Environmental Scanning Electron Microscopy Studies Research Articles

Evaluation of root repair using an environmental scanning electron microscope after intentional contact with microscrew

Objective: The purpose of this study was to evaluate the amount of root repair that took place at varying intervals of 1 day, 2 weeks, 4 weeks and 8 weeks after intentional contact with microscrews. The results were evaluated by an environmental scanning electron microscope study (E-SEM). Material and Methods: Ten orthodontic patients with 2 maxillary and 2 mandibular first premolars (40 premolars) to be extracted as part of the orthodontic treatment were included in this study (age 18–25 years). The position of the roots of the 4 premolars to be extracted was clinically determined and under local anesthesia, microscrew implants were placed in such a way that they directly hit the root from the buccal aspect. Implants were removed immediately after the above-mentioned procedure was performed. On the same day, premolar of the 1st quadrant (Group I) was extracted. Premolar of the 2nd quadrant (Group II) was extracted 2 weeks later. Premolar of the 3rd quadrant (Group III) was extracted 4 weeks later and premolar of the 4th quadrant (Group IV) was extracted 8 weeks later, from the day of intentional damage. Results: Significant changes were observed in the deposition of cementum over 8 weeks which were analyzed using ESEM under magnifications of × 50, × 200, × 500, and × 5000. Conclusion: The damaged root surfaces due to intentional contact with microscrews showed swift repair and healing within 8 weeks. In case, the root is damaged due to improper placement technique or wrong biomechanics which may result in the implant touching the root surface, a minimum healing period of 8–10 weeks is advocated before commencing further tooth movement.

Effect of the process atmosphere on glass foam synthesis: A high-temperature environmental scanning electron microscopy (HT-ESEM) study

The effect of the process atmosphere composition on the foam formation of cathode-ray tube (CRT) glass containing graphite and MnO2 was studied using in situ environmental scanning electron microscopy at high temperature (HT-ESEM). When compared to He+4% H2, O2 or air, water steam facilitates glass grain sintering. This is probably due to the formation of hydroxyl groups at the glass grain surface that locally decrease the glass viscosity. We have shown that increasing the steam pressure from 50 Pa to 750 Pa decreases both sintering and foaming onset temperatures by approximately 100 °C, favouring the formation of closed pores in viscous glass. At high temperature, the presence of water steam or oxygen promotes foam formation, while the presence of a reducing atmosphere (He+4%H2) limits glass melt foaming. A synergetic effect of O2 and H2O on the onset temperature of glass sintering and foam formation is evidenced.

Consideraţii privind osteointegrarea implanturilor dentare endoosoase

Implant osseointegration has not been accepted over time, considering that in fact the implant integration is performed only in the soft tissue of the host. For this reason, the implant has never been sufficiently integrated into the host tissue immediately after insertion. Experiments performed in Branemark laboratories in the early 1960s, with a new type of implant, which required a direct anchorage to bone tissue for clinical function, this anchorage was called osseointegration. It has been shown that it is possible to achieve direct osseointegration if the Branemark method is considered, which was published a few years later in the first clinical report. The authors of this article come up with new contributions that validate the implant osseointegration process. Inside this article we present our methodology for evaluating the osseointegration of endosseous implants: ESEM (environmental scanning electron microscope) studies of the implant-bone tissue interface.

Development of a rapidly made, easily personalized drug-eluting polymer film on the electrode array of a cochlear implant during surgery

