Preparation Of Monocomponent Moisture-Curing Polyurethane Cold Patch Liquid For Pavement And Study On Road Performance Of Cold Patch Mixtures

Asphalt pavement potholes affect the normal passage of vehicles and endanger traffic safety.The existing solvent based asphalt pavement pothole cold patching materials have shortcomings such as slow strength development and difficulty in repairing in harsh weather.This article had developed monocomponent moisture-curing polyurethane cold patch liquid for pavement.The formed asphalt pavement pothole cold patching material had advantages such as fast strength development,good road performance,and could be used for repairing in rainy days.The specific research content and results are as follows:(1)The material composition,synthesis process,and performance characteristics of monocomponent moisture-curing polyurethane cold patch liquid were studied.The influence of raw material composition and synthesis process on the road performance of polyurethane was investigated by measuring the viscosity,tensile strength,elongation at break,Shore hardness,and pull-out strength of polyurethane.The microstructure of polyurethane was characterized by ATR-FTIR.The results show that when the molar ratio of the isocyanate group to the hydroxyl group is 3.5-4.5;the molar ratio of N210 to N330 is 5/5-7/3;the content of DBTDL is 0.1%;the content of TMP is 0.5%-1%;the reaction temperature and stirring rate are80-90 ℃ and 400-500 r/min respectively,the isocyanate group successfully reacts with the hydroxyl group.The polyurethane synthesized has good mechanical strength and fluidity.(2)The design method and road performance of polyurethane asphalt pavement cold patching materials were studied.Based on the Marshall test,a method for testing and formula design of polyurethane cold patch materials is proposed,and the optimal amount of polyurethane cold patch liquid is ultimately determined to be 5.3%.A comparative study was conducted on the road performance of three different types of cold patch liquid,PU-I,PU-II,and PU-III,with the PU-I type having the best performance.And as the amount of binder increases,the water stability and skid resistance performance gradually improve.When the amount of polyurethane binder exceeds 5.5%,the rutting resistance ability begins to decrease;When the amount of polyurethane binder exceeds 6.0%,the low-temperature crack resistance of the polyurethane mixture shows a negative increase.(3)The curing behavior of polyurethane cold patching mixture under different curing conditions and compaction times was studied.The expansion rate and Marshall stability were measured at curing time of 2h,6h,12 h,24h,48 h,curing temperature of 5 ℃,25 ℃,45 ℃,65 ℃,and compaction times of 55,65,75,85,95.The results show that after curing for 24 hours,the Marshall stability tends to the maximum value of stability,and the Marshall stability basically does not change after 48 hours.In order to meet the traffic opening requirements of the pavement and the strength requirements after molding as soon as possible,the appropriate curing time for cold patching mixture is 24 hours.The suitable curing temperature range is 15 ℃-30 ℃.Properly increasing the curing temperature can speed up the opening time of traffic,which is conducive to the strength of the mixture rapid prototyping.In order to avoid excessive changes in the volume expansion of the mixture,it is appropriate to determine 85 compaction times,while also ensuring a relatively high Marshall stability.