Fracture Properties Research On Fiber Reinforced Emulsified Asphalt-Cement Concrete

Compared with cement concrete,Emulsified Asphalt–Cement Concrete has moderate modulus strength ratio,good plasticity,energy saving,environmental protection and convenient construction,which can better adapt to the service environment with large deformation,such as dam,steel bridge deck pavement,etc.However,there are still some problems in flexural tensile strength and crack resistance,which needs to be improved.In this paper,the idea of adding PVA fiber was put forward to improve its flexural tensile strength and crack resistance,and balance the relationship between strength,plasticity and crack resistance.Firstly,on the basis of theoretical analysis of material design,a group of materials laboratory mix ratio was determined according to the relevant literature to prepare the PVA fiber reinforced Emulsified Asphalt–Cement Concrete.The fiber content was0.7kg/m~3.And the elastic modulus,strength,interface fracture energy and other basic performance parameters were tested.The microstructures were characterized by mercury injection test(density,pore size,distribution,porosity),scanning electron microscopy(cement hydration product,fiber geometry,distribution)and energy dispersive analysis(chemical element).Secondly,the research ideas of multiscale composite materials were applied.Based on the two-dimensional image digitization and bilinear cohesive zone constitutive relation,the meso-finite element fracture model could be established by inserting two-dimensional zero-thickness cohesive interface elements into the interface between aggregate and asphalt cement mortar and asphalt cement mortar.Uniaxial tensile fracture and dynamic cracking of three-point bending beam were simulated and the effect of PVA fiber on fracture toughness was discussed.The results showed that fiber reinforced Emulsified Asphalt–Cement Concrete was composed of three phase media in mesoscale,which were aggregate,fiber-asphalt cement mortar,and pore.The PVA fiber had little effect on the porosity of the material,but it could improve the uniformity of pore size,enhance the filling and thinning of the pore,and improve the microstructure of the material to a certain extent.There was no chemical reaction between fiber and emulsified asphalt,cement and aggregate,and no new chemical products were formed.Three-point bending test and uniaxial compression test showed that PVA fiber could significantly improve the macroscopic flexural tensile strength and fracture energy of the mixture,which had an increase more than 100%and 50%,but had little effect on the compressive strength and elastic modulus,which had an increase about 3%.The results of microfracture analysis showed that the interface between aggregate and asphalt mortar was a weak phase,and the fracture began from the interface.PVA fiber could effectively enhance the tensile strength of the mixture and delay the crack propagation.The critical fracture load and the corresponding mid-span displacement of meso-numerical simulation were slightly smaller than the experimental values,but the difference of tensile strength was not obvious.The numerical simulation value of fracture energy was slightly larger than the experimental value,and the meso-fracture analysis was in good agreement with the macroscopic test results,and the two-dimensional meso-fracture model was relatively accurate.Through the above research,it was proved that the fiber reinforced Emulsified Asphalt–Cement Concrete had better reinforcement and crack resistance effect,which could provide a theoretical reference for improving the comprehensive properties of this kind of composite materials and had important potential application prospects.