| Corn straw fiber is widely used in the construction of asphalt pavement as a new green material to improve the performance of asphalt pavement and prolong its service life.Currently,there are few studies on how to prepare corn straw fiber materials that meet the SMA grading type,and no unified technical standards for corn straw fiber used in asphalt pavement construction have been proposed.Therefore,this paper proposes a modified corn straw fiber preparation process suitable for SMA pavement structure,summarizes the effects of fiber length and content on the performance of asphalt mortar and mixture,and analyzes the permanent deformation resistance of modified corn straw fiber SMA asphalt mixture on this basis.Firstly,the corn straw husks obtained from the separation of the skin and pulp are subjected to mechanical crushing,screening,and alkali solution erosion treatment to obtain 3mm,6mm,and 9mm modified corn straw fibers.The oil absorption and heat resistance of modified corn straw fibers were tested,and the modification mechanism was revealed by scanning electron microscopy(SEM).By reasonably designing orthogonal tests,the rheological properties of fiber asphalt mortar were tested to analyze the impact of fiber length,dosage,and modifier concentration.The results showed that Na OH modification improved the oil absorption and heat resistance of corn straw fibers,making them similar to the physical properties of lignin fibers;The concentration of Na OH solution has a significant impact on the rheological properties of corn straw fiber slurry.Based on the comprehensive improvement effect,the optimal concentration of Na OH solution for corn straw fiber modification treatment is 5%.Secondly,the effects of fiber length and content on the pavement and rheological properties of asphalt mortar were analyzed,and the microscopic mechanism of the impact of fiber content on the performance of asphalt mortar was analyzed using a fluorescence microscope.The results showed that three lengths of modified corn straw fibers significantly improved the high-temperature performance of asphalt mortar,but had a negative impact on the low-temperature performance of asphalt mortar.The degree of improvement and reduction of the impact varied with the fiber content.Fluorescence microscope observation showed that when the fiber content was1.5%,the fiber could blend with SBS particles inside the latex to form a stable two connected state,enhancing the overall stability of the structure.Through comprehensive analysis of road use,high and low temperature rheological properties,and microscopic mechanism of action,it is concluded that the optimal blending amount of modified corn straw fibers with different lengths is 1.5%.Thirdly,the influence of the addition of modified corn straw fiber on the pavement performance of asphalt mixture was studied,and regression analysis was conducted on the fatigue life and stress level of the mixture based on the phenomenological analysis model of mixture fatigue damage.The results show that the high temperature rutting resistance,low temperature cracking resistance,water stability,and fatigue resistance of asphalt mixtures with different lengths of fiber first increase and then decrease with the increase of fiber content.Through comprehensive analysis of the improvement of road performance,it is concluded that the optimal fiber content for lengths of 3,6,and 9 mm is 0.8%,0.6%,and 0.4%,respectively.Finally,the rutting behavior of modified corn straw fiber asphalt mixture under the combined action of high temperature and load was studied using a small loop accelerated loading device independently developed by the research team.Using a temperature load rutting prediction model,the rutting deformation law of fiber asphalt mixture was analyzed,and it was found that the resistance to permanent deformation of C-9-0.4% and C-6-0.6% mixtures was the best.Therefore,it is recommended to use 6mm and 9mm modified corn straw fibers with a content of 0.6% and 0.4% for asphalt pavement construction. |
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