Roofing Slate Research Articles

Characteristics of an underground stope channel supplied by atmospheric precipitation and its water disaster prevention in the karst mining areas of Guizhou

Atmospheric precipitation floods mining areas, which seriously affects the safe production of coal mines. However, research on the mechanism underlying precipitation supplying coal mines, particularly in karst landform areas, remains far from sufficient. Based on the collection of a large amount of geological and hydrogeological mining data and some data related to mine atmospheric precipitation and mine water inflow, the channels of atmospheric precipitation supplying mines in the main coal-producing areas of Guizhou, China, are systematically analysed and studied. They are divided into weathering zone fractures, mining fractures, water diversion faults, water diversion collapse columns and karst channels. Recharge channels have the characteristics of surface infiltration, pipeline flow and layered recharge, as well as self-healing after being filled by surface loess and other materials. The supply of atmospheric precipitation to the coal mine stope is seasonal. The mine water inflow in the rainy season is 1.2 ~ 12 times that in the dry season, with an average of 1.9 times. The supply has hysteresis. The lag time of surface infiltration, pipeline flow and layered flow is 2 ~ 4 days, within 24 h and more than 2 days, respectively. The recharge is affected by the burial depth of the coal seam and the characteristics of the combined upper roof slate. Among the mines affected by atmospheric precipitation and water disasters, some mines have carried out research on the comprehensive treatment of water disasters, implemented supplementary exploration projects such as surface hydrogeological drilling and geophysical exploration, or carried out hydrochemical research. Some mines have adopted water prevention and control projects, such as blocking ground water diversion cracks, constructing water diversion projects, adjusting the mining time of the working face, transforming the drainage system and improving the drainage capacity, to ensure the safe production of mines. This research achievement may provide a theoretical basis and practical experience for the prevention and control of atmospheric precipitation infiltration in coal mines in karst areas.

Construction of Asbestos Slate Deep-Learning Training-Data Model Based on Drone Images.

The detection of asbestos roof slate by drone is necessary to avoid the safety risks and costs associated with visual inspection. Moreover, the use of deep-learning models increases the speed as well as reduces the cost of analyzing the images provided by the drone. In this study, we developed a comprehensive learning model using supervised and unsupervised classification techniques for the accurate classification of roof slate. We ensured the accuracy of our model using a low altitude of 100 m, which led to a ground sampling distance of 3 cm/pixel. Furthermore, we ensured that the model was comprehensive by including images captured under a variety of light and meteorological conditions and from a variety of angles. After applying the two classification methods to develop the learning dataset and employing the as-developed model for classification, 12 images were misclassified out of 475. Visual inspection and an adjustment of the classification system were performed, and the model was updated to precisely classify all 475 images. These results show that supervised and unsupervised classification can be used together to improve the accuracy of a deep-learning model for the detection of asbestos roof slate.

Fire resistance of roofing slates: Mechanical, mineralogical and aesthetic changes alongside temperature increase

Fire is a major destructive agent for dimension stone. Practically all historic buildings have suffered one or more fires over the course of their lifespan. There are numerous studies on the effect of fire on stone. Generally speaking, these effects can be divided into aesthetic and structural. Aesthetic effects involve a color shift to reddish hues, due to the oxidation processes triggered by temperature increase. Moreover, structural effects involve the formation of cracks and delaminations that may cause the rock to disintegrate. However, even though roofing slates are a group of metamorphic rocks that are widely represented in the historical architectural heritage of many European countries, none of the scientific studies alluded to above have taken them into account. The present study examines 6 lithotypes, covering the metamorphic range of rocks used as roofing slates. The roofing slates were subjected to a heating test reaching 900 °C, and then analyzed using X-ray diffraction and fluorescence, Thermogravimetric and Differential Thermal analyses, and were also tested for bending strength and water absorption following the European standard for roofing slates, EN 12326. All samples studied exhibited a reduction in their bending strength, together with an increase in water absorption. Likewise, the oxidation processes triggered by the high temperatures induced a general oxidation of the iron, lending all of the samples a reddish hue. On the other hand, the roofing slate samples proved to be non-combustible and did not release any toxic or hazardous fumes.

