Special Issue "Minerals and Other Phases in Constructional Geomaterials"

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Crystallography and Physical Chemistry of Minerals & Nanominerals".

Deadline for manuscript submissions: closed (1 December 2020).

Special Issue Editors

Prof. Dr. Richard Přikryl
E-Mail Website
Guest Editor
Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles University, 128 43 Prague 2, Czech Republic
Interests: geology of mineral resources; industrial minerals and rocks; constructional geomaterials; natural stone; mortar; render; hydraulic binders; lime; bricks; mineral/phase composition; rock mechanics; quantitative methods for rock fabric; petrographic image analysis; material testing; material research of cultural heritage objects; weathering and decay of constructional geomaterials; provenance analysis of natural stone
Prof. Dr. Ákos Török
E-Mail Website
Guest Editor
Department of Engineering Geology and Geotechnics, Budapest University of Technology and Economics, H-1111 Budapest, Hungary
Interests: construction materials; natural stone; mortar; render; hydraulic binders; lime; bricks; mineral/phase composition; engineering geology; material testing; monuments; cultural heritage; decay; radioactive waste disposal; landslides

Special Issue Information

Dear Colleagues,

Constructional geomaterials are key mineral raw materials contributing to more than 70% of total mineral raw materials extracted from the lithosphere annually. Being genetically linked with processes in upper parts of the solid Earth, they are primarily composed of minerals that built up the respective source rocks. The processing of selected constructional geomaterials (e.g., inorganic binders, structural ceramics) results in phase transformation—the newly formed phases are essential for functionality of these materials. Once being used in construction (e.g., residential/non-residential buildings, infrastructural projects, heritage structures, artistic objects), minerals in rocks and/or phases in processed constructional geomaterials have to fulfil certain roles, specifically when contributing to the structural stability and to durability (service life) of the respective usages. The interaction of constructional geomaterials with the surrounding environment leads to the partial transformation of original phases on the interface, resulting in the formation of decayed layers, exocrusts, etc., with each being characterized by specific phase composition. Therefore, the knowledge of the mineral/inorganic phase composition of constructional geomaterials is fundamental in terms of the effective usage of mineral raw materials in relation to sustainable development, in the effective planning of their service life, or in the understanding of historical technologies of materials used in cultural heritage objects.

This Special Issue aims to collect papers that will show the importance of studies related to mineral(phase)-compositional aspects of constructional geomaterials focusing both on raw materials and final products, with an outlook to their physical properties and/or durability. Papers describing wide ranges of new materials, final products, and historic resources, such as natural stone, crushed stone, sand and gravel, clay, inorganic binders (cement, lime, natural cements, hydraulic lime, gypsum and other renders) organic compounds, earth, and adobe are welcome. This Special Issue is also dedicated to the mineralogical aspects of material testing, the geological characterization of construction materials, in-situ and laboratory testing of geomaterials in natural and built environments.

Prof. Dr. Richard Přikryl
Prof. Dr. Ákos Török
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Minerals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • construction geomaterials
  • natural stone
  • aggregates
  • crushed stone
  • sand and gravel
  • hydraulic binders
  • lime
  • bricks
  • mortar
  • render
  • concrete
  • mineral/phase composition
  • engineering geology
  • material testing
  • monuments
  • cultural heritage
  • decay
  • sustainable development
  • service life

Published Papers (15 papers)

