Composition Design And Performance Study Of Ultra-high Performance Geopolymer Concrete Based On Sand And Fine Powder Of Iron Tailing

The ‘14th Five-Year Plan’ clearly states that it is necessary to vigorously promote the preparation of aggregate and admixtures from metal tailings,so as to reduce the environment and safety problems caused by their massive accumulation.It promotes the application research of iron tailings in geopolymer and ultra-high performance concrete(UHPC).Although the use of iron tailings increases the greenness of UHPC,the use of a large amount of cement with high energy consumption and carbon emissions in UHPC is still inevitable,which does not meet the requirements of ‘carbon emissions peak ’and ‘carbon neutrality’.Geopolymer,a clinker free and low carbon bonding material,has been successfully developed for the preparation of ultrahigh performance geopolymer concrete(UHPGC)in recent years.Based on this,the present study utilized iron tailings as a substitute for both the binder and aggregate to prepare a lowcost and sustainable UHPGC,and investigated its properties and microstructure.The main research content and results are as follows:Firstly,the influence of the water-to-precursor ratio(W/B),modulus of water glass(Ms),Fly ash(FA)content,Na2O-to-precursor ratio(N/B),ball milling time of iron tailings powder(ITP),and gradation of iron ore tailings(IOT)on the flowability and strength of UHPGC were studied.The optimal mix ratio was determined as follows: Ms of 1.5,N/B of 7%,FA content of25%,W/B of 0.32,ITP ball milling time of 3.5 hours,IOT gradation of IOT1: IOT2:IOT3=49%:21%:30% and 25% IOT power as filler.Secondly,the influence of content of ITP and IOT on the flowability,strength,flexural strength to compressive strength ratio,impact resistance,damping performance,drying shrinkage,high-temperature resistance,and microstructure of UHPGC were studied.The results showed that the addition of ITP and IOT could reduce the flowability of UHPGC.However,due to the effects of filling,nucleation,and pozzolanic,the proper addition of ITP or IOT could increase the setting time,strength,flexural strength to compressive strength ratio,impact resistance,damping,and high-temperature resistance of UHPGC,and improve the microhardness and compactness of the microstructure.Finally,the comprehensive benefits of traditional and iron tailings-based UHPC and UHPGC were compared using life cycle and internal data normalization analysis.The results showed that compared with traditional UHPC,the carbon emissions per cubic meter of UHPGC with iron tailings were reduced by approximately 27.16%,and the cost was reduced by about4.17%.However,considering the impact of transportation distance on the carbon emissions and the cost of UHPGC,the average transportation distance should be controlled within 22.84 km when preparing UHPGC with iron tailings.