| Presently,the stockpile of large amount of tailings has created great challenge for reasonable utilizing and green high performance concrete are widely used in engineering.This paper choose gold tailings as the main research target,from Shangluo,Shanxi Province.Firstly,through mechanical grinding and high-temperature ways to stimulate the volcanic ash activity,then studied the volcanic ash activity and mineral properties of gold tailings.Secondly,based on the studied of mineralogical characteristics of activated tailings,useing gold tailings to preparate cementitious materials,study on mechanical properties and binding of chloride ion into cementitious materials,the test methods of XRD,SEM and FT-IR are used to reveal the hydration products of gold tailings in cementitious materials and its fixation of action to chlorine ions.Lastly,useing the best cementitiongs materials make up C30and C40 concrete,it was excellent workability and durability,conform to the standard requirements.The research of this project can provide theoretical and technical references for tailings in the application of modern concrete,at the same time,it can provide an effective way to achieve high value-added applications of tailings.By studying the basic characteristics and activation of gold tailings,the main mineral composition is quartz,calcite,dolomite,and a small amount of kaolinite?plagioclase,Its belonging to the volcanic materials,which physical and chemical properties are extremely stable,because it has small aluminum and silicon ratio.The active activation of single mechanical force does not increase the activity of gold tailings.Adopt to composite activation technology?thermal activation of gold tailings activated by mechanical activation?,it is found that the activity of gold tailings is enhanced,the unstable mineral components in tailings are decomposed,and the active SiO2 and Al2O3 components are increased.The best activation condition of gold tailings is in grinding 75min and heating treat 1h at 750°C high temperature environment,the activity is the best.It is perfect for curing of chloride ion in cement.Considering the synergistic effect of particle size and activity,through single factor and orthogonal experiments,the optimal ratio of tailings cementing material is obtained:gold tailings:cement clinker:slag:desulphurization gypsum=27:37:27:9?mass ratio?.The specific surface area of gold tailings,cement clinker,slag and desulfurization gypsum in cementing materials is 702m2/kg,355m2/kg,473m2/kg and346m2/kg respectively.The effect of the prepared cementitious material on the curing of Cl-has been significantly improved,and its 28d Cl-curing amount was 5.07mg/g.Compared with 42.5#portland cement,the effect of Cl-curing was increased by15.2%.By analysing the hydration products and the mechanism of chlorination of the cementitious material,it revealed that the early hydration products of the cementitious material were AFt,C-S-H gels,Ca?OH?2 and a small amount of friedel salt.With the deepening of the hydration degree,the active components in the gold tail mineral powder are hydrated the second time in the alkaline environment.And it prompted Cl-to combine with the hydrated mineral chemistry to produce more Friedel salts,C-S-H gels and AFt products.Thus,C-S-H has a strong physical adsorption to Cl-,which makes the structure of the hardened slurry become dense and makes the effect of solid chlorine be increase.Through the test of mechanical properties,the mortar specimen 3days and28days compressive strength of the gold tailings cementitious material is 18.2MPa and 37.4MPa,which reach the standard of 32.5#portland cement specified in GB/175-2007 general portland cement.And the compressive strength of C30 concrete at 3days and 28days is 11.8MPa?35.6MPa.The compressive strength of C40 concrete at 3days and 28days is 12.2MPa?45.4MPa.In the shrinkage of concrete,the shrinkage value of each age is lower than cement concrete,it has well performance and durability,meeting the requirements of engineering application. |
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