Study on the Deformation Mechanism of the Bottom Plate along the Empty Lane of Deep Mining and the Control Technology of the Bottom Drum

Aiming at the problem of the deformation of the roadway floor plate during the laneway during the retention period, the mechanical model of the roadway floor is established, and the deformation characteristics of the roadway floor and the change law of the bottom drum are studied and analyzed through theoretical calculation and calculus simulation, revealing the instability mechanism of the surrounding rock of the roadway under the stress disturbance environment, and when not affected by the adoption, the roadway forms a certain stress concentration area within the effective range of support. During mining, under the comprehensive action of the original peripheral stress field and the mining stress field, the cliffhanger is unstable under the comprehensive action of the original peripheral stress field and the mining stress field, and the extrusion and stretching effect of the unflapped part of the rock layer above the goaf section of the coal seam is set up along the air, resulting in violent deformation such as the bottom drum, and the rotational sinking of this part of the unflinted rock layer further aggravates the transfer of the overburden load to the surrounding rock of the lane, so that the surrounding rock along the empty lane is subjected to a large additional stress, and the mining stress field plays a leading role, and the mining stress “far field” is the compound stress field, of which the tensile stress is the leading destructive factor. The deformation of the surrounding rock is mainly based on the bottom, and the horizontal stress on the bottom plate along the empty lane is mainly generated by the horizontal strain that occurs after the lower rock layer of the filling body and the coal gang is subjected to the supporting pressure transmitted by the top plate. With the mining of the working surface, the roof of the goaf area is broken and collapsed to form the characteristics of “vertical three belts,” which is affected by the “large support” of the coal body of the working surface and the “small support” of the surrounding rock along the empty roadway, and the pressure relief of the cut roof can make the roof plate along the empty lane change from the “long arm beam” structure when the roof is not cut into the “short arm beam” structure, blocking the lateral stress of the goaf area to the roof plate of the alley and significantly reducing the degree of stress superposition of the roof plate of the alley. The technical means of blasting cutting roof active pressure relief and protective lane are used to block the transmission of lateral support pressure, the roof slate layer is precracked in advance, the sinking of the rock layer is accelerated, the disturbance time is reduced, the vertical stress of the rock layer and the rock layer above it along the empty roadway is reduced, the vertical stress concentration of the roadway is reduced, the stress concentration coefficient is reduced, the degree of damage of the surrounding rock after the top is weakened, the damage range is reduced, and the technical problem of large deformation prevention and control along the bottom drum of the empty alley can be solved. Constructing the mechanical structure model of the top plate of the cut top pressure relief and the uncut top pressure relief along the empty lane, the stress change characteristics of the active protective rock surrounding rock along the hollow top of the cut top pressure relief were calculated, and after the technical scheme of the blasting cut top active pressure relief and protection lane was adopted, the deformation along the empty roadway was significantly weakened, the stability of the surrounding rock of the roadway after the blasting of the cut roof was significantly improved, the maintenance state along the section of the empty roadway was good, and the cross-sectional convergence rate was reduced by 37.3% compared with the original section. Cutting the roof active pressure relief and protective lane can effectively improve the stability of the surrounding rock.

Methods for assessing asbestos-containing roofing slate distribution in an area with poor dwelling conditions

In South Korea, asbestos has been used in large quantities for manufacturing asbestos cement roofing slates (ACRS) and the production and use of all types of asbestos were completely banned in 2009. Asbestos containing materials in buildings and ACRS are linked to environmental and human health problems. An area with poor dwelling conditions was selected as the study area, and all buildings (76) were examined for ACRS. Three survey methods were compared, namely, field investigation, building registers, and data collection using unmanned aerial vehicles (UAVs). The field investigation results reported 2785.3 m2 of ACRS in a total of 38 buildings. The results were significantly different from those of the building register survey (1255.8 m2 for 11 buildings) and the UAV survey (1043.7 m2 for 18 buildings). The building register and UAV survey methods were limited by incomplete data or data unavailability, when compared with the data associated with the field investigation. However, the former approaches require less labor and time, with decreased exposure of the investigators to asbestos. Therefore, the organic combination and proper application of such methods can reduce labor and time required to conduct surveys and yield sufficient accuracy.

Crystallographic preferred orientation, seismic velocity and anisotropy in roofing slates

Mica-rich rocks (shales, slates, schists) are a major and significant component of the continental crust. They are often characterized by a strong seismic anisotropy, a key factor in the seismic interpretation of the architecture of the continental crust. Roofing slates are a group of natural rocks used in construction that must possess a continuous and undeformed slaty cleavage. This makes roofing slates an exceptional benchmark to study the relation between the rock microstructure and the development of seismic anisotropy in single-foliated low-grade slates. Direct measurements of seismic velocities using an ultrasonic wavemeter at room conditions were done on eight cubic samples from active quarries in the NW Iberian Peninsula. Seismic velocities were also calculated using the Hill averaging method from crystallographic preferred orientation (CPO) maps of slate-forming minerals on the same sample blocks using electron backscatter diffraction (EBSD), achieving unprecedented coverages of up to 87%. The seismic velocities estimated by both methods are similar parallel to the slaty cleavage but much slower using direct measures in the axial direction, producing anisotropies for Vp and Vs1 up to 7 and 5 times higher than the calculated velocities. The results are indicative of the highly anisotropic contribution that cracks, pores and fractures have in single-foliated slates, given the strong shape fabric that the rocks present. The samples selected also show that not all slates exhibit near-transverse isotropy, as it has been commonly assumed.