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Research

Jump to: Review

Article
Freeze–Thaw and Salt Crystallization Durability of Silica Acid Ester Consolidated Porous Limestone from Hungary
Minerals 2021, 11(8), 824; https://doi.org/10.3390/min11080824 - 29 Jul 2021
Viewed by 373
Abstract
The durability of consolidated highly porous limestones was tested after salt and freeze–thaw cycles. Three porous limestone lithotypes that were commonly used in construction in the Central-European region during previous centuries were selected for the tests. Specimens of Miocene limestone were consolidated with [...] Read more.
The durability of consolidated highly porous limestones was tested after salt and freeze–thaw cycles. Three porous limestone lithotypes that were commonly used in construction in the Central-European region during previous centuries were selected for the tests. Specimens of Miocene limestone were consolidated with four different types of ethyl silica-based consolidants (KSE 100, KSE 300, KSE 300 E, KSE 300 HV). After consolidation, the samples were exposed to freeze thaw cycles and salt crystallization tests. Water saturation under atmospherically pressure, capillary water absorption and splitting tensile strength were measured on treated and untreated samples to assess change attributed to consolidation in the open porosity and mechanical parameters. The increase in the tensile strength of the medium-grained samples was higher than that of the consolidated fine-grained lithotypes. The effect of consolidation treatment was very different in terms of pore-size distribution as obtained by Mercury intrusion porosimetry (MIP). Untreated and consolidated samples were subjected to 10 cycles of sodium sulphate crystallization (EN 12370) and 10 freeze–thaw cycles (EN 12371) tests. Experiments concluded that in addition to the initial strength increase after the conservation, the modified pore structure is the crucial factor to evaluate the long-term efficiency of stone conservation. Full article
(This article belongs to the Special Issue Minerals and Other Phases in Constructional Geomaterials)
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Article
Recovery of Some Critical Raw Materials from Processing Waste of Feldspar Ore Related to Hydrothermally Altered Granite: Laboratory-Scale Beneficiation
Minerals 2021, 11(5), 455; https://doi.org/10.3390/min11050455 - 26 Apr 2021
Viewed by 520
Abstract
Feldspar for ceramic/glass industries requires sufficiently low content of harmful colourants (Fe-, Ti-, Mn-bearing mineral phases). Hydrothermally altered albite-rich granites are increasingly used as feldspar raw material nowadays; however, they are often marked by increased content of colourants, which must be removed during [...] Read more.
Feldspar for ceramic/glass industries requires sufficiently low content of harmful colourants (Fe-, Ti-, Mn-bearing mineral phases). Hydrothermally altered albite-rich granites are increasingly used as feldspar raw material nowadays; however, they are often marked by increased content of colourants, which must be removed during the processing of feldspar ore. Parallel to the content of colourants, these phases show enrichment in some critical raw materials (CRMs), specifically of Nb, Ta, and Li. In the current study, the laboratory trials focused on the possibility of reprocessing of waste generated during basic magnetic separation of feldspar ore. Major aim of these trials was to search for a processing scheme that would allow for obtaining of mineralogically homogeneous fractions, part of which could be utilised as a source of CRMs. According to the results, combination of gravity, magnetic and heavy liquid separation is highly effective in obtaining of desirable concentrates. Feldspar ore processing waste thus presents potential source of CRMs; however, semi-industrial and full-scale trial must follow in order to prove the economic and environmental suitability of the suggested processing scheme. Full article
(This article belongs to the Special Issue Minerals and Other Phases in Constructional Geomaterials)
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Article
Mechanical Activation of the Ca-Rich Circulating Fluidized Bed Combustion Fly Ash: Development of an Alternative Binder System
Minerals 2021, 11(1), 3; https://doi.org/10.3390/min11010003 - 22 Dec 2020
Viewed by 631
Abstract
Mechanical activation of the calcium-rich fly ash formed in circulating fluidized bed combustion (CFBC) boilers was investigated to enhance the compressive strength performance of the pastes. We studied the effect of the activation on the physical, chemical, and mineral characteristics of fly ash [...] Read more.
Mechanical activation of the calcium-rich fly ash formed in circulating fluidized bed combustion (CFBC) boilers was investigated to enhance the compressive strength performance of the pastes. We studied the effect of the activation on the physical, chemical, and mineral characteristics of fly ash and its pastes. Our study shows that already a short mechanical activation yields a 10-fold improvement in the compressive strength of the pastes, reaching 60 MPa after 90 days of curing without any chemical activation or blending. Mechanical activation caused fragmentation of large porous aggregates in the raw ash enhancing the physical properties and reactivity of fly ash particles. Similarly to calcium sulfoaluminate cements, the mechanical strength was provided by the formation of abundant ettringite and possibly C-(A)-S-H gel-like phase that created a highly compact microstructure. Our findings suggest that mechanically activated Ca-rich CFBC fly ash can be successfully used as an alternative binder. Full article