ObjectiveTo develop a drug-eluting polymer film which can be easily personalized and rapidly made on the electrode array of a cochlear implant during surgery. MethodsA precursor solution was prepared with poly lactic-co-glycolic acid (PLGA) and trichloromethane. Using a dip-coating method, the silicone electrode array (HiFocus 1J, Advanced Bionics) was coated in polymer film produced from the precursor solution containing one of three drugs: dexamethasone sodium phosphate (DSP), cytosine arabinoside hydrochloride (Ara-C), or nicotinamide adenine dinucleotide (NAD), and the release of these drugs from the polymer film was studied. The drug-eluting film on the electrode array was analyzed by environmental scanning electron microscopy (ESEM). The water contact angle and the impedance of the electrode array were measured before and after coating. Drug release kinetics was evaluated in a quasi-stationary release model, using high performance liquid chromatography every 24 h for 15 days. ResultsFive electrode arrays were tested with each of the three drugs in the polymer film coating. Before and after coating, ESEM studies revealed that the drug-loaded PLGA coating yielded a smooth covering with an average thickness of 1.02 ± 0.05 μm. The mass of the coated electrode increased by 1.00 ± 0.03 mg. The water contact angle decreased after coating (102 ± 0.6° vs 77 ± 1.6°, p < 0.01) but there was no significant change in the average impedance of the electrodes after coating (0.9 ± 0.22 kΩ vs 1.0 ± 0.18 kΩ, p > 0.05). An in vitro drug kinetics study revealed a faster release in the first 24 h (63.4 ± 0.6%) and a sustained release over the following 15 days (78.3 ± 1.7% in 2 days, 95.6 ± 1.0% in 7 days and 99.1 ± 0.4% in 14 days). The release rate was not affected by the drug, dose or the thickness of the coating. ConclusionThe dip-coating method is feasible for rapid casting of a drug-eluting PLGA film on an electrode array during CI surgery. The coated electrode array maintained its original morphology and became more hydrophilic. The loaded drug is released in a sustained manner and is easily regulated, and so the method might represent a potential application for clinical use in cochlear implantation.

Applications of ESEM on Materials Science: Recent Updates and a Look Forward

AbstractThe microscopic understanding of materials relies on the development of microscopy. Historically, the technological evolution from optical microscopes to electron microscopes has directly stimulated many discoveries of new physical and chemical fundamentals as well as advanced materials. Scanning electron microscopy (SEM) is, undoubtedly, the most widely used tool for microscopic characterization in modern materials science. Especially, the incorporation of a gas pressure around the sample area of conventional SEM, i.e., the environmental scanning electron microscope (ESEM), has opened new possibilities in observing samples in their natural states, leading to unprecedented chances for studying the details of biological, organic, and hydrated samples. What is more, in recent years, in situ ESEM studies concerning materials change and chemical reactions have played a more important role in the field of materials science. Herein, the recent applications of ESEM in materials science are comprehensively reviewed, in terms of common static observations for various materials and in situ investigations of dynamic processes in controlled experimental environments. Moreover, the problems concerning state‐of‐the‐art ESEM experiments are discussed, as well as possible solutions. Looking forward, the rapid developments on instrumentation and fundamental science of ESEM can bring a clear vision of materials in the near future.

Corneal incision architecture after IOL implantation with three different injectors: an environmental scanning electron microscopy study.

To evaluate by Environmental Scanning Electron Microscopy (ESEM) the corneal incision architecture after intraocular lens (IOL) implantation in pig eyes, using manual, automated injectors or preloaded delivery systems. Twenty-four pig eyes underwent IOL implantation in the anterior chamber using three different injectors: manual (Monarch III) (n=8), automated (AutoSert) (n=8), or a preloaded system (UltraSert) (n=8). Acrysof IQ IOLs, 21 Dioptres (D) (n=12) and 27D (n=12), were implanted through 2.2mm clear corneal incisions. Incision width was measured using corneal calipers. The endothelial side of the incision was analyzed with ESEM. In each group, the final size of the corneal wound after IOL implantation, measured by calipers, was 2.3-2.4mm. The incision architecture resulted more irregular in the Monarch group compared with the other injectors. In every group the 27D IOL-implanted specimens showed more alterations than in 21D IOL-implanted samples, and this was less evident in the UltraSert group. The Descemet tear length was higher in the Monarch group than AutoSert and UltraSert group. The automated and preloaded delivery systems provided a good corneal incision architecture; after high-power IOL implantation the incisions were more regular and less damaged with the preloaded system than with the other devices.

Therapeutic efficacy and safety of a 1927-nm fractionated thulium laser on pattern hair loss: an evaluator-blinded, split-scalp study.

Laser- or light-assisted therapies have been used to improve the perifollicular environment by upregulating the expression of growth factors and signaling molecules for hair restoration. The aim of our study was to preclinically and clinically evaluate the therapeutic efficacy and safety of a 1927-nm fractionated thulium laser on pattern hair loss (PHL). An in vivo hairless mouse study and an in vivo human skin environmental scanning electron microscopy (ESEM) study were performed with different power and energy settings. Thereafter, an evaluator-blinded, split-scalp study was conducted to evaluate hair thickness and density in 10 PHL patients treated with 12 sessions of fractionated thulium laser treatment with or without post-laser treatment application of a growth factor-containing (GF) solution. In in vivo hairless mouse skin, inverted cone-shaped zones of thulium laser-induced tissue coagulation (LITC) were noted immediately after treatment in the epidermis and upper to mid-dermis without remarkable ablative tissue injury. The ESEM study revealed round to oval-shaped zones of non-ablative LITC on the surface of the stratum corneum of a human subject immediately after laser irradiation. In PHL patients, 12 sessions of thulium laser monotherapy at 1-week intervals resulted in significantly increased hair density and thickness. Post-laser treatment application of GF solution offered additional therapeutic efficacy by improving hair density and thickness on the split scalp. The use of a fractionated thulium laser with or without post-laser therapy application of GF solution to treat PHL elicited remarkable improvements in hair thickness and hair counts.

