Experimental study on effect of molybdenum tailings powder on strength and microstructure of mortar
Molybdenum tailings powder(MTs) was used as an admixture,and mortar and paste were prepared by standard curing and steam curing. The effects of MTs content and curing methods on the mechanical strength of mortar were studied. The effects of MTs on the pore structure,microstructure characteristics,and the types and contents of hydration products under different curing conditions were discussed by means of mercury intrusion porosimetry(MIP),thermogravimetric(TG),and scanning electron microscopy(SEM). The results show that with the increase of age,the flexural and compressive strengths of standard curing and steam curing mortar gradually increase,but the early strength of steam curing mortar is higher than that of the corresponding standard curing group. When the content of MTs is not more than 15％,the strength of steam-cured MTs mortar at 1 d is not less than 70％ of that of the corresponding standard-cured paste at 28 d,and the strength of standard-cured and steam-cured MTs mortar at 28 d is not less than 90％ of that of the corresponding pure cement paste. Under standard curing and steam curing conditions,the proportion of harmful pores is significantly reduced,the proportion of less harmful pores is increased,and the pore structure of the paste is optimized after adding an appropriate amount of MTs to the paste. Comparing with the reference group,especially when the content of MTs is 15％,under the condition of steam curing,the less harmful pores of[20,50) nm in the paste increase by 64.7％,the more harmful pores above 200 nm decrease by 26.7％,and the most probable pore size decreases by 11.6％. After the addition of MTs,no new types of hydration products are generated,and due to the pozzolanic effect of MTs,the secondary hydration reaction of cement slurry is promoted,and more hydration products are generated to fill the pores,so that the microstructure of the slurry becomes dense. After adding an appropriate amount of MTs,the mechanical strength of the mortar does not decrease significantly,and the generated hydration products refine the pore size of the cementitious materials and increase its compactness. Using MTs as an admixture to prepare low-carbon cement-based materials can reduce the amount of cement in cement-based materials and reduce the carbon emissions of the construction industry,strengthen the popularization and application of molybdenum tailings in cement-based materials and realize the resource utilization of molybdenum tailings.
万方数据
维普