(This article belongs to the Special Issue Minerals and Other Phases in Constructional Geomaterials)
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Article
Effect of the Cooling Regime on the Mineralogy and Reactivity of Belite-Sulfoaluminate Clinkers
Minerals 2020, 10(10), 910; https://doi.org/10.3390/min10100910 - 15 Oct 2020
Cited by 5 | Viewed by 830
Abstract
This study investigated the influence of different cooling regimes on the microstructure and consequent reactivity of belite-sulfoaluminate clinkers. The cement clinkers were synthesized by incorporating secondary raw materials, such as titanogypsum and bottom ash, to the natural raw materials. Clinker phases were determined [...] Read more.
This study investigated the influence of different cooling regimes on the microstructure and consequent reactivity of belite-sulfoaluminate clinkers. The cement clinkers were synthesized by incorporating secondary raw materials, such as titanogypsum and bottom ash, to the natural raw materials. Clinker phases were determined by Rietveld quantitative phase analysis, while the distribution morphology and the incorporation of substitute ions in the phases were characterized by scanning electron microscopy using energy-dispersive X-ray spectroscopy (SEM/EDS). Clinker reactivity was studied using isothermal calorimetry and was additionally investigated through compressive strength, which was determined for the cement prepared from the synthesized clinkers. X-ray diffraction analysis showed that, as well as the three main phases (belite, calcium sulfoaluminate, and ferrite), the clinkers contained additional minor phases (mayenite, gehlenite, arkanite, periclase, and perovskite), the ratios of which varied according to the cooling regime utilized. Microscopic observations indicated that the cooling regime also influenced the crystal size and morphology of the main phases, which consequently affected clinker reactivity. Furthermore, a smaller amount of substitute elements was incorporated in the main phases when cooling was slowed. Results showed that, in comparison to clinkers cooled at slower rates, air quenched clinkers reacted faster and exhibited a higher compressive strength at 7 days. Full article
(This article belongs to the Special Issue Minerals and Other Phases in Constructional Geomaterials)
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Article
Potential of Natural and Recycled Concrete Aggregate Mixtures for Use in Pavement Structures
Minerals 2020, 10(9), 744; https://doi.org/10.3390/min10090744 - 22 Aug 2020
Cited by 1 | Viewed by 619
Abstract
This study investigates the feasibility of using recycled concrete aggregate (RCA) as a partial substitution of natural aggregate in pavement engineering. Despite RCA’s good properties, such as polishing value and freeze-thaw resistance, its use is limited by low resistance to fragmentation and high-water [...] Read more.
This study investigates the feasibility of using recycled concrete aggregate (RCA) as a partial substitution of natural aggregate in pavement engineering. Despite RCA’s good properties, such as polishing value and freeze-thaw resistance, its use is limited by low resistance to fragmentation and high-water absorption. This paper parent the experimental results of mineralogical-petrographic and physical-mechanical properties of RCA, natural stone (dolerite) and their combination (RCA content—15%, 30%, 45%, and 60%). The tested granular mixtures showed good resistance to fragmentation and wear (LA 22–27%, MDE 14–15%), as well as satisfactory Polished Stone Value of 55–57, which means they can be used in different layers of pavement structures. According to the obtained testing results, the application of RCA is possible in different flexible and rigid pavement layers and for various traffic loads. Full article
(This article belongs to the Special Issue Minerals and Other Phases in Constructional Geomaterials)
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Article
Cement Render and Mortar and Their Damages Due to Salt Crystallization in the Holy Trinity Church, Dominicans Monastery in Cracow, Poland
Minerals 2020, 10(7), 641; https://doi.org/10.3390/min10070641 - 20 Jul 2020
Cited by 3 | Viewed by 741
Abstract
The investigations focused on the façade of the 17th-century Myszkowskis chapel at the 13th-century Church of the Holy Trinity in Cracow, Poland. Most of the chapel’s façade is made of rusticated limestone blocks, but its lower part is covered with cement render, and [...] Read more.
The investigations focused on the façade of the 17th-century Myszkowskis chapel at the 13th-century Church of the Holy Trinity in Cracow, Poland. Most of the chapel’s façade is made of rusticated limestone blocks, but its lower part is covered with cement render, and the basement consists of irregular pieces of limestone and sandstone, bound and partly replaced with cement mortar. The façade exhibited clearly visible damages: gray soiling of the surface, cracks, scaling, and efflorescence. The study presents characteristics of the cement render and mortar used for stone repair and/or substitution, as well as efflorescence from the lower part of the Myszkowskis chapel façade. The materials were analyzed with optical microscopy, scanning electron microscopy (SEM-EDS), Raman microspectroscopy, X-ray diffractometry (XRPD), and mercury intrusion porosimetry. The analyses demonstrated that the render covering some of the decayed limestone blocks was prepared using Portland cement (residual clinker grains represent alite and belite) as a binding agent, mixed with crushed stone as an aggregate. The cement mortar consisted of rounded quartz grains, rock fragments, and feldspars in very fine-grained masses of calcite and gypsum, also containing relics of cement clinker (alite, belite, ferrite, and aluminate). All these components point out the use of the ordinary Portland cement. Analyses of the efflorescence allowed us to distinguish several secondary salts, among others, thenardite, aphthitalite, and darapskite. The appearance of these phases is related to the composition and physicochemical properties of the building materials, atmospheric alteration agents, air pollution, and some other anthropogenic factors. Full article
