Study On Mix Proportion Design And Durability Of High Performance Concrete For High Speed Railway

Durability of concrete is of great significance to prolong the service life of concrete structures in corrosive environments.Aiming at the economical and environment-friendly production of concrete by comprehensive utilization of the supplementary cementitious materials made of industrial byproducts,the resistances to chloride penetration,sulfate attack,and frost of high-performance concrete were studied in this paper.Fifteen concretes were designed at different water–binder ratio with the changes of contents of fly ash(FA),silica fume(SF),ground granulated blast-furnace slag(GGBS),and admixture of sulfate corrosion-resistance(AS).The compressive strength,the total electric flux of chloride penetrability,the sulfate resistance coefficient,and the indices of freezing and thawing were measured.Results indicate that:(1)Due to the difference of chemical composition,fineness,and pozzolanic activity,the supplementary cementitious admixtures present different effects on the strength and durability of concrete.In general,SF and FA benefit the compressive strength and durability of concrete,and the negative effect of GGBS can be overcome with the hybrid use of SF,FA,and AS.AS benefits the compressive strength and the resistances of concrete to chloride penetration and sulfate corrosion,while showing no obvious effect on the resistance of concrete to frost.(2)With the different combinations of the supplementary cementitious admixtures,the concrete can be produced with the compressive strength ranging from 70 MPa to 110 MPa.With the binary use of FA and SF,FA and GGBS,or the ternary use of SF,FA,and GGBS,the compressive strength of concrete increases with the reduction of water to binder ratio.With the admixing of proper content of 7%FA and 8%SF,the concrete can be prepared with compressive strength of about 100 MPa,in which the cement can be replaced by equal weight of 8%GGBS and 10～12%AS.(3)Except for the concrete only mixed with GGBS or with GGBS and FA,other concrete can be produced with ideal resistance to chloride penetration.With proper content of FA and SF,the concretes present a superior resistance to chloride penetration of the highest grade over Q-V with the index of total electric flux lower than 500 C specified in the China code,in which the cement can be replaced by equal weight of 8%GGBS and 10～12%AS.SF,can effectively improve the compactness of concrete,the chloride ion diffusion coefficient of concrete of 10 group were within the specification of RCM-Ⅴlevel.(4)Except for the concrete only mixed with GGBS or with GGBS and FA,other concretes reaching the highest grade over KS150 withstood the 150 dry-wet cycles of sulfate corrosion specified in the China code.The concretes with the AS appeared to have a superior ability to resist the sulfate corrosion.(5)All concretes are at the highest grade over F400 for the resistance to frost,with the relative dynamic elastic modulus no less than 60%and the weight loss rate no larger than 5%specified in the China code,although the concrete admixed only with GGBS appears to have a relatively low resistance.(6)The durability is positively related to the compressive strength of concrete with hybrid admixtures.With water to binder ratio of 0.29 and total binders of 500 kg/m~3,the highest grades of resistances specified in the China codes to chloride penetration,sulfate corrosion,and frost can be reached for the concrete admixed with 7%FA+8%SF+8%GGBS or7%FA+8%SF+8%GGBS+(10～12)%AS,while the compressive strength was about 100 MPa.