The Relevance of the Green Phyllites of Lugo (Spain) in the Architectonical Heritage: an Exceptional Roofing Slate Resource

In the NW of the Iberian Peninsula, in the region of Lugo, a very exclusive Cambrian phyllite has been quarried and used for construction since prehistoric times, the Filita Verde or green phyllite. There are three varieties of this stone, all of them with the characteristic glitter of phyllites given by the metamorphic recrystallization of the phyllosilicates. Most of the architectural heritage of the area was built with this stone, which is currently being exported abroad. Its exceptional aesthetic and constructional characteristics have been historically used to build fortified settlements (Castros) by ancient pre-Roman cultures and also to construct churches and other ecclesiastic buildings during the middle age. Nowadays it is highly appreciated by architects. Because of these facts, this stone is a good candidate for the designation as a Global Stone Heritage Resource.

Stone roofing in the Aosta Valley, Italy: Technical properties and durability of traditional Lithotypes

The Aosta Valley Region has promulgated in 1990 a law to partially finance stone roofs to the owners of houses in the historic centers of the valley, provided that the stone material chosen was suitable for this use. This suitability was certified by physical, mechanical and durability tests. More than twenty years ago, roofing slabs were extracted in north-western Alps mainly from schistose rocks. In recent time instead roofing slabs, according to global market, have an international origin. All the traditional stones tested showed excellent technical features according to the local legislation on roof slates. One of these traditional stones is a phyllite whose trade name is “Porfiroide” having the best physical and mechanical properties compared to the other kinds of traditional stones, but with a high standard deviation in the results of flexural strength performed after the freeze and thaw cycles. In the roofing installed 40 years ago, despite their best technical features, the “Porfiroide” roof slabs show a poor state of conservation with widespread detachments, fractures, growth of mosses and lichens, variations in colours. Otherwise, stones with a lower value of flexural strength and higher water absorption instead show good behaviour in the roofing in situ and also in terms of colour change.Evidently the only characterisation of the stone materials is not sufficient but it must be associated to a on-site verification, comparing each slab to be installed with a reference sample, part of the sample submitted to the tests, and to a control on site of the resistance of the stones to degradation.

The Relationship between Surface Roughness, Capillarity and Mineral Composition in Roofing Slates

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.

Definition of Roofing Slate Lithotypes for an International Roofing Slate Classification

The term “roofing slate” comprises all natural rocks that can be used for roofing. Some of the characteristics that define their performance as construction materials are water absorption, bending strength, mineral composition, and aesthetics. From a sustainability point of view, roofing slates also have the largest life expectancy and lowest carbon emissions of all covering materials. This work reviews the constructive characteristics of roofing slates, from technical data provided by producers from all over the world. These data, supported by the petrological characterization of several roofing slate samples, are used to propose a general classification for this special type of rock. Thus, roofing slates are sorted in twelve lithotypes, depending of their petrographical characteristics, defined by the color. The resulting classification is named International Roofing Slate Classification (IRSC), formally defined in this paper.

Slatecalculation—A Practical Tool for Deriving Norm Minerals in the Lowest-Grade Metamorphic Pelites and Roof Slates

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.

Deformation Mechanism and Stability Control of Roadway Surrounding Rock with Compound Roof: Research and Applications

In view of problems with roadways with a compound roof, such as the occurrence of instability in the roof strata, ease of separation of the layer caving, difficulty of maintenance, and poor safety, we established a mechanical calculation model of a roadway with compound roof using the elastic mechanics theory, taking the stability control of a roadway with compound roof at a coal mine in Guizhou Province, China as the research background, and based on the actual characteristics of the coal seam and the roof and floor slate. Expressions of the separation layer and instability limit load of compound roof were derived, and the calculation and verification were carried out in combination with the actual conditions. By means of numerical simulation, the distribution and evolution laws of stress, displacement and plastic zone of roadways with a compound roof were studied, and the deformation characteristics and instability mechanism of roadways with a compound roof were revealed: (1) in early stage deformation of roadway, the amount is large, the speed is fast, and the scale is wide; (2) compound roofs are vulnerable to abscission and instability, the bearing capacity of the two sides is low due to softness and cracking, the shear failure of side angles and vertex angles weakens the strength of surrounding rock, and the self-bearing capacity of surrounding rock is low; (3) the bolt and anchor bear relatively large tensile force, and the support structure is easy to be broken up. On this basis, the stability control principle of a roadway with compound roof tunnel was put forward: fast and timely support; high-strength bolt strong support; improving the stability of the roof and the bearing capacity of the two sides; restraining the shear failure of the key bearing parts such as the side angles and the bottom angles, and targeted stability control technology for roadways with a compound roof was developed. The field industrial test showed that the deformation of this roadway with a compound roof was effectively controlled and the overall stability of the roadway was effectively improved. The results of this study could provide useful reference for a roadway with a compound roof under similar conditions.

