The Study On Mix Proportion Design Method Of High Performance Porous Cement Concrete For Tunnels’ Pavement

The paper had focused on the work environment of tunnels’ pavement,considered the special requirements in materials and structure of tunnels’ pavement,put forward the concept of high performance porous cement concrete pavement. Asthe material for tunnel’s pavement, porous cement concrete has good developmentpotential and wide application prospects. According to the existing problems thatordinary porous concrete materials used in tunnel’s pavement, the paper had studiedthe all-round technical measures of manufacturing high performance porous cementconcrete which has high-strength, high durability, good drainage and noisereduction, which has provided technical reference for applying in tunnelengineering.From the view of gradation design for porous cement concrete, this topic hadmainly studied raw materials selection, orosity measuring method, the relationbetween strength and porosity, additive materials’ effects on the strength of porousconcrete, mechanical properties and indoor molding method, etc.First, the raw materials which used in preparing porous cement concrete hadbeen selected and tested. According to these eight initial gradations, based on thestrength and porosity test, this paper had preliminarily selected gradation2#-2(5-10mm aggregate accounted for80%) for the optimum gradation, and putforward porosity measuring method of the porous cement concrete. Next, usingcement slurry wrapping experiment and concrete strength test to identify, thenverify water-cement ratio and cement-aggregate ratio. The optimum water-cementratio is0.27and the cement-aggregate ratio is0.25. At the same time, by comparingdifferent indoor molding method, we had chosen the vibration-rolling moldingmethod as the ideal molding method. Then, we can further confirm gradation2#-2bethe best gradation.Second, the paper had adopted different additive dosage of fly ash and siliconash as the inside-doped or outside-doped mixed material, and chosen fly ash andsilicon ash mixture as the inside or outside double-doped admixture, preparedcement slurry specimens with additive and cement paste specimens, mainly by comparing their strength in different curing time to select the dosage and addingmode of additive materials. According to these results, preparing concretespecimens which has additive materials, to further define the best proportion andadding mode of additive materials. As to inside-doped method, we recommendusing fly ash(10%) and silicon ash(6%) mixture inside double-doped; and for theoutside-doped method, we had chosen fly ash(10%) and silicon ash(4%) mixtureoutside double-doped.Finally, according to properties of tunnels’ pavement, this paper has presenteda three dimensional finite element mathematical model to make simulation analysisof porous cement concrete pavement’s mechanical response and rules in differentsituations, and proposed design method of porous cement concrete for tunnels’pavement. For tunnels’ pavement structure, due to the high modulus of bothbedrock and base course, and considering every structural layer has better holisticperformance inside the tunnel, we can conduct mechanical analysis and design withthe model which has the combination of face plate and base course in calculation.