Research And Application Of C30 Ultra-retarded Concrete

This article was accorded to the technical performance requirements of the conc rete sub divisional works of Xipu double iron tunnel project under passing through i n Chengdu,that is,the setting time of C30 super retarded concrete is more than 60 h,the working performance of the mixture meets the requirements of underwater pil e construction,moreover,the 3d compressive strength of super-retarded concrete is l ower than that of 3MPa,and the compressive strength of 28 d reaches the design val ue.In this article,the influence of raw materials on super retarding concrete was an alyzed,the raw materials were selected,especially the super retarded admixture.The orthogonal test method is adopted in the concrete test in this article.It analyzed th e representative data and the degree of its influence by studying the experimental da ta obtained from different factors and multiple levels,and then determined the final results.By combing the constituent elements of concrete,four factors such as watercement ratio,admixture ratio,sand ratio and admixture content were listed.The orth ogonal table L9-34 was adopted for three levels per factor.A total of nine tests we re conducted to record the slump,expansion,setting time,workability,longitude loss of concrete mixtures,as well as the strength and impermeability of concrete in 3d,7d and 28 d.By calculating the mean value,standard square difference and range dif ference,the influence of various factors on concrete was analyzed,thus providing a s cientific theoretical basis for the design mixing proportion.C30 super retarded concr ete with initial setting time more than 60 h,and good working performance,3d compr essive strength lower than 3MPa and 28 d compressive strength more than 36 MPa w as developed.The temperature of Chengdu area changes greatly in summer.The meas ures of retaining samples for natural conservation environment are adopted to guide the whole process of construction.By analyzing the test data of the indwelling samp le,the following conclusion was concluded:1)Super retarded concrete is sensitive to temperature and the curing environmen t has great influence on setting time.2)The strength of super retarded concrete of 28 d is greatly affected by the setting time.The compressive strength between 34.6 and 41.8Mpa accounted for 95% of the sample data.The sample is generally positive distributed.3)The initial setting time of super retarded concrete natural curing test piece is 63 ~ 78 h,the average time is 70 h,and the retarding time is stable.The setting time is generally positive distributed,64.8-76 h accounted for 95% of the total sample volume.4)Statistics show that concrete with a retarding time of more than 72 hours indicating that the concrete strength of 28 days will be damaged in varying degrees after the retarding time exceeds 3 days.The average strength of concrete under 72 h retarding time is 40 MPa,which is higher than that of 72 h concrete about 4MPa.This paper comprehensively introduces the construction process and process control measures of super-retarded concrete occlusal pile,the control and deviation correction of opening position and verticality,the cutting construction of the occlusal pile,the drilling sequence,time control and quality control of super retarded concrete under water pouring.