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Beachrocks are generally mapped on the coastline surface and/or in a low depth in the subtidal zone in coastlines and are cemented chiefly by carbonate material. Their outcrops may vary from a tenth of meters to a tenth of kilometers in length. Along the Epirus coast, in Greece, beachrocks outcrops are laying on the coastline for more than ten kilometers. In the present work, we used Unmanned Aerial Vehicles (UAVs), in situ sampling, and the Geographical Information System (GIS) to map three beachrock areas with a length of 500 m to 600 m each. In synergy with extended mineralogical and petrographic analyses, we provide preliminary data about the geographical distribution and the mineralogical differences of these beachrocks. Furthermore, for the first time, we tried to investigate the correlation between the geotectonic setting of the broader area and the beachrock extent, shape, and petrographic parameters. The laboratory analyses proved that the beachrocks belong to a similar depositional zone of a marine–vadose environment. Despite variations in the textural petrographic, features among the specimen’s analyses permit us to consider these sedimentary rocks as not a uniform outcrop. It is indicated that the beachrock formation and the cementation progress in the study area are both controlled by active reverse faults and diapiric or tectonic anticlines.

In this study, siliceous nodules from the world-famous Myrtos beach, as well as from Avithos beach, in the western flanks of Kefalonia Island in Greece are examined by means of petrographical, mineralogical, geochemical and micropaleontological methods. The objectives of this study are to characterize the textural and compositional features of the nodules, with the aim to provide an initial interpretation of their origin and their diagenetic evolution. The studied siliceous nodules are hosted within Lower Cretaceous thin-bedded limestones at Myrtos and Upper Eocene limestones at Avithos. Nodules from both areas display a characteristic concentric texture at a macroscopic and microscopic scale. They both have a dense fine-grained siliceous sedimentary fabric, composed mainly of microcrystalline or cryptocrystalline quartz and moganite with common residual calcite in the case of Avithos. These results, and in particular the shape of the nodules, along the textural and compositional characteristics, indicate different conditions of formation in the two localities, both during the early epigenetic stages, as well as later during the diagenetic processes. Myrtos nodules originated from Si-precursors deposited in a pelagic environment, going through intense Si-replacement. Avithos nodules were deposited in a more proximal environment, being influenced by a less intense silicification. Nevertheless, the higher degree of recrystallization of Avithos samples indicates a syn- or post-diagenetic tectonic activity that resulted in the circulation of geothermal fluids. The conclusions drawn from this work demonstrate the usefulness of thorough studies of siliceous nodules in order to get a more comprehensive understanding of the initial depositional conditions, as well as diagenetic pathways and processes.

The objective of this study was to investigate the valorization potential of clayey overburden sterile materials from lignite-mining activities in the manufacturing of traditional ceramics. This study aims to contribute toward the sustainable management and use of such waste materials in line with the environmental objectives of the 2030 agenda. To assess this issue, clayey steriles were incorporated in a white clay-body at 20, 50, and 80 wt%, whereas reference samples were also formed from the individual raw materials. Laboratory processing of the ceramics was performed by dry pressing loose powder into rectangular samples and firing at 1000 °C for 4 h. Characterization of the raw materials included chemical, mineralogical, and thermal analysis. The fired bodies were tested for their total linear shrinkage, apparent porosity, water absorption, bulk density, and bending strength according to the relevant standards. The microstructural evolution of the final bodies was analyzed by scanning electron microscopy, which observed differences related to the addition of the steriles. The results showed that the tested clayey steriles can be utilized up to 50 wt% as a secondary raw material in the production of ceramic materials (e.g., bricks) with comparable properties to the reference clay-bodies. Furthermore, the color of the final samples changed from white-creamy to reddish as the content of clayey sterile materials increased in the raw mix.

