Study On Design And Properties Of Early Strength Grouting Material For Semi-flexible Pavement

In China,asphalt pavement is the most common form of pavement,and it has so many advantages such as anti-skid,comfortable driving,short construction period and so on.However,rutting is an inherent challenge that restricts its application.In this regard,many studies poured the cement grouting material into asphalt mixture with predesigned voids and product semiflexible pavement(SFP).Due to the existence of cement slurry,SFP shows greater elastic modulus and has better rutting resistance and durability than asphalt pavement.However,the exact curing demands of cement-based materials prolong the time from construction to opening traffic.In addition,the characteristics of cement hydration shrinkage and brittleness make the pavement easier to crack under the action of the external environment and stress.In order to solve the above problems,early high strength grouting material(EHSG)was designed for semiflexible pavement and reinforced with short fine PP fiber.Finally,EHSG is used in pilot production and actual construction to promote the development of SFP.In order to achieve sufficient fluidity,setting time,and early strength,EHSG was prepared by adjusting the water-binder ratio,ordinary Portland cement(OPC),early strength admixture(RA),silica fume(SF)and polycarboxylate superplasticizer(PCE).The initial flow time of slurry is 12.8 s,the initial and final setting time of slurry is 75 min and 83 min respectively,and the compressive strength of EHSG at 3 h and 1 d is 7.6 MPa and 24.5 MPa respectively.Simultaneously,the test results show the water-binder ratio and RA determine the 3 h strength.PCE and SF improve the flowability and flow retention capacity without negatively affecting other properties.The effects of PCE and SF on rheological properties of EHSG were tested.The results suggest that SF addition decreases the viscosity but increases the dynamic yield stress of EHSG.PCE incorporation reduces plastic viscosity and dynamic yield stress but may increase the residual viscosity.The flow time of EHSG has a linear relationship with its dynamic yield stress.The syneigistic mechanism of PCE and SF was analyzed by water film thickness,zeta potential,PCE adsorption,and SEM.Small size polypropylene(PP)fiber was added to EHSG to improve its properties.The test results of basic properties show that the addition of PP fiber reduces slurry fluidity and affects slurry stability.The appropriate amount of PP fiber can not only increase the flexurecompression ratio,but also inhibit water loss and reduce drying shrinkage.The pore structure of EHSG was studied by MIP,X-CT and SEM.The results show that it is feasible to add appropriate PP fibers into EHSG.The research outputs of EHSG were used in pilot production and field grouting.The results show that EHSG has an excellent filling effect and can be appied in construction,while attention should be paid to the selection of mixing equipment and the control of filling temperature.