Search Results (9)

This study analyzes the potential utilization of rock dust as a sustainable alternative to the use of traditional fertilizers, considering the distance between mining areas and areas where agricultural commodities are produced in the state of Mato Grosso, the largest agricultural producing state in Brazil. To this end, agricultural production by municipality and the position of mining areas in the mining phase related to granite, basalt and kimberlite are analyzed, aiming at developing a map of current potential areas of rock dust fertilizer production, namely for phosphorus (P)- and potassium (K)-based rocks for crops. To analyze the future scenario, areas in the research phase for the same types of rocks mentioned are considered. The results indicate three main potential scenarios: (1) municipalities located in areas that produce agricultural commodities and far from mining areas in production; (2) municipalities located near areas that produce rock dust and with high agricultural production of commodities; (3) municipalities near areas that produce rock dust, but with low production of agricultural commodities. In scenario 1, the use of rock dust may be viable in the event of a supply crisis of traditional fertilizer. In scenario 2, rock dust may fully or partially replace traditional fertilizer. And in scenario 3, rock dust may be used to reduce costs and improve the production of small local producers. Thus, this study indicates that rock dust can be an alternative to traditional fertilizers in the state of Mato Grosso, but it requires registrations in accordance with Brazilian legislation. Full article

Concrete and mortar production consumes significant natural resources, leading to environmental concerns and sustainability challenges. Sustainable alternatives, such as industrial byproducts, have been explored to replace clinkers and aggregates. Basalt rock powder (BRP) is a promising option due to its physical and chemical properties, including its better particle size distribution and compatibility with cementitious composites, and studies have highlighted its pozzolanic activity and its potential to improve mechanical properties (compressive strength, flexural strength, and durability). Reusing rock dust as a raw material could transform it into a mineral byproduct, benefiting the new material and reducing waste volumes. This article presents a systematic literature review on the use of BRP in construction materials, conducted using the Scopus, ScienceDirect, PubMed, and Web of Science databases and following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) procedures. The search resulted in 787 articles (up to December 2024) and, after the screening process, 17 met the inclusion criteria. From the selected articles, information regarding the utilization of this waste product; its influence on mechanical properties, pozzolanic activity, and durability; and the sustainability associated with its use was compiled. The risk of bias was low as the search was comprehensive, all the papers were peer-reviewed, and all authors reviewed the papers independently. In conclusion, the studies demonstrate the potential of using BRP as a component of cementitious materials, indicating it as a possible innovative solution to the current challenges in the construction industry. Full article

Rock dust (RD) is a by-product of the precious metal mining industry. Some mining operations produce close to 2,000,000 Mg of RD/year, posing disposal issues. This study evaluated the physicochemical and microbial properties of RD from gold mining and its potential use in RD-based growing media. Ten media formulations were tested: Promix (Control), 100% (RD), 100% topsoil (TS), 50% RD + 50% topsoil (RDT), 25% RD + 75% topsoil (RT), 50% RD + 50% Promix (RP), 50% RD + 25% biochar + 25% Promix (RBP), 50% RD + 25% compost + 25% Promix (RCP), 50% RD + 50% biochar (RB), and Huplaso (negative control). RD particle size ranged from 0.1 to 2 mm with a bulk density of 1.5 g cm⁻³, while RD-based media ranged from 0.8 to 1.1 g cm⁻³ showing increased porosity. Nutrient content was analyzed using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), and the active microbial community assessed using PLFA biomarkers via GC-MS/FID, n = 4 and p = 0.05. Microbial analysis identified five classes (protozoa, eukaryotes, Gram-positive (G+), Gram-negative (G−), and fungi (F)), with a significant increase in G−, G+, and F in RD-based amendment RBP (28%) compared to control P (9%). G+, G−, and F showed a strong negative correlation (r = −0.98) with pH, while calcium correlated positively (r = 0.85) with eukaryotes and a strong positive correlation (r = 0.95) of cation exchange capacity with G+. This study suggests blending RD with organic amendments improves physicochemical quality and microbial activity, supporting its use in crop production over disposal. Full article

