Evaluation of strength and durability of compacted bauxite tailings treated with cement

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This approach becomes even more advantageous when applied to increase the stability of mining tailings deposits and ensure environmental safety. This study investigates the effects of cement addition and dry density on the strength and durability of compacted bauxite tailings-cement blends. The porosity/cement index, widely used in soil-cement mixture research, was adopted to analyze the parameters that control the strength and durability of these blends. Results demonstrate that increasing cement content and dry density significantly improves unconfined compressive strength ( q u ) and reduces accumulated mass loss ( ALM ) during wet/dry cycles. The porosity/cement index effectively describes the variations in q u and ALM , as expressed by an empirical equation, which can be highly beneficial for the practical application of treated mining tailings as construction materials. Mining tailing Porosity/ cement index Compressive strength Durability Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1. Introduction The mining industry annually produces a significant amount of tailings, a fine-grained material resulting from ores' physical and chemical processing. For environmental reasons, these mining tailings require appropriate disposal. The most common storage method involves constructing high embankments on the soil surface to retain tailings and water, commonly known as tailings dams. The dam-raising steps often utilize tailings, making this material's properties crucial to the structure's performance (Vick, 1983 ; EPA, 1994; Davies & Martin, 2000 ). Recent failures of Brazilian tailings dams (Morgenstern et al., 2016 ; Robertson et al., 2019 ) with loss of lives and severe environmental damage underscore the urgent need to understand the geotechnical properties of mining tailings and explore alternatives to prevent such disasters. Lottermoser ( 2011 ) outlines various potential alternatives for the reuse and recycling of mining waste, emphasizing the significant environmental benefits they can bring. These benefits include a reduction in the consumption of natural resources and waste production, as well as a decrease in environmental exposure to contaminated materials. The term 'reuse' of mining waste refers to finding new applications for the material in its original form, without the need for reprocessing. In the case of mining tailings, one of the most explored reuse alternatives is the mixing of tailings with cement paste and injecting them underground as backfill to provide ground support. This method, known as cemented tailings backfill (CTB) (Fall et al., 2008 ), not only offers a solution for tailings management but also contributes to environmental sustainability. More recently, there has been a growing interest in utilizing mining waste for geotechnical purposes, primarily through the application of stabilizing admixtures to enhance its properties (Ramesh et al., 2012 ; Kiventerä et al ., 2019; Barati et al., 2020 ). Soil improvement techniques can be employed to treat tailings in existing dams (James et al., 2013 ) and to investigate alternatives for using tailings as construction material, whether in compacted landfills, pavement bases, and subbases, or new storage systems (Consoli et al., 2009 ; Helinski et al., 2011 ; Ahmari & Zhang, 2012 ; Consoli et al., 2017a ). The present study aims to evaluate the mechanical properties of bauxite tailings compacted and treated with small quantities of Portland cement for use as a construction material. The dosage procedure followed the guidelines proposed by Consoli et al. ( 2007 ), developed to analyze the properties of artificially cemented soils. The strength and durability properties of bauxite tailings-cement mixtures were related to the porosity/cement index ( η / C iv ), providing an empirical equation that can be highly useful for applying treated mining tailings as a construction material. Consoli et al. ( 2007 ) developed the dosage methodology based on test results conducted on sandy soil. However, subsequent studies have adapted the original method for other applications, such as in fiber-reinforced cemented fine-grained soils (Consoli et al., 2010 ; Consoli et al., 2013 ; Consoli et al., 2017b ), gold mining tailings treated with cement (Consoli et al., 2018 ), and fiber-reinforced cemented gold tailings (Consoli et al., 2017a ). This methodology considers the η/C iv index, which represents the ratio between the porosity of the compacted admixture and the volumetric content of Portland cement (volume of cement divided by the total volume of the specimen). According to Consoli et al. ( 2007 ), using the η/C iv index in evaluating the mechanical properties of mixtures is more appropriate compared to the water/cement ratio. In compacted fills, soil-cement mixtures are typically unsaturated, so the water/cement ratio does not correlate with compressive strength. The cemented soils' unconfined compressive strength ( q u ) was the first property related to the η/C iv index. Consoli et al. ( 2007 ) demonstrated that q u increases linearly with the increase in cement content and exponentially with the reduction of the mixture's porosity. However, the rates of change of q u with porosity and cement content were different, and applying an exponent to the C iv term was suggested to harmonize the variables. An optimal fit between these variables in fine-grained soils was obtained by raising C iv to 0.28 power. Although initial research indicated that this power could be material-specific, subsequent studies have demonstrated its applicability to fiber-reinforced cemented soils, cemented gold mining tailings, fiber-reinforced cemented gold mining tailings, and other soil properties such as stiffness and durability (Consoli et al., 2017a ; 2017b ; 2018 ). This study will also analyze the applicability of the 0.28 power value for the cemented bauxite tailings mixture properties, which could have significant practical implications for the construction industry. The durability of cement-treated soils is a crucial factor in their use as construction materials. It indicates the ability of the stabilized material to maintain structural integrity under severe environmental conditions. Factors such as temperature and moisture variations, as well as repeated loadings, can lead to reduced durability. On the other hand, soil grain distribution, cement content, curing period, and degree of saturation can enhance mixture durability (Dempsey and Thompson, 1968 ; Marcon, 1977 ). In the laboratory, durability is commonly evaluated by quantifying the loss of mass ( LM ) through abrasion during wetting and drying (ASTM, 2015) and freezing and thawing (ASTM, 2013) processes. The Portland Cement Association (PCA) and the U.S. Army Corps of Engineers (USACE) have established criteria for the durability of soil-cement mixtures used as base and subbase construction materials. The PCA criteria allow a maximum LM of 14%, while the USACE criterion allows a maximum LM of 11%. These findings have practical implications for the construction industry, providing guidelines for the using cement-treated soils in various applications. Consoli et al. ( 2018 ) have made significant strides in evaluating the durability of cemented gold mining tailings, finding that LM is more pronounced for higher porosity and lower cement content. The accumulated loss of mass ( ALM ) over a distinct number of wetting-drying cycles was well correlated with η/C iv 0.28 . The normalized ALM values by the number of cycles also correlated well with the η/C iv 0.28 index. Similar conclusions were drawn by Consoli et al. ( 2017a ), which evaluated the durability of fiber-reinforced cemented gold mining tailings. However, only these studies evaluate the sensitivity of η/C iv 0.28 to different mechanical properties of cement-treated mining tailings. Therefore, the present study, which aims to investigate the applicability of this methodology to bauxite mining tailings, holds promise for further advancing our understanding of soil stabilization and construction materials, particularly in the context of bauxite mining tailings, which are finer than gold mining tailings. 2. Materials and Methods This item discusses the materials and methods used in this study. 