Oxidation of UC: An in situ high temperature environmental scanning electron microscopy study

In situ HT-ESEM oxidation of sintered UC fragments revealed the morphological changes occurring during the transformation between UC to UO2 and UO2 to U3O8 at 723–848 K and in an atmosphere of 10–100 Pa O2. Two main oxidation pathways were revealed. Oxidation at 723 K in atmospheres ≤25 Pa O2 showed the transformation from UC to UO2+x, as confirmed by post mortem HRTEM analysis. This oxidation pathway was comprised of three steps: (i) an induction period, where only surface UC particles oxidised, (ii) a sample area expansion accompanied by crack formation and propagation, (iii) a stabilisation of the total crack length inferring that crack propagation had stopped. Samples oxidised under 50 Pa O2 at 723 K and at 773–848 K for 10–100 Pa O2 showed an “explosive” oxidation pathway: (i) sample area expansion occurred as soon as oxygen was inserted into the chamber and crack propagation and crack length followed an exponential law; (ii) cracks propagated as a network and the oxide layer fragmented, (iii) an “explosion” occurred causing a popcorn-like transformation, typical for oxidation from UO2 to U3O8. HRTEM characterisation revealed U3O8 preferentially grow in the [001] direction. The explosive growth, triggered by ignition of UC, proceeded as a self-propagating high-temperature synthesis reaction, with a propagation speed of 150–500 ± 50 μm/s.

Vegetative and floral development in the pistillate plant of Arceuthobium americanum (lodgepole pine dwarf mistletoe): an environmental scanning electron microscopy study of its phenology and shoot organization

Dwarf mistletoes (DM), genus Arceuthobium, are dioecious parasitic flowering plants having prolonged life cycles lasting six years, culminating with explosive discharge of the single seed from the fruit. Arceuthobium americanum Nutt. ex Engelm., the lodgepole pine dwarf mistletoe, infects lodgepole pine (Pinus contorta subsp. latifolia (Engelm.) Critchfield) in western North America, compromising the forest economy. Highly reduced flowers appear no later than two years following shoot development, with female flowers appearing and persisting for over two years. Development of the pistillate plant, including initiation of floral growth, has not been fully explored. Here, we used environmental scanning electron microscopy to demark phenological waypoints throughout the pistillate plant’s development. As successive crops of female flowers emerged every year, up to three generations of flowers/fruit could be found on a single shoot in late summer; we used these three generations to delineate specific developmental stages. Vegetative shoots could initiate growth at any time within the growing season, could assume a terminal position, could also adopt sympodial branching, but were never whorled or adventitious. Floral branches, however, could initiate adventitiously from older nodes in a whorled pattern, and could house flowers/fruits of any generation. Vegetative and floral units were structurally homogeneous, suggesting shared developmental pathways.

Hydroxy propyl β-cyclodextrin complexation of promethazine hydrochloride for the formulation of fast dissolving sublingual film: in vitro and in vivo evaluation

Promethazine hydrochloride (PMZ-HCl) is a classical anti-motion sickness drug which has oral bioavailability (25 %) due to extensive hepatic first pass metabolism. To overcome this drawback, novel, fast dissolving sublingual film (FDSF) of drug was developed. FDSF was formulated using pullulan and propylene glycol (PG) by solvent casting method. Complete taste masking was successfully obtained with HP β-CD, aspartame and grape fruit flavour. Complex of drug was proved using Fourier transfer infrared spectroscopy, differential scanning calorimetry and X-ray diffraction studies. Optimization of concentration of pullulan and PG was done using 32 full factorial design. Batches were evaluated for the parameters like elongation, tensile strength, folding endurance and in vitro disintegration studies. In vitro dissolution indicated 100 % drug release within 7.5 min. Environmental scanning electron microscopy studies also showed uniform drug distribution and integrity of film. In vivo sublingual absorption in human indicated that 70 % of drug absorbed in 10 min. The stability studies indicated that label should state “Store at cool, dry place” at temperature 25 °C. So by formulating the taste masked FDSF of PMZ-HCl will give faster onset of action and avoid unnecessary drug intake leading to traveller friendly formulation.

