of the reactions is reflected in problems with the assessment of the free lime content of the materials and the effect of hydration on different particle size fractions of the ash. The free lime content of the ash is significantly lower than expected based on the elemental analysis. Bed ash from the circulating fluidized bed combustion boilers owned and operated by the Nelson Industrial Steam Company Ltd. (NISCO) was examined in detail to elucidate the fate of calcium in the ash during hydration, using a range of techniques. The objective of the study is to determine the amount of CaO available for hydration/reactivation and to better understand interactions of Ca and other mineral components of the ash. Analysis results indicate that in NISCO ashes up to about 6% of the analytical CaO may be combined as acid soluble and - insoluble OCCs (other calcium compounds). This implies up to about 10% less free lime than would be inferred from standard chemical analyses. About 1% of the missing CaO can be present as acid insoluble Ca and Mg vanadates, with up to 2% bound in soluble OCCs. The remaining 3-4% is still not accounted for It is clear that even very minor quantities of mineral matter, other than CaO or CaSO4, associated mainly with the coarser size fractions, are important. The amount of bound water in the hydrated ash, other than that combined in portlandite or brucite, can be as large as 3-5%. This cannot be ignored when sample mass change on hydration or heating is used as a measure of the extent of CaO to Ca(OH)2 conversion. [ABSTRACT FROM AUTHOR]

Abstract: Prism ZnO nanomaterials coated with Ca(OH)2 were prepared by direct precipitation. TEM micrographs showed that dendritic Ca(OH)2 seemed to attach on the surface of nanosized ZnO. The XRD patterns indicated that the coating was Ca(OH)2·2Zn(OH)2·2H2O. The nanosized ZnO coated with Ca(OH)2 as the anode materials were investigated by the charge–discharge cycle measurement and EIS. The combination of ZnO nanomaterials and Ca(OH)2 prevented the discharge product ZnO from dissolving in the electrolyte. Therefore, the Ca(OH)2-coated ZnO nanomaterials exhibited higher electrochemical activity than the pure nanosized ZnO, including high the discharge capacity and discharge middle voltage, low the charge middle charge voltage. Although Ca(OH)2 resulted in more difficult activation, EIS showed that the charge-transfer resistance was lower than that of the pure ZnO nanomaterials. [Copyright &y& Elsevier]

Abstract: Phenolphthalein indicator has traditionally been used to determine the depth of carbonation in concrete. This investigation uses the thermalgravimetric analysis (TGA) method, which tests the concentration distribution of Ca(OH)2 and CaCO3, while the X-ray diffraction analysis (XRDA) tests the intensity distribution of Ca(OH)2 and CaCO3. The Fourier transformation infrared spectroscopy (FTIR) test method detects the presence of C–O in concrete samples as a basis for determining the presence of CaCO3. Concrete specimens were prepared and subjected to accelerated carbonation under conditions of 23 °C temperature, 70% RH and 20% concentration of CO2. The test results of TGA and XRDA indicate that there exist a sharp carbonation front. Three zones of carbonation were identified according to the degree of carbonation and pH in the pore solutions. The TGA, XRDA and FTIR results showed the depth of carbonation front is twice of that determined from phenolphthalein indicator. [Copyright &y& Elsevier]

The pozzolanic activity of nano-SiO2 and silica fume was comparatively studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and the compressive, bond and bending strengths of hardened paste and concrete were also measured. Results indicate that the compressive strength development of the paste made from Ca (OH)2 and nano-SiO2, the reaction rate of Ca (OH)2 with nano-SiO2 and the velocity of C−S−H gel formation from Ca(OH)2 with nano-SiO2 showed marked increases over those of Ca(OH)2 with silica fume. Furthermore, the bond strength at the interface between aggregate and hardened cement paste, and the bending strength of concrete incorporated with 3% NS increased more than those with SF, especially at early ages. To sum up, the pozzolanic activity of nano-SiO2 was much greater than that of silica fume. The results suggest that with a small amount of nano-SiO2, the Ca(OH)2 crystal at the interface between hardened cement paste and aggregate at early ages may be effectively absorbed in high performance concrete. [ABSTRACT FROM AUTHOR]

