Study On Preparation And Properties Of C80 Manufactured Sand High Performance Concrete

At present,the society has paid more and more attention to sustainable development.In the field of civil engineering,sustainable development requires not only natural sand conservation and environmental protection,but also durable building structures.Therefore,high performance concrete with manufactured sand came into being.In order to solve the problem of poor workability of manufactured sand concrete,it is proposed to use manufactured sand conditioner to improve its workability,and C80 manufactured sand high performance concrete was prepared by using basalt manufactured sand and metakaolin which are abundant in Inner Mongolia.Then carried out experiments to study the effect of metakaolin with different content on the working performance,mechanical performance and durability of the manufactured sand concrete,and compared it with the common admixture silica fume.In the study of frost resistance,it should be considered that there are freeze-thaw and deicing agent erosion damage of road and bridge concrete components in the cold area of North China,so the salt erosion freeze-thaw coupling test of frost resistance should be simulated.The main research results are as follows:1.Compared with natural sand,manufactured sand has an adverse effect on the workability of concrete,but it can improve the splitting tensile strength and flexural strength of concrete by 10%and 8.4%,respectively.2.Through the contrast test of adding the regulator,it is found that 3%of the regulator can solve the problem of poor workability of the manufactured sand concrete more economically,and improve its 28d mechanical properties.The compressive strength is increased by 8.3%,the splitting tensile strength is increased by 3.8%,and the flexural strength is increased by 4.5%.3.By mixing silica fume and metakaolin,two mineral admixtures,respectively,to prepare manufactured sand concrete for comparative test.Found:(1)The workability test shows that with the increase of the content of silica fume or metakaolin,the wrapping and workability of fresh manufactured sand concrete will increase,while the slump,expansion and mobility will decrease.The effect of the two admixtures on the fresh manufactured sand concrete is similar.However,the apparent quality of the samples’mixed with metakaolin is better.(2)Mechanical tests show that with the increase of silica fume or metakaolin,the compressive strength,splitting tensile strength and flexural strength of the specimens increase first and then decrease.Both of the two admixtures can improve the early and later strength of the specimen.However,the compressive strength and splitting tensile strength of the specimens mixed with silica fume are slightly better,and the flexural strength of the specimens mixed with metakaolin is slightly better.(3)Microscopic test shows that appropriate amount of silica fume and metakaolin can promote hydration,fill pores,effectively improve pore structure,and reduce harmful pore volume.But the effect of metakaolin is better than that of silica fume.(4)On the basis of compressive strength test and microscopic test,the characteristics of compression full stress-strain curve are analyzed,and a piecewise nonlinear constitutive model is established.The Kumar strength pore model is validated by analyzing the characteristics of pore strength variation.(5)The durability test shows that appropriate amount of silica fume or metakaolin can improve the impermeability,chloride ion permeability and frost resistance of the specimen.The impermeability of the two admixtures is the same,but the permeability and frost resistance of metakaolin are better.4.The results show that metakaolin has similar effect with silica fume,and can be used as high performance sand concrete admixture.It is found that C80 manufactured sand high performance concrete with good workability,slump>160mm,compressive strength 98.5MPa,impermeability P12,chloride ion penetration resistance RCM-Ⅳ and frost resistance F350 can be prepared when metakaolin content is 8%,water binder ratio is 0.33,sand ratio is 42%,glue material content is only 500 kg/m3,cement content is only 410 kg/m3,and regulator is used.