2.1 Materials The bauxite mining tailings, a crucial component of this study, were sourced from a disposal site in northern Brazil. Their physical properties, detailed in Table 1 , play a pivotal role in understanding their behavior. These tailings, primarily composed of silt-sized particles, exhibit a low Plasticity Index (PI), have a specific gravity of 2.88, and a maximum dry unit weight of 14.2 kN/m³ at an optimum moisture content of 32.2%, as determined by the Standard Proctor compaction test. The Unified Soil Classification System (USCS) (ASTM, 2006) and the AASHTO system (ASTM, 2015) classify these tailings as ML (low plasticity silt) and A-4, respectively. The mineralogical characteristics of the bauxite tailings were identified through an X-ray diffractometer analysis. This analysis revealed the presence of five compounds, as depicted in Fig. 1 : hematite (Fe 2 O 3 ), quartz (SiO 2 ), gibbsite (Al(OH) 3 ), anatase (TiO 2 ), and calcium oxide (CaO). The primary chemical elements in the tailings are iron (Fe), silicon (Si), aluminum (Al), titanium (Ti), and calcium (Ca), among others. In this study, Type II Portland Cement, which has a specific gravity of 3.15, was used to stabilize the bauxite tailings. Distilled water was used for characterization tests and specimen preparation. Table 1 Bauxite mining tailing main physical properties Property Bauxite Tailing Liquid Limit (LL) (%) 32.2 Plastic Limit (PL) (%) 29.9 Plastic Index (PI) (%) 2.3 Specific Gravity (G) 2.88 Fine sand (0.075 mm < diameter < 0.425 mm) (%) 3.7 Silt (0.002 mm < diameter < 0.075 mm) (%) 63 Clay (diameter < 0.002 mm) (%) 33.3 Mean particle diameter, D 50 (mm) 0.005 Maximum dry unit weight for standard Proctor compaction effort (kN/m³) 14.2 Optimum moisture content for standard Proctor compaction effort (%) 32.2 USCS Classification ML (low plasticity silt) AASHTO Classification A-4 2.2 Methods 2.2.1 Moulding and curing of specimens Cylindrical specimens with a diameter of 50 mm and a height of 100 mm were used for the unconfined compressive strength tests. Conversely, cylindrical specimens with a diameter of 100 mm and a height of 127 mm were used for durability tests. To properly define the dosage for specimen preparation, target values for the mixtures' dry density ( γ d ) and cement content ( C ) were established. This procedure involved simulating a condition close to the maximum dry density obtained from the Standard Proctor compaction effort (14 kN/m³) (Table 1 ). Additionally, two other states (13 and 12 kN/m³) were tested to simulate potential flaws in the compaction effort during in situ construction, representing lower dry densities than the maximum value obtained from the Standard Proctor compaction effort. The cement content was selected based on national and international experience with soil-cement stabilization (Mitchell, 1981 ; Consoli et al., 2009 ). Initial tests were conducted with 3%, 5%, and 7% Portland cement contents. However, 3% and 5% of cement contents were insufficient to maintain specimen stability during the saturation process, likely due to the deleterious effects of the calcium oxide identified by the X-ray diffraction analysis (Fig. 1 ). Consequently, a new test series was conducted using 7%, 9%, and 11% cement contents. After defining the γ d and C values and considering the specific gravities of the cement ( γ sC ) and bauxite tailings ( γ sBT ), the mixture porosity ( η ) was determined using Eq. 1, proposed by Consoli et al. ( 2011 ): \(\eta =100-100\left[\left(\frac{{\gamma }_{D}}{1+\frac{C}{100}}\right)\bullet \left(\frac{\frac{1}{100}}{{\gamma }_{sBT}}+\frac{\frac{C}{100}}{{\gamma }_{sC}}\right)\right]\) Eq. 1 The mixture preparation began with the dry materials (tailings and cement), followed by the addition of distilled water at a proportion of 32% (optimum moisture content for Standard Proctor compaction effort – Table 1 ). All materials were mixed until a homogeneous mass was achieved. Three small samples of the mixture were taken to verify moisture content. The specimens were then statically compacted in five equal layers using a bipartite metallic cylindrical mold for the unconfined compression tests and a metallic cylindrical mold for the durability tests. After demolding, the specimens' weight and dimensions were measured, and they were cured for seven days under controlled temperature and humidity conditions. 2.2.2 Unconfined compression tests For the unconfined compression tests, three specimens for each combination of γ d and C were molded according to the standard guidelines of ASTM C39 (2010). Before the unconfined compression tests, the specimens were submerged in distilled water for 24 hours. This procedure aims to increase the degree of saturation, thereby reducing the influence of suction on strength measurements. The unconfined compressive strength was determined using an automatic loading machine with a maximum capacity of 50 kN and a proving ring with a 50 kN capacity and a resolution of 0.01 kN. The maximum load reached by each specimen was recorded. The results were considered acceptable if the individual strengths of the three specimens, molded with the same characteristics, did not differ by more than 10% from the average strength of the set. 2.2.3 Durability tests Durability tests were conducted according to ASTM D559 (2015), employing wetting-drying cycles. For this analysis, six specimens, molded as described in section 2.2.1 , were tested. The influence of γ d and C on the loss of mass ( LM ) was evaluated; thus, the three dry densities were assessed with the lowest cement content (7%), and the lowest dry density (12 kN/m³) was evaluated with the three cement contents. The LM was recorded for each specimen over 12 wet-dry cycles, following the sequence detailed in Table 2 . After a seven-day curing period, the first step of the process involved drying the specimens in an oven for 42 hours. Subsequently, the specimens were brushed with a metal bristle brush, applying a force of approximately 15 N, with 18–20 strokes equally distributed on the faces and perimeter of the specimens (Fig. 2 ). The LM was determined by weighing the material detached from the specimens. Finally, the specimens were submerged in water for 5 hours, initiating a new cycle. Table 2 – Wetting-drying cycles steps and duration Durability tests steps Duration period (h) Specimens underwater (23 ± 2º C) 5 Oven drying (71 ± 2º C) 42 Specimen brushing and LM weighting 1 Total time for one wetting-drying cycle 48 3. Results 3.1 Unconfined Compression strength Figure 3 shows the unconfined compressive strength ( q u ) values related to the three cement contents and the three different tested dry densities. It was observed that an increase in cement content and dry density contributes to the strength gain. For each dry density, the q u values can be correlated to the cement content by an equation that describes a linear trend (Eq. 2 to Eq. 4). These equations allow the estimation of strength values for different cement contents, making it possible to determine the appropriate dosage according to the project requirements in which the treated tailings will be applied. However, these equations do not yet provide a combined correlation between cement content and dry density. \({q}_{u}=27.396C+27.184 \therefore for {\gamma }_{d}=12 kN/m³\) Eq. 2 \({q}_{u}=65.318C+0.435 \therefore for {\gamma }_{d}=13 kN/m³\) Eq. 3 \({q}_{u}=136.013C-307.716 \therefore for {\gamma }_{d}=14 kN/m³\) Eq. 4 Based on the observations from Fig. 3 , the increase in resistance due to the higher cement content is more pronounced for a dry density ( γ d ) of 14 kN/m³. This fact suggests that mixtures with higher densities had a more significant interaction between the tailings and the cement, resulting in increased strength. In response to this behavior, trend lines representing the strength gain of specimens with dry densities of 12 and 13 kN/m³ have a similar slope, dependent only on the dry density of the material. However, the slope of the trend line is much steeper for specimens with a dry density of 14 kN/m³. The strength values obtained for mixtures with a dry density of 12 kN/m³ are approximately 215 kPa for 7% cement content, 460 kPa for 9%, and 640 kPa for 11% cement content, respectively. For a dry density equal to 13 kN/m³, the strength values reach around 280 kPa for 7% cement content, about 580 kPa for 9%, and approximately 925 kPa for 11% cement content, respectively. Finally, for a dry density of 14 kN/m³, the strength values, depending on the cement content, are approximately 325 kPa for 7%, around 720 kPa for 9%, and 1184 kPa for 11% cement content. As a means of illustrating the impact of cement content and dry density of the mixtures on strength ( q u ), values were correlated with the η/C iv index using the same equation. Figure 4 demonstrates this correlation and shows that the adjusted η/C iv 0.28 index exhibits a strong correlation with q u values obtained for bauxite mining tailings and Portland cement ( R² =0.98). Notably, Eq. 5 offers a unique formulation that allows for strength estimation considering distinct combinations of cement content and porosity of mixtures. This unique formulation could prove to be a valuable tool for the practical use of bauxite tailings and Portland cement mixture as a construction material. \({q}_{u}=2.314 x {10}^{12}{\left(\frac{\eta }{{C}_{iv}^{0.28}}\right)}^{-6.048}\) Eq. 5 3.2 Durability The loss of mass ( LM ) recorded during each drying-wetting cycle was expressed as a percentage value relative to the specimen's total weight. These values are plotted in Fig. 5 , illustrating the behavior of the tested specimens across the cycles. The higher cement content (11%) appears to influence reducing LM values similarly to the high dry density (14 kN/m³). The higher and more dispersed LM values are associated with specimens having lower dry densities ( γ d = 12 kN/m³ and γ d = 13 