Characterization of Slate Powder Wastes from Minas Gerais - Brazil

Abstract

Research and development related to the processing of recycled materials has grown progressively in recent times, as scientists endeavour to integrate sustainability criteria, depletion of natural resources, reducing the energy of technological processes involving extraction and processing of raw materials, etc. When it comes to processing slate, industries have to pass over several steps ranging from the extraction of rock blocks until the final products consisting of plates, leaving behind a considerable amount of waste in the form of a mud composed mainly of water, lubricants and crushed rock. This waste with no defined destination accumulates in yards, reservoirs and streams, affecting the environment. Slate powder has great prospects for recovery, recycling and further applications once it has chemical composition and components similar to raw materials used in ceramic and building construction industries. Therefore, a complete characterization of this powder is important and here we present some results of XRD, SEM, EDS, G3 morphology and thermal analysis of slate powder samples from the southeastern state of Minas Gerais in Brazil.

Towards a Sustainable Mining: Reuse of Slate Stone Cutting Sludges for New Geopolymer Binders

“…This low value reflected that organic material (caused by an unburned percentage of carbon) was not present. These results corroborated the state of the art related to the mineralogical classification of slate stone as a low-grade metamorphic grade, with mainly the presence of quartz and phyllosilicates [30,33]. Table 4 shows the XRD quantitative analysis expressed in wt.%.…”

“…The presence of iron oxide also improves the overall properties of the final geopolymer. As reported in the previous literature about the high percentage of silica and alumina of slate stones [30][31][32][33], the SiO 2 /Al 2 O 3 relation accounts for 2.28 wt.%. The SiO 2 /Al 2 O 3 ratio has a relevant role in the bulk density and compressive strength of the geopolymer, and their variations can decrease or increase the compressive strength value.…”

“…Therefore, the motivation for the present research paper was to develop and study the properties of a new mining waste geopolymer-based slate stone as a source of aluminosilicates for potential construction applications. Previous scientific studies have demonstrated, by mineralogical and chemical analysis, that slate stone from Brazil [30], Angola [31], Indonesia [32], and Spain [33], among others, has a high percentage of alumina and silica in its composition. Therefore, slate stone cutting sludge (hereinafter referred to as SSCS) from metamorphic rocks becomes a potential source of aluminosilicates for geopolymers.…”

Evaluación de la reactividad puzolánica de residuos de pizarras del depósito Tchihingue en Angola: Influencia de la composición mineralógica

“…Según una declaración ambiental realizada por la Asociación Galega de Pizarristas (AGP), la pizarra es uno de los productos más sostenibles para cubiertas, si se compara con otros materiales usados para esta aplicación, el fibrocemento y la teja cerámica que emiten más dióxido de carbono y consumen más agua y energía en su producción [15]. Sin embargo, la extracción de pizarra para su uso como material de construcción genera grandes cantidades de residuos (entre 75 % y 90 % en masa), que son vertidos en escombreras, y por consiguiente trae problemas económicos, ambientales y sociales [2,[16][17][18]. Se han realizado varias investigaciones para el empleo de estos residuos, los cuales se enmarcan fundamentalmente en su valorización como áridos ligeros [19][20][21][22][23][24][25][26], empleo en mejoramiento de pavimento [18,21,27,28] y como materia prima para la industria cerámica [16,28,29].…”

“…Sin embargo, la extracción de pizarra para su uso como material de construcción genera grandes cantidades de residuos (entre 75 % y 90 % en masa), que son vertidos en escombreras, y por consiguiente trae problemas económicos, ambientales y sociales [2,[16][17][18]. Se han realizado varias investigaciones para el empleo de estos residuos, los cuales se enmarcan fundamentalmente en su valorización como áridos ligeros [19][20][21][22][23][24][25][26], empleo en mejoramiento de pavimento [18,21,27,28] y como materia prima para la industria cerámica [16,28,29]. El uso de estos residuos como material puzolánico ha sido poco extendido debido a su baja reactividad [13,[30][31][32].…”