Experimental Study On The Influence Of Stone Powder On The Performance Of Manufactured Sand High Strength Concrete

With the rapid development of the construction industry,natural sand resources are becoming increasingly scarce.In view of the country’s emphasis on ecosystem protection,it has become an inevitable trend of the sustainable development of the concrete industry that manufactured sand replaces natural sand to prepare concrete,and manufactured sand has a particle size of less than 75μm.The fine stone powder,which constitutes the fine particle gradation of manufactured sand,is an important component of manufactured sand.The influence of the mixing amount of stone powder in the manufactured sand concrete is the core issue of the current research on manufactured sand concrete.In this paper,local materials are used to prepare C70 high strength manufactured sand concrete,which is rich in basalt gravel,manufactured sand,fly ash and silica fume or metakaolin in Inner Mongolia.Through experiments,the effects of different stone powder content on the working performance,macro-mechanical performance,micro-performance and frost resistance of silica fume group or metakaolin group manufactured sand concrete were explored.The research on frost resistance was simulated in northern my country.The freeze-thaw conditions and icing characteristics of pavement concrete in winter,using the effects of rapid freeze-thaw cycles and the erosion mechanism of snow-melting agents,provide experimental basis for the popularization and application of manufactured sand concrete in cold northern regions.The main results of this research are:1.After mixing two kinds of fine aggregates of manufactured sand and natural sand into concrete,and carrying out comparative experiments,it is found that the workability of natural sand concrete is significantly better than manufactured sand concrete,mainly in terms of fluidity and encapsulation.However,because the hardness of manufactured sand is higher than that of natural sand,and the bite force of manufactured sand is stronger than that of natural sand during the hardening process,the strength growth rate of manufactured sand concrete is significantly higher than that of natural sand concrete.2.By mixing the stone powder into the silica fume group and the metakaolin group respectively,high strength manufactured sand concrete was prepared,and comparative tests were carried out.Find:(1)In terms of working performance,a proper amount of stone powder can effectively improve the workability,cohesion and encapsulation of manufactured sand concrete,but it has an adverse effect on fluidity.As the amount of stone powder increases,it will cause slump.And the expansion degree decreases.When the stone powder content is 11%,the expansion loss of the silica fume group and the metakaolin group are both larger,which are25.53%and 23.4%,respectively.(2)The mechanical test shows that with the increase of the stone powder content,the compressive strength,splitting tensile strength and flexural strength of the specimens all increase first and then decrease.Although the activity of stone powder is low,a certain amount of stone powder can significantly improve the mechanical properties of machine-made sand concrete.Through experimental analysis,the optimal stone powder content of the silica fume group is 5 to 7%,and the optimal stone powder content of the metakaolin group is 7 to 9%.(3)Microscopic tests show that adding a proper amount of stone powder to concrete can effectively fill the gaps between cement particles,optimize the gradation,and further enhance the density of the transition zone between the slurry and the interface.As the curing age increases and the hydration reaction is completed,the proportion of harmless pores increases,and the proportion of harmful pores and harmful pores decreases.(4)The frost resistance test shows that a certain amount of stone powder can effectively improve the frost resistance of the manufactured sand concrete specimens.The silica fume group specimens have reached the design frost resistance grade M-SP5-SF6,M-SP7-SF6There are two groups,and the metakaolin group has three groups M-SP5-MK8,M-SP7-MK8 and M-SP9-MK8 that have reached the designed anti-freezing grade.(5)Freeze-thaw damage mechanism analysis and model establish research show that the freeze-thaw resistance and service life of manufactured sand concrete have a greater relationship with different freeze-thaw media.Under the same medium,the higher the strength,the longer the freeze-thaw cycle life;The value of the dynamic elastic modulus index is larger than the mass loss rate index,indicating that the data model fits better.Therefore,it further shows that the relative dynamic elastic modulus index is more suitable as a damage variable to establish a freeze-thaw damage model of manufactured sand concrete.3.Through the above-mentioned experimental research,it is proved that basalt rock powder can be used as high-performance manufactured sand concrete admixture.When the amount of silica fume is 6%,the amount of cement is only 420 kg/m~3 or the amount of metakaolin is 8%,the amount of cement is only 410 kg/m~3,the glue material is 500 kg/m~3,the sand rate is 42%,and the water binder ratio is 0.33,which can be formulated into C70high-strength manufactured sand concrete with excellent working performance,slump>160mm,compressive strength of silica fume group 102.2MPa,metakaolin group81.47MPa,and frost resistance grade F350.