高硫尾矿充填体强度演化规律及其机理分析

Analysis of Strength Evolution and Its Mechanism of Cemented Paste Backfill with High-sulfidic Tailings

针对国外部分金属矿山由于脱硫工艺及运输成本高等原因倾向于直接使用采选后的高硫尾矿(含硫量>30%)用作充填材料的现象,采用全面法试验设计,研究灰砂比和料浆浓度对高硫尾矿充填体的长期强度影响规律,并通过XRD和SEM等方法对高硫尾矿充填体中水化产物和微观结构进行微观机理分析,判断高硫尾矿是否适合直接用作充填材料。结果表明:灰砂比和料浆浓度对充填体强度影响非常明显,提高灰砂比或料浆浓度能够明显增大充填体强度。当料浆浓度为72%和74%时,充填体长期强度损失率随着灰砂比的提高先增大后减小;当料浆浓度为76%时,充填体长期强度损失率与灰砂比则成正比关系。在1∶24灰砂比条件下,74%浓度料浆和76%浓度料浆的充填体长期强度损失率相近;在1∶12灰砂比条件下,充填体长期强度损失率随着料浆浓度的提高先增大后减小;在1∶8灰砂比条件下,充填体长期强度损失率与料浆浓度成反比。XRD及SEM研究结果显示充填体水化反应中除了含有大量未反应的黄铁矿,还会生成石膏和少量钙矾石等膨胀性产物,不仅会造成C-S-H凝胶发生脱钙现象,还会引起充填骨架出现裂隙,导致充填体长期强度的减小。因此,矿山使用高硫尾矿进行充填必须考虑充填体在不同龄期的劣化程度,以及是否满足该龄期下的强度要求。

Since some foreign metal mines tend to directly use high-sulfidic tailings(sulfur content >30%) as filling materials due to the high desulfurization technology and high transportation cost,adopts a comprehensive experimental design to study the effect of cement-sand ratio and slurry concentration on the long-term strength of cemented paste backfill(CPB) with high-sulfidic tailings,and analyzes the microscopic mechanism of hydration products and microstructure of CPB by XRD and SEM,so as to judge whether high-sulfidic tailings are suitable to be directly used as filling materials. The research results show that the cement-sand ratio and slurry concentration have obvious influence on the strength of CPB,and increasing cement-sand ratio or slurry concentration can increase the strength of CPB obviously. When the slurry concentration is 72% and 74%,the long-term strength loss rate of CPB first increases and then decreases with the increase of cement-sand ratio. When the slurry concentration is 76%,the long-term strength loss rate of CPB is proportional to the cement-sand ratio. Under the condition of 1 ∶24 cement-sand ratio,the long-term strength loss rate of CPB of 74% and 76% slurry concentration is similar. Under the condition of cement-sand ratio of 1 ∶12,the long-term strength loss rate of CPB first increases and then decreases with the increase of slurry concentration. Under the condition of 1 ∶8 cement-sand ratio,the long-term strength loss rate of CPB is inversely proportional to the slurry concentration. XRD and SEM results show that the hydration reaction of backfill contains a large amount of unreacted pyrite but also produces expansive products such as gypsum and ettringite,which will not only cause decalcification of C-S-H gel but also cause cracks in the skeleton of CPB resulting in the decline of the long-term strength of CPB.Therefore,it is necessary to consider the deterioration degree of CPB at different ages and whether it meets the strength requirements when filling with high-sulfidic tailings in mines.