Effect of diode laser on periodontally involved root surfaces: An in vitro environmental scanning electron microscope study

Context: Diode laser has been used as adjunct to scaling and root planing in the treatment of periodontitis. However, inadvertent effect of diode laser on root surface needs more evaluation. Aims: The aim of this study was to evaluate and compare the structural and compositional changes in extracted human permanent teeth following scaling, root planing, and diode laser (980 nm) application in noncontact mode. Settings and Design: This was an in vitro environmental scanning electron microscope (ESEM) study. Materials and Methods: Thirty single rooted periodontally involved teeth indicated for extraction were selected and divided into two groups. In Group 1, 15 teeth were treated with scaling and root planing followed by diode laser application in noncontact mode (2 W, 30 s) and in Group 2, 15 teeth were treated with scaling and root planing alone. An ESEM was used to examine the cemental surface. Compositional changes were assessed using EDAX software. Statistical Analysis Used: The statistical comparison of compositional changes and root surface alterations in two groups was carried out using independent sample t-test and Chi-square test, respectively. P < 0.05 was considered as statistically significant. Results: About 53.3% of teeth in Group 1 showed mild surface changes (Score 4) as compared to only 13.3% of teeth in Group 2. The results were statistically significant ( P - 0.001). This study also reveals a significant amount of compositional changes in Group 1 as compared with Group 2. Mass % of carbon and oxygen is significantly increased in Group 1 as compared with Group 2. Conclusions: In this study, mild root surface alterations were seen in the form of cracks and charring after diode laser application in noncontact mode.

ESEM Study of the Humidity-Induced Swelling of Clay Film

We measured the humidity-induced swelling of thin self-standing films of montmorillonite clay by a combination of environmental scanning electron microscopy (ESEM) and digital image correlation (DIC). The films were about 40 μm thick. They were prepared by depositing and evaporating a suspension of clay and peeling off the highly oriented deposits. The rationale for creating such original samples was to obtain mesoscopic samples that could be used to bridge experimentally the gap between the scale of the clay layer and the engineering scale of a macroscopic clay sample. Several montmorillonite samples were used: the reference clay Swy-2, the same clay homoionized with sodium or calcium ions, and a sodium-exchanged Cloisite. The edges of the clay films were observed by ESEM at various relative humidity values between 14% and 95%. The ESEM images were then analyzed by DIC to measure the swelling or the shrinkage of the films. We also measured the adsorption/desorption isotherms by weighing the film samples in a humidity-controlled environment. In order to analyze our results, we compared our swelling/shrinkage and adsorption/desorption data with previously published data on the interlayer spacing obtained by X-ray diffraction and with numerical estimates of the interlayer water obtained by molecular dynamics simulation. The swelling and the hysteresis of this swelling were found to be comparable for the overall macroscopic films and for the interlayer space. The same correspondence between film and interlayer space was observed for the amount of adsorbed water. This suggests that, in the range of relative humidities values explored, the films behave like freely swelling oriented stacks of clay layers, without any significant contribution from the mesoporosity. The relevance of this result for the behavior of clayey sedimentary rocks and the differences with the behavior of nonoriented samples (powders or compacted powders) are briefly discussed.

Coefficients of sliding friction of single crystals of high explosives under different rubbing conditions

The coefficients of sliding friction of single crystals of commonly used high explosives pentaerythritol tetranitrate (PETN), cyclotrimethylene trinitramine (RDX) and beta-cyclotetramethylene tetranitramine (β-HMX) under several rubbing configurations and at a relative sliding speed of 0.22 mm s−1 were measured. The sliding configurations were (1) crystal–polished steel pairs, (2) like-crystal pairs and (3) unlike-crystal pairs. For every rubbing configuration the friction force showed oscillations, which are thought to be caused by the formation and shearing of the adhesive junctions formed at the surface of the rubbing crystals. This shearing of the adhesive junctions led to the formation of microscopic and sub-microscopic particles, which were confirmed by an environmental scanning electron microscope study. For every rubbing configuration and for relatively high normal loads pressing the rubbing crystals together, the coefficient of friction was generally in the range 0.2–0.25 and it has been concluded that the coefficient of friction is controlled by the adhesion with almost negligible contribution from the ploughing component. From a knowledge of the coefficient of friction and the uniaxial yield stress values of single crystals of RDX and β-HMX, the shear strength of these crystals were determined to be ∼13.4 MPa and ∼16.8 MPa, respectively.