(This article belongs to the Special Issue Minerals and Other Phases in Constructional Geomaterials)
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Article
Brucite-Aragonite Precipitates as Weathering Products of Historic Non-MgO-Based Geomaterials
Minerals 2020, 10(7), 599; https://doi.org/10.3390/min10070599 - 30 Jun 2020
Viewed by 960
Abstract
This paper analyses the mineralogical composition, texture, and structure of a stalactite sampled from the city-wall storerooms of the Nueva Tabarca fortress (southeast Spain). This speleothem presents an uncommon mineral assemblage: aragonite, brucite, gypsum, silica, and halite. Internally, it shows complex structure: (1) [...] Read more.
This paper analyses the mineralogical composition, texture, and structure of a stalactite sampled from the city-wall storerooms of the Nueva Tabarca fortress (southeast Spain). This speleothem presents an uncommon mineral assemblage: aragonite, brucite, gypsum, silica, and halite. Internally, it shows complex structure: (1) a central soda-straw composed by aragonite; (2) an external puff-pastry cone-crust formed preferentially by aragonite and brucite; and (3) an internal branching of coralloids, showing a subtle layering between brucite and aragonite. Gypsum, halite, and silica locate in the outer coating of the cone-crust. The sequent mineral precipitation sequence has been established: aragonite > brucite > gypsum/silica > halite. Speleothem formation is directly related to the chemical weathering of the rocks and mortars used as building materials of the city-wall. Brucite precipitates has been always linked to the presence of MgO-based geomaterials. However, the lack of these compounds as building materials in Nueva Tabarca fortress makes this investigation a unique example of brucite precipitation. PHREEQC calculations showed that interaction between pore waters and the minerals of mortar aggregates (dolomite, pyroxene, and amphibole) leads to rich-magnesium solutions. Evaporation modelling of lixiviated waters describes the precipitation of the mineral assemblage of the brucite-aragonite speleothems. Full article
(This article belongs to the Special Issue Minerals and Other Phases in Constructional Geomaterials)
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Article
Multi-Technique Characterization of a Fine Fraction of CDW and Assessment of Reactivity in a CDW/Lime System
Minerals 2020, 10(7), 590; https://doi.org/10.3390/min10070590 - 30 Jun 2020
Cited by 4 | Viewed by 856
Abstract
This study analysed the fine particle (<5 mm) waste generated during siliceous or calcareous (depending on the composition of the original aggregate) concrete waste crushing. In the absence of industrial applications, such waste is amassed in open-air stockpiles on construction and demolition wastes [...] Read more.
This study analysed the fine particle (<5 mm) waste generated during siliceous or calcareous (depending on the composition of the original aggregate) concrete waste crushing. In the absence of industrial applications, such waste is amassed in open-air stockpiles on construction and demolition wastes (CDW) management plant grounds. The aim pursued was to find an outlet for that material in the cement industry. The starting waste, sourced from six Spanish management facilities, was characterised for its chemical and mineralogical composition, physical properties and pozzolanicity. The mineralogical phases in the CDW/lime system and their variations during the pozzolanic reaction were likewise identified. The findings showed that the fine waste consisted primarily in quartz, calcite, micas and feldspars, with smaller fractions of kaolinite and cement anhydrous phases. No portland cement hydration phases were identified. All six types analysed exhibited medium to low pozzolanicity, with the highest values recorded for the siliceous waste. Ettringite, C–S–H gels and calcium aluminate hydrates (C4AH13, C4AcH12) were identified during the pozzolanic reaction in CDW/lime system. Therefore, this type of waste can be reused as supplementary cementitious material with low-medium pozzolanic activity. Full article
(This article belongs to the Special Issue Minerals and Other Phases in Constructional Geomaterials)
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Article
The Relationship between Surface Roughness, Capillarity and Mineral Composition in Roofing Slates
Minerals 2020, 10(6), 539; https://doi.org/10.3390/min10060539 - 15 Jun 2020
Viewed by 607
Abstract
Roofing slates are a category of building stones which have a very distinctive feature: High fissility, which allows them to be split into tiles that are thin, regular and large. There are several types of roofing slates, depending on their lithology. The four [...] Read more.
