Research On Material And Structure Of Ecc Overlay On Airfield Pavement

With the development of the transportation in China,airfield construction is in a rapid development period.However,flight and aircraft weight increase have led to premature deteriorations that could reduce the service life of airfield pavement and affect the normal operation of the airfield.Further,surface spalling of airfield pavement could endanger aircrafts through engine suction of spalls.In order to solve the cracking problem of airfield pavement and extend its service life,the ECC overlay on airfield pavement was proposed in this study.ECC material has the excellent mechanical properties,which can meet the design requirments on airfield pavement.The ECC material with properties of ultra high ductility and multiple cracking behavior can effectively restrain the occurrence and delay the propagration of reflective cracks.In addition,the self-healing behavior of ECC material significantly extends the durability and decreases the maintainence frequency of airfield pavement.There are five parts of this study,including including reflective cracking resistance of ECC overlay,ECC self-healing mechanism on multiple scales,low cost ECC with local aggregrates,the structure calculation and the life cycle assessment of ECC overlay on airfield pavement.Firstly,the reflective cracking rsistance behavior of ECC overlay was researched through combined theoretical and experimental methods.The mechanism of reflective cracking resistance for ECC overlay was researched based on the interface fracture mechanics.When a crack propagates from the concrete substrate towards the ECC layer,crack penetration into the ECC layer can be expected if the ration of cracking driving force to fracture toughness of ECC is higher than the ration of interface crack driving force to interface fracture toughness.Otherwise,the crack bifurcates into the ECC/concrete interface.However,the crack penetrated into ECC layer could be trapped due to the R-curve property(toughness increases with crack length increasing)of ECC material.In addition,the reflective cracking resistance behavior and influence factors of ECC/concrete beam were investigated experimentally under four-point bending loading,fatigue loading and impact loading.The results indicate that the interface bonding and interface initial crack length have the significant influence on reflective cracking resistance behavior of the ECC overlay.Secondly,the self-healing behavior of ECC was researched on multiple scales.In macro-scale,the crack patterns(average crack width and crack number)of ECC specimens were researched through statistic theory,and the crack patterns were modeled by lognormal distributions.In meso-scale,the self-healing behavior of single crack was researched,and the stiffiness recovery of a single crack as a function of crack width was modeled.Combined with macro and meso scales,a scale linking model was built to predict the stiffness recovery of ECC specimen at varying tensile strains.The scale linking model was verified by experimental results.Thirdly,in order to reduce the cost of ECC overlay on airfield pavement,low cost ECC materials were developed with local ingredients(especially PVA fiber)based on the design theory of micro-mechanics.The fiber and matrix interface properties including chemical bond and friction bond strength was tailored through varying fly ash content and incorporation of crumb rubber.In addition,CaCO3 whisker was used to reinforce the domestic ECC with a lower strength.The developed low cost ECC materials can meet the requirements of airfield pavement overlay.Fourthly,based on the mechanical properties of the developed low cost ECC,the thickness of ECC overlay with different bonding were calculated using bi-layer theory.Compared to normal concrete overlay and asphalt concrete overlay,the thickness of ECC overlay can be reduced by 42.5%and 52%,respectively.Finally,the life cycle assessments of ECC overlay,normal concrete overlay and asphalt concrete were conducted and compared using eBalance software.The life-cycle primary energy consumption of ECC overlay is 34%and 87%less than that of concrete overlay and asphalt concrete,respectively.The Global Warming Potention(GWP)of ECC overlay is 42%and 66%of concrete overlay and asphalt overlay,respectively.The assessment results indicate that ECC overlay is environment friendly and sustainability.