kN/m³) and lower cement content (7%). Conversely, lower values of loss of mass ( LM ) were observed for specimens with high cement content (11%), even when the dry density was 12 kN/m³, and for specimens with high dry density (14 kN/m³), even with a cement content of 7%. A more uniform distribution of LM values across the cycles is observed for higher cement contents and γ d equal to 14 kN/m³. Figure 6 illustrates the accumulated loss of mass ( ALM ) for each tested specimen over the drying-wetting cycles. The results demonstrate that increasing the cement content and dry density enhances the durability of the bauxite mining tailing-Portland cement mixtures. This finding is of utmost importance as it suggests that by adjusting the cement content and dry density, we can improve the durability of these mixtures, making them more suitable for use as base and subbase construction materials. Notably, except for specimens with γ d equal to 12 kN/m³ and a cement content of 7%, all other specimens meet both the PCA and USACE criteria for the durability of soil-cement mixtures. The correlation between ALM and mixtures' porosity/cement content was also evaluated using the adjusted index, η/C iv 0.28 , as presented in Fig. 7 . The data analysis indicates that the index η/C iv 0.28 exhibits a good correlation ( R ²≥0.90) with ALM values, allowing for the establishment of relationships (Eq. 6 to Eq. 9) to estimate ALM values for distinct combinations of cement content and porosity of mixtures for each evaluated drying-wetting cycle. \(ALM=2.406 x {10}^{18}{\left(\frac{\eta }{{C}_{iv}^{0.28}}\right)}^{-11.032} \therefore for 3 cycles\) Eq. 6 \(ALM=2.480 x {10}^{20}{\left(\frac{\eta }{{C}_{iv}^{0.28}}\right)}^{-12.416} \therefore for 6 cycles\) Eq. 7 \(ALM=3.091 x {10}^{20}{\left(\frac{\eta }{{C}_{iv}^{0.28}}\right)}^{-12.459} \therefore for 9 cycles\) Eq. 8 \(ALM=3.942 x {10}^{18}{\left(\frac{\eta }{{C}_{iv}^{0.28}}\right)}^{-11.249} \therefore for 12 cycles\) Eq. 9 A single correlation between ALM and η/C iv 0.28 was established by normalizing the ALM values by the number of cycles ( ALM/NC ). Figure 8 illustrates the ALM/NC values correlated with η/C iv 0.28 . The normalized data exhibited slight scattering ( R ² = 0.87); nonetheless, the authors posit that the relationship expressed by Eq. 10 could be highly beneficial for predicting ALM values based on cement content and porosity for applying bauxite tailings-Portland cement mixtures. 4. Conclusion Based on these research results, several conclusions can be drawn: Bauxite mining tailings exhibit improved strength and durability properties with the addition of Portland cement and reduced porosity. However, due to potentially deleterious effects from certain elements in the bauxite tailing composition, stability testing of specimens is only viable, with cement contents exceeding 7% by mass; The relationship between unconfined compressive strength and cement content was successfully modeled as a linear trend, showing good agreement, contingent on the dry density of mixtures; The adjusted porosity/cement index ( η/C iv 0.28 ) strongly correlates with the unconfined compressive strength ( q u ) of compacted bauxite mining tailings-Portland cement blends. The utilization of the exponent 0.28 was effective in predicting the compressive strength of these mixtures, consistent with prior studies on soil and mining tailings mixed with cement (e.g., Consoli et al ., 2016; Consoli et al., 2017a ); The adjusted porosity/cement index ( η/C iv 0.28 ) also significantly correlates with the accumulated loss of mass ( ALM ) from proper wetting-drying cycles of compacted bauxite tailings-Portland cement mixtures. This fact supports previous findings (Consoli et al., 2017a ; Consoli et al., 2018 ) suggesting the potential use of the exponent 0.28 for predicting durability characteristics of mining tailings-Portland cement mixtures; The ratio between ALM and the number of cycles ( ALM/NC ) demonstrates a reasonable correlation with the adjusted porosity/cement index ( η/C iv 0.28 ), allowing for a single equation to comprehensively describe mixture behavior, which is practical; This research provides equations for estimating q u and ALM values using the adjusted porosity/cement index. Consequently, appropriate dry densities and cement content can be established to meet strength and durability project requirements for bauxite mining tailing-Portland cement blends as construction material. Declarations Author Contribution Helena Paula Nierwinski: Conceptualization, Methodology, Investigation, Formal analysis, Writing - Original Draft. Jonatas Sosnoski: Formal analysis, Writing - Review & Editing. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4438338","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":307475266,"identity":"2ea84e43-7b68-4d2d-a5fa-a80260cd5660","order_by":0,"name":"Helena Paula Nierwinski","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA40lEQVRIiWNgGAWjYBACAwbmBigTyPjAIAdk8BDSwgjTwtjAOIPBmEQtzDzEaDFnb2x8XFDDkMc/I7Hxs22bgT1/A++xD/i0WPYcbDaecYyhWOJGYrN0bptB4owDfMkz8DrsRmKbNA8bQ2LDjcQGoJY/CQYMPMb4/XL/Yftvnn8MifOBtvy2BDqMsJYbjG3MvG0MiRtA1jG2GTBuIKjlDNALvH0SxYZnHrZZ9pwD+uUwXzJ+LccPH/zM880mT+548uEbP8qAIdbeexivFiiQSECwmYnRAAQJBFWMglEwCkbByAUAuX5HX4V0wFEAAAAASUVORK5CYII=","orcid":"","institution":"Federal University of Santa Catarina","correspondingAuthor":true,"prefix":"","firstName":"Helena","middleName":"Paula","lastName":"Nierwinski","suffix":""},{"id":307475267,"identity":"81630ccb-bad0-4699-91b0-d1da61790a7a","order_by":1,"name":"Jonatas Sosnoski","email":"","orcid":"","institution":"Federal University of Santa Catarina","correspondingAuthor":false,"prefix":"","firstName":"Jonatas","middleName":"","lastName":"Sosnoski","suffix":""},{"id":307475268,"identity":"30639d07-8bf1-490a-8078-aa025ac747c6","order_by":2,"name":"Marcelo Heidemann","email":"","orcid":"","institution":"Federal University of Santa Catarina","correspondingAuthor":false,"prefix":"","firstName":"Marcelo","middleName":"","lastName":"Heidemann","suffix":""}],"badges":[],"createdAt":"2024-05-17 18:53:18","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4438338/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4438338/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s10098-025-03212-x","type":"published","date":"2025-06-07T15:57:29+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":57416403,"identity":"d0a561a8-68b7-4066-ba94-61cb8ce4d6d2","added_by":"auto","created_at":"2024-05-30 11:45:58","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":74555,"visible":true,"origin":"","legend":"\u003cp\u003eX-ray diffractometer of studied bauxite mining tailing\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4438338/v1/722f1ab9a458f69fad13f473.jpg"},{"id":57417075,"identity":"3518c40a-2cb7-4609-9661-4f7fb80be65c","added_by":"auto","created_at":"2024-05-30 11:53:58","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":73958,"visible":true,"origin":"","legend":"\u003cp\u003eBrushing process\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4438338/v1/c5f4f3a498ea7967d4715c5a.jpg"},{"id":57416404,"identity":"efec76fc-1083-457b-aa71-c99d4c380238","added_by":"auto","created_at":"2024-05-30 11:45:59","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":45727,"visible":true,"origin":"","legend":"\u003cp\u003eVariation of unconfined strength (\u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003eu\u003c/em\u003e\u003c/sub\u003e) with cement content (\u003cem\u003eC\u003c/em\u003e) and dry density (\u003cem\u003eg\u003c/em\u003e\u003csub\u003e\u003cem\u003ed\u003c/em\u003e\u003c/sub\u003e)\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4438338/v1/fe3c5309529adfdb0404dd29.jpg"},{"id":57417076,"identity":"2543e854-c902-4c41-9f4b-438f39705bd6","added_by":"auto","created_at":"2024-05-30 11:53:59","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":34172,"visible":true,"origin":"","legend":"\u003cp\u003eVariation of unconfined strength (\u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003eu\u003c/em\u003e\u003c/sub\u003e) with adjusted porosity-cement index (\u003cem\u003eh/C\u003c/em\u003e\u003csub\u003e\u003cem\u003eiv\u003c/em\u003e\u003c/sub\u003e\u003csup\u003e\u003cem\u003e0.28\u003c/em\u003e\u003c/sup\u003e)\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4438338/v1/9ea56966c6616fdacf4e1bdf.jpg"},{"id":57416408,"identity":"6c64952a-4123-4af3-9fac-88b2c6605f94","added_by":"auto","created_at":"2024-05-30 11:45:59","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":65527,"visible":true,"origin":"","legend":"\u003cp\u003eLoss mass (\u003cem\u003eLM\u003c/em\u003e) for each drying-wetting cycle for specimens with distinct dry densities and cement content\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4438338/v1/1d37911c5f1b9a9f861999d1.jpg"},{"id":57416405,"identity":"24479563-41fb-4c92-9984-8e315ebed7e8","added_by":"auto","created_at":"2024-05-30 11:45:59","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":61807,"visible":true,"origin":"","legend":"\u003cp\u003eAccumulated loss of mass (\u003cem\u003eALM\u003c/em\u003e) for each drying-wetting cycle for specimens with distinct dry densities