Roofing slates are a category of building stones which have a very distinctive feature: High fissility, which allows them to be split into tiles that are thin, regular and large. There are several types of roofing slates, depending on their lithology. The four main lithologies are low-grade slates, slates stricto sensu, phyllites, and mica-schist. Occasionally, other rocks such as quartzites, serpentinites, or shales, can also be used as roofing slates. Roofing slates must ensure waterproofing, a quality that depends on both the rock and the installation. Installation must therefore take into account parameters such as the pitch, orientation, and overlap of the tiles in order to avoid capillarity, which could jeopardize waterproofing. These parameters are usually included in installation manuals. However, despite the fact that roughness is a parameter known to have an important effect on capillarity, it has never been thoroughly analyzed. Roughness varies depending on the type of roofing slate, but installation manuals do not take this factor into account. This study has measured surface roughness in different types of roofing slates using a laser scanner and determined the capillarity values along and across the grain direction. Furthermore, the role of dissolved salts in capillarity has likewise been studied. Full article
(This article belongs to the Special Issue Minerals and Other Phases in Constructional Geomaterials)
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Article
Slatecalculation—A Practical Tool for Deriving Norm Minerals in the Lowest-Grade Metamorphic Pelites and Roof Slates
Minerals 2020, 10(5), 395; https://doi.org/10.3390/min10050395 - 29 Apr 2020
Cited by 1 | Viewed by 648
Abstract
Roof and wall slates are fine-grained rocks with slaty cleavage, and it is often difficult to determine their mineral composition. A new norm mineral calculation called slatecalculation allows the determination of a virtual mineral composition based on full chemical analysis, including the amounts [...] Read more.
Roof and wall slates are fine-grained rocks with slaty cleavage, and it is often difficult to determine their mineral composition. A new norm mineral calculation called slatecalculation allows the determination of a virtual mineral composition based on full chemical analysis, including the amounts of carbon dioxide (CO2), carbon (C), and sulfur (S). Derived norm minerals include feldspars, carbonates, micas, hydro-micas, chlorites, ore-minerals, and quartz. The mineral components of the slate are assessed with superior accuracy compared to the petrographic analysis based on the European Standard EN 12326. The inevitable methodical inaccuracies in the calculations are limited and transparent. In the present paper, slates, shales, and phyllites from worldwide occurrences were examined. This also gives an overview of the rocks used for discontinuous roofing and external cladding. Full article
(This article belongs to the Special Issue Minerals and Other Phases in Constructional Geomaterials)
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Article
Nephrite-Bearing Mining Waste As a Promising Mineral Additive in the Production of New Cement Types
Minerals 2020, 10(5), 394; https://doi.org/10.3390/min10050394 - 28 Apr 2020
Cited by 3 | Viewed by 705
Abstract
A growing demand for products made of jewelry and ornamental stones, including nephrite, requires an increase in mining volume. However, only less than 30% of the extracted raw material is suitable for processing. The rest of the low grade nephrites are substandard and [...] Read more.
A growing demand for products made of jewelry and ornamental stones, including nephrite, requires an increase in mining volume. However, only less than 30% of the extracted raw material is suitable for processing. The rest of the low grade nephrites are substandard and unclaimed, and they negatively affect various life spheres. In this regard, their involvement in industrial turnover is an actual task. One of the directions of mining waste use is production of building materials, in particular, cements. The low grade nephrite can act here as mineral additives. In the course of the research, the optimal amount of low grade nephrite waste additive was determined, which is 30% of the cement mass. The grinding time of a raw mix is 10 min. It was found that introduction of the additive affects the hydration activity of cement compositions. Compressive strength of the mixed cement is 25% higher than that of the control sample. At the same time, new phases in the hydrated cement were not recorded. Good physical and mechanical properties of the obtained cements are achieved when hardening in normal humidity conditions. Heat and humidity treatments do not facilitate the hydration processes in binary systems. The conducted studies have shown that low grade nephrite can be used as mineral additives in cement production. This will allow development of not only a new type of product, but also reduction of the negative impact of cement production on the environment. Full article
(This article belongs to the Special Issue Minerals and Other Phases in Constructional Geomaterials)
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Article
Surface Weathering of Tuffs: Compositional and Microstructural Changes in the Building Stones of the Medieval Castles of Hungary
Minerals 2020, 10(4), 376; https://doi.org/10.3390/min10040376 - 21 Apr 2020
Cited by 7 | Viewed by 1035
Abstract
Volcanic tuffs have a historical tradition of usage in Northern Hungary as dimension stones for monumental construction, Ottoman architecture, common dwellings, etc., admirable at its best in the medieval castles of Eger and Sirok. This research explores tuff deterioration in the castle walls, [...] Read more.
