Study On The Effect Of Rice Husk Ash On The Performance Of Asphalt And Asphalt Mixture

Rice husk is a very abundant agricultural waste.The rice husk ash obtained by controlling the combustion conditions of rice husk has the characteristics of high amorphous silica content,large specific surface area and porosity,which has high activity.It can be considered as an asphalt modifier to improve the performance of the matrix asphalt and its mixture.However,how to obtain the rice husk ash which is the most beneficial to asphalt modification and how to prepare the modified asphalt is a key issue in the research of rice husk ash modified asphalt.Therefore,this paper aims to summarize the preparation process of high-activity rice husk ash and rice husk ash modified asphalt through orthogonal experiments,and evaluate the effect of rice husk ash on the road performance of asphalt mixture.In addition,the adverse effect of rice husk ash on low temperature performance of asphalt is minimized by optimizing the preparation process.By referring to the preparation process of other solid modifier modified asphalt,the parameters of heat preservation and defoaming are determined,and the control variables of premixed insulation are studied.The preparation process of rice husk ash modified asphalt is preliminarily explored.Studies have shown that the modified asphalt can be fully defoamed by holding at 135? for 1 hour.In addition,the pre-mixed insulation can make the rice husk ash more uniform in the asphalt,improve the performance of the modified asphalt,and achieve the goal in 10 minutes.In order to obtain the optimal preparation process of active rice husk ash,factors such as combustion equipment,heating rate,cooling rate,incineration temperature,incineration time and grinding time are considered.And with the average particle size,specific surface area,silica crystalline state and silica content of rice husk ash,as well as the three major indexes and rotational viscosity of rice husk ash modified asphalt,the incineration temperature,the incineration time and the grinding time are subjected to an orthogonal test study.The research shows that the rice husks are placed in a muffle furnace and raised from room temperature to 700? for 2 hours.After incineration,the rice husk ash is directly taken out from the furnace and scattered in a tray.The rice husk ash is cooled at room temperature and finally wet-milled in a vertical square planetary ball mill for 15 minutes.The rice husk ash can improve the high temperature performance while minimizing the adverse effect on the low temperature performance of asphalt.On the basis of preliminary proposing the preparation technology of rice husk ash modified asphalt,four factors affecting the high-speed shearing process including shearing time,shearing temperature,shearing rate and the content of rice husk ash,are optimized by orthogonal test.The results show that the high-activity rice husk ash is sieved through 0.075 mm sieve.Then mix the sieve bottom into asphalt by 3% of asphalt mass,and hold the mixture at 150? for 10 minutes.The mixture is then sheared at a rate of 5000r/min for 10 minutes at a constant temperature of 150?.Finally,the prepared modified asphalt is placed in a constant temperature oven and defoamed at 135? for 1 hour.The modified asphalt can minimize the adverse effect of rice husk ash on the low temperature performance of asphalt and improve its high temperature performance.Finally,the mechanical properties,water stability,high temperature performance and low temperature performance of rice husk ash modified asphalt and base asphalt mixture are studied by Marshall stability test,immersion Marshall test,freeze-thaw splitting test,rutting test and low temperature bending test.The results show that rice husk ash can improve the strength,deformation resistance,water stability and high temperature stability of asphalt mixture.Although rice husk ash can slightly reduce the low temperature crack resistance of asphalt mixture,it can still meet the practical engineering needs.