and cement content\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4438338/v1/342798a37bff61408dfb0196.jpg"},{"id":57416410,"identity":"14469341-420f-4bda-8d78-aa9d65a875b1","added_by":"auto","created_at":"2024-05-30 11:46:00","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":66479,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eALM versus\u003c/em\u003e (\u003cem\u003eh/C\u003c/em\u003e\u003csub\u003e\u003cem\u003eiv\u003c/em\u003e\u003c/sub\u003e\u003csup\u003e\u003cem\u003e0.28\u003c/em\u003e\u003c/sup\u003e) index after three, six, nine, and 12 wetting–drying cycles\u003c/p\u003e","description":"","filename":"7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4438338/v1/2683b6ec6eb63d3d429b87ce.jpg"},{"id":57416409,"identity":"e494cca4-8c43-43bc-b8e6-8d3942631a8d","added_by":"auto","created_at":"2024-05-30 11:45:59","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":42633,"visible":true,"origin":"","legend":"\u003cp\u003eNormalized durability data (\u003cem\u003eALM/NC\u003c/em\u003e) \u003cem\u003eversus\u003c/em\u003e (\u003cem\u003eh/C\u003c/em\u003e\u003csub\u003e\u003cem\u003eiv\u003c/em\u003e\u003c/sub\u003e\u003csup\u003e\u003cem\u003e0.28\u003c/em\u003e\u003c/sup\u003e) for bauxite tailing-Portland cement mixtures\u003c/p\u003e","description":"","filename":"8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4438338/v1/515322755d162cdf762dbc2c.jpg"},{"id":84242568,"identity":"0638d8fd-7f4e-4877-a9bd-51ef23918dcb","added_by":"auto","created_at":"2025-06-09 16:09:39","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1077648,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4438338/v1/3ea71fba-4e0d-47e3-89b6-675ca4d1912e.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Evaluation of strength and durability of compacted bauxite tailings treated with cement","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe mining industry annually produces a significant amount of tailings, a fine-grained material resulting from ores' physical and chemical processing. For environmental reasons, these mining tailings require appropriate disposal. The most common storage method involves constructing high embankments on the soil surface to retain tailings and water, commonly known as tailings dams. The dam-raising steps often utilize tailings, making this material's properties crucial to the structure's performance (Vick, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e1983\u003c/span\u003e; EPA, 1994; Davies \u0026amp; Martin, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2000\u003c/span\u003e). Recent failures of Brazilian tailings dams (Morgenstern et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Robertson et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) with loss of lives and severe environmental damage underscore the urgent need to understand the geotechnical properties of mining tailings and explore alternatives to prevent such disasters.\u003c/p\u003e \u003cp\u003eLottermoser (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2011\u003c/span\u003e) outlines various potential alternatives for the reuse and recycling of mining waste, emphasizing the significant environmental benefits they can bring. These benefits include a reduction in the consumption of natural resources and waste production, as well as a decrease in environmental exposure to contaminated materials. The term 'reuse' of mining waste refers to finding new applications for the material in its original form, without the need for reprocessing. In the case of mining tailings, one of the most explored reuse alternatives is the mixing of tailings with cement paste and injecting them underground as backfill to provide ground support. This method, known as cemented tailings backfill (CTB) (Fall et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2008\u003c/span\u003e), not only offers a solution for tailings management but also contributes to environmental sustainability. More recently, there has been a growing interest in utilizing mining waste for geotechnical purposes, primarily through the application of stabilizing admixtures to enhance its properties (Ramesh et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Kiventer\u0026auml; \u003cem\u003eet al\u003c/em\u003e., 2019; Barati et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eSoil improvement techniques can be employed to treat tailings in existing dams (James et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) and to investigate alternatives for using tailings as construction material, whether in compacted landfills, pavement bases, and subbases, or new storage systems (Consoli et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Helinski et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Ahmari \u0026amp; Zhang, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Consoli et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2017a\u003c/span\u003e). The present study aims to evaluate the mechanical properties of bauxite tailings compacted and treated with small quantities of Portland cement for use as a construction material. The dosage procedure followed the guidelines proposed by Consoli et al. (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2007\u003c/span\u003e), developed to analyze the properties of artificially cemented soils. The strength and durability properties of bauxite tailings-cement mixtures were related to the porosity/cement index (\u003cem\u003eη\u003c/em\u003e/\u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003eiv\u003c/em\u003e\u003c/sub\u003e), providing an empirical equation that can be highly useful for applying treated mining tailings as a construction material.\u003c/p\u003e \u003cp\u003eConsoli et al. (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2007\u003c/span\u003e) developed the dosage methodology based on test results conducted on sandy soil. However, subsequent studies have adapted the original method for other applications, such as in fiber-reinforced cemented fine-grained soils (Consoli et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Consoli et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Consoli et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2017b\u003c/span\u003e), gold mining tailings treated with cement (Consoli et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), and fiber-reinforced cemented gold tailings (Consoli et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2017a\u003c/span\u003e). This methodology considers the \u003cem\u003eη/C\u003c/em\u003e\u003csub\u003e\u003cem\u003eiv\u003c/em\u003e\u003c/sub\u003e index, which represents the ratio between the porosity of the compacted admixture and the volumetric content of Portland cement (volume of cement divided by the total volume of the specimen). According to Consoli et al. (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2007\u003c/span\u003e), using the \u003cem\u003eη/C\u003c/em\u003e\u003csub\u003e\u003cem\u003eiv\u003c/em\u003e\u003c/sub\u003e index in evaluating the mechanical properties of mixtures is more appropriate compared to the water/cement ratio. In compacted fills, soil-cement mixtures are typically unsaturated, so the water/cement ratio does not correlate with compressive strength.\u003c/p\u003e \u003cp\u003eThe cemented soils' unconfined compressive strength (\u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003eu\u003c/em\u003e\u003c/sub\u003e) was the first property related to the \u003cem\u003eη/C\u003c/em\u003e\u003csub\u003e\u003cem\u003eiv\u003c/em\u003e\u003c/sub\u003e index. Consoli et al. (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2007\u003c/span\u003e) demonstrated that \u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003eu\u003c/em\u003e\u003c/sub\u003e increases linearly with the increase in cement content and exponentially with the reduction of the mixture's porosity. However, the rates of change of \u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003eu\u003c/em\u003e\u003c/sub\u003e with porosity and cement content were different, and applying an exponent to the \u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003eiv\u003c/em\u003e\u003c/sub\u003e term was suggested to harmonize the variables. An optimal fit between these variables in fine-grained soils was obtained by raising \u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003eiv\u003c/em\u003e\u003c/sub\u003e to 0.28 power. Although initial research indicated that this power could be material-specific, subsequent studies have demonstrated its applicability to fiber-reinforced cemented soils, cemented gold mining tailings, fiber-reinforced cemented gold mining tailings, and other soil properties such as stiffness and durability (Consoli et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2017a\u003c/span\u003e; \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2017b\u003c/span\u003e; \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). This study will also analyze the applicability of the 0.28 power value for the cemented bauxite tailings mixture properties, which could have significant practical implications for the construction industry.