Volcanic tuffs have a historical tradition of usage in Northern Hungary as dimension stones for monumental construction, Ottoman architecture, common dwellings, etc., admirable at its best in the medieval castles of Eger and Sirok. This research explores tuff deterioration in the castle walls, dealing with the mineralogical composition, microstructure, trace-element geochemistry, and microporosity of the surface weathering products and the near-surface stone substrate. The classic microscopic and mineralogical techniques–optical microscopy, SEM-EDS, and XRD–were supported by ICP-MS and nitrogen adsorption analyses. The textures and mineral assemblages of the tuffs are partly diverse, and so are the weathering characteristics, although including common features such as secondary crystallization of gypsum, swelling clay minerals, and iron oxides-hydroxides; deposition of airborne pollutants, i.e., carbon particles and heavy metals; formation of crusts and patinas; decreased surface microporosity. Nonetheless, the entity of deterioration varies, in relation to air pollution–involving changing emissions from road and rail transport–and the specific tuff texture, porosity, and durability–affecting pollutant absorption. The studied stone monuments offer the possibility to examine materials with analogue composition and petrogenesis but utilized in different environmental contexts, which allow pointing out the environmental and lithological constraints and cause-effect relationships related to surface weathering. Full article
(This article belongs to the Special Issue Minerals and Other Phases in Constructional Geomaterials)
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Article
Characterization of Rock Samples by A High-Resolution Multi-Technique Non-Invasive Approach
Minerals 2019, 9(11), 664; https://doi.org/10.3390/min9110664 - 29 Oct 2019
Cited by 4 | Viewed by 1198
Abstract
Three different non-invasive techniques, namely Structure from Motion (SfM) photogrammetry, Terrestrial Laser Scanner (TLS) and ultrasonic tomography integrated with petrographic data, were applied to characterize two rock samples of a different nature: A pyroclastic rock and a carbonate rock. We started a computation [...] Read more.
Three different non-invasive techniques, namely Structure from Motion (SfM) photogrammetry, Terrestrial Laser Scanner (TLS) and ultrasonic tomography integrated with petrographic data, were applied to characterize two rock samples of a different nature: A pyroclastic rock and a carbonate rock. We started a computation of high-resolution 3D models of the two samples using the TLS technique supported by a digital SfM photogrammetry survey. The resulting radiometric information available, such as reflectivity maps, SfM photogrammetry textured models and patterns of geometrical residuals, were interpreted in order to detect and underline surface materials anomalies by a comparison of reflectance and natural colour anomalies. Starting from the 3D models from previous techniques, a 3D ultrasonic tomography on each rock sample was accurately planned and carried out in order to detect internal defects or sample heterogeneity. The integration of the above three geophysical non-invasive techniques with petrographical data—especially with the textural characteristics of such materials—represents a powerful method for the definition of the heterogeneity of the rocks at a different scale and for calibrating in situ measurements. Full article
(This article belongs to the Special Issue Minerals and Other Phases in Constructional Geomaterials)
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Article
Mineralogy and Leachability of Natural Rocks–A Comparison to Electric Arc Furnace Slags
Minerals 2019, 9(8), 501; https://doi.org/10.3390/min9080501 - 20 Aug 2019
Cited by 6 | Viewed by 1857
Abstract
In waste management, recycled and industrial aggregates (e.g., electric arc furnace (EAF) slags) for construction applications have to fulfil the limit values with respect to the total and/or leachable contents of potentially environmentally problematic chemical elements (PEPE, e.g., Cr, Ni, Cu, Mo, V). [...] Read more.
In waste management, recycled and industrial aggregates (e.g., electric arc furnace (EAF) slags) for construction applications have to fulfil the limit values with respect to the total and/or leachable contents of potentially environmentally problematic chemical elements (PEPE, e.g., Cr, Ni, Cu, Mo, V). Natural aggregates, i.e., quarried hard rocks, are neither tested nor regulated for these parameters in most EU member states, e.g., Austria, prior to using them as a construction material. The purpose of this study was to relate the mineralogy to the leachability of natural aggregates with a special emphasis on PEPE and to interpret these findings in comparison with EAF slags. Five samples of Austrian rocks were investigated by polarization microscopy, electron probe microanalyses (EPMA), X-ray diffraction (XRD), and leaching tests as well as by hydrogeochemical modelling using LeachXSTM. Two samples showed elevated total contents of Cr, Ni, and Mo which were present as Cr-spinel, (Fe,Mg)(Al,Cr)2O4, Ni-olivine, (Fe,Mg,Ni)2SiO4, and molybdenite, MoS2. Whereas the former two phases also controlled the leaching of Cr and Ni, the observed leaching of Mo was higher than expected in the case of solubility control by molybdenite. In summary, the leachability of PEPE in natural and industrial aggregates was controlled by similar mineralogical mechanisms. Full article
(This article belongs to the Special Issue Minerals and Other Phases in Constructional Geomaterials)
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Review

