矿渣基胶凝材料充填试验及胶结体微观结构演化研究

Study on Filling Test of Slag-Based Binder and Microstructure Evolution of Backfill

采用矿粉-水泥复合胶凝材料作为胶结剂,细尾砂作为骨料,开展了不同浓度、砂灰比下充填流动度、泌水率、沉缩率及抗压强度试验。利用扫描电镜-能谱(SEM-EDS)、压汞(MIP)对特定养护龄期下充填体中水化产物种类、分布及孔结构变化进行了表征。结果表明:充填浓度的提高,料浆流动度、泌水率及沉缩率明显降低,而砂灰比对其影响相对较小。充填浓度66%~72%时,料浆流动度为16.1~27.1cm,满足充填泵送及自流输送流动度要求;充填浓度74%时,料浆流动度仅为12.25~13.40cm,且泌水率及沉缩率均较小,不适宜于输送。充填体抗压强度随充填浓度的提高而增加,随砂灰比的提高而下降。养护早期(3d),充填体强度普遍较低,但后期强度发展较快,尤其是28~60d仍有一定幅度的增长。矿粉在水泥碱环境作用下持续发生火山灰反应并生成大量水化硅酸钙(C-S-H)、钙矾石(AFt)等产物细化了充填体内部孔径,增加了体系密实程度是导致充填体强度稳定增长的重要原因。

With mineral powder-cement composite cementitious material as a binder and fine tailings as aggregate,filling fluidity,bleeding rate,sedimentation rate and compressive strength were tested at different concentrations and sand cement ratios.SEM-EDS and MIP were used to characterize the variety,distribution,and pore structure change of hydration products in the backfill at a specific curing age.The results showed that with the increase of concentration,the fluidity,bleeding rate,and sedimentation rate of slurry decreased significantly.However,the influence of sand cement ratio is relatively small.The concentration is 66%-72%,and the fluidity of the slurry is 16.1-27.1cm,which meets the requirements of filling pumping and gravity conveying fluidity.When the concentration is 74%,the fluidity of the slurry is only 12.25-13.40cm,and the bleeding rate and sedimentation rate are low,but it is not suitable for transportation.The compressive strength of the backfill increases with the concentration and decreases with the sand-cement ratio.In the early curing period(3d),the compressive strength of the backfill is generally low,but the compressive strength develops rapidly in the late curing period,especially 28-60d.The continuous pozzolanic reaction of mineral powder under the action of cement alkali environment and the formation of a large number of hydrated calcium silicate(C-S-H),ettringite(AFt),and other products refine the internal pore diameter of the backfill and increase the system compactness is an important reason for the stable growth of the strength of the backfill.