钼尾矿水泥免烧砖压制工艺及着色特性

Pressing process and coloring property of baking-free bricks made of molybdenum tailing and cement

  • 摘要: 以承德钼尾矿和水泥构成的简单免烧砖体系,对其在成型工艺、微观结构和着色特性方面进行基础工艺研究.结果显示,水泥-钼尾矿免烧压砖适宜的水泥/钼尾矿质量比为0.18~0.25,成型水/固体原料质量比为0.1,成型压强25 MPa,保压时间30 s,在阶梯式成型施压方式下可改善砖块性能.经长期养护后,压砖中Ca (OH)2、钙矾石和CaCO3的相对含量会随水泥掺量增加而逐渐升高,而云母含量则逐渐降低.当水泥量质量分数达25%时,会有低硫型水化硫铝酸钙相(AFm)形成.此外,在试块中可见大量水化硅酸钙(C-S-H)凝胶、钙矾石和Ca (OH)2矿相形成.掺加9%以内氧化铁型红、黄、绿颜料,对试块强度无不利影响,而掺加蓝、黑颜料会使试块强度损失,在保证砖材强度前提下,添加量宜控制在6%~9%.

     

    Abstract: As a by-product of mining and the extensive production of industrial solid waste, tailing has many types, has a low utilization rate, and seriously affects the surrounding ecological environment. With the protection of natural resources and ecology in China, the traditional methods of obtaining clay and natural stone by mining cultivated land and preparing building materials by utilizing a high-temperature process will be avoided and eliminated gradually. In the face of the increasing demand for construction and decoration materials in the engineering construction sector in the Jing-Jin-Ji region, the use of tailing resources, which are stockpiled in large amounts in Chengde, Hebei Province, for the preparation of baking-free and decorative bricks is characterized by high usage of solid waste, low energy consumption, low environmental pollution, and considerable savings. In this study, for the simple system of molybdenum tailing-cement brick, the press molding process, microstructure, and coloring property after the addition of pigment were investigated. Results show that, for the baking-free brick, the appropriate cement-to-tailing ratio is 0.18~0.25, water-to-solid raw materials ratio for pressing is 0.10, pressing strength is 25 MPa, pressing holding time is 30 s, and brick performance is improved by the step-style pressing mode. After curing for a long time, the relative contents of Ca(OH)2, ettringite, and CaCO3 increase with the increase in the content of cement in the brick samples, whereas the content of mica decreases. If the mass content of cement reaches 25%, then the AFm phase (low sulfur calcium aluminum sulfate) will form. Large quantities of hydrated calcium silicate (C-S-H) gel, ettringite, and Ca(OH)2 can also be observed in the brick samples. The addition of red, yellow, and green pigments of iron oxide type within 9% has only a slight effect on brick strength. By contrast, the addition of blue and black pigments causes strength loss. Thus, their contents should be appropriately controlled within 6% to 9%.

     

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