基于超细粒级尾砂的水泥基充填复合材料性能研究

Study on Properties of Cement-Based Composite Filling Materials with Ultrafine Tailings

为提高超细粒级尾砂消纳量,降低充填成本,以尾砂替代部分水泥,研究尾砂取代率、粉煤灰掺量和偏高岭土掺量对复合充填材料流动性能、抗压强度、抗氯离子渗透能力、抗硫酸盐侵蚀性能及抗冻融性能的影响。研究结果表明:料浆流动度和抗压强度与尾砂取代率呈负相关,粉煤灰能够改善料浆流动性能,对充填体早期强度具有削弱作用,对后期强度的发展具有改善效果,当粉煤灰掺量为12%时,28 d和90 d抗压强度分别达最大值,为8.03 MPa和8.92 MPa;偏高岭土能够吸附自由水,加速水化反应进程,对料浆具有明显的增稠作用,促进C-S-H凝胶成核,改善充填体内部孔细结构,阻断氯离子传输通道,提高充填体力学性能和抗氯离子渗透性能;在硫酸盐和温度协同侵蚀作用下,充填体试块质量和抗压强度均呈先升高后降低的趋势,钙矾石和石膏的生成,增加了试块质量和抗压强度,但过量的钙矾石导致结构挤压膨胀,充填体出现损伤劣化;随着冻融循环次数的增多,充填体质量损失率和强度损失率逐渐增大,低温降低了水化反应速率,冰晶的膨胀作用,导致水化产物对骨料颗粒的黏结包裹作用减弱。

In order to improve the consumption of ultrafine tailings and reduce the cost of filling,tailing was used to replace part of the cement,and the effects of tailings replacement rate,fly ash dosing and metakaolin dosing on the flowability,compressive strength,chloride ion penetration resistance,sulfate erosion resistance and freeze-thaw resistance of composite filling materials were investigated.The results show that the slurry flowability and compressive strength are negatively correlated with the tailings replacement rate,and fly ash could improve the slurry flowability,weaken the early strength of the filling body and improve the later strength development.The 28 d and 90 d compressive strength can reach the maximum value of 8.03 MPa and 8.92 MPa,respectively,when fly ash content is 12%.Metakaolin can adsorb free water,accelerate the hydration reaction process,have obvious thickening effect on the slurry,promote the nucleation of C-S-H gel,improve the fine structure of the pores inside the filling body,block the chloride ion transport channel,and improve the mechanical properties and chloride ion penetration resistance of the filling body.Under the synergistic effect of sulfate and temperature erosion,the mass and compressive strength of the filling specimens show a tendency of first increasing and then decreasing.The generation of calcium alumina and gypsum increase the mass and compressive strength of the specimens,but the excessive calcium alumina leads to the extrusion and expansion of the structure and the damage deterioration of the filling body.With the increase of the number of freeze-thaw cycles,the mass loss rate and strength loss rate of the filling body gradually increase.The low temperature can reduce the rate of hydration reaction and the expansion effect of ice crystals,which leads to the weakening of the adhesive wrapping effect of hydration products on aggregate particles.