Study On Fast And Hard ECC Thin Layer Overlay Material And Structure Performance Of Cement Concrete Pavement

ECC(Engineered Cementitious Composites)materials have significant strain-hardening properties and multi-slit cracking.Currently,it widely used in building special components,hydropower dam repair and steel bridge deck pavement.The traditional thin layer overlay material has obvious shortcomings,which hinders the popularization and application of the thin layer overlay technology.In this paper,ECC materials were applied to the thin layer of cement concrete pavement,combined with the use of early strength cement,the material had a flexural strength of more than 5 MPa at 1 d age,which could open traffic quickly,and had high impact resistance and wear resistance,and good at wear resistance,which had good social and economic benefits.In this paper,based on the ECC material mix ratio,the preliminary mix ratio was determined by the flexural strength,bending toughness index and dry shrinkage performance.Based on the initial mix ratio,the fiber type,the amount of blending and the binary fiber blending ratio were changed.Thin layer overlay materials were systematically studied from mechanical properties and road performance.The specific tests and conclusions are as follows:(1)By searched the previous research data,the water-to-binder ratio was initially determined.Through the experimental research,the flexural strength,bending toughness index and dry shrinkage performance were used as evaluation indexes to determine the sand-to-binder ratio,aggregate particle size,fiber length,expansion agent and fly ash content,finalize the test material usage and test mix ratio.The final result is: water-to-binder ratio of 0.28,sand-to-binder ratio 1,fine aggregate particle size of 2.36 mm or less,fiber length of 12 mm,expansion agent content of 10%,fly ash content of 30%.(2)In this paper,the mixing ratio of 6 groups of single fibers and the ratio of 1group of control were prepared.Flexural strength,compressive strength,flexural toughness,fracture toughness and flexural modulus of the 7 groups were tested.For the mixing ratio of 9 sets of binary fibers,the experimental research on flexural strength,compressive strength,flexural toughness and fracture toughness was carried out.The results show that compared with the blending ratio of the added fiber,the blending ratio of the unfibered fiber is obviously poor in the above basic mechanical properties,and the fiber blending amount can increase the above properties,but when the fiber content is large,the fiber agglomerates is serious,and there are many internal pores in the test piece,which had a great influence on flexural strength and compressive strength.In the hybrid of binary fibers,the fiber content increases,the larger the proportion of PVA fiber,the stronger the mechanical properties.There is a set of binary hybrid fiber mixing ratio,which makes the basic mechanical properties better than the single fiber blending ratio,a blending effect of "1+1>2" is achieved.(3)In this paper,the abrasion resistance,dry shrinkage and impact resistance tests were carried out on the mixing ratio of the 7 groups.Under the fixed mixing ratio,the interface flexural test and the "Z" type specimen shear test were carried out on the bonding properties of the thin layer covering material and the old cement concrete through six different interface treatment methods.The test results show that the increase of fiber content had a positive effect on wear resistance,shrinkage and impact properties.The PVA fiber had a greater effect on the wear resistance,dry shrinkage and impact resistance than the PP fiber.Among the six different interface treatment methods,the polymer interface agent can effectively improve the interface flexural strength and shear strength.Among them,(6)cement: polymer = 2:1 polymer interface agent in the interface flexural test and "Z" The strength of the shape test piece shear test is the highest.(4)In this paper,using the ABAQUS finite element software,an extended finite element model with a superficial layer was established.By analyzing different overcoat materials and different axle load parameters,the stress intensity factor of the preset crack tip,the tensile stress and shear stress of the overcoat layer,and the shape of the reflective crack were studied.The results show that the PP-ECC material was superior to the PVA-ECC material in the stress intensity factor at the crack tip,the tensile stress and shear stress of the overcoat layer,and the reflective crack propagation morphology.Ordinary concrete materials are the worst.