Department of Engineering "Enzo Ferrari ", University of Modena and Reggio Emilia, 41125 Modena, Italy.
Sibelco Ankerpoort NV, 6223 EP Maastricht, The Netherlands.
Molecules. 2021 Mar 2;26(5):1325. doi: 10.3390/molecules26051325.
In this study, the role of two reactive fillers, specifically a sand from a clay washing process as an alternative to waste glass powder and a commercial metakaolin (MK), into the geopolymerization process of waste clay-based materials was assessed. Three kinds of clayey wastes from mining operations-halloysitic, kaolinitic and smectitic clays-were tested as potential precursor of geopolymeric materials in view of a potential valorisation of these by-products. A mix-design based on the addition of low percentages (20%) of these fillers or MK to improve the mechanical and chemico-physical properties of geopolymeric formulations was evaluated. All the clays were thermally treated at a temperature of 650 °C, while the geopolymeric pastes were cured at room temperature. In particular, the chemical stability in water (pH and ionic conductivity of leachate water, weight loss), the variations in the microstructure (XRD, SEM), and in the mechanical performance (compressive strength) were analysed. The most reactive additive was MK, followed by sand and waste glass at very similar levels-1:1 or 2:1-depending upon the type of the clay but not strictly related to the clay type. The increase of geopolymeric gel densification due to the presence of MK and sand was replaced by a crack deflection mechanism in the case of the WG grains. The worst performance (chemical stability and mechanical properties) was found for the halloysitic clay, while kaolinitic and smectitic clays developed strengths slightly below 30 MPa.
在这项研究中，评估了两种反应性填料（一种是粘土洗涤过程中的沙子，可替代废玻璃粉，另一种是商业偏高岭土（MK））在废粘土基材料的地质聚合过程中的作用。三种来自采矿作业的粘土废物——针铁矿、高岭石和蒙脱石粘土——被测试为潜在的地质聚合材料前体，以实现这些副产品的潜在增值。基于添加低百分比（20%）这些填料或 MK 的混合设计，评估了改善地质聚合配方的机械和化学物理性能。所有的粘土都在 650°C 的温度下进行热处理，而地质聚合糊剂则在室温下固化。特别分析了化学稳定性（水的 pH 值和浸出液水的离子电导率、失重）、微观结构的变化（XRD、SEM）以及机械性能（抗压强度）。最具反应性的添加剂是 MK，其次是沙子和废玻璃，水平非常相似-1:1 或 2:1-取决于粘土的类型，但与粘土类型没有严格的关系。在 WG 颗粒的情况下，由于 MK 和沙子的存在导致地质聚合凝胶致密化的增加被裂缝偏转机制所取代。针铁矿粘土的性能最差（化学稳定性和机械性能），而高岭石和蒙脱石粘土的强度略低于 30 MPa。
