Quartzite Mining Waste: Diagnosis of ASR Alkali-Silica Reaction in Mortars and Portland Cement Concrete

Abstract

The main objective was to determine the deleterious potential of quartzite mining tailings subjected to different ASR alkali–silica reaction tests. The studies included petrographic analysis, chemical analysis of cements, expansion tests in mortar bars and concrete prisms, and microstructural analysis. Petrographic analysis of quartzites indicated high percentages of deformed quartz (95%), and were classified as potentially reactive. Two types of HES high early strength cement with alkaline equivalents of 0.749% and 0.61%, respectively, were selected. Of the 8 samples analyzed by the accelerated method in mortars, only 2 quartzite samples and 1 diabasium sample indicated potentially reactive behavior. The accelerated and long-term methods in concrete prisms proved to be effective and were consistent with the deleterious potential of the samples. All analyzed samples were diagnosed with the ASR gel. In the microstructural analysis, in addition to the ASR products, other expansive products of late ettringite were detected. Reaction mitigation methods are proposed so that quartzite waste can be used as an alternative aggregate in concrete, and thus contribute to the reduction of mine tailings and, consequently, reduce the negative environmental impact from mining.

Amethyst quartz tailings in cement mortars production

“…The second factor is low compaction of the internal structure of quartzite has been incorporated. This leads to a significant decrease in internal stresses [22,44].…”

“…As a substitute for quartz sands, quartzites can be used as long as they have an adequate granulometry for their application in the civil construction industry [18]. Some relevant research that evaluated the use of quartzites, for example, as recycled aggregates in self-compacting concrete for environmental sustainability [19]; incorporation of fillers from marble and tile wastes in the composition of self-compacting concretes [20]; quartzite residues on concrete and mortars, analyzing mechanical behavior and reaction alkali-silica [21,22]; verifying compactness and properties of the hardened state of mortars with quartzite residues [3] verifying its mechanical behavior and its durability when attacked by sodium sulfate [23], investigating the specific heat of cement-based composites and the factors influencing it coating mortars friable quartzite [24] as well as several studies that aim at the processing and application of quartzite tailings acting as a non-plastic material in mortar traces or even as a substitute for part of the silica in the production of these materials [25,26], but few on amethyst quartz tailings used in civil construction.…”

Rejeitos de quartzitos do Sul de Minas Gerais: estudo da fração fina para a produção de concretos de pós reativos e diagnóstico da reação álcali-agregado

“…Isto acontece porque o quartzito comercializável é extraído em placas padronizadas, que atendem a padrões de espessura, largura e comprimento. O rejeito gerado nos processos de lavra e de beneficiamento da "pedra mineira", portanto, constitui um grave problema para os empreendedores, dados os impactos socioambientais negativos, tais como: desconfiguração da paisagem, alterações na conformação natural do relevo, assoreamento dos corpos d'água, supressão da vegetação nativa, instabilidade em taludes de rejeitos de mineração, dentre outros (FRANCKLIN JUNIOR et al, 2021;REIS et al, 2020). É o que demonstra a Figura 1.1.…”