\u003c/p\u003e \u003cp\u003eThe durability of cement-treated soils is a crucial factor in their use as construction materials. It indicates the ability of the stabilized material to maintain structural integrity under severe environmental conditions. Factors such as temperature and moisture variations, as well as repeated loadings, can lead to reduced durability. On the other hand, soil grain distribution, cement content, curing period, and degree of saturation can enhance mixture durability (Dempsey and Thompson, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1968\u003c/span\u003e; Marcon, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e1977\u003c/span\u003e). In the laboratory, durability is commonly evaluated by quantifying the loss of mass (\u003cem\u003eLM\u003c/em\u003e) through abrasion during wetting and drying (ASTM, 2015) and freezing and thawing (ASTM, 2013) processes. The Portland Cement Association (PCA) and the U.S. Army Corps of Engineers (USACE) have established criteria for the durability of soil-cement mixtures used as base and subbase construction materials. The PCA criteria allow a maximum \u003cem\u003eLM\u003c/em\u003e of 14%, while the USACE criterion allows a maximum \u003cem\u003eLM\u003c/em\u003e of 11%. These findings have practical implications for the construction industry, providing guidelines for the using cement-treated soils in various applications.\u003c/p\u003e \u003cp\u003eConsoli et al. (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) have made significant strides in evaluating the durability of cemented gold mining tailings, finding that \u003cem\u003eLM\u003c/em\u003e is more pronounced for higher porosity and lower cement content. The accumulated loss of mass (\u003cem\u003eALM\u003c/em\u003e) over a distinct number of wetting-drying cycles was well correlated with \u003cem\u003eη/C\u003c/em\u003e\u003csub\u003e\u003cem\u003eiv\u003c/em\u003e\u003c/sub\u003e\u003csup\u003e\u003cem\u003e0.28\u003c/em\u003e\u003c/sup\u003e. The normalized \u003cem\u003eALM\u003c/em\u003e values by the number of cycles also correlated well with the \u003cem\u003eη/C\u003c/em\u003e\u003csub\u003e\u003cem\u003eiv\u003c/em\u003e\u003c/sub\u003e\u003csup\u003e\u003cem\u003e0.28\u003c/em\u003e\u003c/sup\u003e index. Similar conclusions were drawn by Consoli et al. (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2017a\u003c/span\u003e), which evaluated the durability of fiber-reinforced cemented gold mining tailings. However, only these studies evaluate the sensitivity of \u003cem\u003eη/C\u003c/em\u003e\u003csub\u003e\u003cem\u003eiv\u003c/em\u003e\u003c/sub\u003e\u003csup\u003e\u003cem\u003e0.28\u003c/em\u003e\u003c/sup\u003e to different mechanical properties of cement-treated mining tailings. Therefore, the present study, which aims to investigate the applicability of this methodology to bauxite mining tailings, holds promise for further advancing our understanding of soil stabilization and construction materials, particularly in the context of bauxite mining tailings, which are finer than gold mining tailings.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cp\u003eThis item discusses the materials and methods used in this study.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Materials\u003c/h2\u003e \u003cp\u003eThe bauxite mining tailings, a crucial component of this study, were sourced from a disposal site in northern Brazil. Their physical properties, detailed in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, play a pivotal role in understanding their behavior. These tailings, primarily composed of silt-sized particles, exhibit a low Plasticity Index (PI), have a specific gravity of 2.88, and a maximum dry unit weight of 14.2 kN/m\u0026sup3; at an optimum moisture content of 32.2%, as determined by the Standard Proctor compaction test. The Unified Soil Classification System (USCS) (ASTM, 2006) and the AASHTO system (ASTM, 2015) classify these tailings as ML (low plasticity silt) and A-4, respectively.\u003c/p\u003e \u003cp\u003eThe mineralogical characteristics of the bauxite tailings were identified through an X-ray diffractometer analysis. This analysis revealed the presence of five compounds, as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e: hematite (Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e), quartz (SiO\u003csub\u003e2\u003c/sub\u003e), gibbsite (Al(OH)\u003csub\u003e3\u003c/sub\u003e), anatase (TiO\u003csub\u003e2\u003c/sub\u003e), and calcium oxide (CaO). The primary chemical elements in the tailings are iron (Fe), silicon (Si), aluminum (Al), titanium (Ti), and calcium (Ca), among others.\u003c/p\u003e \u003cp\u003eIn this study, Type II Portland Cement, which has a specific gravity of 3.15, was used to stabilize the bauxite tailings. Distilled water was used for characterization tests and specimen preparation.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eBauxite mining tailing main physical properties\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eProperty\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBauxite Tailing\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLiquid Limit (LL) (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e32.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePlastic Limit (PL) (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e29.9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePlastic Index (PI) (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpecific Gravity (G)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.88\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFine sand (0.075 mm\u0026thinsp;\u0026lt;\u0026thinsp;diameter\u0026thinsp;\u0026lt;\u0026thinsp;0.425 mm) (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSilt (0.002 mm\u0026thinsp;\u0026lt;\u0026thinsp;diameter\u0026thinsp;\u0026lt;\u0026thinsp;0.075 mm) (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e63\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eClay (diameter\u0026thinsp;\u0026lt;\u0026thinsp;0.002 mm) (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e33.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMean particle diameter, D\u003csub\u003e50\u003c/sub\u003e (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.005\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaximum dry unit weight for standard Proctor compaction effort (kN/m\u0026sup3;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e14.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOptimum moisture content for standard Proctor compaction effort (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e32.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUSCS Classification\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eML (low plasticity silt)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAASHTO Classification\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eA-4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Methods\u003c/h2\u003e \u003cdiv id=\"Sec5\" class=\"Section3\"\u003e \u003ch2\u003e2.2.1 Moulding and curing of specimens\u003c/h2\u003e \u003cp\u003eCylindrical specimens with a diameter of 50 mm and a height of 100 mm were used for the unconfined compressive strength tests. Conversely, cylindrical specimens with a diameter of 100 mm and a height of 127 mm were used for durability tests. To properly define the dosage for specimen preparation, target values for the mixtures' dry density (\u003cem\u003eγ\u003c/em\u003e\u003csub\u003e\u003cem\u003ed\u003c/em\u003e\u003c/sub\u003e) and cement content (\u003cem\u003eC\u003c/em\u003e) were established. This procedure involved simulating a condition close to the maximum dry density obtained from the Standard Proctor compaction effort (14 kN/m\u0026sup3;) (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Additionally, two other states (13 and 12 kN/m\u0026sup3;) were tested to simulate potential flaws in the compaction effort during in situ construction, representing lower dry densities than the maximum value obtained from the Standard Proctor compaction effort. The cement content was selected based on national and international experience with soil-cement stabilization (Mitchell, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e1981\u003c/span\u003e; Consoli et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). Initial tests were conducted with 3%, 5%, and 7% Portland cement contents. However, 3% and 5% of cement contents were insufficient to maintain specimen stability during the saturation process, likely due to the deleterious effects of the calcium oxide identified by the X-ray diffraction analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Consequently, a new test series was conducted using 7%, 9%, and 11% cement contents.\u003c/p\u003e \u003cp\u003eAfter defining the \u003cem\u003eγ\u003c/em\u003e\u003csub\u003e\u003cem\u003ed\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003eC\u003c/em\u003e values and considering the specific gravities of the cement (\u003cem\u003eγ\u003c/em\u003e\u003csub\u003e\u003cem\u003esC\u003c/em\u003e\u003c/sub\u003e) and bauxite tailings (\u003cem\u003eγ\u003c/em\u003e\u003csub\u003e\u003cem\u003esBT\u003c/em\u003e\u003c/sub\u003e), the mixture porosity (\u003cem\u003eη\u003c/em\u003e) was determined using Eq.