Mineral powder concrete – effects of powder content on concrete properties

The effects of partial replacement of Portland cement with non-pozzolanic mineral powders on normal-strength concretes were studied. The observed concrete properties were workability, pumpability, compressive strength and microstructure. Superplasticisers were used in every test concrete. With the addition of mineral powders, the water requirement of the concrete mixes decreased and the compressive strength of the mineral powder concretes was kept at the same level as in a reference mix by using on average a 75 kg/m3 lower cement amount. Studies of the microstructure of the concretes were made using resin-impregnated and polished specimens that were prepared from three concretes, each containing a different mineral powder. In the environmental scanning electron microscopy study, the specimens showed densification of the interfacial transition zone when mineral powders were used. The effects of the mineral powders on the workability, water requirement and compressive strength values of the concretes were evaluated in relation to grading curves.

An insight into the water retention properties of compacted clayey soils

Experimental data from different testing methodologies on different compacted clayey soils, with dominant bimodal pore size distribution, are presented and analysed, to provide a comprehensive picture of the evolution of the aggregated fabric along hydraulic and mechanical paths. Fabric changes are analysed both from the porous network viewpoint, by means of careful mercury intrusion porosimetry investigation, and from the soil skeleton viewpoint, by quantifying swelling and shrinkage of the aggregates in an environmental scanning electron microscopy study. The consequences of the aggregated fabric evolution on the water retention properties of compacted soils are analysed and discussed. A new model for water retention domain is proposed, which introduces a dependence of the intra-aggregate pore volume on water content. The model succeeds in tracking correctly the evolution of the hydraulic state of the different soils investigated along generalised hydromechanical paths. The proposed approach brings to light coupling between intra-aggregate and inter-aggregate pores in the retention properties of compacted clayey soils. Dependence of the air entry and the air occlusion values on swelling and shrinking of aggregates, besides void ratio, is introduced and discussed.

Delivery of polymeric particles into skin using needle-free liquid jet injectors

Needle-free liquid jet injectors have been developed for the delivery of several drugs including insulin and growth hormone. Here, we assess the ability of liquid jet injectors to deliver polymeric nanoparticles into skin. As a first step, polystyrene particles of several sizes and two shapes were injected into skin using a jet injector. The dispersion area of particles, measured in the cross section of the skin, was found to inversely relate to the particle size and directly proportional to the injection volume. Environmental scanning electron microscopy studies confirmed that particles indeed penetrate into the skin and are generally located around the injection site. Next, poly lactide co-glycolide (PLGA) particles, containing a model solute, coumarin-6, were synthesized and delivered into the skin using the jet injector. PLGA particles were effectively delivered into the skin and released coumarin-6 into the skin.

Effect of Air-Jet Texturing on Adhesion Behaviour of Technical Polyester Yarns to Rubber

Air-jet texturing of technical polyester yarns was performed in order to improve its adhesion to rubber. The air-jet texturing parameters were selected with great care to minimize the mechanical loss. H-adhesion tests were used to characterize the adhesion of the yarns to rubber. A significant increase in the adhesion of dimensionally stable polyethylene terephthalate yarn, textured with an overfeed level of 15% (DSPET15), was recorded, while a decrease in the adhesion of high tenacity polyethylene terephthalate (HTPET) yarn was observed for all overfeed levels. The effects of air-jet texturing on the adhesion of technical polyester yarns were discussed in terms of changes in the yarn geometry and changes on the single fiber surfaces. Changes in the yarn geometry were investigated by optical microscopy studies, while changes on the fiber surface were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and environmental scanning electron microscopy (ESEM) studies. It was observed that air-jet texturing alters both the yarn geometry and the single fiber surfaces, leading to a change in the adhesion to rubber.

