Experimental Study On Mechanical Properties And Permeability Of Modified Rubber Cement-based Materials

As China continues to see the development of the economy,there has been a rapid growth in the number of bridges and vehicles.Bridge decks are an important accessory part of the bridge structure,and their quality directly affects the safety and life of the bridge.The damage incurred by long-term vehicle loading on concrete pavement needs to be repaired.However,replacing the deck pavement material during the service life of a bridge not only costs a lot of money,but also causes traffic jams during the maintenance period,which seriously affects the normal traffic flow.The rubbercement-based materials not only have better dynamic mechanical properties,but also have better impermeability,which can effectively improve the service life of bridge deck pavement materials.In this paper,the mechanical properties and infiltration properties of modified rubbercement-based materials are studied experimentally,and the main conclusions are as follows:（1）Organic modifier（silane coupling agent KH570）and inorganic modifier（Na OH）were selected to modify the rubber particles respectively.Compressive strength and impact strength tests were conducted on rubbercement-based materials with different amounts of rubber doping.It was found that the compressive strength of rubbercement-based materials gradually decreased with the increase of rubber doping.The impact strength reached the highest at 20%of rubber doping.Both organic and inorganic modifications can improve the compressive strength and impact strength of rubbercement-based materials.（2）The mechanical properties of rubbercement-based materials differed greatly under different curing environments.Among them,the compressive strength is significantly higher in natural and high temperature curing than the other two curing environments.The flexural strength is the lowest in the natural curing environment.The splitting tensile strength was the highest in the high temperature curing environment,and the effect of organic modification was significantly better than that of inorganic modification.The ratio of bending strength to compressive strength was calculated for rubbercement-based materials and it was combined with the impact strength.It was found that rubbercement-based materials had the best toughness in the water-cured environment.The BP neural network prediction model was used to predict the compressive strength and flexural strength of rubbercement-based materials.（3）The porosity,T₂ spectrum distribution and pore size distribution of rubbercement-based materials were measured by NMR technique,and the sum of peak areas was calculated.It was found that the porosity,sum of peak areas,and the percentage of holes with diameters larger than 200 nm of rubbercement-based materials increased with the increase of rubber particle doping.Both organic and inorganic modifications of rubber particles can slow down the growth trend.The formulae for calculating the compressive strength of rubbercement-based materials with respect to the sum of porosity and peak area were developed based on gray correlation,and the value of equation R² reached 0.87.The X-ray diffractometer（XRD）and scanning electron microscope（SEM）were used to analyze the hydration product composition and micromorphological characteristics of the rubbercement-based materials.（4）The RCM method was used to test the rubbercement-based materials for resistance to chloride ion penetration.The results showed that the chloride ion diffusion coefficient of rubbercement-based materials had a significant decreasing trend with the increase of rubber particle doping.And after the modification of rubber particles,its chloride ion diffusion coefficient shows a slight increase.Under different curing environments,the size of its chloride ion diffusion coefficient is ranked as follows:water curing>standard curing>natural curing>high temperature curing.The accuracy level of the grey GM（1,1）model was used to predict the chloride ion diffusion coefficient of rubbercement-based materials as level 1.