Zhang Chen, Xiao Dingkan, Zhang Jun, Li Haoran, Xu Wei, Zhou Yong
Rigid polyurethane foam,with its advantages of short reaction time,high expansion ratio,ease of operation,and high strength,holds great potential for use in rapid airport pavement repair.In airport repair projects,key reaction parameters such as temperature and time significantly impact the performance of this material.To guide repair practices,this study set four temperatures (5℃,15℃,23℃,and 35℃) and four curing times (0.5h,2h,4h,and 24h).Under these conditions,experiments were conducted to measure reaction time,expansion ratio,and unconfined compressive strength (UCS),along with microstructural analysis using CT scanning.The results indicated that as the temperature increased,the reaction time of the material gradually decreased,achieving 20 minutes 30 seconds at 5℃ and 3 minutes 20 seconds at 35℃.The expansion ratio of the material decreased with rising temperature,with the highest expansion ratio of 7.02 occurred at 35℃.The compressive strength of the material first increased and then decreased with rising temperature,reaching its peak strength at 23℃.At low temperatures,the internal pores of the material were denser,and some unreacted material remained even after full curing.At high temperatures,the internal pores were larger,resulting in lower density and strength.After 0.5h of curing,the material's strength reached 80% of its final strength,and after 4h,it nearly reached its final strength.In the early stage of curing,some pores were not fully formed,with more pores at the bottom than at the top.Once fully cured,the bottom pores became denser than the top ones,leading to higher strength at the bottom.For optimal repair outcomes,it was recommended to mix the rigid polyurethane foam at around 23℃.After 0.5h of curing,the material's strength was sufficient to fully support the weight of the surface materials and accommodated the passage of vehicles and machinery.