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Review
Establishment of Intrinsic Permeability of Coarse Open-Graded Materials: Review and Analysis of Existing Data from Natural Air Convection Tests
Minerals 2020, 10(9), 767; https://doi.org/10.3390/min10090767 - 29 Aug 2020
Viewed by 533
Abstract
This paper presents a review and analysis of large-scale air convection tests and the establishment of intrinsic permeability in coarse open-graded materials. Natural air convection can make a significant contribution to heat transfer during cooling periods. In seasonally freezing environments this can result [...] Read more.
This paper presents a review and analysis of large-scale air convection tests and the establishment of intrinsic permeability in coarse open-graded materials. Natural air convection can make a significant contribution to heat transfer during cooling periods. In seasonally freezing environments this can result in excessive frost penetration and subsequent frost-related problems. Intrinsic permeability largely defines the onset of convective heat transfer in granular materials. Conventional methods for measuring intrinsic permeability cannot be applied to very coarse materials. Large-scale laboratory experiments on natural air convection can serve as an alternative method for determining this crucial parameter. This paper gives an overview of four different experimental test setups for measuring natural air convection, all differing in physical shape, boundary conditions and heat flux/temperature measurement devices. Comparison between these is difficult because the air convection pattern can differ and in some cases the shape and number of convection cells cannot be validated. Most of the studies available in the literature use theoretical equations to approximate intrinsic permeability. A method based on the analytical Nu-Ra number relationship is employed to establish the values of intrinsic permeability. Tests that provide enough data to enable the use of the Nu-Ra relationship are very limited. The overall results show a reasonable correlation between experiment-based intrinsic permeability and theoretical approximation. However, several issues must be addressed: first, differences may exist between the intrinsic permeability of natural and of crushed materials due to the shape effect. Second, the method used is in theory valid only for two-dimensional air convection within a square enclosure heated from below. Yet the results show that this method could be extended to other conditions with a certain degree of confidence. Third, a good estimate of intrinsic permeability is possible only with accurate experimental measurement. Full article
(This article belongs to the Special Issue Minerals and Other Phases in Constructional Geomaterials)
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