Landslides are posing a significant global hazard as they occur instantaneously with devastating consequences. The development of new remote sensing technologies and innovative processing techniques over the past few years opened up new horizons and perspectives in landslide monitoring research. The purpose of the current research is the integrated monitoring of an active landslide, located in Western Greece, using low-cost and high-repeatability remote sensing data like those obtained by unmanned aerial vehicles (UAVs). Repeated UAV campaigns and global navigation satellite systems (GNSS) surveys were performed to assess the activity of the landslide and determine its kinematic behavior. UAV data were processed using structure from motion (SfM) photogrammetry and the generated high-detailed orthophotos and digital surface models (DSMs) were submitted in further processing procedure in an ArcGIS environment. Regarding the GNSS data, a new low-cost technique for the estimation of the direction and the rate of movement of the displaced material was developed. The repeated measurements were displayed in a vector format in a three-axis diagram. In addition, GNSS measurements were used to verify the results of the photogrammetric processing. The final assessment was carried out taking into account geological data such as petrographic and crystallographic features of the material of the landslide. It was observed that the lithology and consequently the petrographic properties of the material plays a key role regarding the activity of the landslide.

The presence or the absence of swelling clay minerals in rocks, which are used in various construction applications, constitutes a determinant factor for their strength, and consequently, in their general behavior in various construction applications, as they have the ability to swell up to 400 times of their usual volume, causing failures to any application in which they participate. The aim of this study is to respond to the question of whether the empirical method of methylene blue yields equally safe and correct results in different types of igneous rocks and if not, which is the determining factor affecting the results. The answer to this complex question is feasible by investigating the microscopic structure and the mineralogy of the studied rocks, and particularly, using the content of specific phyllosilicate minerals which may be related or not with the methylene blue values. According to the results, the methylene blue test seems to work correctly for the intermediate (Group I) and mafic (Group II) examined rocks, but it seems to be wrong for the highly serpentinized ultramafic rocks (up to 70% of serpentine) (Group III).

This paper investigates an alternative use of sterile aggregate materials which may arise from various construction applications in conjunction with other low-cost mineral raw materials to remediate the acid mine drainage phenomenon. This study is based on the combination of unprocessed mineral raw materials, as well as on the basic concept of the cyclic economy where the conversion of a waste into a raw material for another application can be achieved. In this study, in order to examine the remediation, in lab scale, of the drainage waste water of Agios Philippos mine, an experimental electrically continuous flow-driven forced device was constructed, enriching the research gap relative to this type of remediation approach. Through this experimental device, the use of certain mixes of mineral raw materials (serpentinite, andesite, magnesite, peat, and biochar) was studied. Our results focus on the impact of the studied mineral raw materials and especially on their synergy on the water purification potential under continuous water flow operation. Using the new 7-day experimental electrically continuous flow-driven forced device with certain mixes of mineral raw materials, the increase of pH values from 3.00 to 6.82 was achieved. Moreover, with use of the experimental device, the removal of toxic load was achieved, and more specifically the concentration of Fe was decreased from 6149 to 1300 ppb, Cu from 8847 to 35 ppb, and Zn from 285,458 to 50,000 ppb.

This study examines how the chemical composition of ultramafic and mafic rocks effects their physicomechanical properties and therefore how influences the concrete strength of the produced concrete specimens. For this scope, ultramafic (Group I) and mafic rocks (Group II) derived from the Veria–Naousa and Edessa ophiolite complexes (Greece) were selected in order to identify their chemical composition and their engineering properties according to international standards. Additionally, representative rocks were used as concrete aggregates in order to produce concrete specimens, whereas their mechanical strength was calculated. A geochemical index (Ga) was proposed and correlated with the engineering properties of the examined rocks as well as with the widely used alteration degree LOI (loss on ignition). Correlation diagrams between engineering properties and the proposed geochemical index (Ga) have showed that these properties were strongly influenced by the alteration processes expressed via Ga index. More particularly, mainly serpentine in ultramafic and chlorite in mafic rocks, minerals indicators for the alteration of ultramafic and mafic rocks, respectively, seem to determine their engineering properties. Concerning the mechanical strength of the produced concrete specimens, the results have showed that the increasing values of Ga index negatively effect concrete strength.