\u0026nbsp;1, proposed by Consoli et al. (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2011\u003c/span\u003e):\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taba\" border=\"1\"\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\eta =100-100\\left[\\left(\\frac{{\\gamma }_{D}}{1+\\frac{C}{100}}\\right)\\bullet \\left(\\frac{\\frac{1}{100}}{{\\gamma }_{sBT}}+\\frac{\\frac{C}{100}}{{\\gamma }_{sC}}\\right)\\right]\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEq.\u0026nbsp;1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe mixture preparation began with the dry materials (tailings and cement), followed by the addition of distilled water at a proportion of 32% (optimum moisture content for Standard Proctor compaction effort \u0026ndash; Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). All materials were mixed until a homogeneous mass was achieved. Three small samples of the mixture were taken to verify moisture content. The specimens were then statically compacted in five equal layers using a bipartite metallic cylindrical mold for the unconfined compression tests and a metallic cylindrical mold for the durability tests. After demolding, the specimens' weight and dimensions were measured, and they were cured for seven days under controlled temperature and humidity conditions.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section3\"\u003e \u003ch2\u003e2.2.2 Unconfined compression tests\u003c/h2\u003e \u003cp\u003eFor the unconfined compression tests, three specimens for each combination of \u003cem\u003eγ\u003c/em\u003e\u003csub\u003e\u003cem\u003ed\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003eC\u003c/em\u003e were molded according to the standard guidelines of ASTM C39 (2010). Before the unconfined compression tests, the specimens were submerged in distilled water for 24 hours. This procedure aims to increase the degree of saturation, thereby reducing the influence of suction on strength measurements. The unconfined compressive strength was determined using an automatic loading machine with a maximum capacity of 50 kN and a proving ring with a 50 kN capacity and a resolution of 0.01 kN. The maximum load reached by each specimen was recorded. The results were considered acceptable if the individual strengths of the three specimens, molded with the same characteristics, did not differ by more than 10% from the average strength of the set.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section3\"\u003e \u003ch2\u003e2.2.3 Durability tests\u003c/h2\u003e \u003cp\u003eDurability tests were conducted according to ASTM D559 (2015), employing wetting-drying cycles. For this analysis, six specimens, molded as described in section \u003cspan refid=\"Sec5\" class=\"InternalRef\"\u003e2.2.1\u003c/span\u003e, were tested. The influence of \u003cem\u003eγ\u003c/em\u003e\u003csub\u003e\u003cem\u003ed\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003eC\u003c/em\u003e on the loss of mass (\u003cem\u003eLM\u003c/em\u003e) was evaluated; thus, the three dry densities were assessed with the lowest cement content (7%), and the lowest dry density (12 kN/m\u0026sup3;) was evaluated with the three cement contents. The \u003cem\u003eLM\u003c/em\u003e was recorded for each specimen over 12 wet-dry cycles, following the sequence detailed in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. After a seven-day curing period, the first step of the process involved drying the specimens in an oven for 42 hours. Subsequently, the specimens were brushed with a metal bristle brush, applying a force of approximately 15 N, with 18\u0026ndash;20 strokes equally distributed on the faces and perimeter of the specimens (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The \u003cem\u003eLM\u003c/em\u003e was determined by weighing the material detached from the specimens. Finally, the specimens were submerged in water for 5 hours, initiating a new cycle.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003e\u0026ndash; Wetting-drying cycles steps and duration\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDurability tests steps\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDuration period (h)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpecimens underwater (23\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026ordm; C)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOven drying (71\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026ordm; C)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e42\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpecimen brushing and \u003cem\u003eLM\u003c/em\u003e weighting\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTotal time for one wetting-drying cycle\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e48\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Unconfined Compression strength\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e shows the unconfined compressive strength (\u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003eu\u003c/em\u003e\u003c/sub\u003e) values related to the three cement contents and the three different tested dry densities. It was observed that an increase in cement content and dry density contributes to the strength gain. For each dry density, the \u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003eu\u003c/em\u003e\u003c/sub\u003e values can be correlated to the cement content by an equation that describes a linear trend (Eq.\u0026nbsp;2 to Eq.\u0026nbsp;4). These equations allow the estimation of strength values for different cement contents, making it possible to determine the appropriate dosage according to the project requirements in which the treated tailings will be applied. However, these equations do not yet provide a combined correlation between cement content and dry density.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabb\" border=\"1\"\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({q}_{u}=27.396C+27.184 \\therefore for {\\gamma }_{d}=12 kN/m\u0026sup3;\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEq.\u0026nbsp;2\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({q}_{u}=65.318C+0.435 \\therefore for {\\gamma }_{d}=13 kN/m\u0026sup3;\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEq.\u0026nbsp;3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({q}_{u}=136.013C-307.716 \\therefore for {\\gamma }_{d}=14 kN/m\u0026sup3;\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEq.\u0026nbsp;4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eBased on the observations from Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, the increase in resistance due to the higher cement content is more pronounced for a dry density (\u003cem\u003eγ\u003c/em\u003e\u003csub\u003e\u003cem\u003ed\u003c/em\u003e\u003c/sub\u003e) of 14 kN/m\u0026sup3;. This fact suggests that mixtures with higher densities had a more significant interaction between the tailings and the cement, resulting in increased strength. In response to this behavior, trend lines representing the strength gain of specimens with dry densities of 12 and 13 kN/m\u0026sup3; have a similar slope, dependent only on the dry density of the material. However, the slope of the trend line is much steeper for specimens with a dry density of 14 kN/m\u0026sup3;.\u003c/p\u003e \u003cp\u003eThe strength values obtained for mixtures with a dry density of 12 kN/m\u0026sup3; are approximately 215 kPa for 7% cement content, 460 kPa for 9%, and 640 kPa for 11% cement content, respectively. For a dry density equal to 13 kN/m\u0026sup3;, the strength values reach around 280 kPa for 7% cement content, about 580 kPa for 9%, and approximately 925 kPa for 11% cement content, respectively. Finally, for a dry density of 14 kN/m\u0026sup3;, the strength values, depending on the cement content, are approximately 325 kPa for 7%, around 720 kPa for 9%, and 1184 kPa for 11% cement content.\u003c/p\u003e \u003cp\u003eAs a means of illustrating the impact of cement content and dry density of the mixtures on strength (\u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003eu\u003c/em\u003e\u003c/sub\u003e), values were correlated with the \u003cem\u003eη/C\u003c/em\u003e\u003csub\u003e\u003cem\u003eiv\u003c/em\u003e\u003c/sub\u003e index using the same equation. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e demonstrates this correlation and shows that the adjusted \u003cem\u003eη/C\u003c/em\u003e\u003csub\u003e\u003cem\u003eiv\u003c/em\u003e\u003c/sub\u003e\u003csup\u003e\u003cem\u003e0.28\u003c/em\u003e\u003c/sup\u003e index exhibits a strong correlation with \u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003eu\u003c/em\u003e\u003c/sub\u003e values obtained for bauxite mining tailings and Portland cement (\u003cem\u003eR\u0026sup2;\u003c/em\u003e=0.98). Notably, Eq.\u0026nbsp;5 offers a unique formulation that allows for strength estimation considering distinct combinations of cement content and porosity of mixtures. This unique formulation could prove to be a valuable tool for the practical use of bauxite tailings and Portland cement mixture as a construction material.