Selbukassa - A Case Study for Aiming at Low Emission Buildings through Extensive Reuse of Materials

Recent reports from UN International Resource Panel call for double decoupling – decoupling of material use and related environmental impacts from economic growth. The construction and use of buildings constitute a significant portion of energy use, GHG emissions and extraction of materials in Europe. One of the central strategies addressing double decoupling in the construction industry is reuse and recycling of building materials and components that would limit raw material extraction and embodied emissions related to new products. A recent IPCC report states the urgency of limiting GHG emissions already by 2030 to remain below the 1.5-degree target. Given this timeframe, reducing emissions in the early stages of a buildings lifetime appears worth considering, meaning prioritizing embodied over operational emissions. The case study used for this article is an ongoing building project “Selbukassa” (“the Selbu box”) situated in Svartlamon – an experimental neighbourhood for urban ecology in Trondheim, Norway. It is a bottom-up, self-build project with a strong focus on reuse of materials. The 300 m2 building will house 4 families and is built reusing an old log house, as well as CLT-elements from a former pavilion used for exhibiting an art piece by the local artist Killi Olsen. Other salvaged materials and components include windows, doors, roof slate and most of the internal and external finishes. Due to the experimental status of the area and to allow for reuse of building components with lower energy performance, the fulfilment of energy requirements in the building code TEK 17 was not required by the local building authorities. The article examines the embodied and operational emissions of Selbukassa, and compares it with a reference building with no reused components and complying with energy requirements in the building code TEK17. Simien v.6.009 is used for energy simulations of the two cases, and LCA tool One Click LCA Norge for NS 3720:2018 with data sourced from Norwegian and other European EPDs is used for estimating embodied emissions. The article investigates the possible savings in emissions linked to reuse of materials, as well as the trade-offs between reused components with worse energy performance and the consequential higher energy demand. The article contributes to the discussion about the various implications of reuse of materials and more generally on how the built environment could respond more optimally to a combined emission and resource use reduction challenge.

Archaeological prospections in the Roman vicus Belginum (Rhineland-Palatinate, Germany)

Abstract. The Roman vicus Belginum and the associated Celtic–Roman cemetery have been the subject of systematic archaeological research since 1954. Since 2004, archaeological prospections have been carried out in and around Belginum. Participants included students from the universities of Leipzig, Trier, and Munich as part of study-accompanying field work. This paper deals with the prospections of 2004 and 2016, when nearly 2 ha of land south of the federal road B327 (Hunsrückhöhenstraße) were surveyed. The study area is located on a NW-to-SE-running hillside. All non-local objects present on the surface were collected and three-dimensionally recorded. Previously in 2013, the area was geomagnetically prospected by Posselt & Zickgraf (Marburg). Both surveys revealed a hitherto unknown extent of the vicus about 200 m to the southwest. The findings date back to the late first to third centuries common era. All finds (ceramic, bricks, roof slate, glass, and metal) were recorded and analysed in a QGIS and ArcGIS environment together with lidar scans, the geomagnetic data, and other geographical information. The overall distributions of bricks and pottery were studied in detail. The distribution of bricks is in particular connected to the individual plots, while the pottery is mainly concentrated in the backyards. Regarding surveys in other Roman vici, the brick distribution could be a helpful indicator to identify plots, when no geophysical information is available.