Abstract: Mortars and plasters composed of a mixture of brick powder and lime have been used since ancient times due to their hydraulic properties. In this study, raw material compositions, basic physical, mineralogical, microstructural and hydraulic properties of some historic Ottoman Bath brick-lime mortars and plasters were determined by XRD, SEM-EDS, AFM, TGA and chemical analyses. The mineralogical and chemical compositions, microstructures, morphologies and pozzolanicities of the brick powders and fragments used as aggregates in the mortars and plasters were examined to find out the relationship between hydraulic properties of the mortars and the bricks. The characteristics of bricks used in the bath domes were also determined to investigate whether the brick aggregates used in mortar and plasters were prepared from these bricks. The results indicated that the mortars and plasters were hydraulic owing to the presence of crushed brick powders that have good pozzolanicity. The brick powders had high pozzolanicity because they contained high amounts of calcium-poor clay minerals in their raw materials that were fired at low temperatures. On the other hand, bricks used in the domes had poor pozzolanicity with different mineralogical and chemical compositions from bricks used in mortars and plasters. Based on the results of the analysis, it was thought that the bricks manufactured with high amounts of clays were consciously chosen in the preparation of hydraulic mortars and plasters. [Copyright &y& Elsevier]

Abstract: An experimental investigation was carried out to determine the setting time of cement based materials (cement paste, mortar, concrete, etc.). An original method based on measurements of both total lateral pressure and hydraulic pressure has been investigated. An original device has been engineered to measure the pressure kinetics. Just after mixing and filling of the device, a simultaneous drop and an equal value of the both hydraulic and total lateral pressures has been recorded. A definitive cessation of total lateral pressure and negative hydraulic pressures are then observed. The proposed setting time was defined as the elapsed time between the end of mixing and the time at which the hydraulic pressure becomes zero. In addition to the usual W/C parameter, the influence of the vibration and the height of the material tested on the pressure based method were studied. Comparing to other classical methods (Vicat, calorimetry, ultrasonic pulse-echo …), the presented device is efficient with major types of cement based materials (concrete, SCC …) and was able to give a simple and direct information about the mechanical state of the material. [Copyright &y& Elsevier]

Abstract: A broad experimental study has been performed, from the end of mixing up to 2 years, on a set of plain cement pastes prepared with the same type I ordinary portland cement (OPC) and various water-to-cement ratios (W/C), and cured at various constant temperatures. Several parameters have been measured on the hydrating materials, such as chemical shrinkage, volumetric and one-dimensional autogenous deformations, degree of hydration of the cement, Ca(OH)2 content and Vicat setting times. Drying shrinkage has also been measured on the mature materials. In this part II of the paper, the effects of W/C within the range 0.25–0.60 have in particular been analysed in relation to the microstructural characteristics of the materials. This micro–macro analysis has highlighted a W/C threshold value (located around 0.40) both at the macro-level (on autogenous, but also on drying deformations and durability-related properties) and at the micro-level (characteristics of the hydration products, MIP porosity and pore size distribution, etc.). In addition, volumetric and one-dimensional autogenous shrinkage deformations have been compared in the case of W/C=0.25 and T=20 °C. Finally, a critical twofold (chemical and structural) effect of calcium hydroxide has been found. When significant structural effects, generated by the formation and the growth of large-size Ca(OH)2 crystals, take place, swelling can become prominent, as observed for one-dimensional autogenous deformations in the case of medium and high W/C, and deviations are recorded on linear relationships. [Copyright &y& Elsevier]

Abstract: We have studied the carbonation process in different types of mortars, with and without pozzolana or air-entraining additives, subject to a CO2-rich atmosphere and compared the results with those of similar naturally carbonated mortars. We used X-ray diffraction technique to demonstrate that high CO2 concentrations favour a faster, more complete carbonation process with 8 days being sufficient to convert portlandite into 90 wt.% calcite. Full carbonation, however, is not reached during the life-span of the tests, not even in forced carbonation experiments. This could be due to at least one of the following phenomena: a premature drying of samples during carbonation reaction, the temperature at which the carbonation process was carried out or the reduction of pore volume occupied by newly formed calcite crystals. This last option seems to be the least probable. We observed a more prolific development of calcite crystals in the pores and fissures through which the carbonic anhydride flows. Under natural conditions, carbonation is much slower and similar levels are not reached for 6 months. These differences suggest that the carbonation process is influenced by the amount of CO2 used. Both the mineralogy and texture of mortars vary depending on the type of additive used but the speed of the portlandite–calcite transformation does not change significantly. Pozzolana produces hydraulic mortars although the quantity of calcium aluminosilicate crystals is low. The air-entraining agent significantly alters the texture of the mortars creating rounded pores and eliminating or reducing the drying cracks. [Copyright &y& Elsevier]

