An overview of the production and usage of quartz sand as a special sort of sand for civil engineering is presented – from the formation of sand deposits, through mining and processing methods, to its final use, with an emphasis on its use in civil engineering, i.e. in water filtration. Quartz is found in sedimentary, metamorphic, and igneous rocks. During sand formation in the fluvial environment, quartz grains are highly resistant to weathering and mechanical wear, and can be transported a long way without changes to size and form. Therefore, quartz is the main constituent of most natural sands. Quartz and quartz sand are ubiquitous raw materials used in a wide range of products in civil engineering due to their chemical inertia and high temperature resistance. An example of a quartz sand deposit and processing plant in Slovenia is presented as a practical case study on quartz sand application. The described applications using quartz sand are the best available technologies in sanitary and hydraulic engineering to be used for a move towards a circular economy, smart houses, and smart cities.
<p>Optical sensors are widely used for turbidity measurements in suspended sediment concentration studies. When conducting continuous measurements of turbidity in the field with optical sensors, results are determined according to the calibration curve (relationship between suspended sediment concentration and turbidity readings from the optical sensors). The calibration curve is developed based on the samples of the material present in and/or around the investigated stream. The concentration data are useful in water-quality-related investigations as well as for evaluating the amounts of transported (flushed, eroded) material from the catchments as suspended load. The amounts and particle sizes of transported material depend on the hydrological conditions. Usually, the particles&#8217; size is not directly considered when developing the calibration curve. However, different particle sizes of the material from the same study site can result in different turbidity readings. Taking into account one general calibration curve for suspended sediment concentration determination can lead to misestimation of the transported material amounts. Here, the results of turbidity sensor calibration for different particle size classes are presented. Additionally, the uncertainty of the suspended material concentrations due to this effect is estimated. Further, we show how different calibration curves affect the assessment of the amount of the transported suspended load from the selected experimental catchment.</p>
<p>Quartz sand deposit Ravno is the biggest quartz sand deposit in the Dolenjska region in Slovenia with an area of 1.25 km<sup>2</sup>. Quartz sand at the site is selectively excavated using mechanical methods. Presently, at the processing plant near the deposit, the main final mineral processing technique is flotation. Prior to the flotation, quartz sand undergoes classification and attrition. Final products produced at the plant are natural sand, washed sand and floated sand.<br>Recently, mining companies have been turning to simpler processing systems, such as gravity concentration, due to the price increase of floatation reagents, simplicity of the process and lower environmental impact.<br>Overview of the deposit and current methods used in the processing plant are presented, as a prologue to further work on the process alteration possibilities &#8211; a change from flotation to gravity concentration.</p>
<p>The Dynamic Image Analysis (DIA), standardised in ISO 13322-2:2006 and ISO 9276-6:2008 standards, introduces a simple and fast analysis of diverse particle shape and size parameters, compared to a manual method or static image analysis, respectively. While the DIA method is time conserving, as it is a quasi-3D method, it is susceptible to greater variations in results compared to a real-3D, time consuming static image analysis. A variation analysis of the DIA results as a function of the analysed particles&#8217; shape was the focus of our study. The particle shape plays a role in various processes, including wearing off (mechanical abrasion) during sediment transport or due to in-situ abrasion of larger sediment particles in fluvial environments.</p><p>More than 40 particles were randomly selected for the DIA analysis. Analysed particles included quarried, angular rock particles and rounded fluvial sediment particles. The selected particles had a geometric mean diameter in the range between 15 mm and 70 mm (coarse gravel to cobble size). The mass of particles was between 10 and 400 g. All particles were divided into four shape groups (bladed, prolate, equant, and oblate) according to Zingg&#8217;s shape classification. Axes' lengths used for shape classification were manually measured using a caliper. All particles were also individually analysed in a dynamic image analyser (quasi-3D image analyser) Microtrac Camsizer XL, using the accompanying software, PartAn 3D. The software evaluates 33 size and shape parameters of analysed particles, including dimensional (e.g. length, width, thickness, surface area, etc.) and dimensionless (e.g. ellipticity, sphericity, convexity, etc.) parameters. Three DIA repetitions of each particle were applied to estimate the mean values and variation (coefficients of variation, CV) in its results.</p><p>Furthermore, the effect of particles&#8217; size, mass, and Zingg&#8217;s shape on the variability of the DIA results was investigated. Particles&#8217; size, as well as particles&#8217; angularity, showed no obvious effect on the variation in the DIA results. Quarried, angular particles had CV of 3.54% on average for all parameter results, while rounded, fluvial particles had CV of 3.68% for all parameter results. On the other hand, Zingg&#8217;s shape class showed an effect on the variation of both, dimensional and dimensionless DIA resulting parameters. Bladed particles displayed the greatest variations of all the resulting parameter values, with an average CV of 6.85%, and the greatest scatter of parameters&#8217; CVs. When analysing such particles, it would be beneficial to conduct more than three repetitions for more accurate results. Since the DIA analysis is a fast method, this is not a problem in order to get a robust estimation of coarse particle shape. Additionally, observing the parameters themselves, &#8220;concavity&#8221; and &#8220;angularity&#8221; had the highest CVs, namely 13.35% and 10.24%, as well as the greatest scatter of the CVs. Parameters &#8220;convexity&#8221;, &#8220;solidity&#8221;, and &#8220;sphericity&#8221; had the lowest CVs, namely 0.12%, 0.26%, and 0.96%, respectively, as well as the lowest scatter of the CVs.</p>
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