Study On The Influence Of The Way And Amount Of Admixture On The Durability Of Plastic Concrete

Plastic concrete is widely used in impervious walls,underground cofferdams and other buildings because it can maintain a certain strength and has the characteristics of far lower than the elastic modulus of ordinary concrete.However,at present,the research on plastic concrete is mainly about its working performance and mechanical properties,lacking in-depth study on durability.This paper studies the influence of different admixtures and different mixing methods on the durability of plastic concrete by means of experiments,and analyzes and summarizes the influence law and mechanism.In this paper,based on the engineering analogy method,9 groups of plastic concrete mix proportion needed in the test are determined.Secondly,the influence of the amount and the way of plastic concrete admixture on its flow performance including slump and expansion is studied;Then,the rapid chloride migration coefficient method(RCM)is used to test the chloride resistance of plastic concrete.The chloride migration coefficient is measured,and the influence rules of the amount and the way of admixture on the chloride resistance of plastic concrete are analyzed,and the influence mechanism is analyzed with theoretical research;Finally,the influence of the amount of admixture and the way of admixture on the sulfate resistance of plastic concrete was studied by the wet and dry cycle test of sulfate.The results are as follows:(1)All 9 groups of plastic concrete specimens have good working performance.The slump and expansion range of plastic concrete are 185mm-240mm and 315mm-395mm respectively.The slump and expansion of plastic concrete mixture get bigger when fly ash(FA)and silica fume(SF)is more,and decrease as the increase of fly ash and mineral powder(MP),SF and MP and FA,SF and MP;When different admixtures are mixed,the slump and expansion of the plastic concrete mixture mixed with SF and MP reach the minimum value,and the slump and expansion of the plastic concrete mixture mixed when FA and SF reach the maximum value.(2)In the chloride penetration test,when the things get more,the chloride migration coefficient of all plastic concrete specimens gradually decreases,and the degree of reduction is also gradually becoming low;In the case of a certain amount of admixture,when FA,SF and MP are mixed,the chloride ion transfer coefficient of plastic concrete decreases the most.The decrease range of other groups is from large to small,which are the mixture of SF and MP,the mixture of FA and SF,the mixture of FA and MP.(3)In the wet and dry cycle test of sulfate,the mass,relative dynamic modulus of elasticity and compressive strength of all plastic concrete is bigger first and then decrease as the increase of wet and dry cycles of sulfate.For the quality,under the same admixture mixing mode,the change range of the quality of plastic concrete in the way of FA and SF,FA and MP and FA,SF and MP mixing mode gradually increases with the increase of the admixture content;the change range of the quality of plastic concrete in the way of SF and MP mixing mode increases first and then is bigger when admixture content get more.When the amount of admixture is fixed,the change range of specimen quality is the smallest in the whole process of sulfate dry wet cycle test when FA,SF and MP are mixed;For the relative dynamic modulus of elasticity and compressive strength,the change rate of relative dynamic modulus of elasticity and compressive strength of plastic concrete is the smallest when the content of 30%admixture is the same;When the amount of admixture is fixed,the change rate of relative dynamic modulus of elasticity and compressive strength is the smallest when FA,SF and MP are added at the same time.In this paper,the research on the durability of plastic concrete can provide a theoretical basis for the popularization and application of plastic concrete in a wider range,and also provide a reference for future researchers in the study of related topics.