Abstract: Water permeability resistant behavior and microstructure of concrete with nano-SiO2 were experimentally studied. A water permeability test shows that, for concretes of similar 28-day strength, the incorporation of nano-SiO2 can improve the resistance of water penetration of concrete. An ESEM test reveals that the microstructure of concrete with nano-SiO2 is more uniform and compact than that of normal concrete. Mechanism about the effect of nano-SiO2 on concrete is described. [Copyright &y& Elsevier]

Abstract: Analyses of microsamples collected from Roman catacombs and samples of lime–pozzolana mortars hardened in the laboratory display higher contents in carbonated binder than other subaerial Roman monuments. The measured environmental data inside the Saint Callistus and Domitilla catacombs show a constant temperature of 15–17 °C, a high CO2 content (1700 to 3500 ppm) and a relative humidity close to 100%. These conditions and particularly the high CO2 concentration speed-up the lime calcitization roughly by 500% and reduce the cationic diffusion to form hydrous calcium aluminosilicates. The structure of Roman catacomb mortars shows (i) coarser aggregates and thicker beds on the inside, (ii) thin, smoothed, light and fine-grained external surfaces with low content of aggregates and (iii) paintings and frescoes on the outside. The observed high porosity of the mortars can be attributed to cracking after drying linked with the high binder content. Hardened lime lumps inside the binder denote low water/mortar ratios for slaking. The aggregate tephra pyroclasts rich in aluminosilicate phases with accessorial amounts of Ba, Sr, Rb, Cu and Pb were analysed through X-ray diffraction (XRD), electron microprobe analysis (EMPA) and also by environmental scanning electron microscopy (ESEM) to identify the size and distribution of porosity. Results support procedures using local materials, special mortars and classic techniques for restoration purposes in hypogeal backgrounds. [Copyright &y& Elsevier]

Thermobalance was employed to study the drying characteristic and desulfurization of Ca(OH)2 slurry at low temperature (80 °C). The experimental results show that the drying characteristic is different under the different mass ratio of H2O/Ca(OH)2 and SO2 concentration. When the Ca(OH)2 slurry is dried in the atmosphere of SO2, drying rate would be slower because of more crystals of CaSO3 ⋅ 0.5H2O precipitating on the surface of the slurry. The critical moisture content is different under the different drying conditions. It could be found from experimental results that the more the crystals precipitating on the surface of the slurry, the larger the critical moisture content. The Ca(OH) 2 conversion increases with the increasing of SO2 concentration when SO2 concentration is low. The Ca(OH)2 conversion increases slowly with the increasing SO2 concentration when SO2 concentration is high. [ABSTRACT FROM AUTHOR]

Abstract: Calcium and calcium magnesium putty-limes (C-L and C-M-L) were characterized, through SEM, Porosimeter and Chemical Analysis, to obtain information on the microstructure of their solid-phases. Irregular agglomerates of portlandite grains and large acicular crystallites of brucite are differently interconnected to form a cellular solid matrix dispersed into the saturated aqueous solution of the hydroxides. The setting of these putty-limes was followed also in a thermobalance with a thermostatic chamber designed to keep the temperature in the range 15–30 °C. The tests were done at a constant humidity of 80%, under isothermal conditions, and a wet and carbonated N2 flux with 1% of CO2 was added. The microstructure of the final samples was characterized by the usual methods of investigation at micro–macro scale. Drying kinetics and the related shrinkage processes were discussed on the basis of a modified Kelvin equation, which predicts for the C-L lime putty a larger shrinkage (50.3%) than for C-M-L (35.5%). The binding mechanisms of the calcium carbonate in the strengthening of the putty-lime systems is due to the interconnected texture formed by the calcium carbonate fine crystallites formed during the precipitation process. The scientific reasons for this microstructure evolution have been discussed and explained on the basis of experimental data and theory, leading to a better understanding of the complex relationships between drying, shrinkage and the chemical processes occurring in the setting of putty-lime. [Copyright &y& Elsevier]