Study On Technical Performance Of Noise Reduction Ultra Thin Full-asphalt Concrete(UFAC)

With the large increase of the mileage of high-grade highways in China,the maintenance of old road surfaces such as national roads,provincial roads and expressways is not only more and more prominent to effectively improve the driving function(smoothness,anti sliding,etc.)of the old pavement,but also the demand for travel comfort(noise,etc.)is more and more urgent.On the other hand,with the improvement of highway construction technology level and the restriction of maintenance funds,the thicker(?4cm)overlay technology which tends to strengthen the structure is no longer necessary maintenance countermeasures for the subgrade section with the largest mileage proportion.The hot mix asphalt mixture overlay technology scheme with 2cm thickness,which takes into account the structural reinforcement to a certain extent,is widely favored due to its outstanding cost performance and technical advantages that can facilitate the realization of specific functional design.At present,there are relatively few asphalt overlay technology schemes about 2cm,some of the existing technical schemes have relatively high unit price and complex process.2cm dense hot mix asphalt mixture overlay technology scheme has obvious advantages in cost,road performance,durability,technical difficulty of secondary maintenance and so on.Therefore,in the design stage of thin-layer asphalt mixture,it is very necessary and urgent to further highlight the noise reduction performance design of 2cm thin-layer overlay material on the basis of reasonable improvement of raw material processing quality and optimization of gradation,and on the basis of balancing its conventional road performance.First of all,in terms of raw material quality,the size of main aggregate is 5-8mm,and the maximum nominal particle size is reduced from 9.5mm to 8mm.On the basis of conventional three-stage breaking technology,the impact breaking process was further optimized.The elongated and flaky particles content of 5-8mm aggregate was improved to ?12%,and the technical index of 2:1 needle flake was adjusted to ?15%.SBS modified asphalt and rubber modified asphalt were selected for noise reduction test.Secondly,in the aspect of gradation design,CAVF method is adopted for grading design,and 2.36 mm particles are interrupted to ensure good UFAC framework structure and high temperature performance,and at the same time,more VMA and asphalt content are obtained.The test results show that the VMA of UFAC is about 17.5%,which is about 2% higher than GAC-16 C,and the asphalt content can reach 6%,which is about 1.2% higher than GAC-16 C.Thirdly,SBS and rubber modified asphalt binders were selected to carry out the experimental study on noise reduction performance of UFAC with different gradation composition.The results show that the noise reduction performance of rubber asphalt is better than that of SBS modified asphalt.Two factor analysis of variance is used to analyze SBS modified asphalt.The results show that the maximum nominal particle size and asphalt type jointly affect the overall noise reduction performance of the mixture,and the influence of asphalt type is more significant.Improving the asphalt modulus or viscosity toughness can effectively improve the noise reduction ability.The orthogonal test range analysis method is used to analyze the rubber asphalt mixture.It can be seen that different rubber powder mesh number,rubber powder content,gradation type and mixing temperature of rubber asphalt have different primary and secondary relations and different influence on different noise reduction performance indexes of dense graded asphalt mixture.Through the orthogonal test optimization design,the rubber asphalt mixture with 60 mesh rubber powder,21% of the mass of base asphalt,190 ? mixing temperature and dense graded asphalt mixture with the maximum nominal size of 9.5mm has the relatively best noise reduction performance.Finally,the corresponding UFAC test section is paved in the expressway maintenance project in Guangdong Province.The measurement results show that the interior noise of UFAC is about 58.5-62.5d B,which is about 5d B lower than that of uncoated cement pavement and GAC-16 C pavement.Obviously,the technical scheme has good noise reduction effect,and can provide a new technical design idea and scheme for similar engineering problems.