The Research On Mixture Design And Performance Of Paved Rubber Asphalt Stress-absorbing Layer

With the proposal of the "Outline for Building a Powerful Transportation Country".our country’s transportation construction and development strategy has been transformed into"equal emphasis on construction and maintenance",road construction and maintenance and reconstruction tasks have increased significantly.Among them,in the cement pavement overlay and semi-rigid base asphalt pavement renovation and upgrading project,due to the existence of joints or cracks in the original pavement,reflection cracks are prone to occur soon after construction,which further induces more pavement disease and seriously affects the quality of pavement.The paved rubber asphalt stress-absorption layer is a thin layer structure formed by paving and compaction of the fine-grained asphalt mixture mixed with rubber asphalt,which has the advantages of strong stress absorption effect and fast construction speed,which can effectively prevent or delay the occurrence of launch cracks.However,there is no specific design and evaluation method for it,so it is very necessary to conduct in-depth research on it.The requirements of domestic and foreign standard guidelines on the performance of asphalt materials for rubber asphalt stress absorbing layers and the scope of mineral grading are summarized in this article.It is found that softening point,penetration,180℃ rotational viscosity,and elastic recovery are the main technical indicators of rubber asphalt,and the corresponding control range is obtained.There are mainly two types of mineral grading with a nominal maximum particle size of 4.75mm and 9.5mm.The grading of mineral materials with a nominal maximum particle size of 9.5mm is widely used in our country,and 3 grading ranges(A,B,C)and 9 groups of mineral grading have been drawn up.In terms of mixture design research,the void ratio(VV)is quite different from ordinary asphalt mixtures,which mainly in the two ranges of 0.5-3.0%and 3.0-6.0%.The Marshall test method is used to determine the best oil-stone ratio and the corresponding volume index under the design porosity of 4.0%and 2.5%respectively,and the passage rate of 4.75mm,2.36mm sieve and CA and FAf are used to establish the void ratio(VV)and the voids of mineral aggregate(VMA)predictive model.Through rutting test and beam bending test,SCB low temperature test,SCB crack propagation test,OT test and immersion Marshall test and freeze-thaw splitting test,study the influence of design porosity and mineral grading on the performance of asphalt mixture is analyzed.The results show that:The stress absorption performance of asphalt mixture is mainly manifested in two aspects-fracture performance and resistance to crack development.The-10℃small beam bending test,the SCB low temperature test,the SCB crack propagation test,and the OT test are the evaluation methods of reactive fracture performance and resistance to crack development,respectively.From the voidage,the change in voidage from 4.0%to 2.5%has a limited effect on the high-temperature performance and water stability of the mixture,while the 2.5%voidage of asphalt mixture has excellent performance in stress absorption,so it is recommended that 0.5%-3.0%be used as the design voidage range of the paved rubber asphalt stress-absorbing layer.From the aggregate gradation,for the gradation range covered in this article,the range B and C mixtures have better high temperature performance,the range B mixture has better fracture performance,the range C mixture has better resistance to crack development,and the range A and B mixtures has better water stability.Further agree on the range of grading parameters,when the 2.36mm mesh pass rate is 20%～40%,the PCSI is between-20～-10,the Dc is controlled within 2.10～2.40,and the thickness of the asphalt film does not exceed 18.0μm,can show certain advantages in high temperature,stress absorption and water stability at the same time.Based on the Pavecool software,the.software principle and the specific value method and scope of the three software parameters of environmental parameters,asphalt mixture and underlying layer were explained in detail.The temperature,wind speed,paving layer thickness and The effect of the paving temperature on the temperature drop of the rubber asphalt stress absorption layer and the effective compaction time.The results show that:as the temperature rises and the thickness of the paving layer increases,the cooling rate of the asphalt mixture slows down,and the effective compaction The time is significantly prolonged,and with the increase of wind speed,the cooling rate of the mixture is intensified,and the effective compaction time is significantly shortened.The paving temperature has no obvious effect on the cooling of the asphalt mixture,but increasing the paving temperature can extend the effective pressure to a certain extent.At the same time,based on the single factor simulation test,a prediction equation for the effective compaction time of the asphalt mixture under the influence of multiple factors is established,and the predicted value of the prediction model can effectively fit the Pavecool simulation value.