This study investigated young and mature coconut fibers as an asbestos replacement in fiber–cement flat sheets. The ratio of fiber content ranged from 5% to 9.5% in increments of 0.5% by weight of binder. Crushed rock dust (CRD) was also utilized in this study at a ratio of 50% as sand replacement. The results showed that the addition of young coconut fiber (YCF) and mature coconut fiber (MCF) in flat sheets increased with decreasing bulk density and thermal conductivity. The optimum fiber content was 6.5%–7% by weight of binder for two types of fiber with the highest modulus of rupture of 12–13 MPa. The modulus of rupture and density of fiber–cement flat sheets using YCF were higher than that of fiber–cement flat sheets using MCF, which was clarified by SEM results due to the denser structure of MCF. Moreover, the modulus of rupture was directly proportional to the modulus of elasticity in fiber–cement flat sheets. Full article

Ternary blended cements, such as limestone calcined clay cement (LC³), represent a type of strategic binder for the mitigation of environmental impacts associated with cement production. These are estimated to reduce CO₂ emissions by about 40% compared to ordinary Portland cement (OPC). In this paper, we explore the possibility of producing such ternary blends by utilizing secondary raw materials that may be locally available. Specifically, the primary limestone that is commonly used in LC³ is herein substituted with quarry dust obtained by sourcing “kunkur”, a carbonate-rich sedimentary rock (also known as caliche) that can be locally utilized for the production of ordinary OPC clinker. To optimize the blending proportions of ternary cement consisting of OPC, calcined clay, and kunkur fines, a “design of experiment” (DoE) approach was implemented with the goal of exploring the possibility of reducing the amount of the OPC fraction to values lower than 50%. The properties of the formulated blends were assessed by a combination of techniques that comprise mechanical strength testing, XRD time-dependent quantitative phase analysis, and SEM–EDS microstructural and microchemical analyses. The results suggest that ternary blended cement based on kunkur fines forms hydration products, such as hemicarboaluminates, which are also observed in LC³. This shows that such waste materials can potentially be used in sustainable cement blends; however, the presence of kaolinite in the kunkur fines seems to affect their strength development when compared to both OPC and conventional LC³. Full article

The use of planetary regolith can be explored via the utilization of simulants. The existing Martian simulants have differences due to varying source materials and design parameters. Additional simulants are needed because the few available simulants do not replicate the compositional diversity of Martian regolith. This study discusses the development of a low-cost construction simulant of Mars. The area of Winder Nai in Pakistan was selected for field sampling of basalt because of local availability and easy access. The dust was produced from rock samples through mechanical crushing and grinding. The physical properties, composition, mineralogy, and surface morphology were evaluated via geotechnical tests, Energy Dispersive X-ray (EDX) spectroscopy, X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM), respectively. The designed simulant has a well-graded particle size distribution with a particle density and bulk density of 2.58 g/cm³ and 1.16 g/cm³, respectively. The elemental composition of Winder Nai Mars Simulant (WNMS) is within ±5 wt% of the Rocknest and the average Martian regolith composition except for SO₃. For SiO₂, Al₂O₃, and Fe₂O₃, WNMS has a good match with the Martian regolith. The content of CaO and TiO₂ in WNMS is higher than, and content of MgO is lower than, the average Martian values. The rock can be classified as basalt based on the Total Alkali Silica (TAS) diagram. XRD spectrum indicates the occurrence of plagioclase and pyroxene as the main signature minerals of basalt. The particle morphology of WNMS is angular to subangular, and the simulant indicates the presence of 3.8 wt% highly paramagnetic particles. The volatile loss is 0.25 wt% at 100 °C, 1.73 wt% at 500 °C, and 3.05 wt% at 950 °C. The composition of WNMS, basaltic mineralogy, morphology, magnetic properties, and volatile content are comparable with MMS-2 and a few other simulants. Full article