Discussion on ‘Utilization of X-ray computed micro-tomography to evaluate iron sulphide distribution in roofing slates’: Quarterly Journal of Engineering Geology and Hydrogeology , Vol. 51, 2018, pp. 169–178

The paper presented by Vavro et al . (2018) is an interesting application of a relatively new technique, X-ray computed micro-tomography (MCT), for the determination of iron sulphides in roofing slates. Once the slate shingles are installed on a roof, these iron sulphides may oxidize, creating unattractive red stains running along the roof surface. This pathology is considered to be the main technical problem for the roofing slate industry (Cardenes et al . 2016 a ). In their paper, Vavro et al . (2018) explain how the use of MCT allows quantification of the amount, size and spatial distribution of the iron sulphides on two samples of roofing slates. However, their work misses some important …

Utilization of X-ray computed micro-tomography to evaluate iron sulphide distribution in roofing slates

Slate is a traditional stone product that has long been used for roofing widely around the world. The presence of iron sulphides is one of the most significant factors affecting roofing slate resistance to weathering and, therefore, the quality of slates and their use in construction. Iron sulphide oxidation is the main process of roofing slate degradation. Qualitative and quantitative analyses to determine iron sulphides in roofing slates are usually conducted using transmitted and reflected light microscopy, and X-ray diffraction techniques. However, this paper presents X-ray computed micro-tomography as a new laboratory method in this field, which also allows for 3D visualization and analysis of iron sulphide distribution in roofing slates. It also discusses some technical limits of this technique and tomographic scan interpretation pitfalls. The results obtained by tomographic observations were subsequently verified by optical microscopy, X-ray powder diffraction and scanning electron microscopy, as well as energy-dispersive X-ray spectroscopy analyses. Spanish slate from the Ordovician Luarca Formation and Culm slate from the Moravice Formation in the Czech Republic are both characterized by low to extremely low iron sulphide content, and for this reason were selected for this study.

Design of Post-Consumer Modification of Standard Solar Modules to Form Large-Area Building-Integrated Photovoltaic Roof Slates

Building-integrated photovoltaic (BIPV) systems have improved aesthetics but generally cost far more than conventional PV systems because of small manufacturing scale. Thus, in the short and medium term, there is a need for a BIPV mounting system that utilizes conventional modules. Such a design is provided here with a novel modification of conventional photovoltaic (PV) modules to allow them to act as BIPV roofing slates. The open-source designs for the mechanical components necessary to provide the post-consumer conversion for a conventional PV module are provided, and prototypes are fabricated and installed on a mock roof system along with control modules mounted conventionally. The approximately U.S.$22/module BIPV roof-mounted system is direct mounted on the roof to eliminate the need for roofing shingles or other coverings, which effectively provides a 20% total cost reduction from conventional racking systems that demand a roof to mount upon without considering the savings from the rack itself. The results of the outdoor system testing found no water leaks. An increased operating temperature was observed, which would reduce the output from a silicon-based PV module by less than 10%. The results found significant potential for this design to further reduce total PV systems costs.

Revitalising Collyweston limestone slate production by artificial freeze/thaw splitting

Extraction of limestone roofing slate from Collyweston was an industry which was considered extinct by the early 1990′s, with building repairs relying on wholesale recycling of roofing from demolished buildings. Traditionally stone extracted from the mines was exposed to natural cycles of freeze/thaw to facilitate splitting. Work was undertaken over several years to investigate the resources available and whether these could be artificially frozen to produce slates. The work identified a freeze/thaw regime which could be used to produce roofing slates for historic buildings and which were used in the Historic England restoration of Apethorpe Palace. Mining of the Collyweston limestone stone has now resumed and uses artificial freezing to achieve production of slates which is economically feasible due to the faster process time.

Roofing Slate Industry in Spain: History, Geology, and Geoheritage

Spain is one of the leading producers of dimension stone and the biggest producer of roofing slate in the world. As a result, the roofing slate industry has shaped the landscape in some regions of Spain. The industry goes back to the 1500s, and over the centuries it has had its ups and downs. In the 1960s, Spain became the industry’s undisputed leader, accounting for up to 90% of world production. Today, Spain’s roofing slate industry continues to be the largest in the world, despite the emergence of new slate-producing countries. The intensive modern extraction methods used in mines and quarries tend to destroy the vestiges from earlier periods in the history of the industry. On the other hand, quarry work has unearthed exceptional geological structures that form part of the geoheritage of this industry. This paper describes the history and geology of the Spanish roofing slate industry and evaluates the potential geoheritage linked to this industry.

A Low Temperature Detoxification Method for Treatment of Chrysotile-Containing Waste Roofing Slate

In this study, we evaluated a two-step process for detoxification of waste roofing slate, involving cement hydrate removal and low temperature detoxification using oxalic acid. These treatments were conducted on raw material and intermediate product, respectively. Cement hydrate removal effectively eliminated most Ca-containing cement hydrate components from the raw material under the following conditions: HCl to solid ratio: 0.456 g/g, reaction time: 2 h, and solid to liquid ratio: 0.124 g/mL. Following low temperature (~100 °C) detoxification of intermediate product obtained after cement hydrate removal, chrysotile in waste roofing slate was effectively transformed to Mg-oxalate under conditions of oxalic acid to solid ratio of >0.67 g/g.