Research On Freeze-thaw Damage Of Permeable Concrete Pavement

In order to meet special use requirements and environmental requirements,the use of permeable concrete structures in some airport pavements has better overall advantages;however,in the low temperature environment in winter,the freezing and thawing caused by the aqueous solution containing deicing agent on the pavement concrete such as deicing flats The damage is worrying.In order to investigate the damage characteristics of permeable pavement under the coupling effect of deicing agent and freeze-thaw environment,the freeze-thaw damage law of permeable concrete was studied.According to the characteristics of the internal pore structure,the constitutive equation of the permeable concrete pore flow is established based on the hydrodynamic drag factors,and the characteristics and porosity of the internal pore structure of the concrete are tested and analyzed.Based on the icing process and icing law of different pores in porous concrete,the stress-mechanical effect equation around the pores during the icing expansion of the circular closed pores is established;the multi-pore model is established based on the pore distribution of the true cut section of the permeable concrete specimen.Theoretical analysis results show that the peak value of the icing expansion stress near the surface pores of the pervious concrete is located at the surface layer above the icing pores and decreases uniformly to both sides;in the vertical direction of the porous concrete pavement slab,with the distance from the center of the pore o The distance increases,the stress component gradually decreases,and the stress distribution is inversely proportional to the square of the distance d from the center of the pore.The finite element software was used to simulate the analysis of the large pores,semi-open pores on the surface,and closed pores with different shapes caused by the expansion of frozen ice.In this paper,the frost heave damage process of the connected pores under the blocked state was studied,and the stress distribution at the upper surface layer was simulated.The controlled variable method was used to carry out the laboratory test study of porous water-permeable concrete,and the frost resistance indexes of the test pieces under the combined action of different deicing fluid concentration,temperature,freezing rate,porosity and other factors were measured;It shows that the higher the concentration of ethylene glycol,the main component of the deicing agent,the stronger the frost resistance of the porousconcrete when the freezing speed and the minimum temperature are the same.When the other conditions are the same,the lower the minimum temperature,the worse the frost resistance;the faster the freezing speed,the worse the frost resistance;under the same environment,the larger the non-connected pores,the worse the frost resistance.Therefore,when designing the mix ratio of permeable concrete,the proportion of non-connecting holes should be reduced as much as possible to ensure permeability and frost resistance.In addition,the use of epoxy resin with higher bonding strength to cement permeable concrete can significantly enhance the frost resistance of permeable concrete.