Research On Properties Of Cement Concrete Pavement With Polypropylene Fiber Reinforced Concrete Overlay

Under the load coupled with the environment effect, the service conditions arefairly complex. In recently years, the strengthening, rehabilitation and mending of thepavement structure are greatly needed, owing to increasing traffic, pavement structure’saging, insufficient load bearing, and so on. The bonded overlay is a preferable choice insituations, such as there is little damage on the pavement structure or functionality andload bearing are shortage, of which the overlay thickness is usually smaller. However,research on the bonded overlay repair and its application are just at the initial stage,without integrated design method. Therefore further study are expected about overlaymaterials, the bonded properties of overlay-to-existing structure, performance afteroverlaying, factors on the bonded overlay etc. As a result, polypropylene fiberreinforced concrete (PFC) was adopted as the overlay concrete in this paper to discussseveral properties, including the mechanical performance of PFC, the bonded agentsand the overlay specimens and durability of the pavement, coupling with the analysis onthe sensitivity to overlay. The conclusions obtained are as follows:(1) Properties studied include the mechanical performance, durability of thepavement, flexural tensile strength under freeze-thaw cycle and/or simulating wheelload of hardened concrete mixed with polypropylene fiber (PP) at different contents.The results indicate that the optimum content of PP is0.2%when the mechanicalproperties reached a better value. With the increase of PP contents, the durability of thepavement and flexural tensile strength after freeze-thaw cycle and/or simulating wheelload improved.(2) Tests designed to analyze the effect of the bonded agents on the hardenedconcrete contain bonding split strength, bonding sheer strength, rapid freeze-thaw cycle,interface salt frost, dry-moisture cycle and slow freeze-thaw cycle. The resultsdemonstrate that the bonding strength of group D and group C1are larger, while groupD1and group C1displayed better durability.(3) The study on the overlay specimens consist of the effect of overlay thickness,mechanical properties after freeze-thaw cycle and/or simulating wheel load, restraintshrinkage deformation and free shrinkage deformation. The consequence manifest thatthe thicker of the overlay, the higher the flexural strength before and after single ordouble factors. The restraint shrinkage deformation decreased when the test spot wasclose to the bonding surface. Besides, the shrinkage deformation of PFC was smallerthan OPC and the higher the fiber content, the smaller the shrinkage deformation.(4) Three factors on thickness of overlay and fatigue strain on the bottom of slabare analyzed including the flexural strength of old pavement concrete, strength of overlay concrete, composite resilient modulus of foundation and thickness of overlay. Inaddition, the effect of thickness of overlay on the comprehensive fatigue stress on thebottom of slab is also analyzed. The results imply that with the same load bearing, theincreased former three factors benefited reducing the thickness of overlay. Enlargingany of all the latter three factors can decrease the comprehensive fatigue stress on thebottom of slab to different extents.