This paper examines the effect of the aggregate type on concrete strength, and more specifically, how the petrographic characteristics of various aggregate rocks as well as their physico-mechanical properties influences the durability of C 25/30 strength class concrete. The studied aggregate rocks were derived from Veria-Naousa and Edessa ophiolitic complexes as well as granodiorite and albitite rocks from their surrounding areas in central Macedonia (Greece). Concretes were produced with constant volume proportions, workability, mixing and curing conditions using different sizes of each aggregate type. Aggregates were mixed both in dry and water saturated states in concretes. Six different types of aggregates were examined and classified in three district groups according to their physicomechanical properties, petrographic characteristics and surface texture. The classification in groups after the concrete compressive strength test verified the initial classification in the same three groups. Group I (ultramafic rocks) presented the lowest concrete strengths, depending on their high alteration degree and the low mechanical properties of ultramafic aggregates. Group II (mafic rocks and granodiorite) presented a wide range of concrete strengths, depending on different petrographic characteristics and mechanical properties. Group III (albite rocks) presented the highest concrete strengths, depending on their lowest alteration degree and their highest mechanical properties. Therefore, mineralogy and microstructure of the coarse aggregates affected the final strength of the concrete specimens.

Up until the last ten years, remote sensing data and especially high-resolution satellite data and airphotos were mainly used in shallow water mapping. The evolution and low cost of unmanned aerial vehicles (UAVs) provides a new tool for coastal area monitoring. This paper presents the synergistic use of a small commercial UAV and an unmanned surface vehicle (USV) for beachrock mapping in Syros Island, Greece. RGB images collected with a quadcopter were processed using Structure from Motion (SFM) photogrammetry in order to create digital surface models (DSMs) and orthophotos of the coastline. A beachrock lying in shallow waters was detected and mapped using the UAV derived products. At the same time, a USV equipped with a compact side scan sonar (SSS) and bathymetric sonar system, provided the shape of the beachrock by mosaicking the backscatter strength of the SSS. In order to evaluate the results of the UAV and USV data derivatives, the beachrock perimeter and its depth were also mapped using a differential global navigation satellite system (GNSS) receiver. During the fieldwork, samples from the beachrock were collected and analyzed in the laboratory. The mineralogical composition of the bulk samples was determined by powder X-ray diffraction (XRD). Further petrographic study was also performed by petrographic polarizing microscope, macroscope, and scanning electron microscopy (SEM). Beachrock samples are classified as fine to medium grain sandstones and conglomerates. The mineral compositions of their grains and lithoclasts reflect the bedrocks of Syros Island (mainly metamorphic rocks) while a micritic high-Mg calcite constitutes the cement of these rocks.

This paper investigates the effect of alteration on the physicomechanical properties of igneous rocks used as aggregates, from various areas from Greece. The studied lithologies include serpentinized dunites, serpentinized harzburgites, serpentinized lherzolites, metamorphic gabbros, diabases, dacites and andesites. Quantitative petrographic analysis shows that the tested samples display various percentages of secondary phyllosilicate minerals. Mineral quantification of the studied rock samples was performed by using the Rietveld method on X-ray diffraction patterns. The samples were also tested to assign moisture content (w (%)), total porosity (nt (%)), uniaxial compressive strength (UCS (MPa)) and Los Angeles abrasion test (LA (%)). The influence of secondary phyllosilicate minerals on the physicomechanical behavior of the tested samples was determined using regression analysis and their derived equations. Regression analysis shows a positive relationship between the percentage of the phyllosilicate minerals of the rocks and the moisture content as well as with the total porosity values. In mafic and ultramafic rock samples, the relationships between the secondary phyllosilicate minerals and their physicomechanical properties have shown that the total amount of the secondary phyllosilicate minerals results negatively on their physicomechanical properties. On the other hand, the low percentage of phyllosilicate minerals in volcanic rocks can’t be able to define their engineering properties.