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabc\" border=\"1\"\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({q}_{u}=2.314 x {10}^{12}{\\left(\\frac{\\eta }{{C}_{iv}^{0.28}}\\right)}^{-6.048}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEq.\u0026nbsp;5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Durability\u003c/h2\u003e \u003cp\u003eThe loss of mass (\u003cem\u003eLM\u003c/em\u003e) recorded during each drying-wetting cycle was expressed as a percentage value relative to the specimen's total weight. These values are plotted in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, illustrating the behavior of the tested specimens across the cycles. The higher cement content (11%) appears to influence reducing \u003cem\u003eLM\u003c/em\u003e values similarly to the high dry density (14 kN/m\u0026sup3;). The higher and more dispersed \u003cem\u003eLM\u003c/em\u003e values are associated with specimens having lower dry densities (\u003cem\u003eγ\u003c/em\u003e\u003csub\u003e\u003cem\u003ed\u003c/em\u003e\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;12 kN/m\u0026sup3; and \u003cem\u003eγ\u003c/em\u003e\u003csub\u003e\u003cem\u003ed\u003c/em\u003e\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;13 kN/m\u0026sup3;) and lower cement content (7%). Conversely, lower values of loss of mass (\u003cem\u003eLM\u003c/em\u003e) were observed for specimens with high cement content (11%), even when the dry density was 12 kN/m\u0026sup3;, and for specimens with high dry density (14 kN/m\u0026sup3;), even with a cement content of 7%. A more uniform distribution of \u003cem\u003eLM\u003c/em\u003e values across the cycles is observed for higher cement contents and \u003cem\u003eγ\u003c/em\u003e\u003csub\u003e\u003cem\u003ed\u003c/em\u003e\u003c/sub\u003e equal to 14 kN/m\u0026sup3;.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e illustrates the accumulated loss of mass (\u003cem\u003eALM\u003c/em\u003e) for each tested specimen over the drying-wetting cycles. The results demonstrate that increasing the cement content and dry density enhances the durability of the bauxite mining tailing-Portland cement mixtures. This finding is of utmost importance as it suggests that by adjusting the cement content and dry density, we can improve the durability of these mixtures, making them more suitable for use as base and subbase construction materials. Notably, except for specimens with \u003cem\u003eγ\u003c/em\u003e\u003csub\u003e\u003cem\u003ed\u003c/em\u003e\u003c/sub\u003e equal to 12 kN/m\u0026sup3; and a cement content of 7%, all other specimens meet both the PCA and USACE criteria for the durability of soil-cement mixtures.\u003c/p\u003e \u003cp\u003eThe correlation between \u003cem\u003eALM\u003c/em\u003e and mixtures' porosity/cement content was also evaluated using the adjusted index, \u003cem\u003eη/C\u003c/em\u003e\u003csub\u003e\u003cem\u003eiv\u003c/em\u003e\u003c/sub\u003e\u003csup\u003e\u003cem\u003e0.28\u003c/em\u003e\u003c/sup\u003e, as presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e. The data analysis indicates that the index \u003cem\u003eη/C\u003c/em\u003e\u003csub\u003e\u003cem\u003eiv\u003c/em\u003e\u003c/sub\u003e\u003csup\u003e\u003cem\u003e0.28\u003c/em\u003e\u003c/sup\u003e exhibits a good correlation (\u003cem\u003eR\u003c/em\u003e\u0026sup2;\u0026ge;0.90) with \u003cem\u003eALM\u003c/em\u003e values, allowing for the establishment of relationships (Eq.\u0026nbsp;6 to Eq.\u0026nbsp;9) to estimate \u003cem\u003eALM\u003c/em\u003e values for distinct combinations of cement content and porosity of mixtures for each evaluated drying-wetting cycle.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabd\" border=\"1\"\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(ALM=2.406 x {10}^{18}{\\left(\\frac{\\eta }{{C}_{iv}^{0.28}}\\right)}^{-11.032} \\therefore for 3 cycles\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEq.\u0026nbsp;6\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(ALM=2.480 x {10}^{20}{\\left(\\frac{\\eta }{{C}_{iv}^{0.28}}\\right)}^{-12.416} \\therefore for 6 cycles\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEq.\u0026nbsp;7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(ALM=3.091 x {10}^{20}{\\left(\\frac{\\eta }{{C}_{iv}^{0.28}}\\right)}^{-12.459} \\therefore for 9 cycles\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEq.\u0026nbsp;8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(ALM=3.942 x {10}^{18}{\\left(\\frac{\\eta }{{C}_{iv}^{0.28}}\\right)}^{-11.249} \\therefore for 12 cycles\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEq.\u0026nbsp;9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eA single correlation between \u003cem\u003eALM\u003c/em\u003e and \u003cem\u003eη/C\u003c/em\u003e\u003csub\u003e\u003cem\u003eiv\u003c/em\u003e\u003c/sub\u003e\u003csup\u003e\u003cem\u003e0.28\u003c/em\u003e\u003c/sup\u003e was established by normalizing the \u003cem\u003eALM\u003c/em\u003e values by the number of cycles (\u003cem\u003eALM/NC\u003c/em\u003e). Figure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e illustrates the \u003cem\u003eALM/NC\u003c/em\u003e values correlated with \u003cem\u003eη/C\u003c/em\u003e\u003csub\u003e\u003cem\u003eiv\u003c/em\u003e\u003c/sub\u003e\u003csup\u003e\u003cem\u003e0.28\u003c/em\u003e\u003c/sup\u003e. The normalized data exhibited slight scattering (\u003cem\u003eR\u003c/em\u003e\u0026sup2; = 0.87); nonetheless, the authors posit that the relationship expressed by Eq.\u0026nbsp;10 could be highly beneficial for predicting \u003cem\u003eALM\u003c/em\u003e values based on cement content and porosity for applying bauxite tailings-Portland cement mixtures.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eBased on these research results, several conclusions can be drawn:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eBauxite mining tailings exhibit improved strength and durability properties with the addition of Portland cement and reduced porosity. However, due to potentially deleterious effects from certain elements in the bauxite tailing composition, stability testing of specimens is only viable, with cement contents exceeding 7% by mass;\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eThe relationship between unconfined compressive strength and cement content was successfully modeled as a linear trend, showing good agreement, contingent on the dry density of mixtures;\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eThe adjusted porosity/cement index (\u003cem\u003eη/C\u003c/em\u003e\u003csub\u003e\u003cem\u003eiv\u003c/em\u003e\u003c/sub\u003e\u003csup\u003e\u003cem\u003e0.28\u003c/em\u003e\u003c/sup\u003e) strongly correlates with the unconfined compressive strength (\u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003eu\u003c/em\u003e\u003c/sub\u003e) of compacted bauxite mining tailings-Portland cement blends. The utilization of the exponent 0.28 was effective in predicting the compressive strength of these mixtures, consistent with prior studies on soil and mining tailings mixed with cement (e.g., Consoli \u003cem\u003eet al\u003c/em\u003e., 2016; Consoli et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2017a\u003c/span\u003e);\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eThe adjusted porosity/cement index (\u003cem\u003eη/C\u003c/em\u003e\u003csub\u003e\u003cem\u003eiv\u003c/em\u003e\u003c/sub\u003e\u003csup\u003e\u003cem\u003e0.28\u003c/em\u003e\u003c/sup\u003e) also significantly correlates with the accumulated loss of mass (\u003cem\u003eALM\u003c/em\u003e) from proper wetting-drying cycles of compacted bauxite tailings-Portland cement mixtures. This fact supports previous findings (Consoli et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2017a\u003c/span\u003e; Consoli et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) suggesting the potential use of the exponent 0.28 for predicting durability characteristics of mining tailings-Portland cement mixtures;\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eThe ratio between \u003cem\u003eALM\u003c/em\u003e and the number of cycles (\u003cem\u003eALM/NC\u003c/em\u003e) demonstrates a reasonable correlation with the adjusted porosity/cement index (\u003cem\u003eη/C\u003c/em\u003e\u003csub\u003e\u003cem\u003eiv\u003c/em\u003e\u003c/sub\u003e\u003csup\u003e\u003cem\u003e0.28\u003c/em\u003e\u003c/sup\u003e), allowing for a single equation to comprehensively describe mixture behavior, which is practical;\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eThis research provides equations for estimating \u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003eu\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003eALM\u003c/em\u003e values using the adjusted porosity/cement index. Consequently, appropriate dry densities and cement content can be established to meet strength and durability project requirements for bauxite mining tailing-Portland cement blends as construction material.