Preparation And Application Of Self-compacting And Non-shrinkage Concrete

In this paper,C55 concrete-filled steel tube arch bridge of Matan Hongshuihe river is prepared by studying the self-compacting and non-shrinking of concrete,so as to reduce the probability of concrete-filled steel tube void and debonding.The following aspects are studied in this paper:1)Based on the relevant theories and control mechanism of self-compacting and non-shrinkage concrete,and combined with the analysis of influencing factors of concrete performance,prepare C55self-compacting non-shrinkage concrete.It is determined that the water-binder ratio of concrete mixing ratio is 0.30,the sand rate is 45%,the dosage of cementing material is 530 kg/m³,the dosage of water-reducing agent and expansion agent is 2.3%and 10%of cementing material respectively,and the dosage of fly ash,slag powder,expansion agent and other admixtures is 150 kg/m³.2)The effect of expansive agent on self-compaction of concrete is tested by comparing the test results of concrete without,single and double calcium-magnesium expansive agent,the results shows that:No matter whether the expansion agent is added or not,under the action of admixture and retarding and highly efficient water-reducing agent,the self-compacting performance of concrete?filling,gap passing,anti-segregation?can reach the design target of mixing ratio,and achieve large fluidity,no segregation and no bleeding;3)By comparing the test results of concrete properties with different amounts of cementitious materials and expansive agents,the results shows that:Adding enough cementitious materials and proper expansion agent can ensure the overall expansibility and expansion of concrete to reach the target.The more cementitious materials is,the more obvious the expansion is.4)C55 self-compacting non-shrinking concrete is applied to concrete-filled steel tube members.Through monitoring the temperature and deformation process of its core concrete,the following conclusions are obtained through analysis:The maximum temperature of double-mixed concrete after entering the mould is 47?.The early concrete expansion double admixture group is the largest;The temperature drop shrinkage deformation of the double-doped group in the later shrinkage stage is the smallest.Within 7 days after condensation,the expansion of concrete in the double mixing group is close to 0.After 7d,Mg O expansion agent in double-mixed group concrete will continue to act and slightly expand,and restrain concrete shrinkage.At the temperature rise stage,the overall expansion deformation of core concrete is about 20%radial.5)In the application of C55 self-compacting non-shrinkage concrete in the Matan Hongshui river steel tube arch bridge,after monitoring the temperature-deformation process of core concrete in steel tube,the results show that:At the stage of temperature rise,significant volume expansion occurs in concrete.Under the constraint condition,the peak value of expansion deformation is around 450×10^-6,and the shrinkage value of concrete at the stage of temperature drop is lower than the concrete autogenous linear expansion coefficient 10×10^-6,which has a significant effect of inhibiting shrinkage.In this paper,the preparation of self compacting non-shrinkage concrete and its application in CFST structure are studied,which provides some reference value for solving the problem of void and debonding in practical engineering application.