Sands are naturally hydrophilic granular materials, yet, rendering them hydrophobic could lend them to a wide range of geotechnical applications. This study describes a powder-coating procedure performed after chemically modifying the surfaces of coarse, medium and fine sands and examines its effect on their hydrophobicity. The purpose is to render these granular materials more hydrophobic than what is conventionally achieved by chemical methods using a simple technique. The procedure consists of first silanising both the sands and silica powder at a similar concentration by means of an organosilane to modify their surface chemistry, then the silica powder is adhered to the sands at a mass mixing ratio to alter their hydrophobicity. Irrespective of the concentrations and mixing ratios, the powder-coating procedure enhances the hydrophobicity of sands in comparison to the sole use of the chemical method. Changes in the morphology of the sand grains, such as their particle size, particle shape and surface roughness, resulting from the powder-coating procedure are examined by means of dynamic image analysis, profilometry and scanning electron microscopy. The effects of surface chemistry, surface roughness and air on the hydrophobicity of the sands are discussed based on theoretical wetting models to analyse the experimental results.

中文翻译：

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通过硅烷化和粉末涂层优化沙子的疏水性

沙是天然的亲水性粒状材料，然而，使其具有疏水性可使其更广泛地应用于岩土工程中。这项研究描述了对粗砂，中砂和细砂的表面进行化学改性后进行的粉末喷涂程序，并研究了其对疏水性的影响。目的是使这些粒状材料比传统上使用简单技术通过化学方法获得的疏水性更好。该过程包括首先通过有机硅烷对砂子和二氧化硅粉末进行硅烷化，以改变浓度，以改变其表面化学性质，然后将二氧化硅粉末以质量混合比粘附到砂子上，以改变其疏水性。不管浓度和混合比例，与仅使用化学方法相比，粉末涂层工艺可增强沙子的疏水性。通过动态图像分析，轮廓测定法和扫描电子显微镜检查了由粉末涂覆过程引起的沙粒形态的变化，例如粒度，颗粒形状和表面粗糙度。在理论润湿模型的基础上，讨论了表面化学，表面粗糙度和空气对砂粒疏水性的影响，以分析实验结果。轮廓测定法和扫描电子显微镜。在理论润湿模型的基础上，讨论了表面化学，表面粗糙度和空气对砂粒疏水性的影响，以分析实验结果。轮廓测定法和扫描电子显微镜。在理论润湿模型的基础上，讨论了表面化学，表面粗糙度和空气对砂粒疏水性的影响，以分析实验结果。