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eHelena Paula Nierwinski: Conceptualization, Methodology, Investigation, Formal analysis, Writing - Original Draft. Jonatas Sosnoski: Formal analysis, Writing - Review \u0026amp; Editing. Marcelo Heidemann: Investigation, Resources, Writing - Review \u0026amp; Editing.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAhmari S, Zhang L (2012) Production of eco-friendly bricks from copper mine tailings through geopolymerization. Construction and Building Materials, v. 29, p. 323\u0026ndash;331, 2012. https://doi.org/10.1016/j.conbuildmat.2011.10.048. \u003c/li\u003e\n\u003cli\u003eASTM - American Society for Testing and Materials (2006) Standard classification of soils for engineering purposes (Unified Soil Classification System). ASTM standard D2487. ASTM. West Conshohocken, Philadelphia, Pa.\u003c/li\u003e\n\u003cli\u003eASTM - American Society for Testing and Materials (2010) Standard test method for compressive strength of cylindrical concrete specimens. ASTM standard C39. ASTM, West Conshohocken, Philadelphia, Pa.\u003c/li\u003e\n\u003cli\u003eASTM - American Society for Testing and Materials (2013) Standard test methods for freezing and thawing compacted soil-cement mixtures. ASTM standard D560. ASTM, West Conshohocken, Philadelphia, Pa.\u003c/li\u003e\n\u003cli\u003eASTM - American Society for Testing and Materials (2015) Standard test methods for wetting and drying compacted soil-cement mixtures. ASTM standard D559. ASTM, West Conshohocken, Philadelphia, Pa.\u003c/li\u003e\n\u003cli\u003eBarati S, Shourijeh P T, Samani N, Asadi S (2020) Stabilization of iron ore tailings with cement and bentonite: A case study on Golgohar mine. Bull Eng Geol Environ 79, 4151\u0026ndash;4166. https://doi.org/10.1007/s10064-020-01843-6\u003c/li\u003e\n\u003cli\u003eConsoli N C, Foppa D, Festugato L, Heineck K S (2007) Key parameters for strength control of artificially cemented soils. Journal of Geotechnical and Geoenvironmental Engineering, v. 133, n\u0026ordm; 2, p. 197\u0026ndash;205. https://doi.org/10.1061/(ASCE)1090-0241(2007)133:2(197).\u003c/li\u003e\n\u003cli\u003eConsoli N C, Dalla Rosa F, Fonini A (2009) Plate load tests on cemented soil layers overlaying weaker soil. 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Canadian Geotechnical Journal, v. 55, p. 486\u0026ndash;494. https://doi.org/10.1139/cgj-2016-0391.\u003c/li\u003e\n\u003cli\u003eDavies M P, Martin T E (2000) Upstream constructed tailings dams - A review of the basics. Tailings and Mine Waste 00. Colorado, USA, A.A. Balkema, Rotterdam: 3-15.\u003c/li\u003e\n\u003cli\u003eDempsey B J, Thompson M R (1968) Durability properties of lime-soil mixtures. Highway Research Record, v. 235, p. 61\u0026ndash;75.\u003c/li\u003e\n\u003cli\u003eEPA - Environmental Protection Agency (1994) Desing and evaluation of tailings dams. Technical report, U.S. Environmental Protection Agency (EPA), Washington, USA, 59 p.\u003c/li\u003e\n\u003cli\u003eFall M, Benzaaaoua M, Saa E G (2008) Mix proportioning of underground cemented tailings backfill. 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Elements, v. 7, n. 6, https://doi.org/ 10.2113/gselements.7.6.405.\u003c/li\u003e\n\u003cli\u003eKiventera J, Yliniemi J, Golek L, Deja J, Ferreira V M, Illikainen M (2019) Utilization of sulphidic mine tailings in alkali-activated materials. MATEC Web of Conferences, v. 274: 01001. https://doi.org/10.1051/matecconf/201927401001.\u003c/li\u003e\n\u003cli\u003eMarcon A (1977) Durability and modulus of elasticity of sand-lime-fly ash mixtures. Master\u0026apos;s thesis presented to the Graduate Program in Civil Engineering, UFRJ, Rio de Janeiro.\u003c/li\u003e\n\u003cli\u003eMitchell J K (1981) Soil improvement\u0026mdash;state-of-the-art report. Proceedings of the 10th International Conference on Soil Mechanics and Foundation Engineering, International Society of Soil Mechanics and Foundation Engineering, Stockholm. pp. 509\u0026ndash;565.\u003c/li\u003e\n\u003cli\u003eMorgenstern N R, Vick S G, Viotti C B, Watts BD (2016) Fund\u0026atilde;o Tailings Dam Review Panel. Report on the Immediate Causes of the Failure of the Fund\u0026atilde;o Dam. Available from http://fundaoinvestigation.com/the-report/.\u003c/li\u003e\n\u003cli\u003eRamesh P, Rao A V N, Murthy N K (2012) Efficacy of sodium carbonate and calcium carbonate in stabilizing a black cotton soil. Int. Journal of Emerging Technology and Advanced Engineering, v. 2, n\u0026ordm; 10. https://api.semanticscholar.org/CorpusID:7225899.\u003c/li\u003e\n\u003cli\u003eRobertson P K, Melo L, Willians D J, Wilson G W (2019) Report of the Expert Panel on the Technical Causes of the Failure of Feij\u0026atilde;o Dam I. December.\u003c/li\u003e\n\u003cli\u003eVick S G (1983) Planning, design and analysis of tailing dams. New York: John Wiley \u0026amp; Sons, 369p.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"clean-technologies-and-environmental-policy","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ctep","sideBox":"Learn more about [Clean Technologies and Environmental Policy](https://www.springer.com/journal/10098)","snPcode":"10098","submissionUrl":"https://submission.nature.com/new-submission/10098/3","title":"Clean Technologies and Environmental Policy","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Mining tailing, Porosity/ cement index, Compressive strength, Durability","lastPublishedDoi":"10.21203/rs.3.rs-4438338/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4438338/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eImproving soil properties by adding stabilizing materials, such as cement, has garnered significant attention from researchers, particularly for enhancing soils often deemed poor geotechnical quality. This approach becomes even more advantageous when applied to increase the stability of mining tailings deposits and ensure environmental safety. This study investigates the effects of cement addition and dry density on the strength and durability of compacted bauxite tailings-cement blends. The porosity/cement index, widely used in soil-cement mixture research, was adopted to analyze the parameters that control the strength and durability of these blends. Results demonstrate that increasing cement content and dry density significantly improves unconfined compressive strength (\u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003eu\u003c/em\u003e\u003c/sub\u003e) and reduces accumulated mass loss (\u003cem\u003eALM\u003c/em\u003e) during wet/dry cycles. The porosity/cement index effectively describes the variations in \u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003eu\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003eALM\u003c/em\u003e, as expressed by an empirical equation, which can be highly beneficial for the practical application of treated mining tailings as construction materials.\u003c/p\u003e","manuscriptTitle":"Evaluation of strength and durability of compacted bauxite tailings treated with cement","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-05-30 11:45:54","doi":"10.21203/rs.3.rs-4438338/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-04-02T02:38:01+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-06-27T11:12:41+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"194123647339627173155912578851520872868","date":"2024-06-20T08:23:04+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-06-15T10:47:47+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"251251742447561998346042884547483161838","date":"2024-06-03T13:12:26+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"290212379853397235290437213887329778313","date":"2024-06-01T01:27:50+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-05-31T12:58:32+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-05-28T02:32:39+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-05-18T04:06:41+00:00","index":"","fulltext":""},{"type":"submitted","content":"Clean Technologies and Environmental Policy","date":"2024-05-17T18:42:34+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"clean-technologies-and-environmental-policy","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ctep","sideBox":"Learn more about [Clean Technologies and Environmental Policy](https://www.springer.com/journal/10098)","snPcode":"10098","submissionUrl":"https://submission.nature.com/new-submission/10098/3","title":"Clean Technologies and Environmental Policy","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"8b477b1e-f239-4bc5-b74c-2c7d3eb88d55","owner":[],"postedDate":"May 30th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-06-09T16:02:15+00:00","versionOfRecord":{"articleIdentity":"rs-4438338","link":"https://doi.org/10.1007/s10098-025-03212-x","journal":{"identity":"clean-technologies-and-environmental-policy","isVorOnly":false,"title":"Clean Technologies and Environmental Policy"},"publishedOn":"2025-06-07 15:57:29","publishedOnDateReadable":"June 7th, 2025"},"versionCreatedAt":"2024-05-30 11:45:54","video":"","vorDoi":"10.1007/s10098-025-03212-x","vorDoiUrl":"https://doi.org/10.1007/s10098-025-03212-x","workflowStages":[]},"version":"v1","identity":"rs-4438338","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4438338","identity":"rs-4438338","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}