The Influence Of Water-reducing Agent On The Properties Of Total Tailings Cemented Paste Backfill

With the growth of China,s national economy sustained and rapidly, the miningindustry has been developed with a high speed.The mining industry providesamounts of raw materials for the national economy but also generates a lot of waste–tailings.The large tailings pillling at the surface will destroy the land and pollutethe environment, and there are a lot of underground mined-out area, all those canbring negative impact on the natural environment and social and economic life,which has become an urgent major problem to be solved at present.For the handling of total tailings, the most important method is using it toprepare total tailings cemented paste backfill (CPB) and filling into undergroundmined area, which not only solves the problem of environmental pollution broughtby the total tailings deposited on the surface, but also ensures the balance of ecologythat the mining empty area does not collapse and the balance of ecology.By retrieving relevant literature to understand the research status and presentproblems of total tailings cemented paste backfill, this paper carried out thefollowing tasks:(1) Analyzing and testing physical properties of raw materials used in this paperas well as chemical properties.Understanding experimental principle andmethods.Mastering operational processes of experiment.(2) Researching fluidity test methods of cemented paste backfill (CPB)prepared by fulltailings.The main performance of CPB is its fluidity. In present, the method to measurethe flowability of CPB in our country is referenced in the measurement method ofthe concrete fluidity—slump method.In addition,the rheometer can measure therheological properties of CPB, and learn the material parameters when transported.The principles,advantages and disadvantages of the two experimental methods forCPB have been ananlsised and studied.The method using fluidity electric jumpingtable to measure the flowability of CPB have been proposed,the principle is explained,and the feasibility and the accuracy of this method is proofed.Then theflowability of CPB prepared by fulltailings have been tested in subsequentexperiments.(3) Researching the dispersion effect of water reducer on kinds of powdercommonly used in CPB.Five categories of water reducer commonly used in the field of concrete (i.e.polycarboxylate superplasticizer, aliphatic superplasticizer,amino superplasticizer,naphthalene superplasticizer and lignosulfonate water reducer) and five kinds ofpowder commonly used in CPB (i.e. Portland cement,fly ash,slag powder, tailingspowder and limestone powder) are selected to conduct a comparative experimentalstudy on the dispersion degree of water reducing agent on the powders.Experimentalresults showed that polycarboxylate superplasticizer has the best dispersion effect onPortland cement,slag powder and fly ash,and aliphatic superplasticizer on limestonepowder and tailings powder,aliphatic superplasticizer,s dispersion effect on fly ashis also better (after polycarboxylate superplasticizer).Since the content of tailingspowder and fly ash and/or limestone powder in CPB of fulltailings is much greaterthan Portland cement and slag powder,and the unit price of aliphatic superplasticizeris about a quarter of polycarboxylate superplasticizer.Therefore,the aliphaticsuperplasticizer will be the most valueable water reducer to prepare CPB.(4) Researching the influence of water reducer on performance of CPB.18groups of specimens are prepared in this article, the fluidity of CPB slurry isfixed (fluidity–slump is180mm),comparative study on the slurry and curedsamples with and without superplasticizer samples,in which Portland cementcontent is3%,5%and7%(by total mass of solid) and curing period is from7d,14dto28d.The results show that the solid concentration in the slurry can increase4percentage points by adding superplasticizer.The experimental results of pore sizedistribution obtained by mercury porosimetry and compressive strength test resultsprove that water reducer can open slurry flocculation structure and refine pore size insolidified samples to increase compressive strength of CPB.