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.

The quartzite found in rock formations in the Southwestern Minas Gerais - Brazil has been, along the years, explored and commercialized as “coating stone”. The quantity of waste coming from the processing and exploration process, however, is superior to 90% from the extracted product in most of the mining sites, determining a serious environmental passive. This work presents results which can motivate the alternative use of the materials that are dumped on piles of waste. The research involved a petrographic analysis of quartzite occurring in the principal mines of the region; evaluation of aggregates produced in two kinds of crushers; evaluation of the physical and mechanical properties of the rock and evaluation of the physical and mechanical properties of the concrete manufactured with the quartzite aggregate. The results of the technological tests carried out on the rock material were satisfactory and meet all the specifications for the use in concrete. The samples of concrete prepared with the quartzite aggregate presented results of strength similar to the ones manufactured with the aggregate which are used commercially in the region today.

Introduction: The municipality of São Thomé das Letras, in the southeastern region of Brazil, is an important quartzite-producing center. The extraction process generates approximately 90% waste based on the raw material extracted. To mitigate this impact, utilizing this waste in Reactive Powder Concrete (RPC) has emerged as a viable solution. However, studies on its durability are still scarce, especially on the possibility of alkali-silica reactivity. Thus, this study analyzed the potential for alkali-silica reactivity (ASR) in RPC bars produced with quartzite waste. The experimental approach included the characterization of the constituent materials, petrographic analysis of the quartzite, expansion test by the accelerated bar method, and microscopic analysis using Scanning Electron Microscopy (SEM), including active silica to assess its effects in one batche. The petrographic analysis revealed approximately 95% silica content on quartzite, where tests with the inclusion of active silica in RPC samples effectively mitigated the potential negative impacts of ASR. The average expansion index was low, and no typical reaction products were detected by SEM. However, peaks related to silico-alkaline compounds were recorded in the energy dispersive spectroscopy by EDX, therefore, ASR analysis should be conducted on RPC prisms using both accelerated and long-term methods. The diagnosis of ASR in quartzites corroborated the need to investigate the chemical reactions induced by ASR in special concretes made with these aggregates. In conclusion, based on the results obtained, quartzite tailings can be effectively used as an alternative aggregate in RPC, thereby reducing the amount of mining waste and minimizing negative environmental impacts. Objective: The objective of this study is to investigate the alkali-silica reactive potential in reactive powder concretes produced with the fine fraction of quartzite waste, and thereby verify the possibility of using this material as an alternative aggregate in special concretes. Theoretical Framework: Alkali-Silica Reaction (ASR) is a concrete pathology in which alkalis in cement react with silica in the aggregate. This reaction forms an expansive gel that causes structural deterioration. Mitigation involves limiting alkalis, reducing porosity, and using cements with additives. Reactive Powder Concrete (RPC) emerges as a sustainable alternative, using quartzite mining tailings as aggregate. It can also mitigate ASR with the use of silica fume and dosage studies that enable low porosity. Method: The methodology adopted for this research comprises producing two batches of RPC for each quartzite rejetct collected, one batch containing active silica and the other without. The research method included determining the chemical compositions of the cement to determine the alkali content, petrographic analysis of the quartzite samples, expansion testing using the accelerated method, and microstructure analysis using SEM. The batches were made with CP V-ARI concrete, distilled water, a small concentration of NaOH and stainless steel pins fixed at the ends of the molds. Data collection was carried out through the tests described above, and the interpretation of the results. Results and Discussion: The results obtained revealed a low average expansion in RPC samples, no typical reaction products detected by SEM analysis. Despite these results, ASR analyses should be conducted on RPC prisms using accelerated and long-term methods, given the alkali-silica peaks detected in the EDX analysis. In addition, expansion products typical of late ettringite were detected on the surface of the aggregates. The ASR diagnostic tests on quartzites corroborated the importance of investigating the chemical reactions induced by ASR in RPC with this aggregate. Research Implications: The practical and theoretical implications of this research are discussed, providing insights into how the results can be applied or influence practices in the field of reactive powder concrete. These implications could encompass the alkali-silica reactive potential in in reactive powder concrete with aggregates derived from quartzite mining tailings. Originality/Value: This study contributes to the literature by demonstrating the importance of investigating the chemical reactions induced by ASR in CPR with aggregates derived from quartzite mining tailings, showing that theses tests area essential for creating the necessary conditions to propose methods to mitigate the alkali-silica reaction. The relevance and value of this research are evidenced by the conclusion that quartzite tailings can be effectively used as an alternative aggregate for mortars and concrete in general.