无熟料超细金属尾矿基固结材料的早期水化与液相特性

Early hydration and liquid phase characteristics of solidified body of clinker-free superfine tailings

为探明超细金属尾矿粉在石灰-石膏体系中的早期水化固结特性,以生石灰、石膏和铁尾砂为原料,采用超细粉磨制备了无熟料铁尾砂粉固结材料,提取水化浆体3 min~24 h的液相并测试了其离子浓度及电导率,结合水化放热速率曲线及扫描电镜(SEM)、X-ray衍射分析(XRD)、热重-差热分析(TG-DSC)等测试结果,研究了固结浆体早期水化行为与液相特性变化的关系.结果表明:固液混合后液相各离子浓度快速上升,在10~30 min达到峰值后快速下降,180 min之后以较缓的速度继续下降;液相电导率与Ca^(2+)、OH-和SO_(4)^(2-)离子总浓度变化有较高的一致性;固结材料水化过程中有两次放热行为,起止时间分别为0~15 min和20~180 min;水化产物物相分析显示浆体中90 min可见AFt特征峰及C-S-H吸热峰.实验证明:在石灰-石膏-水体系中,铁尾砂粉表面的非晶态SiO_(2)和Al_(2)O_(3)能够快速溶解并发生水化反应,生成AFt及C-S-H,水化产物对未水化铁尾砂颗粒胶结固化,使固结体产生强度;延长粉磨时间可显著提高铁尾砂表面非晶态硅铝成分含量及石灰、石膏的溶解速率,加速浆体的水化并增加水化产物的生成量.

To investigate the early hydration and consolidation mechanism of superfine metal tailings powder in the CaO-CaSO_(4)-H_(2)O system,a clinker-free consolidation material based on iron tailings powder was prepared by superfine grinding lime,gypsum,and iron tailings.From 3 min to 24 h,the liquid phase of the hydrated slurry was extracted by centrifugation and high-pressure extraction.The changes in ion concentration and conductivity were tested,and the relationship between them was analyzed.The relationship between the formation mechanism of early hydration products of a consolidated body and the change of liquid phase characteristics is studied combined with the hydration exothermic rate curve,field emission scanning electron microscope(SEM),X-ray diffraction analysis(XRD),thermogravimetry-differential thermal analysis(TG-DSC),and other test methods.The results show that lime,gypsum,and amorphous components,which are on the surface of iron tailings powder,dissolve rapidly within a few minutes after solid-liquid mixing.The concentration of each ion in the liquid phase rises sharply,reaching the peak or saturated state successively in 10-30 min,and then decreases rapidly.After 180 min,the decline rate slows down but continues to decline.The liquid conductivity has a very high positive correlation with the total concentration of Ca^(2+),OH-,and SO_(4)^(2-)ions;The first hydration exothermic peak of the consolidated material is concentrated within 0-15 min,which is mainly caused by the wetting and dissolution of soluble components in the consolidated material and the exothermic behavior of lime hydration;The starting and ending time of the second hydration exothermic behavior is 20-180 min,which is mainly caused by the phase change heat generated by the formation of hydration products.Increasing the grinding time significantly prolongs the termination time of the second exothermic behavior and increases its peak value;The phase analysis of hydration products showed that AFt characteristic peak and C-S-H endothermic peak could be seen in the slurry after hydration for 90 min.Research has proved that the amorphous SiO_(2) and Al_(2)O_(3)on the surface of superfine iron tailings powder have the characteristics of rapid dissolution in alkaline solutions,and a hydration reaction can occur when lime and gypsum components are encountered.When the solubility product of hydration products is reached,hydration products AFt and C-S-H will be generated.The two hydration products are interspersed and cemented with each other,and the unhydrated iron tailings particles will be consolidated to form a hardened body.Prolonging the grinding time can effectively increase the system’s amorphous SiO_(2) and Al_(2)O_(3)content and the proportion of superfine particles in iron tailings,thus improving the slurry hydration rate.While increasing the amount of the hydration product,the filling effect of the micro powder part is further increased,and the strength of the consolidated body is correspondingly improved.