Durable Antifog Films from Layer-by-Layer Molecularly Blended Hydrophilic Polysaccharides

Mechanically durable, long-lasting antifog coatings based on polysaccharides were developed using a layer-by-layer (LBL) assembly process. The unique properties of these coatings are a result of a molecular-level blending of the polysaccharides, with multilayers containing chitosan and carboxymethyl cellulose providing the best overall properties. The antifog properties resulted from a strong interaction between the polar and H-bonding elements of the assembled polymers and water molecules and the concomitant formation of thin films of water. Environmental scanning electron microscopy (ESEM) studies confirmed that fogging coatings are decorated with light scattering, micrometer-sized droplets of water whereas antifogging coatings remain droplet free. To improve the mechanical durability of the multilayer films on substrates, the surface was modified via self-assembly of epoxy-functionalized silane molecules. Cross-linking chemistry was then applied to improve the mechanical robustness of the LBL films on various surfaces. These films were characterized using several techniques: optical profilometery (PL), spectroscopic ellipsometry (EL), contact angle goniometry (CA), and atomic force microscopy (AFM). The antifog properties of the films were evaluated by several tests under different environmental conditions. This work demonstrates that the unique water-adsorbing properties of polysaccharides can be exploited to create permanent antifog properties, which may be useful for various applications.

Seed coat development, anatomy and scanning electron microscopy of Harpagophytum procumbens (Devil's Claw), Pedaliaceae

Seed coat development of Harpagophytum procumbens (Devil's Claw) and the possible role of the mature seed coat in seed dormancy were studied by light microscopy (LM), transmission electron microscopy (TEM) and environmental scanning electron microscopy (ESEM). Very young ovules of H. procumbens have a single thick integument consisting of densely packed thin-walled parenchyma cells that are uniform in shape and size. During later developmental stages the parenchyma cells differentiate into 4 different zones. Zone 1 is the multi-layered inner epidermis of the single integument that eventually develops into a tough impenetrable covering that tightly encloses the embryo. The inner epidermis is delineated on the inside by a few layers of collapsed remnant endosperm cell wall layers and on the outside by remnant cell wall layers of zone 2, also called the middle layer. Together with the inner epidermis these remnant cell wall layers from collapsed cells may contribute towards seed coat impermeability. Zone 2 underneath the inner epidermis consists of large thin-walled parenchyma cells. Zone 3 is the sub-epidermal layers underneath the outer epidermis referred to as a hypodermis and zone 4 is the single outer seed coat epidermal layer. Both zones 3 and 4 develop unusual secondary wall thickenings. The primary cell walls of the outer epidermis and hypodermis disintegrated during the final stages of seed maturation, leaving only a scaffold of these secondary cell wall thickenings. In the mature seed coat the outer fibrillar seed coat consists of the outer epidermis and hypodermis and separates easily to reveal the dense, smooth inner epidermis of the seed coat. Outer epidermal and hypodermal wall thickenings develop over primary pit fields and arise from the deposition of secondary cell wall material in the form of alternative electron dense and electron lucent layers. ESEM studies showed that the outer epidermal and hypodermal seed coat layers are exceptionally hygroscopic. At 100% relative humidity within the ESEM chamber, drops of water readily condense on the seed surface and react in various ways with the seed coat components, resulting in the swelling and expansion of the wall thickenings. The flexible fibrous outer seed coat epidermis and hypodermis may enhance soil seed contact and retention of water, while the inner seed coat epidermis maintains structural and perhaps chemical seed dormancy due to the possible presence of inhibitors.

Applicability of the standard specifications of ASTM C618 for evaluation of natural pozzolans

Nowadays, the production of binary cements, containing pozzolans (including silica fume, fly ash, natural pozzolans, etc.), is a global practice. Many countries have ample resources of natural pozzolans, capable of being used in binary cements, which reduce environmental impacts while reaping greater economies of scale. The ASTM C618 standard provides one of the most applicable methods for evaluating natural pozzolans. Some research results show contradictions between performance of pozzolans in concrete and the specifications of ASTM C618, as pozzolans having a high pozzolanic activity according to this method do not always exhibit suitable performance in concrete, however, in the other researches ASTM C618 showed compatibility. This treatment analyses the chemical and physical properties of different natural pozzolans by means of ASTM C618 and complementary tests, viz. methods of EN 196-5, X-ray diffraction (XRD) and environmental scanning electron microscopy (ESEM) studies, insoluble residue content and thermo-gravimetric investigations. Measurements of mechanical and transport properties, for concretes containing various fractions of the pozzolans, were performed for further verification. The results illustrate that the pozzolanic properties, determined via the ASTM C618 standard, show some disparities with the performance of concretes, whereas the EN 196-5 standard agrees well with performance.