Research On Design And Application Of Lead-zinc Tailings Backfill

Metal tailings is a kind of byproduct of milling that consists of both metal ore and non-metal ore.Nowadays,a large amount of tailings is generated by the fast development of society and the environment of management of these tailings is required.In recent years,cemented backfill of tailings into underground mine openings has gained importance for their environmental management and the reduction of tailings disposal and rehabilitation costs.FanKou Lead-Zinc?FK?mine has been producing two kinds of tailings based on different technology of ore dressing:CT?coarse tailings?and FT?fine tailings?.More than 50%of CT particles'diameter are larger than 100?m,while more than 90%of FT particles'diameter are smaller than 100?m.There are two obstacles coming up while FK is doing the refill job:the main cemented material they used to produce backfill is P.O Portland cement,Portland cement can generate a large amount of CO₂ while produced,and the cost is rather high;at the same time,FT can not be used directly to make backfill due to its properties.In this pater,we carry out several main experiments based on the solid waste material we get:on the one hand,we use GGBS as a replacement for Portland cement and use GGBS-Cement as the main cemented material for backfill,we also add some alkali to activate the system given that the GGBS-Cement has a poor early strength performance.On the other hand,physical and chemical properties of FT were studied,then FT were used in GGBS-Cement as a replacement of cemented materials and in backfill as a replacement of CT,XRD?SEM?MIP and other modern analysis technology were employed to study the changes of samples'hydration products and microstructure.Several conclusions have been made:?1?The results of experiment show that an appropriate amount of sodium silicate as alkali-activated can dramatically accelerate the early hydration process of GGBS-Cement,which results in more hydration products such as C-S-H gel and a denser construction and higher mechanism performance of samples.?2?With not exceeding 15%of FT,not only can the hydration heat of GGBS-Cement be reduced and hydration time be prolonged,and more hydration products like C-S-H gel would emerge to form network structure and fill the pores among the system,this leads to a better microstructure improved by decrease the diameter of pores,which can result in a better compressive strength performance of GGBS-Cement samples.?3?It has been proved by engineering project that the workability,mechanical properties and long-term durability of GGBS-Cement backfill can meet the requirements of the mine.At the same time,compared with cement as the backfill cemented material,using GGBS-Cement as cemented material can reduce the amount of binders by decrease the Cement/tailings ratio.?4?FT can be used to improve the properties of backfill.When the replacement of FT for CT is less than 15%,the resulting integral grading curves of the recipes is closer to target curves as the amount of FT increases,coupled with filling effect of FT,the fluidity of backfill increases.However,the fluidity of backfill will drop dramatically when the replacement of FT is beyond 15%due to its requirement for more water.On the aspect of strength,because of its filling effect and nucleation effect,the addition of FT can leads to a better microstructure by decrease the diameter of pores,which not only results in a better compressive strength performance of GGBS-Cement backfill,but it can also prevent the carbonation and shrinkage of GGBS-Cement backfill by impeding the penetration of CO2 from air.