Study On The Material Design Of The Porous Concrete Drainage Road Base

Serious water damage is brought about by the free seeping water,the porous concrete drainage road base can induce seeping water away from the pavement structure efficiently.Many works on the porous concrete drainage road base have been carried in our country,but most of them focus on the project application of it and the drainage structure design,the mix design of the porous concrete drainage road base material has not formed a theoretical system.The materials composition, structure and property of the porous concrete drainage road base are studied with material approach,and a kind of mix design method fitting for the porous concrete drainage road base is put forward,based on volumetric analysis.A new kind of contacting point model is set up according to the structural characteristics of the porous concrete drainage road base material:a framework is formed by the interlocking of the coarse aggregates,so a bulk is formed,and the strength of porous concrete is related to the contacting point strength,area and number.The mix design is carried according to the contacting point model:An optimum limit of the aggregate gradation for the porous concrete drainage road base material is recommended,according to the optimization of maximum size of coarse aggregate,the proportion of fine aggregate,the gradation of aggregate and calculation of Weymouth theory;the optimize design of composition and structure of paste is processed,by choosing cement variety,adding mineral admixtures and thickening agent to improve paste strength,contacting area and promote paste enrichment at the contacting position for enhancing ITZ.In this paper,the permeability of porous concrete is studied,permeability coefficient is tested with the apparatus developed by the author,and correlativity among permeability coefficient,whole porosity and effective porosity are studied. The strength,stress-strain and dry shrinkage of porous concrete are investigated. Result indicated that:the porous concrete drainage road base researched in this paper decreases the cement content by 30～50kg/m~3,the whole content of cementing material is only 150 kg/m~3,7d compressive strength can reach 7～8MPa and 28d's approach to 10MPa while the porous concrete cured in the condition of 100% humidity.Its permeability coefficient is between 1.8～3.2cm/s,so the road base made with porous concrete gains a good drainage property,and the dry shrinkage ratio is declined markedly.According to the relative research on the literatures and the experimental research in the paper,the design index and standard of the porous concrete are put forward.In this paper,the mix design method for the porous concrete drainage road base is brought forward,the gradation design,the computational method of cement content and the experiential formula of water content are all included.