The utilization of manufactured lightweight aggregates adds another dimension to the cost of the preparation of self-compacting concrete (SCC). The common practice of adding absorption water to the lightweight aggregates before concreting leads to inaccurate calculations of the water-to-cement ratio. Moreover, the absorption of water weakens this interfacial bond between aggregates and the cementitious matrix. A particular type of black volcanic rock with a vesicular texture known as scoria rocks (SR) is utilized. With an adapted sequence of additions, the occurrence of water absorption can be minimized to overcome the issue of calculating the true water content. In this study, the approach of preparing the cementitious paste first with adjusted rheology followed by the addition of fine and coarse SR aggregates enabled us to circumvent the need for adding absorption water to the aggregates. This step has improved the overall strength due to the enhanced bond between the aggregate and the cementitious matrix, rendering a lightweight SCC mix with a target compressive strength of 40 MPa at 28 days, which makes it appropriate for structural applications. Different mixes were prepared and optimized for the best cementitious system that achieved the goal of this study. The optimized quaternary cementitious system included silica fume, class F fly ash, and limestone dust as essential ingredients for low-carbon footprint concrete. The rheological properties and parameters of the optimized mix were tested, evaluated, and compared to a control mix prepared using normal-weight aggregates. The results showed that the optimized quaternary mix satisfied both fresh and hardened properties. Slump flow, T50, J-ring flow, and average V-funnel flow time were in the ranges of 790–800 mm, 3.78–5.67 s, 750–780 mm, and 9.17 s, respectively. Moreover, the equilibrium density was in the range of 1770–1800 kg/m³. After 28 days an average compressive strength of 42.7 MPa, a corresponding flexural load of over 2000 N, and a modulus of rupture of 6.2 MPa were obtained. The conclusion is then drawn that altering the sequence of mixing ingredients becomes a mandatory process with scoria aggregates to obtain high-quality lightweight concrete for structural applications. This process leads to a significant improvement in the precise control of the fresh and hardened properties, which was unachievable with the normal practice used with lightweight concrete. Full article

Research on the utilization of the Earth’s heat focuses mainly on effective sourcing of energy accumulated in rock mass. One of the most important parameters is thermal conductivity, which can be modified using various compositions of cement grouts. Hardened cement slurry is intended to improve thermal conductivity. It should function as a sort of extension of the rock mass to the outer diameter of heat exchanger tubes. Regardless of the thermal conductivity of the rock, high conductivity of the grout increases the energy efficiency of the BHE. Heat accumulated in the rock mass can be extracted using borehole heat exchangers (BHE), in which high thermal conductivity of cement slurry is wanted over the entire length of the exchanger. Generally, in case of deep borehole heat exchangers (DBHE), it is recommended to use two types of cement slurry, one with reduced thermal conductivity in the upper part of the exchanger and grout with increased thermal conductivity in its lower part. When cementing geothermal wells, cement grout with decreased thermal conductivity along the entire length of the borehole is most commonly used. Geothermal boreholes extract geothermal water which, at the surface, is used for heating, for example. Then, after use, the cooled water is injected through injection holes. In this article, two different basalt dusts are examined. These dusts were obtained by crushing basalt boulders in open-pit mines. They were examined for their effect on thermal conductivity when added to grout. According to the Polish Ordinance of the Minister of Environment dated 9 December 2014 regarding the waste catalogue, they were classified as waste. The materials, named basalt dust A and basalt dust B, were used to create cement slurries with a water–cement ratio of 0.5–0.7 with a wide range of percentage concentration of basalt dust. The test results show that as concentrations in the slurry increase, the values of thermal conductivity and strength decrease. This correlation occurred for both tested additives. Full article

Respirable rock dust poses serious long-term health complications to workers in environments where mechanical rock excavation is utilized. The purpose of this study is to characterize respirable dust generated by cutting limestone with new, partially worn, and fully worn conical pick wears. Characterizing limestone respirable dust can aid in decision making for respirable dust suppression levels and exposures throughout the lifetime of a pick in underground mining and engineering activities. The methods include full scale cutting of a limestone sample in the laboratory with three conical picks at different stages of wear. Dust samples were collected during cutting with various instruments connected to pumps and subsequently analyzed to determine the concentrations, mineralogy, particle shapes, and particle size distributions. The results show that the worn pick generated the highest concentration of dust, all picks generated dust containing quartz, all three picks generated dust particles of similar shapes, and all three picks generated various particle size distributions. In conclusion, a preliminary suite of respirable dust characteristics is available and with further future additional studies, results could be used for the evaluation of possible strategies and methods of dust suppression and exposures during mining, tunneling, or drilling activities. Full article