Research On Dynamic Mechanical Properties And Fiber Reinforcement Mechanism Of Polyoxymethylene Fiber Reinforced Airport Pavement Concrete

Cement concrete is widely used in airport road surface because of its high durability,high strength and low cost.However,the poor flexural and impact resistance of airport roadway concrete can easily lead to damage such as roadway panel fracture,sinkage and concrete breakage,which seriously affects flight safety.The study of dynamic mechanical properties of POM fiber airport concrete(PFAPC)is particularly important because the structure needs to be subjected to dynamic loading.Fiber distribution,fiber-cementitious interfacial bond strength and concrete internal pore structure all affect the dynamic mechanical properties of concrete,therefore,it is necessary to investigate the distribution of POM fibers in concrete,POM fiber-cementitious interfacial bond strength and concrete pore structure to reveal the strengthening mechanism of POM fibers on concrete.Firstly,this article carried out the design of the baseline mix ratio of airport road surface concrete according to the relevant specifications,and the response surface method was used to optimize the design of the baseline mix ratio.Secondly,the effect of POM fiber length and admixture on the workability of concrete was investigated by using the Vibro consistency method.The effect of fiber length and admixture amount on the distribution of fibers in concrete and the pore size and distribution of concrete was analyzed using CT scanning technique.Then,the bond strength between POM fibers and cement matrix was investigated by monofilament pulling test,and the nano-mechanical properties of the transition zone at the interface between POM fibers and cement matrix were studied by nanoindentation technique.Finally,the dynamic mechanical properties of PFAPC with different fiber lengths and doping amounts were investigated,and the dynamic intrinsic model of PFAPC was established.The main research results obtained are:(1)The response surface optimization design method can be used to optimize the design in the concrete mix ratio quickly,economically and effectively.Considering the maximum compressive strength and flexural tensile strength of PFAPC,the optimal length of POM fiber is 12 mm and the optimal admixture amount is 0.9%.(2)suitable for the airport pavement with dry hard concrete should not be mixed with a dose higher than 0.9%,the length of more than 12mm POM fiber.POM fiber in concrete will increase the porosity of concrete and the proportion of air pores,with the increase in fiber dosing,the porosity of concrete gradually increased.12mm POM fiber length and dosing of 0.6%in the concrete dispersion is better.(3)The interfacial bond strength between POM fibers and cement matrix was calculated to be 0.2 MPa,and the minimum fiber volume that must be incorporated for POM fibers to make the load-bearing capacity of the cement matrix composite matrix not decrease after cracking was 0.6%.The nanoindentation test revealed that the elastic modulus and hardness of the interfacial transition region near the fibers were higher,and the modulus and hardness of the cement paste were significantly higher than those of the fiber region and the interfacial transition region.(4)The dynamic mechanical parameters of PFAPC all exhibited strain rate effects.The dynamic mechanical properties of PFAPC with the length of 8 mm and the dose of 0.6%were the best.The established dynamic principal structure model of PFAPC can better describe the stress-strain relationship of PFAPC under different strain rates.(5)The research results of this thesis have important reference significance for the application of POM fiber in airport road surface concrete and can further expand the application field of POM fiber.